The sperm ultrastructure of three Naididae (Paranais frici, P. litoralis and Stylaria lacustris) ... more The sperm ultrastructure of three Naididae (Paranais frici, P. litoralis and Stylaria lacustris) and two Lumbriculidae (Rhynchelmis brachycephala and R. alyonae) is decribed to supply spermatological evidence towards a better understanding of the phylogeny of the two families. Naidid spermatozoa were found to be similar to one another, particularly with regard to the acrosome (with the acrosome tube bent to one side), and the shape and number of mitochondria. The various morphological characters do not militate against the previously proposed inclusion of naidids within the Tubificidae. The two lumbriculid species examined showed a characteristic conical indentation at the apex of the nucleus, a feature up to now described only in Branchiobdellida, an annelid group with possible affinities to Lumbriculidae.
In Antarctic waters, the superfamily Lysianassoidea is one of the most important amphipod groups ... more In Antarctic waters, the superfamily Lysianassoidea is one of the most important amphipod groups both in terms of species number and abundance. Dominant members of this superfamily are species of the orchomenid complex, found throughout the Southern Ocean. This study presents the first molecular phylogenetic analysis based on a representative subset of the Antarctic species belonging to different orchomenid genera and hence provides a framework for a systematic revision of these taxa. The current classification of the orchomenid genera is mainly based on mouthpart morphology. The validity of these morphological characters was assessed by resolving phylogenetic relationships using nuclear 28S rRNA and mitochondrial cytochrome oxidase subunit I sequences. The molecular data rejected most of the previously proposed taxonomic subdivisions within this complex. The genera Abyssorchomene and Orchomenella as well as the subgenus Orchomenopsis appeared to be non-monophyletic. This implies that the supposed diagnostic characters are likely a result of convergent evolution. Further, our results indicated the necessity of a revision of the family-level systematics.
Sperm morphology and spermatogenesis were examined in the oligochaete annelid Isochaetides arenar... more Sperm morphology and spermatogenesis were examined in the oligochaete annelid Isochaetides arenarius, a species belonging to the subfamily Tubificinae inhabiting the sediments of Lake Baikal. As all tubificines, Isochaetides produces two types of spermatozoa, named eusperm and parasperm. The eusperm are the fertilizing male gametes and consist, in sequence, of an acrosome, a nucleus, a mitochondrial mid-piece, and a tail. The parasperm have the same general architecture, but differ in cytological details: the acrosome is shorter, devoid of a perforatorium, and the acrosome vesicle has a different, simpler, shape. The nucleus is much shorter and rectilinear (the eusperm nucleus is twisted). The mid-piece mitochondria are less numerous but their overall volume is larger. The flagellum has a plasma membrane largely separated from the axoneme, and is devoid of glycogen granules. After mating, the two sperm types gather in the spermathecae to form spermatozeugmata; in these structures the parasperm form an external sheath involving the centrally located eusperm and their tails are connected by conspicuous septate junctions. Parasperm nuclei are produced through a process of fragmentation of the 'spermatocytes', whereas the flagellar basal bodies are produced by a process similar to that giving rise to basal bodies in ciliated epithelia.
The phylogenetic relationships of the Clitellata were investigated using a data set with publishe... more The phylogenetic relationships of the Clitellata were investigated using a data set with published and new complete or partial 18S rRNA and mtCOI gene sequences of 13 and 49 taxa representing 8 and 14 families, respectively. Three different alignments were considered for 18S, and the possible influence of departures from rate constancy among sites was evaluated by analyses using a Gamma model of rate heterogeneity. Maximum-likelihood estimates of the shape parameter alpha of the Gamma distribution were very low, whatever the alignment or the gene considered, suggesting that phylogenetic reconstructions taking into account the rate heterogeneity among sites are likely to be the most reliable. Analyzed separately, the two genes did not resolve the relationships among the Clitellata, but the consensus tree was congruent with the morphology-based relationships. Our data suggest the inclusion of the Euhirudinea, Acanthobdellida, and Branchiobdellida in the Oligochaeta and suggest the Lumbriculidae as the link between both assemblages. Although separate analyses of both genes, as well as different alignments for the 18S rRNA sequences, yielded conflicting results concerning the phylogenetic position of leeches and leech-like worms vis-à-vis the Oligochaeta, subsequent analyses using the Gamma model greatly reduced the observed inconsistencies. Our analyses show that among the Clitellata, the leeches and the leech-like and gutless worms represent significantly faster evolving lineages. It is suggested that the observed higher mutation rates may be explained by the fact that these lineages contain almost exclusively commensal and/or parasitic taxa.
