Fig 3 - uploaded by M. Antonio Todaro
Content may be subject to copyright.
Three-dimensional reconstruction of the drumstick-like sensory organs of Pleurodasys helgolandicus with some details. a Three-dimensional reconstruction of the whole sensory organ. b Sagittal sections through the stalk and the bulbous tip. Note the cilium extending through the stalk sub-cylindrical cavity, and the spherical body inside the bulbous tip. Nucleus, mitochondria, multivesicular bodies and Golgi apparatus are visible inside the sensory receptor cell cytoplasm. c Detail of the distal portion of the sensory cell membrane. Note the collar of short microvilli radially arranged around the cilium (four out of ten microvilli shown), the corresponding longitudinal infoldings along the invaginated plasma membrane, and the electrondense material. d Detail of the apical portion of the stalk. Note the
Source publication
The drumstick-like organs of the marine interstitial gastrotrich Pleurodasys helgolandicus Remane, 1927 were studied using optical and electron microscopy, in order to widen our knowledge of the sensory organs among gastrotrichs.
The drumstick-like sensory organs are paired, symmetrical structures located on the dorsal side of the post-cephalic reg...
Citations
... In this framework of exciting new data, it is pity that information on the gastrotrich fauna from some biogeographic crucial regions remains very scarce. In Europe, for example, prior to investigation in Lanzarote, only 7 species have been reported in print from Spain (Giere 1979;Marotta et al. 2008;Rothe and Schmidt-Rhaesa 2010;Todaro et al. 2003a, b). Spain, including the Canary archipelago, hosts an extreme varied fauna made up of cold, temperate-cold and warm-subtropical elements (e.g., Marina et al. 2015). ...
... All the observed specimens carried the paired, flexible rod-like organs along the pharyngeal region, a feature that appears to be unique among Gastrotricha. Very likely, these structures represent sensorial organs, perhaps similar in function to the drum-stick organs found in the cephalodasyid Pleurodasys helgolandicus Remane, 1927 for which a sensorial function as graviceptors has recently been demonstrated (Marotta et al. 2008). ...
Sampling campaign took place in October 2011 and included 7 locations and 16 stations along the eastern coast of the island of Lanzarote (Spain). Samples yielded 61 species for a total of 96 records. Thirty-six species (27 genera and 11 families) belong to Macrodasyida while 25 species (18 genera, 7 families) to Chaetonotida. Thirty-two are known species while 29 appear to be undescribed taxa or putatively so. The finding at Lanzarote of some of the known species bear particular significance: Oregodasys cirratus and Tetranchyroderma canariense are recorded for the second time ever, while Musellifer delamarei and Urodasys acanthostylis were previously known only from the Mediterranean, and Urodadys mirabilis was acknowledged only for northern Europe. Furthermore, the presence of Chaetonotus apechochaetus, C. apolemmus, C. siciliensis, Heterolepidoderma loricatum, Lepidodasys unicarenatus, Musellifer delamarei, Thaumastoderma mediterraneum, and Urodasys acanthostylis strongly suggest them to be part of the temperate/warm fauna that invaded the Mediterranean basin after the Missinian crisis during the different climate eras. Of the new species, one is described as its characteristics substantially widen our knowledge of the entire genus. Urodasys completus sp. nov. is unique in that it possesses, among others, two testes and a sclerotic stylet. Results of a phylogenetic analysis indicated that the sequence of the evolutionary transformation that have occurred in the reproductive system of the species of Urodasys are likely dissimilar from the ones proposed thus far. The overall results testify the need to continue the exploration in the Canary Islands.
... The pharyngeal knobs, also known as drumstick-like organs, have recently been found to be unique gravireceptor organs (Marotta et al. 2008). From their first discovery, these peculiar structures, together with the noticeable lateral accessory adhesive tubes, have been considered to be autoapomorphic traits of the genus Pleurodasys. ...
This study is part of a larger research program aimed at shedding light on meiofauna and macrofauna communities of the subtropical Eastern Province of KwaZulu-Natal, South Africa. Previous articles on the phylum Gastrotricha have detailed faunistic and preliminary taxonomic data on marine and freshwater species found in the iSimangaliso Wetland Park. Here, two new interesting marine macrodasyidan species, in the families Cephalodasyidae and Turbanellidae, are reported from a wider area of the KZN coast. Descriptions are based on observations carried out on living specimens using differential interference contrast microscopy. Pleurodasys incomptus new species is the second species in the genus; surprisingly, it lacks the peculiar gravireceptor organs (pharyngeal knobs) thought to be an autapomorphic trait of the genus. Paraturbanella africana new species is a mid-sized species (up to 520 μm in length), showing a peribuccal swelling; its most obvious autapomorphic trait pertains to the testes, which are located well passed half the body rather than at- or near the pharyngo-intestinal junction as occur in the other species of the genus. The relevant anatomical novelties shown by the two new species testify that current knowledge about gastrotrich basic morphology is far from complete. This holds true also for taxa that are considered to be well-known (e.g. the speciose genus Paraturbanella), and stresses once again the importance of investigating new geographic areas in order to improve our understanding of global gastrotrich morphological diversity and species richness.
