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Result of TWINSPAN using transformed pooled data showing the different communities identified in L. Tana. Indicator species and pseudospecies cutlevels (in bracket) are given for each division. Unstable sample in group formation is marked out in oval.
Source publication
Free-living nematodes from littoral benthic sediments of four lakes, two rivers and a hot spring in Ethiopia are studied. Populations of nematodes encountered are identified to the species level. The general nematode (generic and species) composition of the lakes, rivers and hot spring are appraised by giving special emphasis to the nematodes from...
Context in source publication
Context 1
... it is the chromadorids that dominate the species composition (Traunspurger, 1992, 1996a). In general, a discussion on the possible sources of variation in genus and species number and composition of the nematofauna in different lakes is, at present, premature for two reasons. Firstly, information on factors that play a role in the distribution of free-living nematodes in inland water bodies is still scanty, the best one can do at the moment is assume that those factors that influence the distribution of the relatively well studied marine nematodes also affect nematodes in inland water bodies. Secondly, a large proportion of the studies done on the nematofauna of inland water bodies do not go far beyond collecting a few samples for taxonomic purposes from a relatively small proportion of lakes and rivers. Moreover, as its invariable characteristic, detailed description of study sites in taxonomical studies on nematodes is want- ing, making comparison of results of such studies with others cumbersome. The generally high variability of meiobenthos in freshwater habitats with respect to space and time (Pennak, 1988; Traunspurger, 1996a) also exacerbates the problem of comparison. The classification and ordination techniques show that both the environmental factors and the nematode communities in the three stations of Lake Tana were clearly different. The smaller median grain size and the higher proportion of mud were the main factors separating the Gelda samples from the Gedero and Zegie samples. This is probably correlated with the load of silt deposited by the inflowing River Gelda. Most Ethiopian rivers are characterised by a marked seasonality: over-flooding occurs in the rainy season (June–September), particularly in highland areas, while very low water levels are recorded in the dry season (October–May). During the rainy season they typically wash and carry a significant amount of the topsoil, whence their characteristic reddish-brown col- our. The amount of silt in the water gradually declines from October to November onwards. Still, at the time of sampling in January the water of River Gelda was brown, implying that silt was being deposited even after the rainy season was over. The structuring effects of sediment characteristics on nematode communities are well documented for marine habitats (Tietjen, 1977; Heip et al., 1982, 1985; Giere et al., 1988), but only a few studies have confirmed this for freshwater communities (Zullini, 1974; Schiemer, 1978; Tudorancea & Zullini, 1989). In Gelda and Zegie, the 0.5 and 1.5 m depth strata were clearly characterised by different nematode com- munities. This pattern was not observed at Gedero. This is probably correlated with the exposed nature of this site: it is subject to strong wind action resulting in continuous mixing of the water column and resuspen- sion of the sediments. The fact that nematode density and species composition varies with water depth is widely reported in inland water bodies (Prejs, 1977; Schiemer, 1978; Tudorancea & Zullini, 1989; Traunspurger, 1992, 1996a, b). Most studies revealed that densities are higher at shallower parts of lakes. Our findings confirm this generalisation. P. behningi was absent at Gelda, but it was the second most dominant species in the deeper Gedero and Zegie communities. This may reflect its preference for less muddy sediments. The only other place where this species was reported to be dominant was in the deeper parts of Lake Balaton (Biró, 1968). M. cf. gabaza showed preference for the sheltered site, Zegie. All the indicator species of each of the three communities are species not recorded anywhere else before which are characterised by low density (Fig. 3); this fact coupled with the absence of detailed report on physico-chemical characteristics of the localities from where P. behningi and M . cf. gabaza have been described hinders the making of any generalisation about the relationships between species distribution and habitat. The presence of few dominant species characterised four of the five communities (Fig. 13). The highest species dominance was observed in the two communities at Gelda. Tietjen (1977) noted that high species dominance is characteristic for shallow muds (deposit feeders being the predominant feeding type) and suggested that many species may be excluded through intense competition. In three communities, a member of the genus Monhystera was dominant in conjunction with either a dorylaimid (Gelda 0.5 m) or a tobrilid (Gelda 1.5 m and Zegie 0.5 m). A singu- lar dominance of a Monhystera species or dominance in combination with a tobrilid has been reported for freshwater lakes repeatedly (e.g. Biró, 1968; Traunspurger, 1996b). In the other two communities in Lake Tana, deposit feeding leptolaimids (Zegie 1.5 m) or leptolaimids and monhysterids (Gedero) dominated the nematode communities. In the dominance hier- archy, these taxa are invariably followed by tobrilids (Fig. 12). Such combinations in dominance of deposit feeding monhysterids or leptolaimids with omnivor- ous/predatory tobrilids may rather be associated with niche partitioning than caused by tolerance to environmental factors. R . terrestris has been reported to ...