Spermatogenesis, spermatozoa, seminal receptacles and the transformations of sperm after mating w... more Spermatogenesis, spermatozoa, seminal receptacles and the transformations of sperm after mating were examined for the first time in the polychaete annelid Aeolosoma singulare from Lake BaikaL The structure of the spermatozoon in the coelomic cavity is very similar to that already described for A. litorale, in particular in the presence of a cytoplasmic droplet containing lysosomelike vesicles around the nuclear basis, However, comparison of coelomic spermatozoa with those stored in the sperm receptacles revealed a progressive reduction of the cytoplasmic droplet The cytoplasmic droplet can thus be considered as a sort of remnant of the spermiogenetic process in the mature spermatozoon, The seminal receptacles of A. singulare, like those of the other aeolosomatids, are epidermal formations; but in this species they have a multicellular organisation and penetrate the muscular layers to end deep inside the coelomic cavity. The spermatozoon of A, singulare was compared with those of polychaetes considered close to aeolosomatids, and was found to have characters in common only with potamodrilids,
By their antiquity, history, rarity, great depth in many instances and the presence of highly div... more By their antiquity, history, rarity, great depth in many instances and the presence of highly diverse faunas with many endemics, ancient lakes constitute ecosystems of a special nature, clearly apart from the large majority of extant lakes. While the fauna of these lakes is becoming better and better known for various animals groups, the Oligochaeta are still poorly known. Tubificidae and Naididae are found in each ancient lake. On the other hand, some families are restricted to only one lake, such as Aeolosomatidae and Proppapidae in Lake Baikal or Eudrilidae and Ocnerodrilidae (megadriles) in Lake Tanganyika, but such a distribution is probably due to a lack of knowledge or sampling biases. All ancient lakes have an endemic oligochaete fauna except Lake Kinneret (Israel). The oldest, Lake Baikal (20-25 Ma), holds the most abundant and diverse oligochaete fauna, in which species flocks are even recognizable or suspected. In contrast, the oligochaete fauna of the slightly younger Lake Tanganyika is very scarce. This is partly due to an obvious lack of studies, as the oligochaete fauna of other great African lakes is virtually unknown, but this might be the result of an environment in these lakes less favourable to oligochaetes. Some factors likely to interact with speciation in oligochaetes are discussed but nothing can be concluded to date. A recent interest in African great lakes revealed a more diverse oligochaete fauna than previously assumed but a better study of this fauna is still badly needed.
The impact of bioturbation in Lake Baikal sediments, particularly on rhythmic layering and mixing... more The impact of bioturbation in Lake Baikal sediments, particularly on rhythmic layering and mixing, was assessed by studying the actual vertical distribution of benthic animals in continuous accumulation zones selected by seismic survey (Vydrino Shoulder, Posolskoe Bank, Continent Ridge). To assess the influence of the bioturbation, animals were extracted from short cores and identified at the relevant taxonomic level. The faunal distribution is examined in parallel with the bioturbation tracks observed in thin section. Oligochaeta, Nematoda, Ostracoda, Copepoda, Gammaridae, Chironomidae and Hydrachnidia were found inhabiting the sediment. Among them, only oligochaete worms were assumed to have a significant impact on sediment mixing because of their "conveyor belt" feeding. The other two most abundantly sampled groups, nematods and copepods, belong to the interstitial fauna that has no significant impact on the vertical displacement of sediment particles and do not ingest the sediment. The presence of a benthic fauna as deep as 15 cm in the sediment indicates that the possibility of sediment disturbance by invertebrate activity cannot be dismissed in Lake Baikal. The effect of biological mixing is more limited in the deepest stations because the number of potential bioturbators is reduced, qualitatively as well as quantitatively. Located in the abyssal zone, Continent and Vydrino (but outside turbidites) deep stations appear to be most promising sediment records for tracking climate signal at high resolution.
