No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Systematic Position and Phylogeny
... Although some studies made important attempts to reconstruct the molecular phylogeny of Nematoda [9][10][11][12][13][14][15][16][17][18][19][20], the systematic position of the family Rhabdiasidae in the order Rhabditida is still unclear. Anderson & Bain [21] put Rhabdiasidae, closer to the families Strongyloididae, Rhabditidae, Cylindrocorporidae and Cephalobidae within the superfamily Rhabditoidea (order Rhabditida). ...
... Anderson & Bain [21] put Rhabdiasidae, closer to the families Strongyloididae, Rhabditidae, Cylindrocorporidae and Cephalobidae within the superfamily Rhabditoidea (order Rhabditida). However, De Ley & Blaxter [10,11] placed the Rhabdiasidae, Strongyloididae and Steinernematidae in the superfamily Strongyloidoidea (suborder Tylenchina) [10,11]. Hodda [22,23] erected the superfamily Steinernematoidea to allocate Steinernematidae, and transferred Strongyloidoidea (which includes Rhabdiasidae and Strongyloididae) and Steinernematoidea to Panagrolaimina [22,23]. ...
... Anderson & Bain [21] put Rhabdiasidae, closer to the families Strongyloididae, Rhabditidae, Cylindrocorporidae and Cephalobidae within the superfamily Rhabditoidea (order Rhabditida). However, De Ley & Blaxter [10,11] placed the Rhabdiasidae, Strongyloididae and Steinernematidae in the superfamily Strongyloidoidea (suborder Tylenchina) [10,11]. Hodda [22,23] erected the superfamily Steinernematoidea to allocate Steinernematidae, and transferred Strongyloidoidea (which includes Rhabdiasidae and Strongyloididae) and Steinernematoidea to Panagrolaimina [22,23]. ...
Background
The family Rhabdiasidae (Nematoda: Rhabditida) is a globally distributed group of nematode parasites, with over 110 species parasitic mainly in amphibians and reptiles. However, the systematic position of the family Rhabdiasidae in the order Rhabditida remains unsolved, and the evolutionary relationships among its genera are still unclear. Moreover, the present knowledge of the mitochondrial genomes of rhabdiasids remains limited.
Methods
Two rhabdiasid species: Rhabdias kafunata Sata, Takeuchi & Nakano, 2020 and R. bufonis (Schrank, 1788) collected from the Asiatic toad Bufo gargarizans Cantor (Amphibia: Anura) in China, were identified based on morphology (light and scanning electron microscopy) and molecular characterization (sequencing of the nuclear 28S and ITS regions and mitochondrial cox1 and 12S genes). The complete mitochondrial genomes of R. kafunata and R. bufonis were also sequenced and annotated for the first time. Moreover, phylogenetic analyses based on the amino acid sequences of 12 protein-coding genes (PCGs) of the mitochondrial genomes were performed to clarify the systematic position of the family Rhabdiasidae in the order Rhabditida using maximum likelihood (ML) and Bayesian inference (BI). The phylogenetic analyses based on the 28S + ITS sequences, were also inferred to assess the evolutionary relationships among the genera within Rhabdiasidae.
Results
The detailed morphology of the cephalic structures, vulva and eggs in R. kafunata and R. bufonis was revealed using scanning electron microscopy (SEM) for the first time. The characterization of 28S and ITS regions of R. kafunata was reported for the first time. The mitogenomes of R. kafunata and R. bufonis are 15,437 bp and 15,128 bp long, respectively, and both contain 36 genes, including 12 PCGs (missing atp8). Comparative mitogenomics revealed that the gene arrangement of R. kafunata and R. bufonis is different from all of the currently available mitogenomes of nematodes. Phylogenetic analyses based on the ITS + 28S data showed Neoentomelas and Kurilonema as sister lineages, and supported the monophyly of Entomelas, Pneumonema, Serpentirhabdias and Rhabdias. Mitochondrial phylogenomic results supported Rhabdiasidae as a member of the superfamily Rhabditoidea in the suborder Rhabditina, and its occurrance as sister to the family Rhabditidae.
Conclusions
The complete mitochondrial genome of R. kafunata and R. bufonis were reported for the first time, and two new gene arrangements of mitogenomes in Nematoda were revealed. Mitogenomic phylogenetic results indicated that the family Rhabdiasidae is a member of Rhabditoidea in Rhabditina, and is closely related to Rhabditidae. Molecular phylogenies based on the ITS + 28S sequence data supported the validity of Kurilonema, and showed that Kurilonema is sister to Neoentomelas. The present phylogenetic results also indicated that the ancestors of rhabdiasids seem to have initially infected reptiles, then spreading to amphibians.
Graphical Abstract
... The clade Synoecnema+Acrobeloides clustered with tylenchids under maximal bootstrap support. Contrary to expectations, the combined clade of tylenchids + Synoecnema + Acrobeloides remained outside of the larger clade containing all other Rhabditida (sensu De Ley and Blaxter 2002) and the two studied Plectidae (Plectus aquatilis and P. acuminatus). Additionally, a clade containing oxyurids and spirurids was in a similarly detached position. ...
... Thus, in the multigene phylogram (Fig. 4), plectids were found clustering only with a certain part of the order Rhabditida (precisely with the representatives of infraorders Ascaridomorpha, Diplogasteromorpha, Panagrolaimomorpha, Rhabditomorpha and aphelenchids). Oxyuridomorpha, Spiruromorpha and tylenchids, along with the cephalobid Acrobeloides varius and the ungellid Synoecnema hirsutum, were closer to the base of the nematode tree, thus making the order Rhabditida (sensu De Ley and Blaxter 2002) polyphyletic. Such topology was supported in some phylograms inferred from single mitochondrial genes (atp6, coxI, cob, nad3, nad5 and nad6), but not supported in other (cox2, cox3, nad1 nad2, nad4 and nad4L). ...
... Previous attempts to find the place for ungellids and other Drilonematoidea in the system of Nematoda were based on nuclear ribosomal sequences only (Spiridonov et al. , 2007Ivanova and Spiridonov 2011;). First, LSU and SSU analyses had confirmed that the earthworm parasites from the family Creagrocercidae were not related to the rest of Drilonematoidea (Drilonematomorpha of De Ley and Blaxter 2002), but appeared to be close to Domorganus Goodey, 1947 (Ohridiidae, Plectida) (Ivanova, Spiridonov 2011). Further on, it was shown that at least two evolutionary lines of Drilonematoidea were related to Cephalobomorpha. ...
Synoecnemahirsutum Timm, 1959 (Ungellidae, Drilonematoidea) found in the body cavity of the pheretimoid earthworm at the border of Laos and Vietnam was redescribed and illustrated. It was molecularly characterised for the first time. It is also the first member of the superfamily Drilonematoidea for whom the mitochondrial genome was obtained.
... De Ley & Blaxter (2002, 2004 introduced a classification of the Nematoda based on molecular phylogenetic analyses (small subunit ribosomal DNA, SSU rDNA), but because many nematode taxa remain unsequenced, morphological, ontogenetic, and biological characters were also included. This classification is now the most widely used, although recent molecular phylogenetic investigations suggest that further updates will be required (e.g., Leduc & Zhao 2019a). ...
... The checklist is arranged according to the currently accepted systematics and classificatory scheme of De Ley & Blaxter (2002, 2004, with modification by Leduc et al. (2018a, b) and Leduc & Zhao (2019a), and split into free-living and parasitic nematodes. For the parasitic nematodes, the common and scientific name of the definitive host (DH) and intermediate host (IH) is also provided where known, but we have not included the host taxonomic authorities, which are available in World Register of Marine Species (WoRMS) (https://www.marinespecies. ...
The total number of described and known, but undescribed, extant marine nematode species from the Aotearoa
New Zealand region is 376 species, 254 of which are free-living and 122 parasitic. The current New Zealand species total is about 2–5% of the global total and about 5–20% of the estimated total for New Zealand. Since the previous review by Yeates (2010), nine new genera and 132 new nematode species have been described. The known nematode diversity for New Zealand waters has more than doubled over the last two decades, largely due to the description of new free-living species. A checklist of extant New Zealand Nematoda
is provided.
... Nematode spermatozoa represent a highly modified (aberrant) type of male gametes in that they are characterised by the absence of an axoneme, an acrosome and, with the exception of members of the order Enoplida (the higher classification proposed by De Ley & Blaxter (2002) is used herein), a nuclear envelope (Justine & Jamieson, 1999;Justine, 2002;, 2014. Structure and development of nematode sperm have been studied mainly in the representatives of the diverse order Rhabditida, most of the studied species producing relatively uniform and putatively plesiomorphic sperm of the 'rhabditid' pattern (Slos et al., 2020). ...
... The rhabditid pattern reflects the main characteristics of the typical nematode sperm, but presents only part of the actual sperm diversity, even within the order Rhabditida (Slos et al., 2020). In the classification of nematodes proposed by De Ley & Blaxter (2002), the phylum Nematoda is subdivided into the classes Enoplea and Chromadorea. The latter includes the extensively studied order Rhabditida along with orders of free-living aquatic nematodes (Desmoscolecida, Chromadorida, Desmodorida, Araeolaimida, Monhysterida) whose spermatozoa have been observed in at least one representative by transmission electron microscopy (TEM) (Justine, 2002;Yushin & Malakhov, 2014;Zograf et al., 2016;Yushin et al., 2018;Yushin & Gliznutsa, 2019a, b;Zograf, 2019). ...
This paper presents the first comprehensive detailed transmission electron microscope observations of sperm development and structure of a plectid nematode. Sperm development of Anaplectus granulosus resembles that of nematodes of the order Rhabditida, known as the rhabditid pattern of spermatogenesis. It includes formation of complexes of fibrous bodies (FB) with membranous organelles (MO), which appear in spermatocytes; the complexes dissociate in the spermatids. The mature spermatozoa are bipolar cells subdivided into a pseudopod and a main cell body containing a nucleus with nine singlet centrioles, peripheral mitochondria and MOs. However, the development and structure of sperm in A. granulosus deviates remarkably from the common rhabditid pattern by an unusual early transformation of FBs into large amorphous masses in the spermatids; the subsequent formation of a concentric structure of immature spermatozoa with a predominant amorphous mass around the central nucleus and thin peripheral cytoplasm with organelles (MOs and mitochondria); and by the transformation of MO in mature spermatozoa into simple cisterns. Thus, the pattern of spermatogenesis of A. granulosus supports the close relations of Plectida and Rhabditida, but specific peculiarities of the sperm development delineate Plectida from Rhabditida and other orders.
... The current, most widely used classification of the phylum Nematoda was proposed by De Ley & Blaxter (2002 based on molecular phylogenetic analyses of SSU rDNA sequences, as well as morphological, ontogenetic, and biological characters. However, recent molecular phylogenetic investigations suggest that updates to this higher level classification are required, including: (1) moving the Benthimermithidae Petter, 1980 (previously classified within their own separate order) to the order Plectida Gadea, 1973 (Leduc & Zhao 2019a), (2) moving the Rhaptothyreidae Hope & Murphy, 1969 (previously classified within their own separate order) to the order Enoplida Filipjev, 1929(Leduc et al. 2018a, and (3) moving the Microlaimoidea Micoletzky, 1922(previously classified within the Desmodorida De Coninck, 1965 to their own separate order Microlaimida Leduc, Verdon & Zhao, 2018(Leduc et al. 2018bLeduc et al. 2019). ...