Citations
... In freshwater environments, free-living adult nematodes are usually dominated by females and thus by (facultative) parthenogenetic species, as shown in this study (Table 1) and previous investigations [52][53][54]. The frequency of this reproductive mode may reflect an adaptation to isolation in many freshwater habitats. ...
Nematodes disperse passively and are amongst the smallest invertebrates on Earth. Free-living nematodes in mountain lakes are highly tolerant of environmental variations and are thus excellent model organisms in dispersal studies, since species-environment relationships are unlikely to interfere. In this study, we investigated how population or organism traits influence the stochastic physical nature of passive dispersal in a topologically complex environment. Specifically, we analyzed the influence of female proportion and body size on the geographical distribution of nematode species in the mountain lakes of the Pyrenees. We hypothesized that dispersal is facilitated by (i) a smaller body size, which would increase the rate of wind transport, and (ii) a higher female proportion within a population, which could increase colonization success because many nematode species are capable of parthenogenetic reproduction. The results showed that nematode species with a low proportion of females tend to have clustered spatial distributions that are not associated with patchy environmental conditions, suggesting greater barriers to dispersal. When all species were pooled, the overall proportion of females tended to increase at the highest elevations, where dispersal between lakes is arguably more difficult. The influence of body size was barely relevant for nematode distributions. Our study highlights the relevance of female proportion as a mechanism that enhances the dispersal success of parthenogenetic species, and that female sex is a determining factor in metacommunity connectivity.
... The bulk of research on nematodes until very recently focused mainly on marine habitats, ignoring the inland water bodies of most parts of the world [41]. Nematodes from African water bodies, except for South Africa, have hardly received any attention to date [47]. ...
Fish production has a crucial role in food security. However,
fish production is decreased by infectious and non-infectious
diseases. Parasitic disease is one of the non-infectious diseases
that affects the productivity of the fish in the system through
decreasing growth rates, spoiling the appearance of fish, lowering the quality and quantity of fish, and low reproduction.
The epidemiological occurrence and distribution of parasitic
diseases in fish have not been studied in previous research, and
most people have not focused on fish health situations. Therefore, the main objective of this review is to provide an overview
of the epidemiology of helminths, protozoa, and ectoparasites
in fish. The larvae of helminths usually affect the marketability of commercially produced fish, thus raising a lot of public
health concerns. Nematodes pose an economic threat to the
market value of fish through consumer attitudes towards the
presence of these parasites within food products. Adult cestode infections are benign because they are not invasive, but
the larval stages penetrate the tissues before encysting, causing obstruction and fibrosis, and sometimes the eggs can lodge
in tissues, causing hypertension and a granulomatous reaction.
Ectoparasites cause irritation and breathing difficulties that
lead to the death of fish. Protozoal diseases of fish can act as
ectoparasites and endoparasites that cause mortality in fish.
Parasitic diseases can be controlled through the destruction
of intermediate hosts and treatment. Generally, parasitic diseases of fish have great health and economic importance for
fish farms. Therefore, further studies should be conducted on
fish production.
... Protein denaturation, caused by high temperatures, often leads to subsequent loss (reversible or irreversible) of associated functions (Hochachka and Somero 1984;Tahseen 2012). Several species have been reported to occur in hot springs at temperatures around 40°C (Abebe et al. 2001;Ocaña 1991a, b), and even surviving up to 92°C water. In shallow-water hydrothermal vents, nematodes occurred at sites close to the geyser point, at temperatures around 80°C (Zeppilli and Danovaro 2009). ...