1. Reliable assessments of groundwater biodiversity are urgently needed to resolve current issues... more 1. Reliable assessments of groundwater biodiversity are urgently needed to resolve current issues relating to the protection of aquifers. The assessment of groundwater biodiversity is hampered by the physical complexity and difficult access to the subterranean environment, which is related to the vastness, high degree of fragmentation and environmental heterogeneity of groundwater systems. Knowledge on groundwater biodiversity is also biased towards penetrable karstic habitats (caves), whereas other common habitats such as those found in porous aquifers have been neglected. This situation calls for a standardised and comprehensive strategy to sample an exhaustive and balanced set of groundwater habitats. 2. A standardised sampling protocol aimed at capturing the main sources of environmental heterogeneity within regions was applied in six regions across Europe. Four hierarchical levels were considered: (i) region (c. 400 km 2 ); (ii) basin (c. 100 km 2 ); (iii) aquifer type (karstic or porous) and (iv) habitat (hyporheic and phreatic zones for porous aquifers; saturated and unsaturated zones for karst aquifers). A total of 192 sampling sites equally distributed among habitats were sampled within each region. 3. Stygobiotic species richness significantly varied across regions, probably as a result of important difference in physical and biogeographical characteristics among the regions. Only one species (Graeteriella unisetigera) occurred in all six regions, underlining the narrow geographic range and high degree of endemism of stygobiotic fauna. The low frequency of occurrence of stygobionts also points to the importance of rarity in ground waters and its relevance for drawing up sampling designs. 4. Rarefaction curves were calculated to determine sampling efficiencies within each region. Despite the high sampling effort, the curves did not reach saturation, especially in the Cantabria, Lessinia and Krim regions, which had the greatest numbers of rare species. 5. Species accumulation curves were also calculated by considering the main sources of environmental heterogeneity among basins, aquifer types and habitats captured by the sampling protocol. In two regions (Roussillon and Jura) sampling efficiency was improved
1. The Pleistocene glaciations during the Quaternary appear to have resulted in an impoverished g... more 1. The Pleistocene glaciations during the Quaternary appear to have resulted in an impoverished groundwater fauna in northern Europe. Re-colonisation may have occurred either through long-distance dispersal from unglaciated southern areas or from local refugia. 2. The Belgian groundwater fauna was sampled at multiple sites, and its habitats characterised, to assess whether the composition of present-day stygobiotic assemblages can be attributed to either of these mechanisms. 3. A total of 202 sampling sites were selected in four hydrogeographic units of the Meuse River catchment. Sites were equally divided among the saturated and unsaturated zones of fractured aquifers (karst) and within the hyporheic and phreatic zones of porous aquifers. Seventeen environmental parameters were determined in parallel. 4. More than 140 species were recorded, including representatives of the Amphipoda, Syncarida and Nematoda. Thirty stygobiont species were identified, of which 10 species were new to the Belgian fauna, raising the total number of stygobiotic species in Belgium to 41. 5. The frequency of occurrences of stygobiotic species was always low, with 37% of the sampled sites lacking stygobionts. A few species were exclusive to one hydrological zone, although no statistically significant differences were detected in species richness at any of the four hierarchial levels considered (Meuse catchment = region, hydrogeographic units, aquifer type and hydrological zone). 6. Overall, results suggest that the stygobiotic fauna of Belgium is species-poor and mostly comprises widely distributed species with broad ecological tolerances. This supports the view that eurytopic species re-colonised the area by long-distance dispersal from refugia in southern Europe. The virtual absence of endemic species further suggests that the scenario of an ancient fauna that survived in local refugia is of minor importance.
Patrick Martin1, Liba Granina2, Koen Martens1 & Boudewijn Goddeeris1 1 Royal Belgian Institute of... more Patrick Martin1, Liba Granina2, Koen Martens1 & Boudewijn Goddeeris1 1 Royal Belgian Institute of Natural Sciences, Freshwater Biology Section, rue Vautier 29, B-1000 Brussels, Belgium 2 Limnological Institute of the Siberian Division of the Russian Academy of Sciences, Ulan-...