... The latter change is only moderately well supported by the available molecular evidence, but better reflects the lack of any morphological synapomorphy between the Microlaimoidea and the taxa classified within the Desmodorida. In the classification of De Ley & Blaxter (2002, nematodes are divided into two classes, the Enoplea Inglis, 1983 andChromadorea Inglis, 1983. Within the class Enoplea, most of the free-living marine nematode taxa belong to order Enoplida, although a few are also found within the closely related (but largely terrestrial or freshwater) Triplonchida Cobb, 1920. ...
Full text available for free at: https://niwa.co.nz/oceans/niwa-biodiversity-memoirs
The phylum Nematoda Cobb, 1932, also known as roundworms, is the most abundant metazoan taxon in aquatic sediments worldwide, as well as one of the most diverse. Despite their ubiquitous distribution, our knowledge of nematode taxonomy and diversity in New Zealand, and in particular, free-living species in marine sediments, remains very limited. The nematode fauna of New Zealand’s marine environments, ranging from the most accessible beaches to abyssal plains, remains poorly known, with the total biodiversity of the free-living marine nematode fauna in the New Zealand Exclusive Economic Zone estimated at several thousand species. Prior to this work, the total number of free-living marine nematode species known from the New Zealand region was 190 species.
Unlike previous recent NIWA Biodiversity Memoirs which focus on a particular taxon group rather than a specific region, this work focuses on the nematode fauna of Pāuatahanui Inlet, a drowned river valley and one of two arms of Te Awarua-o-Porirua Harbour in the Wellington region. The main reason for this regional approach is that the New Zealand marine nematode fauna remains largely uninvestigated, and very few specimen collections are available. The most efficient way to increase our knowledge of free-living marine nematode taxonomy in New Zealand is therefore to begin describing the fauna from an easily accessible environment. Pāuatahanui Inlet was chosen because, while it has high ecological and cultural significance, it is also subject to anthropogenic impacts associated with changes in surrounding land use and pollution. A better knowledge of the nematode fauna will thus bring a more complete understanding of the ecological value of this ecosystem and should facilitate ecological monitoring in the future.
A total of 55 nematodes species belonging to two classes, eight orders, 19 families and 41 genera were found. Thirty-nine of the most common species are described here, 26 of which are new to science, four of which are new records for New Zealand, and seven of which [Bathylaimus cf. australis Cobb, 1894; Tripyloides cf. marinus (Bütschli, 1874) de Man, 1886; Chromadora cf. nudicapitata Bastian, 1865; Chromadorina germanica (Bütschli, 1874) Wieser, 1954; Cobbia trefusiaeformis de Man, 1907; Terschellingia cf. longicaudata de Man, 1907; Litoditis cf. marina (Bastian, 1865) Sudhaus, 2011] are cosmopolitan species or species complexes. Together, these species are to be called ‘Ngā toke o Parumoana’: ‘ngā toke’ refering to the worms, and ‘parumoana’ refering to the tidal areas of Te Awarua-o-Porirua which consist of two elements, i.e., the brown mud flats (paru) and the sea (moana).
In addition to line drawings and light micrographs, scanning electron micrographs and molecular sequences are provided for 12 and 28 of the species described here, respectively. Eight seemingly cosmopolitan species, some of which are likely to be cryptic species complexes, were found to occur in the inlet, but the identity of the Pāuatahanui Inlet populations could not be confirmed due to a lack of published molecular sequence data. It is highly likely that additional nematode species not listed here will be found in the inlet as sampling continues in the future. Currently, free-living nematodes are estimated to represent about 40% of the total infaunal diversity in Pāuatahanui Inlet.
... Remarks: Rhabdodemaniidae is a monotypic family with a single genus. The placement of this family within the Triplonchida by De Ley & Blaxter (2002 was not based on any morphological or molecular phylogenetic evidence, and is considered provisional by Holovachov & Shoshin (2014) due to the lack of information on the male copulatory musculature. So far, the only morphological feature thought to be unique for the Triplonchida is the modification of the spicule protractor muscles into two capsule-like structures that surround the anterior part of each spicule and which appear to squeeze out the spicules, as opposed to a musculature which retracts the spicules as in the Enoplida (De Ley & Blaxter, 2002). ...
... The placement of this family within the Triplonchida by De Ley & Blaxter (2002 was not based on any morphological or molecular phylogenetic evidence, and is considered provisional by Holovachov & Shoshin (2014) due to the lack of information on the male copulatory musculature. So far, the only morphological feature thought to be unique for the Triplonchida is the modification of the spicule protractor muscles into two capsule-like structures that surround the anterior part of each spicule and which appear to squeeze out the spicules, as opposed to a musculature which retracts the spicules as in the Enoplida (De Ley & Blaxter, 2002). The 18S ribosomal RNA phylogeny of Smythe (2015) suggests that the Rhabdodemaniidae should be placed within the order Enoplida rather than within the Triplonchida. ...
Little is known about the taxonomy of deep-sea nematode species inhabiting cold seep habitats. An opportunity to characterize the nematode species communities of New Zealand cold seeps was provided by a 2019 research voyage to New Zealand’s Hikurangi Margin, during which macrofauna cores were obtained at two seeps at approximately 1,250 and 2,000 m water depth. Here, six new species of the orderEnoplida are described. Metacylicolaimus catherinae sp. nov. represents the first record of the genus for the New Zealand Exclusive Economic Zone and for the deep sea globally. Halalaimus talaurinus sp. nov., Thalassoalaimus duoporus sp. nov. and Crenopharynx crassipapilla sp. nov. are only the second species of their respective genera to be described/recorded from New Zealand waters, and Oncholaimus adustus sp. nov. is the eighth species of the genus to be recorded from the region. Rhabdodemania zealandiaensis sp. nov. was among the most abundant and widespread species found at the Hikurangi Margin seep sites. A few specimens had been found in a previous ecological study of meiofaunal nematode communities on Chatham Rise, a submarine ridge south of Hikurangi Margin. It is possible that this species has a preference for seep environments due to elevated food availability, however it does not seem to be exclusively found in seeps. We find no evidence for an affinity between nematode seep communities in New Zealand and elsewhere, which is consistent with the high variability in nematode community observed to date among regions. Ongoing work on the ecology and distribution of nematode communities at the Hikurangi Margin seep sites will help determine spatial patterns in abundance and species distributions in more detail, including the identification of any species/taxa with affinities with seeps.
... However, the current genetic database for these nematodes remains very limited. In Rhigonematomorpha, only 21 nominal species have been genetically characterized [14-17, 19, 20], and most of the data available are represented by the 18S and 28S sequences, which are commonly used for molecular phylogeny of higher taxa within Nematoda [21][22][23][24][25][26]. Although the nuclear internal transcribed spacer (ITS) region and the mitochondrial cox1 and cox2 genes are widely used as powerful and practical genetic markers for revealing sibling or cryptic species, delimiting phenotypic variation and identifying species in the infraorders Ascaridomorpha, Spiruromorpha and Oxyuridomorpha [27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44], they have been scarcely employed in studies pertaining to Rhigonematomorpha species. ...
... Although some previous molecular phylogenetic studies made some attempts to solve the evolutionary relationships of Rhigonematomorpha and its related taxa (i.e. Ascaridomorpha, Spiruromorpha and Oxyuridomorpha), as well as the systematic status of some families or genera in the Rhigonematomorpha [3,5,6,15,16,[22][23][24]65], the basic molecular phylogenetic framework for the Rhigonematomorpha is far from complete. The phylogenetic results of the present study are largely congruent with the traditional classifications of the Rhigonematomorpha [1,2,4], which support the division of this taxon into two superfamily Rhigonematoidea and Ransomnematoidea. ...
Background
The infraorder Rhigonematomorpha comprises a group of obligate parasitic nematodes of millipedes (Arthropoda: Diplopoda). The current species identification of Rhigonematomorpha nematodes remains mainly based on morphological features, with molecular-based identification still in its infancy. Also, current knowledge of the phylogeny of Rhigonematomorpha is far from comprehensive.
Methods
The morphology of Rhigonematomorpha nematodes belonging to the genus Rhigonema , collected from the millipede Spirobolus bungii Brandt (Diplopoda: Spirobolida) in China, was studied in detail using light and scanning electron microscopy. Five different genetic markers, including the nuclear small ribosomal subunit (18S), internal transcribed spacer (ITS) and large ribosomal subunit (28S) regions and the mitochondrial cox 1 and cox 2 genes of these Rhigonematomorpha nematodes collected from China and Rhigonema naylae collected from Japan were sequenced and analyzed using Bayesian inference (BI) and Assemble Species by Automatic Partitioning (ASAP) methods. Phylogenetic analyses that included the most comprehensive taxa sampling of Rhigonematomorpha to date were also performed based on the 18S + 28S genes using maximum likelihood (ML) and BI methods.
Results
The specimens of Rhigonema collected from S. bungii in China were identified as a new species, Rhigonema sinense n. sp. Striking variability in tail morphology was observed among individuals of R. sinense n. sp. ASAP analyses based on the 28S, ITS, cox 1 and cox 2 sequences supported the species partition of R. sinense n. sp. and R. naylae , but showed no evidence that the different morphotypes of R. sinense n. sp. represent distinct genetic lineages. BI analyses also indicated that R. sinense n. sp. represents a separated species from R. naylae based on the cox 1 and cox 2 genes, but showed that R. naylae nested in samples of R. sinense n. sp. based on the ITS and 28S data. Phylogenetic results showed that the representatives of Rhigonematomorpha formed two large clades. The monophyly of the families Carnoyidae and Ichthyocephalidae and the genus Rhigonema was rejected. The representatives of the family Ransomnematidae clustered together with the family Hethidae with strong support.
Conclusions
A new species of Rhigonematomorpha, R. sinense n. sp. is described based on morphological and molecular evidence. ASAP analyses using 28S, ITS, cox 1 and cox 2 data indicate the striking variability in tail morphology of R. sinense n. sp. as intraspecific variation, and also suggest that partial 28S, ITS, cox 1 and cox 2 markers are effective for molecular identification of Rhigonematomorpha nematodes. The phylogenetic results support the traditional classification of Rhigonematomorpha into the two superfamilies Rhigonematoidea and Ransomnematoidea, and indicate that the families Carnoyidae and Ichthyocephalidae and the genus Rhigonema are non-monophyletic. The present phylogeny strongly supports resurrection of the family Brumptaemiliidae, and also indicates that the family Ransomnematidae is sister to the family Hethidae.
Graphical Abstract
... Its life cycle is still unknown. Potential sources of human infection encompass vertebrates, invertebrates, plants, soil, and water [5,66]. Speculation suggests that it may rely on an intermediary arthropod host, with humans serving as incidental hosts; or that humans contract the infection through consuming of undercooked bush-meat from infected native fauna [21]. ...
Background
Human parasitic infections caused by Adenophorean nematodes encompass a range of diseases, including dioctophymiasis, trichuriasis, capillariasis, trichinellosis, and myositis. These infection can result in adverse impacts on human health and cause societal and economic concerns in tropical and subtropical regions.