Synopsis
Most invertebrate phyla possess a graviceptive sense. The most common sensor to detect gravity is the statocyst, which developed several times independently in invertebrates. It can be very basic with a statolith inside a cavity and unspecific sensory cells in the wall to very complex organs of the decapod crustaceans or cephalopods. Most of the phyla use the statocyst to detect gravity, linear or even angular acceleration. An exception are some arthropods, such as hexapods or Chelicerata, which developed other organs like force measuring sensilla, the Johnston's organ, or hair fields in joints to detect gravity.
We present a checklist of the macrodasyidan Gastrotricha fauna of India derived from original articles and comprehensive monographies regarding the Indian Fauna. Taxa and specimens described from India are discussed with special attention to their status, especially those species previously known from distant geographic areas. A total of 43 species have been recorded from 4 States and 2 Union territories. A careful taxonomic assessment indicated that many species are in need of re-description as the reported anatomical traits are not sufficient to grant a modern, robust identification. The situation is particularly poor for two species (Macrodasys indicus Govindankutty & Nair, 1969 and Paradasys lineatus Rao, 1980), which consequently, are considered here to be species inquirendae; moreover, the Indian records of Tetranchyroderma hystrix and T. massiliense reported from Kerala are doubtful and consequently the two species should not be included among the fauna of the Indian region until proper evidence is found. It is necessary to unravel the true identities of many Indian species through a comparison to topotypical material. We recommend that future comparisons between related species and conspecifics from different populations to include molecular sequence data
Marine Gastrotricha, both Macrodasyida and Chaetonotida, are the subject of an analytic review, citing taxonomic status of names, authorships of taxa, and those responsible for changes, in accordance with the International Code of Zoological Nomenclature, 4 th ed. (1999). Notes are included with regard to taxonomic usage so as to guide workers in the future. Among the proposed novelties are: within Macrodasyida, to restrict the family Lepidodasyidae Remane, 1927 to the genus Lepidodasys Remane, 1926, and to establish a new family, Cephalodasyidae with Cephalodasys Remane, 1926 as its type-species to house the remaining genera and species that have been contained in the polyphyletic family Lepidodasyidae. Hemidasys agaso Claparède, 1867 is considered extinct, and the new name Tetranchyroderma antenniphorum is proposed for Tetranchyroderma antennatum Luporini, Magagnini & Tongiorgi, 1973; in addition, five species are here considered to be species inquirendae: Dactylopodola weilli d'Hondt, 1965, Paradasys nipponensis Sudzuki, 1976, Macrodasys indicus Kutty & Nair, 1969. Tetranchyroderma forceps d'Hondt & Balsamo, 2009 and Turbanella plana (Giard, 1904b). Among Chaetonotida: the Xenotrichula velox-species group Ruppert, 1979 and the Xenotrichula intermedia-species group Ruppert, 1979 were given each the rank of subgenus. Chaetonotus pleuracanthus Remane, 1926 is rejected as a synonym for Chaetonotus marinus Giard, 1904; Chaetonotus somniculosus Mock, 1979 is transferred to the genus Halichaetonotus, the new name Halichaetonotus euromarinus is proposed for Halichaetonotus spinosus Mock, 1979, and Xenotrichula carolinensis Ruppert, 1979 is re-established. Heteroxenotrichula variocirrata d'Hondt, 1966 is here considered to be species inquirenda.
During a two-week workshop held at the Sven Lovén Centre for Marine Sciences on Tjärnö, an island on the Swedish west-coast, meiofauna was studied in a large variety of habitats using a wide range of sampling tech- niques. Almost 100 samples coming from littoral beaches, rock pools and different types of sublittoral sand- and mudflats yielded a total of 430 species, a conservative estimate. The main focus was on acoels, proseriate and rhabdocoel flatworms, rotifers, nematodes, gastrotrichs, copepods and some smaller taxa, like nemertodermatids, gnathostomulids, cycliophorans, dorvilleid polychaetes, priapulids, kinorhynchs, tardigrades and some other flatworms. As this is a preliminary report, some species still have to be positively identified and/or described, as 157 species were new for the Swedish fauna and 27 are possibly new to science. Each taxon is discussed separately and accompanied by a detailed species list.