... Worms were stained with alcoholic carmine and moun-ted in Canada balsam. ... n. (Fig. 1) Holo... more ... Worms were stained with alcoholic carmine and moun-ted in Canada balsam. ... n. (Fig. 1) Holotype. IRSc.NB, IG 28051, slide 95.065.9, mature specimen, incomplete (first 15 segments only), dissected, stained in alcoholic carmine and mounted in Canada balsam. Type locality. ...
There has been a significant body of literature on species flock definition but not so much about... more There has been a significant body of literature on species flock definition but not so much about practical means to appraise them. We here apply the five criteria of Eastman and McCune for detecting species flocks in four taxonomic components of the benthic fauna of the Antarctic shelf: teleost fishes, crinoids (feather stars), echinoids (sea urchins) and crustacean arthropods. Practical limitations led us to prioritize the three historical criteria (endemicity, monophyly, species richness) over the two ecological ones (ecological diversity and habitat dominance). We propose a new protocol which includes an iterative fine-tuning of the monophyly and endemicity criteria in order to discover unsuspected flocks. As a result nine « full » species flocks (fulfilling the five criteria) are briefly described. Eight other flocks fit the three historical criteria but need to be further investigated from the ecological point of view (here called « core flocks »). The approach also shows that some candidate taxonomic components are no species flocks at all. The present study contradicts the paradigm that marine species flocks are rare. The hypothesis according to which the Antarctic shelf acts as a species flocks generator is supported, and the approach indicates paths for further ecological studies and may serve as a starting point to investigate the processes leading to flock-like patterning of biodiversity.
Recent molecular analyses revealed that several so-called ''circum-Antarctic'' benthic crustacean... more Recent molecular analyses revealed that several so-called ''circum-Antarctic'' benthic crustacean species appeared to be complexes of cryptic species with restricted distributions. In this study we used a DNA barcoding approach based on mitochondrial cytochrome oxidase I gene sequences in order to detect possible cryptic diversity and to test the circumpolarity of some lysianassoid species. The orchomenid genus complex consists of the genera Abyssorchomene, Falklandia, Orchomenella, Orchomenyx and Pseudorchomene. Species of this genus complex are found throughout the Southern Ocean and show a high species richness and level of endemism. In the majority of the studied species, a genetic homogeneity was found even among specimens from remote sampling sites, which indicates a possible circum-Antarctic and eurybathic distribution. In four investigated species (Orchomenella (Orchomenopsis) acanthurus, Orchomenella (Orchomenopsis) cavimanus, Orchomenella (Orchomenella) franklini and Orchomenella (Orchomenella) pinguides), genetically divergent lineages and possible cryptic taxa were revealed. After a detailed morphological analysis, O. (O.) pinguides appeared to be composed of two distinct species, formerly synonymized under O. (O.) pinguides. The different genetic patterns observed in these orchomenid species might be explained by the evolutionary histories undergone by these species and by their different dispersal and gene flow capacities.
The sperm ultrastructure of three Naididae (Paranais frici, P. litoralis and Stylaria lacustris) ... more The sperm ultrastructure of three Naididae (Paranais frici, P. litoralis and Stylaria lacustris) and two Lumbriculidae (Rhynchelmis brachycephala and R. alyonae) is decribed to supply spermatological evidence towards a better understanding of the phylogeny of the two families. Naidid spermatozoa were found to be similar to one another, particularly with regard to the acrosome (with the acrosome tube bent to one side), and the shape and number of mitochondria. The various morphological characters do not militate against the previously proposed inclusion of naidids within the Tubificidae. The two lumbriculid species examined showed a characteristic conical indentation at the apex of the nucleus, a feature up to now described only in Branchiobdellida, an annelid group with possible affinities to Lumbriculidae.