Methods
This review conducted searches in PubMed, Embase and Google Scholar for relevant studies that published in established databases up to April 26, 2024. Studies that focused on the common morphology, life cycle, disease distribution, clinical manifestations, and prevention and control strategies for Adenophorean parasitic diseases in humans were included.
Results
Adenophorean nematodes exhibit shared morphological characteristics with a four-layered cuticle; uninucleate epidermal cells; pseudocoelom with six or more coelomocytes; generally three caudal glands; five esophageal glands; two testes in males with median-ventral supplementary glands in a single row; tail in males rarely possessing caudal alae; amphids always postlabial; presence of cephalic sensory organs; absence of phasmids; and a secretory-excretory system consisting of a single ventral gland cell, usually with a non-cuticularized terminal duct. Humans play two important roles in the life cycle of the nematode class, Adenophorea: 1) as a definitive host infected by ingesting undercooked paratenic hosts, embryonated eggs, infective larvae in fish tissue and meat contaminated with encysted or non-encysted larvae, and 2) as an accidental host infected by ingesting parasitic eggs in undercooked meat. Many organs are targeted by the Adenophorean nematode in humans such as the intestines, lungs, liver, kidneys, lymphatic circulation and blood vessels, resulting in gastrointestinal problems, excessive immunological responses, cell disruption, and even death. Most of these infections have significant incidence rates in the developing countries of Africa, Asia and Latin America; however, some parasitic diseases have restricted dissemination in outbreaks. To prevent these diseases, interventions together with education, sanitation, hygiene and animal control measures have been introduced in order to reduce and control parasite populations.
Conclusions
The common morphology, life cycle, global epidemiology and pathology of human Adenophorean nematode-borne parasitic diseases were highlighted, as well as their prevention and control. The findings of this review will contribute to improvement of monitoring and predicting human-parasitic infections, understanding the relationship between animals, humans and parasites, and preventing and controlling parasitic diseases.
Graphical Abstract
... Formerly grouped as an order within the phylum Nematoda, the Oxyurida was downgraded to be reclassified as the Oxyuridomorpha, 1 of 5 infraorders within the suborder Spirurina (order Rhabditida) along with the Ascaridomorpha, Spiruromorpha, Rhigonematomorpha, and Gnathostomatomorpha (De Ley and Blaxter, 2002;Wijová et al., 2006;Nadler et al., 2007). This group is at times referred to as a member of Clade III nematodes (sensu Blaxter et al., 1998). ...
... The structure and development of nematode sperm have been studied mainly in the representatives of the diverse order Rhabditida (the higher classification proposed by De Ley & Blaxter (2002) and further developed for aphelenchs by Hunt (2008) and parasitaphelenchids by Kanzaki et al. (2018) is used herein), where the most species studied produce relatively uniform sperm of the 'rhabditid' pattern (Slos et al., 2020;Yushin & Ryss, 2021;Rzayev et al., 2023). This type of nematode spermatozoon is seen as an amoeboid bipolar cell with an anterior pseudopod and posterior main cell body that includes a condensed nucleus lacking a nuclear envelope, mitochondria and so called 'membranous organelles' (MO) (Justine & Jamieson, 1999;Justine, 2002;Yushin & Malakhov, 2004, 2014. ...
Sperm development and structure in the wood-inhabiting fungal and plant-feeding nematode, Bursaphelenchus luxuriosae , were studied using transmission electron microscopy to evaluate interspecific similarities and differences of spermatozoa in nematodes. In general, spermatogenesis in B. luxuriosae fits the ‘rhabditid’ pattern supported by morphological and phylogenetic analysis of the order Rhabditida. Spermatocyte development includes formation of complexes of fibrous bodies (FBs) with membranous organelles (MOs), the complexes dissociate in the spermatids into separate components, and the immature sperm contain MOs but lack FBs, which transform into a dense matrix of sperm cytoplasm. The female spermatheca contains mature spermatozoa as bipolar cells subdivided into a pseudopod devoid of organelles and a main cell body containing a nucleus without a nuclear envelope, numerous mitochondria, and peripheral MOs as pouches opening to the exterior via pores. Data on B. luxuriosae are used for analysis of variable quantitative and morphological characteristics of spermatozoa in Aphelenchoidea. General size of spermatozoa and their MOs have little value for comparative analysis. The MO knobbles look uniform in immature spermatozoa of each aphelenchoidid species studied and may be considered as a taxonomically specific ultrastructural feature. The presence or absence of FBs in immature spermatozoa demonstrates the diagnostic value of the aphelenchoidid sperm structure at the species level. Analysis also shows close similarity of spermatozoa in Bursaphelenchus spp. and Caenorhabditis elegans , the model species with comprehensive data on sperm biology. This may be used to identify new ways for the control and suppression of harmful nematode species such as B. xylophilus .
... and separated from Steinernema spp. This supports the nematode classification [47] that classified two separate suborders by clustering Oscheius and Heterorhabditis into Rhabditina while Steinernema was classified into Tylenchina in the Order Rhabditida. ...
An entomopathogenic nematode, Oscheius tipulae, was isolated from a soil sample. The identification of this species was supported by morphological and molecular markers. The nematode isolate exhibited pathogenicity against different target insects including lepidopteran, coleopteran, and dipteran insects. The virulence of this nematode was similar to that of a well-known entomopathogenic nematode, Steinernema carpocapsae, against the same insect targets. A comparative metagenomics analysis of these two nematode species predicted the existence of a combined total of 272 bacterial species in their intestines, of which 51 bacterial species were shared between the two nematode species. In particular, the common gut bacteria included several entomopathogenic bacteria including Xenorhabdus nematophila, which is known as a symbiotic bacterium to S. carpocapsae. The nematode virulence of O. tipulae to insects was enhanced by an addition of dexamethasone but suppressed by an addition of arachidonic acid, suggesting that the immune defenses of the target insects against the nematode infection is mediated by eicosanoids, which would be manipulated by the symbiotic bacteria of the nematode. Unlike S. carpocapsae, O. tipulae showed high virulence against dipteran insects including fruit flies, onion flies, and mosquitoes. O. tipulae showed particularly high control efficacies against the onion maggot, Delia platura, infesting the Welsh onion in the rhizosphere in both pot and field assays.
... The identification of nematodes belonging to the Pneumospiruridae family is frequently based on the morphological characteristics of the cephalic region (Dougherty 1943;Wertheim and Giladi 1977), but the identification and phylogeny of these nematodes could be improved by the use Ley and Blaxter 2002). Specifically, molecular data from nuclear ribosomal RNA genes (18S and 28S rRNAs, internal transcribed spacer (ITS1 and ITS2)) and mitochondrial genes (12S rRNA, 16S rRNAs, and cox1) have been used for the construction of the phylogeny of some group of nematodes (Chan et al. 2020). ...
Metathelazia capsulata (family Pneumospiruridae) is a lungworm parasitizing the bronchi and bronchioles, described in four species of wild carnivores. Very little molecular data are available on this nematode and none on other species of the Pneumospiruridae family. In this work, we describe for the first time the complete mitogenome (mitochondrial genome) of M. capsulata, being the first described of the family Pneumospiruridae. The mitogenome of M. capsulata has 13,659 bp in length, an A + T content of 79.2%. The mitogenome included 12 protein-coding genes (PCGs) (lacking the atp8 gene), 22 tRNA genes, 2 rRNA genes (all the genes are coded by the heavy strand), and an AT-rich region. The PCGs varied in size (232 bp-1645 bp). Only the tRNA-Trp has the standard cloverleaf secondary structure, while the other 21 do not. The AT-rich region, with a 90.5% A + T content and a length of 389 bp, is located between the cox3 and tRNA-Ala genes. Comparison with the mitogenomes of 29 species of Spiruromorpha infraorder, belonging to different families, demonstrates that M. capsulata mitogenome shared the common characteristics of most of them. The phylogeny constructions yielded phylogenies that were in agreement with the obtained previously by using sequences and gene order data of mitogenomes.
... 18S rRNA was the first genetic marker used for phylogenetic classification of nematodes 4 . This and subsequent analyses based on 18S rRNA have led to the recognition of major lineages of nematodes [5][6][7] . Recent molecular analyses of mt genome sequences have provided selectable hypotheses for the phylogenetic relationships of nematodes based on 18S rRNA. ...
Wellcomia compar (Spirurina: Oxyuridae) is a pinworm that infects wild and captive porcupines. Despite clear records of its morphological structure, its genetics, systematics, and biology are poorly understood. This study aimed to determine the complete mitochondrial (mt) genome of W. compar and reconstruct its phylogenetic relationship with other nematodes. We sequenced the complete mt genome of W. comparand conducted phylogenetic analyses using concatenated coding sequences of 12 protein-coding genes (PCGs) by maximum likelihood and Bayesian inference. The complete mt genome is 14,373 bp in size and comprises 36 genes, including 12 protein-coding, two rRNA and 22 tRNA genes. Apart from 28 intergenic regions, one non-coding region and one overlapping region also occur. A comparison of the gene arrangements of Oxyuridomorpha revealed relatively similar features in W. compar and Wellcomia siamensis. Phylogenetic analysis also showed that W. compar and W. siamensis formed a sister group. In Oxyuridomorpha the genetic distance between W. compar and W. siamensis was 0.0805. This study reports, for the first time, the complete W. compar mt genome sequence obtained from Chinese porcupines. It provides genetic markers for investigating the taxonomy, population genetics, and phylogenetics of pinworms from different hosts and has implications for the diagnosis, prevention, and control of parasitic diseases in porcupines and other animals.
... De Man (de Man 1921) recommended formula was used to identify nematode species in addition to paying attention to the systematic signs mentioned above. Classical and modern phylogenetic systematics of nematodes (De Ley and Blaxter 2002;Hodda 2022) were used to analyze species systematically. ...
Narzullayev S, Kambarov S, Mirzaev U, Tursunova S. 2023. Diversity of woody plant nematodes in specially protected biocenosis of Zarafshan Mountain, Uzbekistan. Biodiversitas 24: 3145-3151. Very little information exists on nematodes' diversity and ecological characteristics in small artificial forests. This article provides information on the diversity of the nematode fauna, bioecological characteristics, and species distribution by biotopes of fruit trees growing in the biocenoses of the Omonkutan National Nature Park in the Western Zarafshan mountain range. As a result of the research, 62 species of nematodes were recorded in the nematode fauna of fruit trees. These species were analyzed taxonomically and ecologically. It was determined that the species in the fauna belong to two classes and five orders of the Nematoda type. They are divided into five large and several small groups according to their ecological characteristics. Among the ecological groups, omnivorous and plant-feeding nematodes are the dominant groups in terms of the number of species. The diversity of nematodes was high in the 0-15 and 15-30 cm soil layers. It turned out that the diversity in different biotopes is related to the ecological characteristics of nematodes. In particular, herbivorous nematodes accounted for 72.2% of nematodes in the root system. An increase in the diversity of nematodes was observed in the rhizosphere soil layers. A sharp increase in the number of species and individuals of omnivorous nematodes and bacteriotrophs was observed in the 0-15 cm soil layer, and this trend was also preserved in the 15-30 cm layer. The species richness and diversity (according to the Shannon and Simpson indices) were the lowest in vegetative parts of plants. As a result of the research, it became clear that the diversity of soil nematodes is completely dependent on their trophic characteristics.