... Protein denaturation, caused by high temperatures, often leads to subsequent loss (reversible or irreversible) of associated functions (Hochachka and Somero 1984;Tahseen 2012). Several species have been reported to occur in hot springs at temperatures around 40°C (Abebe et al. 2001;Ocaña 1991a, b), and even surviving up to 92°C water. In shallow-water hydrothermal vents, nematodes occurred at sites close to the geyser point, at temperatures around 80°C (Zeppilli and Danovaro 2009). ...
Great divergences arise when comparing the ecology of meiofauna in freshwater and marine ecosystems. Emphasizing the main differences between freshwater meiofauna and their marine counterparts, we will go on a stepwise journey through three major frontiers in freshwater research, which in turn are hierarchically interrelated: biodiversity, community organization (e.g. food webs structure), and ecosystem processes (e.g. metabolism and organic carbon breakdown). The starting point of this chapter is one of the utmost frontiers, both in marine and freshwater research: meiofaunal diversity. Especially in freshwater ecosystems diversity becomes evident since, here, habitats extend as highly disconnected biotopes, each characterized by an often fundamentally different biocenosis. From the biodiversity level, we move up the theoretical hierarchy to assess the role of meiofauna as an integral part of benthic food webs. Recent research underlines the role of freshwater meiofauna as highly connected nodes and shows their pivotal role in the transfer of energy and carbon along food chains. Distributed over all trophic levels, this structure contrasts with the prevailing conception of meiofauna in food webs, where meiofauna often are considered rather marginal units. Finally, we apply allometric principles from the metabolic theory of ecology in order to assess the role of freshwater meiofauna in the functioning of the benthic systems. With a novel modelling framework we develop an analytical perspective, showing that secondary production of micro- and meiobenthic communities can predict microbial decomposition rates within the benthic interface. Our results demonstrate that productive micro- and meiobenthos act as catalysers in the system of organic carbon breakdown and recycling. These findings underline the relevance of freshwater meiofauna within the biogeochemical carbon cycle. The mechanistic forces behind the processes involved require future experimental research.
... Protein denaturation, caused by high temperatures, often leads to subsequent loss (reversible or irreversible) of associated functions (Hochachka and Somero 1984;Tahseen 2012). Several species have been reported to occur in hot springs at temperatures around 40°C (Abebe et al. 2001;Ocaña 1991a, b), and even surviving up to 92°C water. In shallow-water hydrothermal vents, nematodes occurred at sites close to the geyser point, at temperatures around 80°C (Zeppilli and Danovaro 2009). ...
Meiofauna are ubiquitous members of aquatic ecosystems worldwide. Some of them can thrive under boundary conditions that are challenging to most other organisms. The discovery of well-adapted meiobenthic communities under extreme environments (e.g., sub-glacial sediments or deep in the Earth’s crust) has opened new insights into life under limiting conditions, insights relevant not only with respect to distributional and physiological aspects, but also of potential importance in research on venturous exobiological and medical frontiers. Although meiofauna do not have pelagic dispersal stages and, therefore, are directly exposed to the limiting environment of their immediate habitat, representatives from various taxa can survive environmental conditions often fatal to all other fauna. Typical ‘extremophiles’ belong to the abundant and diverse group of nematodes, but also, tardigrades, rotifers, loriciferans, kinorhynchs, and the protozoan foraminiferans (especially in polar regions). In addition, some can modulate their metabolism by temporarily switching to an ‘alternate life’ where they can ‘escape in time’ (Jönsson 2005). This extraordinary potential explains why they became preferred objects for biochemical, physiological, medical, and even exobiological studies. Natural extremes have always occurred, but under the present conditions of climate change, the frequency of extreme environmental challenges is increasing and represents a planetary threat. Therefore, understanding pertinent adaptations can provide vital information on how organisms may survive stressful challenges such as acidification, lack of oxygen, and rising temperatures. Thus, research on the biology, ecology, and physiology, including genetic studies, of these exotic meiobenthic taxa is gaining importance. As diversified as the taxonomic affiliations of extremophiles are their adaptive patterns that have evolved under hostile life conditions. The variety of pathways leading to their survival, including a temporary metabolic suspension or ‘dormancy’ (see Table 11.1), points to independent routes that have evolved repeatedly over evolutionary time. Pertinent studies may even shed light on their evolutionary diversification and their phylogenetic relationship (see Chap. 1). Since, in addition to nematodes, many specific studies are on tardigrades and rotifers, their life under extreme conditions, mostly in freshwater and desiccating terrestrial habitats, is also considered in this chapter.