In Antarctic waters, the superfamily Lysianassoidea is one of the most important amphipod groups ... more In Antarctic waters, the superfamily Lysianassoidea is one of the most important amphipod groups both in terms of species number and abundance. Dominant members of this superfamily are species of the orchomenid complex, found throughout the Southern Ocean. This study presents the first molecular phylogenetic analysis based on a representative subset of the Antarctic species belonging to different orchomenid genera and hence provides a framework for a systematic revision of these taxa. The current classification of the orchomenid genera is mainly based on mouthpart morphology. The validity of these morphological characters was assessed by resolving phylogenetic relationships using nuclear 28S rRNA and mitochondrial cytochrome oxidase subunit I sequences. The molecular data rejected most of the previously proposed taxonomic subdivisions within this complex. The genera Abyssorchomene and Orchomenella as well as the subgenus Orchomenopsis appeared to be non-monophyletic. This implies that the supposed diagnostic characters are likely a result of convergent evolution. Further, our results indicated the necessity of a revision of the family-level systematics.
Sperm morphology and spermatogenesis were examined in the oligochaete annelid Isochaetides arenar... more Sperm morphology and spermatogenesis were examined in the oligochaete annelid Isochaetides arenarius, a species belonging to the subfamily Tubificinae inhabiting the sediments of Lake Baikal. As all tubificines, Isochaetides produces two types of spermatozoa, named eusperm and parasperm. The eusperm are the fertilizing male gametes and consist, in sequence, of an acrosome, a nucleus, a mitochondrial mid-piece, and a tail. The parasperm have the same general architecture, but differ in cytological details: the acrosome is shorter, devoid of a perforatorium, and the acrosome vesicle has a different, simpler, shape. The nucleus is much shorter and rectilinear (the eusperm nucleus is twisted). The mid-piece mitochondria are less numerous but their overall volume is larger. The flagellum has a plasma membrane largely separated from the axoneme, and is devoid of glycogen granules. After mating, the two sperm types gather in the spermathecae to form spermatozeugmata; in these structures the parasperm form an external sheath involving the centrally located eusperm and their tails are connected by conspicuous septate junctions. Parasperm nuclei are produced through a process of fragmentation of the 'spermatocytes', whereas the flagellar basal bodies are produced by a process similar to that giving rise to basal bodies in ciliated epithelia.
The phylogenetic relationships of the Clitellata were investigated using a data set with publishe... more The phylogenetic relationships of the Clitellata were investigated using a data set with published and new complete or partial 18S rRNA and mtCOI gene sequences of 13 and 49 taxa representing 8 and 14 families, respectively. Three different alignments were considered for 18S, and the possible influence of departures from rate constancy among sites was evaluated by analyses using a Gamma model of rate heterogeneity. Maximum-likelihood estimates of the shape parameter alpha of the Gamma distribution were very low, whatever the alignment or the gene considered, suggesting that phylogenetic reconstructions taking into account the rate heterogeneity among sites are likely to be the most reliable. Analyzed separately, the two genes did not resolve the relationships among the Clitellata, but the consensus tree was congruent with the morphology-based relationships. Our data suggest the inclusion of the Euhirudinea, Acanthobdellida, and Branchiobdellida in the Oligochaeta and suggest the Lumbriculidae as the link between both assemblages. Although separate analyses of both genes, as well as different alignments for the 18S rRNA sequences, yielded conflicting results concerning the phylogenetic position of leeches and leech-like worms vis-à-vis the Oligochaeta, subsequent analyses using the Gamma model greatly reduced the observed inconsistencies. Our analyses show that among the Clitellata, the leeches and the leech-like and gutless worms represent significantly faster evolving lineages. It is suggested that the observed higher mutation rates may be explained by the fact that these lineages contain almost exclusively commensal and/or parasitic taxa.