... Our results on 28S and 18S rRNA genes suggest that genera within Ransomnematoidea (Ransomnema, Heth, Carnoya, Brumptaemilius, Cattiena, Insulanema, Gilsonema) and Rhigonematoidea (Rhigonema, Obainia, Xystrognathus, Trachyglossoides, Ichthyocephaloides) clustered closer than could be expected in view of their morphological differences, these groups having been lumped together mainly on host association, although it would appear from the molecular data that they are actually closely linked (Figures 11, 13). De Ley and Blaxter (2002) questioned the validity of classifying Rhigonematoidea and Ransomnematoidea as sister taxa based on sparse information, but our results based on ribosomal genes (28S and 18S) support the sister relationships of both subfamilies, and to a lesser extent with the mitochondrial gene (COI). Mejia-Madrid (2018) reported that Ransomnema bravoae represents a rogue taxon appearing in an unresolved position within Rhigonematoidea in 18S rRNA phylogeny, whereas in the combined 18S and 28S rRNA analyses, it appears more closely related to the Carnoyidae and Hethidae; however, our 18S and 28S rRNA analyses showed high PP values (Figures 11, 13). ...
Parasitic nematodes of millipedes from Nigeria are molecularly characterized for the first time. During nematode surveys on live giant African millipedes from several localities in Nigeria, 4 species of rhigonematids were identified by application of integrative taxonomical approaches (morpho-anatomy and molecular markers), including Brumptaemilius sp., Gilsonema gabonen-sis, Obainia pachnephorus, and Rhigonema disparovis. The results of morphometric and molecular analyses of D2-D3 28S, ITS, partial 18S rRNA, and cytochrome oxidase c subunit 1 (COI) gene sequences further characterized the rhigonematid species, and clearly separated them from other related species. Phylogenetic relationships based on 28S and 18S rRNA genes suggest that genera within Ransomnematoidea (Ransomnema, Heth, Carnoya, Brumptaemilius, Cattiena, Insulanema, Gilsonema) and Rhigonematoidea (Rhigonema, Obainia, Xystrognathus, Trachyglossoides, Ichthyocephaloides) clustered rather closer than could be expected in view of their morphological differences. Phylogenetic relationships based on ITS and COI are congruent with those of other ribosomal genes; however, they are not conclusive due to the scarcity of available sequences of these genes for these genera in NCBI.
... Our results on 28S and 18S rRNA genes suggest that genera within Ransomnematoidea (Ransomnema, Heth, Carnoya, Brumptaemilius, Cattiena, Insulanema, Gilsonema) and Rhigonematoidea (Rhigonema, Obainia, Xystrognathus, Trachyglossoides, Ichthyocephaloides) clustered closer than could be expected in view of their morphological differences, these groups having been lumped together mainly on host association, although it would appear from the molecular data that they are actually closely linked (Figures 11, 13). De Ley and Blaxter (2002) questioned the validity of classifying Rhigonematoidea and Ransomnematoidea as sister taxa based on sparse information, but our results based on ribosomal genes (28S and 18S) support the sister relationships of both subfamilies, and to a lesser extent with the mitochondrial gene (COI). Mejia-Madrid (2018) reported that Ransomnema bravoae represents a rogue taxon appearing in an unresolved position within Rhigonematoidea in 18S rRNA phylogeny, whereas in the combined 18S and 28S rRNA analyses, it appears more closely related to the Carnoyidae and Hethidae; however, our 18S and 28S rRNA analyses showed high PP values (Figures 11, 13). ...
Parasitic nematodes of millipedes from Nigeria are molecularly characterized for the first time. During nematode surveys on live giant African millipedes from several localities in Nigeria, 4 species of rhigonematids were identified by application of integrative taxonomical approaches (morpho-anatomy and molecular markers), including Brumptaemilius sp., Gilsonema gabonensis, Obainia pachnephorus, and Rhigonema disparovis. The results of morphometric and molecular analyses of D2-D3 28S, ITS, partial 18S rRNA, and cytochrome oxidase c subunit 1 (COI) gene sequences further characterized the rhigonematid species, and clearly separated them from other related species. Phylogenetic relationships based on 28S and 18S rRNA genes suggest that genera within Ransomnematoidea (Ransomnema, Heth, Carnoya, Brumptaemilius, Cattiena, Insulanema, Gilsonema) and Rhigonematoidea (Rhigonema, Obainia, Xystrognathus, Trachyglossoides, Ichthyocephaloides) clustered rather closer than could be expected in view of their morphological differences. Phylogenetic relationships based on ITS and COI are congruent with those of other ribosomal genes; however, they are not conclusive due to the scarcity of available sequences of these genes for these genera in NCBI.
... belongs to the family Mesorhabditidae Andrássy, 1976(De Ley & Blaxter, 2002Andrássy, 2005), which was proposed as a subgenus within the genus Rhabditis by Osche (1952) and erected to genus level by Dougherty (1953). These nematodes feed on a wide range of bacteria species (Wood, 1973). ...
During a survey of soil nematodes in 2022, a free-living bacterivorous nematode, described here as Mesorhabditis
sudafricana n. sp., was discovered in association with kikuyu grass in Limpopo Province, South Africa. The new species was
distinguished by a relatively long body (716-815 μm in females and 605-689 μm in males), long spicules (61-66 μm), and
gubernaculum (22-24 μm) and a short tail (15-20 μm in females and 18-21 μm in males). The vulva is positioned posteriad (93-
95% of body length), and the distance from vulva to anus is long (1.5-1.9 times tail length). Additionally, the new species bears seven
lateral field incisures and a peloderan bursa with the genital papillae in arrangement 2/3+ph+1+3, being two precloacal and eight
postcloacal. The 28S rDNA BlastN showed 94% similarity with an unidentified Mesorhabditis (deposited as Bursilla (EF990722). By
contrast, the ITS rDNA BlastN showed 82% similarity with Mesorhabditis paucipapillata (MT710243). The phylogenetic analysis of
28S and ITS rDNA placed the new species separately from the other Mesorhabditis. Description, measurements, illustrations and SEM
micrographs for M. sudafricana n. sp. are provided.
... Entomopathogenic nematodes (EPNs) belong to the families Steinemernatidae and Heterorhabditidae. They parasitize soil inhibiting pest insects and kill them due to the associated mutualistic bacteria (Xenorhabdus, Photorhabdus, Heterorhabditis) [208,209]. EPNs cause infection in individuals of a number of insect orders e.g., Coleoptera, Dictyoptera, Lepidoptera, Hemiptera, and Orthoptera [210]. ...
Agricultural crops are subject to a variety of biotic and abiotic stresses that adversely affect growth and reduce the yield of crop plantss. Traditional crop stress management approaches are not capable of fulfilling the food demand of the human population which is projected to reach 10 billion by 2050. Nanobiotechnology is the application of nanotechnology in biological fields and has emerged as a sustainable approach to enhancing agricultural productivity by alleviating various plant stresses. This article reviews innovations in nanobiotechnology and its role in promoting plant growth and enhancing plant resistance/tolerance against biotic and abiotic stresses and the underlying mechanisms. Nanoparticles, synthesized through various approaches (physical, chemical and biological), induce plant resistance against these stresses by strengthening the physical barriers, improving plant photosynthesis and activating plant defense mechanisms. The nanoparticles can also upregulate the expression of stress-related genes by increasing anti-stress compounds and activating the expression of defense-related genes. The unique physico-chemical characteristics of nanoparticles enhance biochemical activity and effectiveness to cause diverse impacts on plants. Molecular mechanisms of nanobiotechnology-induced tolerance to abiotic and biotic stresses have also been highlighted. Further research is needed on efficient synthesis methods, optimization of nanoparticle dosages, application techniques and integration with other technologies, and a better understanding of their fate in agricultural systems.
... This group has a significant environmental role (mineralization of soil, pathogenicity on insects, the transmission of bacterial pathogens of vegetables, feed on bacteria, etc.). The taxonomy of these nematodes was revised by different authors (Andrássy 2005;Blaxter et al. 1998;De Ley and Blaxter 2002;Sudhaus and Fitch 2001;Shokoohi et al. 2007;2008;Shokoohi and Abolafia 2019). This order contains numerous species (Andrássy 2005). ...
A new population of Pseudacrobeles (Pseudacrobeles) macrocystis and Poikilolaimus oxycercus is described from South
Africa. Poikilolaimus oxycercus was collected from soil covered by a natural grass in South Africa, which is morphologically similar to the original description. The South African population of P. oxycercus is characterised by having a small size
(807–818 µm in males and 703–779 µm in males), female tail cupola-shaped (24–35 µm), and spicule length (27–35 µm).
The South African population of P. (P.) macrocystis, collected from natural grass, is characterised by having a small size
(611–786 µm), a lateral feld with three incisures, lip region with lips bearing seta-like processes and blunt conoid labial
probolae, primary and secondary axils smooth, nerve ring and excretory pore at the posterior part of the pharyngeal corpus,
spermatheca well developed, postvulval uterine sac poorly developed, female tail conoid-elongate, male tail conoid with
thin acute mucro and spicules small (31–36 µm). Measurements and line illustrations of the species are given. In addition,
LM, SEM photographs and the phylogenetic position of P. (P.) macrocyctis are provided. The 18S and 28S rDNA analyses
show that P. macrocystis is closely related to other species of the genus Pseudacrobeles having lips with seta-like processes.
This is the frst report of P. (P.) macrocystis from South Africa.
... Meiobenthic nematodes are the most diverse and numerically dominant metazoans among-in the marine environment (McIntyre, 1969;Heip et al., 1982;De Ley and Blaxter 2001). Nematodes due to specific biological characteristics (high productivity, short life cycles) quickly respond to environmental changes by reducing species diversity, increasing abundance, and decreasing biomass. ...
Abstract. The suitability of using meiobenthic communities and especially the nematodes-based indices to assess the ecological quality of the Ukrainian Danube delta coastal area was tested in one control and two sites impacted by dredging/dumping activities. The study is based on the results of benthic surveys carried out in November 2015 and August 2018 and 2020 in the area of the “Danube-Black Sea” navigable canal. The values of the taxonomic richness of the meiobenthos varied from 6 taxa in the dredging sites to 9 taxa at background stations. According to the species richness, the ecological quality in the dredging area fell into the Poor class (EQS), while the background and dumping areas into the Moderate class.
TThe Shannon index (H‘) of the nematodes in the dredging sites varied from 0 to 1.8. Low values of these indices indicate Bad ecological status in the dredging sites and Poor in the rest. There was a high percentage of c-p2 (r-strategists) in all sites. Average values of the maturity index (MI) varied from 1.5 ± 0.2 in the dredging sites to 2.3 ± 0.1 at dumping and 2.6 ± 0.1 at background stations. The Maturity Index also indicates that the dredging site is in Bad condition, the dumping one is in Poor and the background stations are in Moderate.
Non-selective deposit feeders (1B) dominated at most stations. According to the values of the trophic diversity index (ITD), the study area can be classified as Poor. For the study sites, species that can be considered potential biological indicators are evinced.