... Regarding to interaction between environmental factors and water level, Abebe et al. (2001) related water level variability in lakes with conductivity fluctuation, clarifying the latter's impact on nematode dispersion. However, Barbuto and Zullini (2005) underlined that little is known about the abiotic conditions that control how various nematode species disperse in flowing water. ...
... The observed disparities in nematode genera abundances corroborated with the findings of Abebe et al. (2001). They reported differential nematode response to fluctuated water level. ...
... The absence of some nematode genera in LWL coincided with the findings of Abebe et al. (2001). They noted that the presence/absence of certain genera is dependent on their opportunistic nature and tolerance to environmental stresses. ...
Quantitative and qualitative responses of subtropical benthic freshwater nematodes to changing water levels (low versus high) have not been considered before. Three distinct locations with different depths in two freshwater channels (Rowaina and Shalma) of the northern Nile delta had been chosen for this purpose. Low and High-water levels (LWL & HWL) were in January and July 2019 respectively. Nematode abundance and diversity were significantly different between water levels, locations, and their interactions. They were categorized into six feeding groups in both water levels, locations and channels (bacterivores, plant ectoparasites, fungivores, Nematovorous, omnivorous, and predators). However, bacterivorous and omnivorous disappeared during HWL in Rowaina channel. The relative dominance of the feeding groups differed between water levels, localities, and channels. Dominancy was generally higher in Shalma. Diversity pattern in Rowaina contrasted that of Shalma. Environmental variables differently influenced nematode community. It could be concluded that water level fluctuation was not the only factor determining benthic nematode abundance, diversity, and trophic categorization. Specific water body conditions affect benthic nematode community structure. Nematode communities are environmentally sensitive agent. Furthermore, the current findings might improve our understanding of aquaculture, as water level fluctuations affect benthic nematodes, which directly or indirectly affect the reared organisms.
... The structuring effect of sediment granulometry on nematode communities is well documented in both marine and limnetic habitats (e.g. Wasilewska, 1973;Zullini, 1974;Schiemer, 1978;Tudorancea and Zullini, 1989;Eyualem-Abebe et al., 2001;Traunspurger et al., 2021). A muddy environment is homogeneous and offers fewer microhabitats for nematodes, although Tobrilids and other taxonomic groups seem to thrive in muddy depositional zones (Zullini, 1974;Beier and Traunspurger, 2003a,b). ...
... Many studies on freshwater habitats have assessed the vertical distribution of nematodes in terms of species numbers (e.g. Traunspurger, 1996a,b;Traunspurger and Drews, 1996;Eyualem-Abebe et al., 2001;Traunspurger et al., 2015). Their general conclusion has been that species numbers are highest at or close to the sediment surface while decreasing in deeper sediment layers. ...
... Nevertheless, in the latter study a simple relationship between species numbers and water depth could not be established. Eyualem-Abebe et al. (2001) reported similarly inconclusive results with respect to depth-specific communities at some sites in Lake Tana, Ethiopia. However, there is also abundant evidence for an association of nematode communities with specific parts or depths of lakes (Schiemer, 1978;Traunspurger, 1995Traunspurger, , 1996aTraunspurger, ,b,c, 1997bTraunspurger, , 1998Eyualem-Abebe et al., 2001). ...
Mean nematode abundance ranges from ca. 1 000 to 10 000 000 individuals per m2.
Species richness usually range from 10 to 100, but >200 species per habitat can be found over the year.
Total biomass is usually between 1 and 100 mg wet weight per m2 (up to 10 g).
Deposit feeders, feeding mainly on bacteria, typically dominate aquatic habitats.
Species structure reacts to different abiotic and biotic drivers.