Key words: meiobenthos, nematodes, ecological quality status, Danube delta coastal area (Black Sea)
... All six major eggshell layers, as defined in our adaptation of Olson's (2012) [83] C. elegans hexalaminar anatomical model, are readily discernible in published TEMs of most nematode groups. Indeed, while Caenorhabditis and Trichuris are near opposite ends of the recent nematode phylogenies we have seen [33,46,59,109], both genera exhibit all six layers of the hexalaminar anatomical model in TEMs of mitotic eggs. However, one group seems to be somewhat exceptionalthe Tylenchida, eggshell ultrastructure of which has been studied rather extensively. ...
A literature review for a recent ultrastructural study of a trichinelloid eggshell revealed consistently occurring errors in the literature on nematode eggshell anatomy. Examples included nematodes of medical, veterinary, and agricultural importance in several orders. Previous researchers had warned of some of these errors decades ago, but a comprehensive solution was not offered until 2012 when a clarifying new anatomical and developmental interpretation of nematode eggshells was proposed by members of the Caenorhabditis elegans Research Community. However, their findings were explained using arcane acronyms and technical jargon intended for an audience of experimental molecular geneticists, and so their papers have rarely been cited outside the C. elegans community. Herein we (1) provide a critical review of nematode eggshell literature in which we correct errors and relabel imagery in important historical reports; (2) describe common reporting errors and their causes using language familiar to researchers having a basic understanding of microscopy and nematode eggs; (3) recommend a new hexalaminar anatomical and terminological framework for nematode eggshells based on the 2012 C. elegans framework; and (4) recommend new unambiguous terms appropriate for the embryonated/larvated eggs regularly encountered by practicing nematodologists to replace ambiguous or ontogenetically restricted terms in the 2012 C. elegans framework. We also (5) propose a resolution to conflicting claims made by the C. elegans team versus classical literature regarding Layer #3, (6) extend the C. elegans hexalaminar framework to include the polar plugs of trichinelloids, and (7) report new findings regarding trichinelloid eggshell structure.
... Phylum Nematoda. Class Chromadorea: order Rhabditida, family Panagrolaimidae (classification according to De Ley & Blaxter, 2002). ...
The sex organs are important for nematode systematics, but the associated muscles are rarely used as phylogenetic characters. This research aimed to study the musculature of Panagrolaimus detritophagus, using confocal microscopy. The ring-shaped anal sphincter is pierced by a biconical X-structure and connected by two pairs of processes to the subventral stomato-intestinal muscles and dorsal body wall. The female has two pairs of vaginal dilators that are connected to the proximally invaginated vaginal sphincter and subventral body wall. The anal depressor is a pair of dorsoventral muscles. The male has 7-8 pairs of caudal diagonal muscles located beneath the ventral body wall muscles, followed by five pairs of postcloacal oblique muscles. The paired posterior longitudinal muscles are connected to the cloacal opening and tail tip. The paired anterior retractors of the spicule connect the spicule capitula to the lateral body wall; a pair of spicule-gubernacular protractors runs from spicule capitula to the anterior part of gubernaculum, and paired ventral protractors run from spicule capitula to anterior cloacal lip. Two pairs of gubernaculum erectors are attached to the mid-gubernaculum, and the unpaired gubernaculum protractor extends ventrally to attach to the body wall at the posterior cloacal lip. The sex muscle pattern is of the Rhabditidae-Cephalobidae type with a 15-character code for phylogenetic reconstructions: 63313-22234-42243.
... Found helminths were placed in Petri dishes with 0.65% NaCl solution; nematode larvae were fixed in AFA (ethanol, formalin, and acetic acid) at 60 °C, preserved in 70% ethanol and later clarified with Amman's lactophenol; acanthocephalan specimens were fixed in cold AFA, preserved in 70% ethanol, stained in Langeron´s carmine, clarified in beechwood creosote, and preserved as whole mounts on Canada balsam, procedures according to . Taxonomic classification of nematodes followed De Ley & Blaxter (2002) and species identification relied on Felizardo et al. (2009) and . Taxonomic classification of acanthocephalans followed Amin (2013), while species identification relied on Pereira & Neves (1993), Sardella et al. (2005) and Fonseca et al. (2019). ...
... Although Jairajpuri and Ahmad (1992) in their monumental book on Dorylaimida accepted Belondiroidea, but recognized only a single family, Belondiridae, with three subfamilies, Belondirinae, Dorylaimellinae and Swangiriinae, as originally envisaged by Jairajpuri (1964). De Ley and Blaxter (2002) and Peña-Santiago (2006) followed Jairajpuri and Ahmad (1992) classification. Andrássy (2009) accepted Belondiroidea with three families, Belondiridae, Dorylaimellidae and Swangeriidae. ...
Timmiella goaense gen. n., sp. n. closely related to genera Swangeria Thorne, 1939, Qudsiella Jairajpuri, 1967 and Timmus Goseco, Ferris and Ferris, 1976 is described and illustrated based on specimens collected from Western Ghats of India. The new genus is characterized by its broadly rounded, continuous lip region; odontostyle short, delicate with indistinct lumen and aperture; guiding ring thick belt-like, conspicuous; anterior part of pharynx slender, a narrow tube; expanded part of pharynx fusiform, enclosed by sinistrally spiral muscular sheath; cardia isthmus-like (spatulate) with intestine attached to its posterior end; female genital system amphidelphic; vulva transverse; male with dorylaimoid spicules; tail long filiform, similar in both sexes.
... Nematode larvae were recovered in Petri dishes containing 0.65% NaCl solution and then fixed with hot (60 °C) AFA, preserved in 70 °GL ethanol plus 5% glycerin and placed between slide and coverslip to be clarified with Aman's lactophenol to permit analysis of structures . The taxonomic classifications used for trypanorhynch cestodes and raphidascaridid nematodes were those of Beveridge et al. (2017) and De Ley & Blaxter (2002), respectively. Species identification followed Campbell & Beveridge (1994), Beveridge & Campbell (1996) and Palm (2004) for trypanorhynch cestodes and Felizardo et al. (2009), and Fontenelle et al. (2015) for raphidascaridid nematodes. ...
... This group has an important ecological role in the soil, i.e., mineralisation of soil, pathogenecity on insects, transmission of bacterial pathogens to vegetables and feeding on bacteria. Identification of these nematodes is difficult, and their systematics and taxonomy have been changed by different authors (Andrássy, 1983(Andrássy, , 2005Blaxter et al., 1998;Sudhaus & Fitch, 2001;De Ley & Blaxter 2002;Shokoohi et al., 2007Shokoohi et al., , 2008Shokoohi & Abolafia, 2019). Several years ago, the authors started a research project on identification of the biodiversity of free-living and plant-parasitic nematodes in South Africa. ...
During a Potato South Africa (PSA) project survey, ‘The succession of nematodes in a Free
State potato rotation’ in the Eastern Free State potato production area in South Africa, a population of
Cruznema tripartitum was recovered. Subsequently, the soil samples were baited with the larvae of
darkling beetles or mealworms (Coleoptera: Tenebrionidae) to recover as many specimens as possible for
morphological and molecular studies. The population of C. tripartitum resembled the original description.
Additionally, 28S rDNA sequence of the South African population showed 99% similarity with the
sequence of this species from Iran. Phylogenetic position of 28S rDNA placed the South African C.
tripartitum in a clade with other Cruznema with a 100 posterior probability support. Line illustration,
SEM photographs, and phylogenetic position of the species are given. This is the first report of the
entomophilic nematode, C. tripartitum, from South Africa. Cruznema minimus is proposed as a junior
synonym of C. tripartitum. An identification key to species of Cruznema is provided
... W. compar is an Oxyuridae nematode that belongs to a few species that live parasitically and can cause serious diseases, whereas nematodes that belong to free-living forms have to some degree been neglected (Smythe et al., 2019). The phylogeny and classi cation of nematodes have been and remain a subject of debate because of the extreme speciosity of this phylum, and the poor resolution conferred by morphologic characters has resulted in incongruent classi cation systems (De Ley and Blaxter 2002). Since 18S rRNA genetic markers have insu cient resolution for Spirurina and single mitochondrial gene provide limited information for such analyses, complete mt genomes offer a wealth of high-resolution information (Galtier et al. 2009; Sullivan et al. 2017). ...
Wellcomia compar (Spirurina: Oxyuridae) is a pinworm which parasitizes in the caecum and colon of animals, and it`s host is mainly porcupines. Despite the importance of pinworms as a pathogen, there is still little knowledge about this pinworm. Parasitic diseases are one of the main diseases that affect the growth and health of animals. Clarifying the species of parasites that animals are infected with is an important reference value for the control of parasitic diseases. This study sequenced for the first time the complete mitochondrial (mt) genome of the pinworm Wellcomia compar that had been sampled from Chinese porcupines, then conducted phylogenetic analyses based on concatenated coding sequences (CDS) of 12 protein-coding genes (PCGs) by maximum likelihood (ML) and MrBayes inference (BI), to ascertain the taxonomic and phylogenetic information of W. compar . The complete mt genome (GenBank no. MW059037) is 14,373 bp in size and contains 36 genes, including 12 PCGs, 2 ribosomal RNA, and 22 transfer RNA genes. In addition to the 28 intergenic regions, there was only one non-coding region (NCR) and one overlapping region. The mt genes of Oxyuridomorpha were compared and found to be more similarly characterized in W. compar and Wellcomia siamensis . Furthermore, the phylogenetic tree indicated that W. compar formed a sister group with W. siamensis . This study reports from Chinese porcupine the first complete W. compar mt genome sequence, and provides genetic markers for investigating the taxonomy, population genetics, and phylogenetics of pinworms from different hosts, and has implications for the diagnosis, prevention, and control of parasitic diseases in porcupines and other animals.
... al., 1998;Blaxter et. al., 1998;Blaxter, 2002 andHolterman et. al., 2006;Meldal et. ...
Salient features of your Ph.D. research work
1. Taxonomic Evaluation of Nematode Parasites of Periplaneta americana.
2. To study the morphological Characters.
3. To observe the genus wise periodicity.
4. Molecular taxonomy of various genera.
5. This investigation will help in the quick identification of different nematodes of various genera and resolving the confusion in various genera of family Thelastomatidae.
6. It will provide baseline for future workers of this field.
Understanding how parasites evolved is crucial to understand the host and parasite interaction. The evolution of entomopathogenesis in rhabditid nematodes has traditionally been thought to have occurred twice within the phylum Nematoda: in Steinernematidae and Heterorhabditidae families, which are associated with the entomopathogenic bacteria Xenorhabdus and Photorhabdus , respectively. However, nematodes from other families that are associated with entomopathogenic bacteria have not been considered to meet the criteria for “entomopathogenic nematodes.” The evolution of parasitism in nematodes suggests that ecological and evolutionary properties shared by families in the order Rhabditida favor the convergent evolution of the entomopathogenic trait in lineages with diverse lifestyles, such as saprotrophs, phoretic, and necromenic nematodes. For this reason, this paper proposes expanding the term “entomopathogenic nematode” considering the diverse modes of this attribute within Rhabditida. Despite studies are required to test the authenticity of the entomopathogenic trait in the reported species, they are valuable links that represent the early stages of specialized lineages to entomopathogenic lifestyle. An ecological and evolutionary exploration of these nematodes has the potential to deepen our comprehension of the evolution of entomopathogenesis as a convergent trait spanning across the Nematoda.
A new species of the genus Acromoldavicus is described from coastal sand dunes and sandy soil in the southeast of the Iberian Peninsula. Acromoldavicus xerophilus n. sp. is characterized by its
557–700 μm body length, cuticle tessellated, lip region with three pairs of expanded lips bearing a large labial expansion, primary axils bearing guard processes with two different morphology,
secondary axils lacking guard processes, stoma short and tubular with prostegostom bearing prominent rhabdia directed towards the stoma lumen, female reproductive system monodelphic-prodelphic, post-vulval sac 0.6–0.9 times body diameter, rectum very large, female tail short with biacute terminus and males unknown. The description, light micrographs, scanning electron microscope images, illustrations, and molecular analyses are provided. Molecular analyses (based on 18S and 28S rDNA) revealed its relationship with some species of the genera Cephalobus (18S tree), Nothacrobeles, Paracrobeles, and Spinocephalus (28S tree). Keys to species identification of this genus are also included.
The family Oncholaimidae comprises ca 350 species of widespread nematodes. They are common in the seas and oceans and are also found in freshwater lakes and rivers. Here we provide the first description of Metoncholaimus species from the South China Sea. Metoncholaimus placatus sp. n. is characterised by the spicules 2.2-2.8 anal body diam. long, gubernaculum small, nearly parallel to the spicules, S-curved. Supplementary organ is composed of transversely elongated prominence with two sensillar structures (receptors). A pictorial key to the species level of Metoncholaimus species is provided. In this study, the D2-D3 domain of the LSU rDNA and the nearly full-length SSU rDNA were selected as targets for species identification. Phylogenetic relationships within the family Oncholaimidae remained unresolved despite of the various sequences analysed in different loci.
Three new species of free-living marine nematodes belonging to the genera Subsphaerolaimus, Halichoanolaimus and Belbolla are described from the mangrove wetlands of western Taiwan Island. Subsphaerolaimus danshuiensis sp. nov. is characterized by a body length of 1345–1693 µm, subcephalic setae 22.5–65.0 µm long, cervical setae 16.5–33.0 µm long, an “L”-shaped spicule 66.9–76.4 μm long, and a gubernaculum with a caudally-dorsally directed apophysis 16.4–23.0 µm long. Halichoanolaimus sicaoensis sp. nov. is characterized by an amphidial fovea with 3.5–3.75 turns, a conico-cylindrical tail with the cylindrical portion approximately 3/4 of the total tail length, and 13–14 not equidistant papillose precloacal supplements. Belbolla forkyspicula sp. nov. is characterized by seven oesophageal bulbs, a short tail, a spicule with a proximal fork, and two winged supplements. Differentiating characteristics of the genera Subsphaerolaimus, Halichoanolaimus and Belbolla are provided. Types are deposited in the College of Fisheries, Jimei University.
Three new species of the genus Pelodera Schneider, 1866 viz., P. indica sp. nov., P. adeeli sp. nov. and P. paratretzeli sp. nov. collected from dung beetles and P. cylindrica (Cobb, 1898) collected from soil samples, are described and illustrated. Pelodera indica sp. nov. is characterised by sexual dimorphism in anterior region, cupola-shaped tail with a spike; males having punctated, striated and lobed bursa with no genital papillae originating anterior to cloaca. Pelodera adeeli sp. nov. is characterised by coarsely annulated cuticle; relatively narrow stoma; tail conoid without spike; males with punctated, lobed bursa and nine pairs of genital papillae arranged in a 2/1+2+P+3+1 configuration. Pelodera paratretzeli sp. nov. is characterised by sexual dimorphism in anterior region, stoma wide with three well-developed metastegostomal denticles; tail cupola-shaped with a long spike; males having spicules fused distally up to 12–14% of spicule length; bursa peloderan, anteriorly closed and punctated with nine pairs of genital papillae arranged in a 3/2+P+3+1 configuration. Pelodera cylindrica is described with additional details. The comparative analysis as well as phylogenetic relationship of the species belonging to the coarctata group have been elaborated by incorporating scanning electron microscopic observations. Information on the biogeographical distribution has also been provided.
The genus Baruscapillaria Moravec, 1982 has six valid species recorded in birds Phalacrocoracidae, namely Baruscapillaria appendiculata Freitas, 1933, B. spiculata Freitas, 1933, B. carbonis (Dubinin & Dubinina, 1940), B. jaenschi (Johnston & Mawson, 1945), B. phalacrocoraxi (Borgarenko, 1975) and B. rudolphii Moravec, Scholz and Našincová, 1994. Helminthological tests carried out on cormorants of the species Phalacrocorax brasilianus (Gmelin), a migratory bird that occurs in the northeast of the State of Pará, Brazil, demonstrate B. appendiculata parasitizing the cloaca of these birds, through light microscopy, scanning electron microscopy and molecular biology. These studies allowed a redescription of males and females of this nematode in these hosts and in this geographical area through integrative taxonomy. The occurrence of lesions in the cloaca caused by this nematode parasite was registered using histological analysis. This is a new geographic report for this nematode.
Purpose
Oscheius tipulae has attracted attention of researchers due to its entomopathogenic character besides serving as a good model for studying development, behaviour, and host-parasite interactions. The main aim of the study is to describe a new isolate O. tipulae first time from India. The study also resolved the exact status of the two species viz., O. siddiqii and O. niazensis described by Tabassum and Shahina (2010) from Pakistan.
Methods
The relationship of the new isolate with congeners was ascertained by D2/D3-based phylogenetic analysis. A haplotype network was also constructed along with the phylogeography of the taxa to evaluate the degree of divergence within the species, and their worldwide distribution. To examine the congruency between morphological and molecular traits, a morphology-based phylogenetic tree was also constructed.
Results
The present paper deals with the integrative approach of taxonomy of O. tipulae reported first time from India. The new isolate of O. tipulae extracted from darkling beetle (Tenebrionidae), from Jammu and Kashmir was re-described using morphological and molecular data. The study also revealed that the species O. siddiqii Tabassum and Shahina, 2010 and O. niazensis Tabassum and Shahina, 2010 are similar and close to O. shamimi Tahseen and Nisa, 2006 except the dissimilar lip morphology of O. niazensis Tabassum and Shahina, 2010 which needed reconfirmation based on the type specimens.
Chromadorina communis sp. nov. is described from Changdao Island at the confluence of the Yellow and the Bohai seas. The new species is characterized by its medium-sized body; finely striated cuticle with homogeneous punctations; absence of ocelli; buccal cavity with three equal-sized, solid teeth; four cephalic setae; oval amphidial fovea which is positioned between cephalic setae; curved spicules with tapered distal ends; simple, boat-shaped gubernaculums; five or six cup-shaped precloacal supplements; and conical tail with a very short spinneret. A phylogenetic analysis of small subunit rRNA gene sequences using maximum-likelihood and Bayesin inference confirmed the taxonomic position of Chromadorina communis sp. nov. within Chromadorinae. Tree topology in Chromadorida shows six morphological families clustered into a monophyletic clade and verifies the taxonomic position of the family Neotonchidae based on morphological and molecular analysis.
Meiofaunal life forms are found all over the animal tree of life, and miniaturization seems to have occurred within otherwise macrofaunal clades multiple times. While sponges, comb jellies and cnidarians suggest a macroscopic ancestry for Metazoa, several phyla are exclusively meiofaunal, however, and may evidence a wider microscopic ancestry of some major groups, such as Ecdysozoa and Spiralia/Lophotrochozoa. This is an unsolved debate, which should be tackled from a synthesis of zoomorphological, palaeontological, molecular and phylogenetic approaches to test alternative scenarios. Advances in microscopic techniques have led to a renaissance in anatomical studies that allows for new and detailed examination of both extant and extinct meiofauna, revealing an unseen wealth of information. Likewise, the rapid development in genomic sequencing and analytical tools makes detailed reconstructions of meiofauna genomes feasible. The anticipated flood of new morphological and molecular data on meiofauna will broaden integrative and comparative studies and hopefully allow scientists of this generation to answer the long-debated questions of how the animal kingdom evolved and ramified into today's amazing diversity of life. In this enormously complex tree of life, what is the significance of minute creatures represented by meiofauna?
A new isolate of Mesorhabditis monhystera (Bütschli, 1873) Dougherty, 1955 is described and illustrated with morphological and molecular data. The phylogenetic analysis based on the D2/D3 segment of 28S rDNA using the Bayesian inference method, revealed monophyly of the genus Mesorhabditis as the subordinate taxa clustered in one clade. The clade further divided into two subclades representing the Monhystera- group and Spiculigera- group with 100% posterior probability values. However, GenBank sequences of several species constituting the Monhystera -group, showed high similarity and very little genetic divergence (98–99%) of up to 4–5 bases. In order to ascertain the status of those isolates, detailed morphological comparison is provided along with a pictorial key. A sequence-based phylogeography of haplogroups of Mesorhabditis using the median-joining network method, was also inferred. The results suggested the need for morphological validation of a species before its sequences are deposited in GenBank.
Plant-parasitic nematodes (PPN), “the unseen enemies” of plants are a threat to the potato (Solanum tuberosum) production affecting their quality and yield. The most destructive species belong to the genera Globodera (Heteroderidae), Meloidogyne (Meloidogynidae), Pratylenchus/Nacobbus (Pratylenchidae), Ditylenchus (Anguinidae), and Nanidorus/Paratrichodorus/Trichodorus (Trichodoridae). Other PPN have been reported associated with the potato crop but the data on their economic importance is limited. Some of these nematodes are considered invasive species and, in a survey based on scientific and economic importance, Meloidogyne spp., Globodera spp., Pratylenchus spp., Radopholus similis, Ditylenchus dipsaci, Rotylenchus reniformis, and Nacobbus aberrans are in the top 10 list. Relevant information on the biology, host range, symptoms and diagnosis, survival and dissemination, environmental factors, disease complexes, economic importance, and management of the most aggressive species is given in this chapter.
The development of molecular tools has dramatically increased our knowledge of parasite diversity and the vectors that transmit them. From viruses and protists to arthropods and helminths, each branch of the Tree of Life offers an insight into significant, yet cryptic, biodiversity. Alongside this, the studies of host-parasite interactions and parasitism have influenced many scientific disciplines, such as biogeography and evolutionary ecology, by using comparative methods based on phylogenetic information to unravel shared evolutionary histories. Parasite Diversity and Diversification brings together two active fields of research, phylogenetics and evolutionary ecology, to reveal and explain the patterns of parasite diversity and the diversification of their hosts. This book will encourage students and researchers in the fields of ecology and evolution of parasitism, as well as animal and human health, to integrate phylogenetics into the investigation of parasitism in evolutionary ecology, health ecology, medicine and conservation.
The development of molecular tools has dramatically increased our knowledge of parasite diversity and the vectors that transmit them. From viruses and protists to arthropods and helminths, each branch of the Tree of Life offers an insight into significant, yet cryptic, biodiversity. Alongside this, the studies of host-parasite interactions and parasitism have influenced many scientific disciplines, such as biogeography and evolutionary ecology, by using comparative methods based on phylogenetic information to unravel shared evolutionary histories. Parasite Diversity and Diversification brings together two active fields of research, phylogenetics and evolutionary ecology, to reveal and explain the patterns of parasite diversity and the diversification of their hosts. This book will encourage students and researchers in the fields of ecology and evolution of parasitism, as well as animal and human health, to integrate phylogenetics into the investigation of parasitism in evolutionary ecology, health ecology, medicine and conservation.