Species distributions form patterns evident at microscopic to global scales.
... Freshwater nematodes proved to be indicators of aquatic pollution or eutrophication, both on the community and on the individual level 6,9,10,13 . ...
The present paper deals with the study of Zooplankton community of Panchaganga river near Ichalkaranji, M.S. India. The qualitative and quantitative analysis of Zooplankton was done from two different sites, S1 - Ganesh temple and S2 - Shiradwad at regular interval of fifteenth day of every month. The different species of zooplanktons were identified. About 26 zooplankton species were recorded in five groups Protozoan, Rotifera , Cladocera, Copepode and Nematode.
... The bulk of research on nematode until very recently focused mainly on marine habitats, ignoring the inland water bodies of most parts of the world. Nematodes from African water bodies, except for South Africa, hardly received any attention to date [12]. The economic loss in the fishing industry and aquaculture and its zoonotic importance caused by nematode infections is not well known. ...
Background: Nile Tilapia a freshwater cichlid that is indigenous to the Nile basin and one of the world’s most
important food fishes. Owing to its hardy nature and its wide range of trophic and ecological adaptations and the
second most important cultured species. Even though, it is susceptible to the parasite.
Methods: A cross-sectional study was conducted from December 2017 to April 2018 to determine the prevalence
of internal nematode parasites of Nile Tilapia (Oreochromis niloticus) fish in a southwestern part of Lake Tana,
Central Gondar, Ethiopia. The study was performed on a total of 384 Oreochromis niloticus fish species which were
purposively selected from local fisherman caught using different mesh sized gill nets.
Results: The overall prevalence of internal nematode parasites in this study was 57.3% (220/384). The genera of
nematode identified in the body of Oreochromis niloticus were Contracaecum the most prevalent 209 (54.4%), the
second genus was Eustrongylides 7 (1.8%) and the list prevalent was Camallanus 4 (1%). The prevalence of nematode
was slightly higher in female 196 (58.2%) than male 188 (56.4%) fishes. Similarly, the infection rate in adult and
young and in larger and medium fish was higher.
Conclusion: This higher prevalence observed was predominantly related to the distribution of piscivorous birds
which are more abundant in an area, where there are high fishing activities and increase the number of discarded
filleted wastes. Peoples who have developed the habit of consuming raw fish are at higher risk of becoming infected
by the zoonotic nematode parasites. Therefore, awareness creation activities and control of fish parasites should be
conducted in the study Lake.
Keywords: Camallanus; Contracaecum; Eustrongylides; Fish; Lake Tana; Nematode; Nile Tilapia
... Approximately 71 % of the earth's surface is covered in water, of which only 3 % is freshwater (Danovaro et al. 2009). Nematodes are the most abundant and possibly the most diverse Metazoa in these water masses with freeliving nematodes present in mostly all freshwater environments (Eyualem-Abebe et al. 2001;Eyualem-Abebe et al. 2008). However, the taxonomy and ecology of this group of nematodes have received the least amount of attention globally compared to those of marine and terrestrial nematodes (Traunspurger 2000;Eyualem-Abebe et al. 2008). ...
Aphanolaimus strilliae n. sp. and Makatinus africanus n. sp. are described from freshwater sources in the Telperion Nature Reserve, Mpumalanga, South Africa. Aphanolaimus strilliae n. sp. is characterised by a body length of 1240–1613 μm, more than 800 body annules, lateral field originating between the first and second lateral body pore at the 34th–46th annule, first lateral body pore located at the 25th–35th annule, vagina V-shaped and bent anteriorly, 142–195 μm long uterus and 165–207 μm long tail with spinneret offset. This species is ovoviviparous and no males were found. Makatinus africanus n. sp. is characterised by a large, thick body (3228–4128 μm long, a = 30–39 wide), slightly set off lip region with amalgamated lips; 31–34 μm long odontostyle; long tongue-shaped cardia, and stout, short tail (30–43 μm long) with a small peg / digitate extension and male absent. Populations of three known species, Chronogaster africana, Eutobrilus annetteae and Neotobrilus ampiei, from fresh water at the Telperion Nature Reserve are described and scanning electron microscope graphs of these species published for the first time.