The development of molecular tools has dramatically increased our knowledge of parasite diversity and the vectors that transmit them. From viruses and protists to arthropods and helminths, each branch of the Tree of Life offers an insight into significant, yet cryptic, biodiversity. Alongside this, the studies of host-parasite interactions and parasitism have influenced many scientific disciplines, such as biogeography and evolutionary ecology, by using comparative methods based on phylogenetic information to unravel shared evolutionary histories. Parasite Diversity and Diversification brings together two active fields of research, phylogenetics and evolutionary ecology, to reveal and explain the patterns of parasite diversity and the diversification of their hosts. This book will encourage students and researchers in the fields of ecology and evolution of parasitism, as well as animal and human health, to integrate phylogenetics into the investigation of parasitism in evolutionary ecology, health ecology, medicine and conservation.
Meloidogyne enterolobii, the guava root-knot nematode, has emerged as a significant problem in tropical and subtropical regions across the continents. Along with Fusarium spp., this nematode plays a crucial role in causing guava decline. In the newer locations, M. enterolobii can parasitize on many crops like other root-knot nematodes, including crops carrying nematode-resistance genes. This article reviews the current state of knowledge on all aspects of M. enterolobii, with a special focus on its management strategies.
The ichthyofauna of the Atlantic and Pacific coasts off the American continent is very rich. Consequently, a high biodiversity of nematodes parasitizing these vertebrates is also expected. Currently, data on nematode parasites of marine fish off the Americas is fragmented. A review of all adult nematode species reported parasitizing marine fish from off the American continent is herein presented, as well as comments on their patterns of diversity, life cycles and advances in the taxonomic and phylogenetic knowledge. A total of 209 valid species, 19 species inquirendae and 6 dubious records have been recorded, the majority from the fish taxa Eupercaria and Perciformes. The families Sciaenidae, Serranidae and Lutjanidae, as well as the tropical and temperate Atlantic waters, exhibited the highest records of parasitic nematodes. The Cucullanidae, Philometridae and Cystidicolidae were the most speciose families of nematodes, which may be related to technological advances and relatively recent efforts of taxonomists, resulting in description of new taxa and the resolution of taxonomic problems. Numerous taxonomic questions still need resolution and, even though genetic data have been important for this process, the database is very scarce. This is the first review on all currently known nematode species parasitizing marine fish off the Americas and may serve as an important basis of reference for future approaches on these organisms.
To examine phylogenetic relationships among the "cladoniiform" lichenized fungi, i.e., the families Cladoniaceae, Baeomycetaceae, Icmadophilaceae, Stereocaulaceae, and Siphulaceae, and to provide evidence for the anticipated independent origins of podetia and pseudopodetia, we conducted phylogenetic analyses of SSU (small subunit) rDNA sequences from 39 lichen-forming fungi. These fungi represent all of the major growth forms of lichen associations, fruticose (including "cladoniiform"), foliose, and crustose. Our analysis suggests that lichen-forming fungi with a "cladoniiform" morphology arose multiple times within the ascomycetes. Additionally, each of the other thallus growth forms, crustose, foliose, and fruticose, have originated multiple times. It also seems to be clear that neither all podetiate nor all pseudopodetiate taxa form a monophyletic group. Therefore the term "podetium" should be restricted to homologous structures that are most probably limited to the genera Cladonia, Cladina, Pycnothelia, and allies. The "pseudopodetia" of Stereocaulon (Stereocaulaceae) and Cladia (Cladiaceae) may represent different states of the same homologous character. Our phylogenetic hypothesis supports the monophyletic origin of the order Lecanorales sensu stricto, including representatives of five suborders Cladoniineae, Lecanorineae, Teloschistineae, Agyriineae and Peltigerineae, but excluding representatives of the suborders Acarosporineae (Acarospora schleicheri and Megaspora verrucosa), Pertusariineae (Pertusaria trachythallina), and Umbilicarineae. The suborder Cladoniineae and the family Cladoniaceae both appear to be polyphyletic assemblages.
Antibody 43C9 accelerates the hydrolysis of a p-nitroanilide by a factor of 2.5 x 10(5) over the background rate in addition to catalyzing the hydrolysis of a series of aromatic esters. Since this represents one of the largest rate accelerations achieved with an antibody, we have undertaken a series of studies aimed at uncovering the catalytic mechanism of 43C9. The immunogen, a phosphonamidate, was designed to mimic the geometric and electronic characteristics of the tetrahedral intermediate that forms upon nucleophilic attack by hydroxide on the amide substrate. Further studies, however, revealed that the catalytic mechanism is more complex and involves the fortuitous formation of a covalent acyl-antibody intermediate as a consequence of complementary side chain residues at the antibody-binding site. Several lines of evidence indicate that the catalytic mechanism involves two key residues: His-L91, which acts as a nucleophile to form the acyl-antibody intermediate, and Arg-L96, which stabilizes the anionic tetrahedral moieties. Support for this mechanism derives from the results of site-directed mutagenesis experiments and solvent deuterium isotope effects as well as direct detection of the acyl-antibody by electrospray mass spectrometry. Despite its partial recapitulation of the course of action of enzymic counterparts, the reactivity of 43C9, like other antibodies, is apparently limited by its affinity for the inducing immunogen. To go beyond this level, one must introduce additional catalytic functionality, particularly general acid-base catalysis, through either improvements in transition-state analog design or site-specific mutagenesis.
Bacterial feeding nematodes in the order Rhabditida including Zeldia punctata (Cephalobidae) and Caenorhabditis elegans (Rhabditidae) differ profoundly in the buccal capsule parts and associated cells. We carried out a range of tests to determine which buccal capsule parts and cells are evolutionarily homologous between the representative species of the two families. Tests included reconstruction of the buccal capsule and procorpus with transmission electron microscopy (TEM), nuclei position and morphology using 4, 6-diamidino-2-phenylindole (DAPI) staining, and cell lineage using four dimensional (4D) microscopy. The lining of the buccal capsule of Z. punctata and additional Cephalobidae includes four sets of muscular radial cells, ma, mb, mc and md, in contrast to C. elegans and additional Rhabditidae, which has two sets of epithelial cells (e1, e3) and two sets of muscle cells (m1, m2). Cell lineage of a nematode closely related to Z. punctata, Cephalobus cubaensis, supports the hypothesis that in cephalobids the e1 and e3 cells become hypodermal cells or are programmed to die. Our findings contradict all previous hypotheses of buccal capsule homology, and suggest instead that ma and mb in Z. punctata are homologous to m1 and m2 in C. elegans respectively. We also hypothesize that ma and mb could be homologous to primary and secondary sets of stylet-protractor muscle cells in the plant parasitic Tylenchida.
Understanding the early evolution of animal body plans requires knowledge both of metazoan phylogeny and of the genetic and developmental changes involved in the emergence of particular forms. Recent 18S ribosomal RNA phylogenies suggest a three-branched tree for the Bilateria comprising the deuterostomes and two great protostome clades, the lophotrochozoans and ecdysozoans. Here, we show that the complement of Hox genes in critical protostome phyla reflects these phylogenetic relationships and reveals the early evolution of developmental regulatory potential in bilaterians. We have identified Hox genes that are shared by subsets of protostome phyla. These include a diverged pair of posterior (Abdominal-B-like) genes in both a brachiopod and a polychaete annelid, which supports the lophotrochozoan assemblage, and a distinct posterior Hox gene shared by a priapulid, a nematode and the arthropods, which supports the ecdysozoan clade. The ancestors of each of these two major protostome lineages had a minimum of eight to ten Hox genes. The major period of Hox gene expansion and diversification thus occurred before the radiation of each of the three great bilaterian clades.
The present study evaluates the evolutionary framework of the Old World fruitbats based on the cytochrome b and 16S rRNA mitochondrial
gene sequences from a wide range of taxa. Phylogenetic analyses indicated that morphology-based subfamilies and most suprageneric
groups are nonnatural assemblages. They also support the existence of an endemic African clade of fruitbats. The discrepancy
between the evolutionary relationships yielded by molecular and morphological data sets may be, at least in part, explained
by the recurrent retention of primitive morphology (Rousettus-like) across different lineages. The maintenance of primitive
characters in different groups of flying foxes, as well as morphological convergence in nectar-feeding bats and possibly also
in short-muzzle bats, may have led to high levels of homoplasy, resulting in misleading taxonomic arrangements. This may be
particularly so with respect to high taxonomic levels based on morphological characters.
A fossil worm-like organism, ca. 0.5 mm long, showing cuticle, gut and setae. is contained in the solid part of the wall of a clitellate cocoon from the Early Cretaceous (Barremian). It is interpreted as having been entrapped and embedded in the intitially viscous cocoon secretion which solidified and thus prevented decay. Size, shape, posture, and an unsegmented but annulated cuticle with irregularly distributed setae have led to the identification of the fossil as a nematode. described as Captivonema cretacea gen. et sp. n., of uncertain family and order affinity. Fossil association end mode of preservation indicate a free-living life habit in damp plant litter.
Canonical discriminant analysis of four morphometric characters of juveniles and restriction enzymes analysis of ribosomal DNA sequences were used to distinguish Heterodera arenaria, H. aucklandica, H. avenae, H. filipjevi, H. hordecalis, H. iri, H. latipons, H. litoralis, H. schachtii and an undescribed species from grasslands. The results of unweighted pair group cluster analysis showed that H. avenae populations formed three groups and H. filipjevi two groups at the 80% level of similarity. Intraspecific polymorphism was revealed by rDNA-RFLP studies and two types of ITS regions within H. avenae populations can be distinguished. The pattern of restriction bands obtained with BsuRI, PstI and TaqI clearly distinguished populations of H. filipjevi from other species of the H. avenae group. Further enzymes and their combinations distinguished the other species. There are no enzymes which differentiate European populations of H. avenae from H. arenaria. Morphometrics, restriction endonuclease cleavage maps of ITS regions and a dendrogram of putative phylogenetic relations of several cyst-forming nematode species are given.
The taxonomic impediment in nematology is expanding rather than receding: in the past decade estimates of nematode species richness have increased by several orders of magnitude, while the number of active nematode taxonomists has continued to decline steadily. In order to survive as a discipline in the new century, nematode taxonomy will therefore have to i) prioritise taxa that are relevant to other scientific investigations, ii) provide identification and classification tools that are easily applicable by nonspecialists, and iii) focus on revealing patterns of relatedness rather than on compiling exhaustive catalogues of species, since the latter will never remotely reach completion. Traditional morphological studies based on light microscopy do not meet these needs because they provide insufficient character resolution and require too much specialist knowledge. Phylogenetic approaches are more promising, especially when incorporating molecular sequence data as well as other non-traditional character suites.
The initiation of genome projects on helminths of medical importance promises to yield new drug targets and vaccine
candidates in unprecedented numbers. In order to exploit this emerging data it is essential that the user community is
aware of the scope and quality of data available, and that the genome projects provide analyses of the raw data to highlight
potential genes of interest. Core bioinformatics support for the parasite genome projects has promoted these approaches.
In the Brugia genome project, a combination of expressed sequence tag sequencing from multiple cDNA libraries
representing the complete filarial nematode lifecycle, and comparative analysis of the sequence dataset, particularly using
the complete genome sequence of the model nematode C.
elegans, has proved very effective in gene discovery.
The generic relationships and higher classification of the family Culicidae are examined on the basis of a phylogenetic analysis. New and traditional morphological characters studied and compared throughout the Culicidae resulted in the acquisition of character data relative to the majority of species within each genus. Polymorphisms and morphological observations are discussed and additional information and illustrations are provided for the majority of characters and their character states. The analysis of seventy-three adult, pupal and fourth-instar larval characters coded for the thirty-eight currently recognized genera of mosquitoes resulted in relationships and groupings which differ significantly from traditional hypotheses. The analysis supports the monophyly of the subfamily Anophelinae and the tribes Culicini and Sabethini. The Anophelinae form the most basal clade of the family. The results indicate that Aedini is a paraphyletic assemblage with respect to the Mansoniini, each of which is monophyletic in itself. The Aedini + Mansoniini form a sister group to the Culicini + Sabethini, with the Aedini and the Culicini placed in ancestral relationships to the Mansoniini and the Sabethini, respectively. Based on the topography of generic relationships among more ‘generalized’ mosquitoes, the boundaries and relationships of the tribes Aedeomyiini, Uranotaeniini, Ficalbiini, Hodgesiini, Orthopodomyiini and Culisetini appear to be problematic. Relationships between genera of the tribe Aedini are generally poorly resolved due to a significant amount of polymorphism, especially within the genus Aedes as currently defined. There is no support for separate subfamily recognition for the genus Toxorhynchites, which is downgraded to tribal status as a result of the analysis. The results are discussed in relation to previous hypotheses based on subjective inference and cladistic analyses.
The appearance of the multicellular animals, or Metazoa, in the fossil record about 600 million years ago marks a revolution in the history of life. Molecular biology is continuing to increase our understanding of metazoan evolution, yet information from fossils is still an important component in deciphering metazoan phylogeny, and data on rapidly radiating animal groups place early metazoan evolution in a new perspective.
During postembryonic development in C. elegans, posterior-specific pattern formation requires the gene mab-5. Within the posterior body region, mab-5 activity controls epidermal, neuronal, and mesodermal cell differentiation, and also the direction of cell migration. Here, we show that mab-5 RNA is localized in the posterior body region, indicating that mab-5 activity is targeted to posterior cells, at least in part, by a mechanism that operates at the level of mab-5 RNA synthesis or stabilization. We also show that mab-5 contains a homeobox similar to that of the Drosophila Antennapedia gene. This suggests that mab-5 influences cell differentiation and cell migration by regulating gene expression, and clearly demonstrates that genes containing homeoboxes influence global aspects of pattern formation in organisms other than Drosophila.
Isoenzyme and random amplified polymorphic DNA (RAPD) markers were used to characterize the genetics of geographic variation among population samples of Ascaris suum from midwestern localities. Independent estimates of fixation indices (FST) based on isoenzyme and RAPD markers showed the same general patterns of differentiation and substantial statistical correlation (r = 0.70). Of the total estimated gene diversity, 9.4% (isoenzyme) and 9.2% (RAPD) was distributed among infrapopulations. Geographic localities accounted for 7.8% (isoenzyme) and 6.2% (RAPD) of the total gene diversity. Only infrapopulations from a single farm were characterized by low fixation indices (isoenzyme and RAPD FST < 0.05). Isoenzyme and RAPD markers revealed moderate genetic differentiation among infrapopulations and localities, which indicates significant population subdivision among A. suum from farms within geographic regions. Departures from random mating were revealed by deficiencies of heterozygotes within infrapopulations and by high positive values of FIS among and between infrapopulations. The average inbreeding (FIS) coefficient among all infrapopulations was 0.22. Thus, the genetic composition of these A. suum infrapopulations, whether from a general geographic region of a single farm, was not consistent with a model of random recruitment from a larger panmictic pool of parasite life cycle stages.
We have begun to reconstruct the ancient history of the nematode phylum based on cytochrome c and globin amino acid sequences. The data suggest that the nematode ancestor diverged from a line leading to mammals about 1 billion years ago and that the most recent common ancestor of the extant species Caenorhabditis elegans, Trichostrongylus colubriformis, Nippostrongylus brasiliensis, Ascaris suum, and Pseudoterranova decipiens lived about 550 MY ago. The rhabditids and strongylids emerged as one offshoot of this ancestor, the ascarids as another. Rhabditids and strongylids diverged some 400 MY ago, whereas the genera Trichostrongylus and Nippostrongylus diverged slightly over 200 MY ago. A gene duplication event in the strongylid branch is predicted to have occurred around 250-335 MY ago. There are two globin genes in Nippostrongylus, expressed in anatomically distinct compartments (body and cuticle), and the single sequence from Trichostrongylus is most like the Nippostrongylus body globin gene. A strikingly different duplication event occurred within the same period in the line leading to the extant ascarid genera, creating a single polypeptide containing two globin domains. The genera Ascaris and Pseudoterranova diverged some 150-250 MY ago. Interestingly, the second globin repeat evolved at a faster rate in both species examined. This is possibly related to the acquisition of an unusual carboxyterminal extension, composed of alternating positively and negatively charged residues, that is necessary for the assembly of several monomers into the native polymeric molecules.
Amino acid sequence data from 57 different enzymes were used to determine the divergence times of the major biological groupings. Deuterostomes and protostomes split about 670 million years ago and plants, animals, and fungi last shared a common ancestor about a billion years ago. With regard to these protein sequences, plants are slightly more similar to animals than are the fungi. In contrast, phylogenetic analysis of the same sequences indicates that fungi and animals shared a common ancestor more recently than either did with plants, the greater difference resulting from the fungal lineage changing faster than the animal and plant lines over the last 965 million years. The major protist lineages have been changing at a somewhat faster rate than other eukaryotes and split off about 1230 million years ago. If the rate of change has been approximately constant, then prokaryotes and eukaryotes last shared a common ancestor about 2 billion years ago, archaebacterial sequences being measurably more similar to eukaryotic ones than are eubacterial ones.
We have used a tag sequencing approach to survey genes expressed in the third stage infective larvae of the human filarial nematode parasite Brugia malayi. RNA was isolated from late vector-stage L3 larvae after days 9 or 10 of infection in mosquitos, and converted to cDNA by reverse transcriptase. Double-stranded cDNA was produced by either conventional methods (non-SL cDNA library) or by PCR using the nematode spliced leader (SLI) and oligo(dT) primers (SL cDNA library). Two clone libraries (one from SL and one from non-SL cDNAs) were constructed in lambda ZapII. A set of these full-length clones was selected and 596 inserts were sequenced from the 5' end. We have identified 364 B. malayi genes (the majority of which are new) that encode housekeeping proteins, structural proteins, proteins of immediate immunological or drug-discovery interest as well as a large class of novel sequences which may prove to have significant involvement in host invasion. Extensive, genome-wide approaches to the analysis of larval gene expression are now possible for B. malayi. We present several examples of this approach.
Support for contradictory phylogenies is often obtained when molecular sequence data from different genes is used to reconstruct phylogenetic histories. Contradictory phylogenies can result from many data anomalies including unrecognized paralogy. Paralogy, defined as the reconstruction of a phylogenetic tree from a mixture of genes generated by duplications, has generally not been formally included in phylogenetic reconstructions. Here we undertake the task of reconstructing a single most likely evolutionary relationship among a range of taxa from a large set of apparently inconsistent gene trees. Under the assumption that differences among gene trees can be explained by gene duplications, and consequent losses, we have developed a method to obtain the global phylogeny minimizing the total number of postulated duplications and losses and to trace back such individual gene duplications to global genome duplications. We have used this method to infer the most likely phylogenetic relationship among 16 major higher eukaryotic taxa from the sequences of 53 different genes. Only five independent genome duplication events need to be postulated in order to explain the inconsistencies among these trees.
Nematodes are known to be a useful system for studies of comparative development. Here we perform a molecular phylogenetic analysis to allow for the independent interpretation of the developmental and morphological changes observed among a selected set of nematode species. Our molecular phylogenetic analysis is based on coding regions of the genes for RNA polymerase II, the small subunit rRNA and an expansion segment of the large subunit rRNA. Sequences were compared from five species in the family (Rhabditidae) that includes the developmental model organism Caenorhabditis elegans and from an outgroup taxon Aduncospiculum halicti (Diplogasterina). The phylogenetic analysis does not support the monophyly of the subfamily Mesorhabditinae and identifies the unnamed strain PS1010 as a sister taxon of C. elegans despite its morphologically divergent buccal capsule. On the basis of the inferred framework, we can begin to interpret the evolution of vulval development and of morphological differences among these nematode species.
This chapter describes genetic approaches to answer a variety of questions in the population biology of parasitic helminths. It lays particular emphasis on nematode parasites. The chapter describes levels of heterozygosity revealed by allozymes and patterns of variation in a variety of different sequence types. It illustrates the ways this variation is distributed in parasite populations, and the ways these patterns can be used to ask questions about the various aspects of nematode biology and epidemiology. It also discusses the interspecific level and describes the way genetic approaches have clarified ideas on nematode speciation and revealed a wealth of sibling species. The chapter presents examples of the use of markers for clarifying life cycles and deals with genes responsible for drug resistance. It also discusses other miscellaneous uses of genetic markers. Much of this section is speculative and describes fields in which genetic markers should see a greater usage in the future.
A thorough and coherent classification of the phylum Nematoda is essential if the evolution of countless phenotypes is to be understood. Here, Mark Dorris, Paul De Ley and Mark Blaxter discuss how the application of molecular phylogenetics is helping to resolve some of the inconsistencies in morphological classification and phylogeny by establishing relationships between free-living and parasitic groups, showing possible patterns underlying the origins of parasitism and placing key nematode species in an evolutionary context for comparative study.
Hookworms are gut-dwelling, blood-feeding nematodes that infect hundreds of millions of people, particularly in the tropics. As part of a program aiming to define novel drug targets and vaccine candidates for human parasitic nematodes, genes expressed in adults of the human hookworm Necator americanus were surveyed by the expressed sequence tag approach. In total 161 new hookworm genes were identified. For the majority of these, a function could be assigned by homology. The dataset includes proteases, protease inhibitors, a lipid binding protein, C-type lectins, an anti-bacterial factor, globins and other genes of interest from a drug or vaccine development viewpoint. Three different classes of small, secreted proteins were identified that may be involved in the host-parasite interaction, including potential potassium channel blocking peptides. One third of the genes were novel. These included highly expressed, secreted (glyco)proteins which may be part of the excretory-secretory products of these important pathogens. Of particular interest are a family of 9 genes with similarity to the immunomodulatory protein, neutrophil inhibitory factor, that may play a role in establishing an immunocompromised niche for this successful parasite.
Aphelenchida, Longidoridae and Trichodoridae: their The lower Metazoa, comparative biology and phylogeny
- D J Hunt
Keys to the genera of the Oxyuroidea
- A J Petter
- L F Farnham
- Khalil
Key to parasitic Nematodes
- K I Skrjabin
- Ed