Spermatogenesis, spermatozoa, seminal receptacles and the transformations of sperm after mating w... more Spermatogenesis, spermatozoa, seminal receptacles and the transformations of sperm after mating were examined for the first time in the polychaete annelid Aeolosoma singulare from Lake BaikaL The structure of the spermatozoon in the coelomic cavity is very similar to that already described for A. litorale, in particular in the presence of a cytoplasmic droplet containing lysosomelike vesicles around the nuclear basis, However, comparison of coelomic spermatozoa with those stored in the sperm receptacles revealed a progressive reduction of the cytoplasmic droplet The cytoplasmic droplet can thus be considered as a sort of remnant of the spermiogenetic process in the mature spermatozoon, The seminal receptacles of A. singulare, like those of the other aeolosomatids, are epidermal formations; but in this species they have a multicellular organisation and penetrate the muscular layers to end deep inside the coelomic cavity. The spermatozoon of A, singulare was compared with those of polychaetes considered close to aeolosomatids, and was found to have characters in common only with potamodrilids,
By their antiquity, history, rarity, great depth in many instances and the presence of highly div... more By their antiquity, history, rarity, great depth in many instances and the presence of highly diverse faunas with many endemics, ancient lakes constitute ecosystems of a special nature, clearly apart from the large majority of extant lakes. While the fauna of these lakes is becoming better and better known for various animals groups, the Oligochaeta are still poorly known. Tubificidae and Naididae are found in each ancient lake. On the other hand, some families are restricted to only one lake, such as Aeolosomatidae and Proppapidae in Lake Baikal or Eudrilidae and Ocnerodrilidae (megadriles) in Lake Tanganyika, but such a distribution is probably due to a lack of knowledge or sampling biases. All ancient lakes have an endemic oligochaete fauna except Lake Kinneret (Israel). The oldest, Lake Baikal (20-25 Ma), holds the most abundant and diverse oligochaete fauna, in which species flocks are even recognizable or suspected. In contrast, the oligochaete fauna of the slightly younger Lake Tanganyika is very scarce. This is partly due to an obvious lack of studies, as the oligochaete fauna of other great African lakes is virtually unknown, but this might be the result of an environment in these lakes less favourable to oligochaetes. Some factors likely to interact with speciation in oligochaetes are discussed but nothing can be concluded to date. A recent interest in African great lakes revealed a more diverse oligochaete fauna than previously assumed but a better study of this fauna is still badly needed.
The impact of bioturbation in Lake Baikal sediments, particularly on rhythmic layering and mixing... more The impact of bioturbation in Lake Baikal sediments, particularly on rhythmic layering and mixing, was assessed by studying the actual vertical distribution of benthic animals in continuous accumulation zones selected by seismic survey (Vydrino Shoulder, Posolskoe Bank, Continent Ridge). To assess the influence of the bioturbation, animals were extracted from short cores and identified at the relevant taxonomic level. The faunal distribution is examined in parallel with the bioturbation tracks observed in thin section. Oligochaeta, Nematoda, Ostracoda, Copepoda, Gammaridae, Chironomidae and Hydrachnidia were found inhabiting the sediment. Among them, only oligochaete worms were assumed to have a significant impact on sediment mixing because of their "conveyor belt" feeding. The other two most abundantly sampled groups, nematods and copepods, belong to the interstitial fauna that has no significant impact on the vertical displacement of sediment particles and do not ingest the sediment. The presence of a benthic fauna as deep as 15 cm in the sediment indicates that the possibility of sediment disturbance by invertebrate activity cannot be dismissed in Lake Baikal. The effect of biological mixing is more limited in the deepest stations because the number of potential bioturbators is reduced, qualitatively as well as quantitatively. Located in the abyssal zone, Continent and Vydrino (but outside turbidites) deep stations appear to be most promising sediment records for tracking climate signal at high resolution.
1. Reliable assessments of groundwater biodiversity are urgently needed to resolve current issues... more 1. Reliable assessments of groundwater biodiversity are urgently needed to resolve current issues relating to the protection of aquifers. The assessment of groundwater biodiversity is hampered by the physical complexity and difficult access to the subterranean environment, which is related to the vastness, high degree of fragmentation and environmental heterogeneity of groundwater systems. Knowledge on groundwater biodiversity is also biased towards penetrable karstic habitats (caves), whereas other common habitats such as those found in porous aquifers have been neglected. This situation calls for a standardised and comprehensive strategy to sample an exhaustive and balanced set of groundwater habitats. 2. A standardised sampling protocol aimed at capturing the main sources of environmental heterogeneity within regions was applied in six regions across Europe. Four hierarchical levels were considered: (i) region (c. 400 km 2 ); (ii) basin (c. 100 km 2 ); (iii) aquifer type (karstic or porous) and (iv) habitat (hyporheic and phreatic zones for porous aquifers; saturated and unsaturated zones for karst aquifers). A total of 192 sampling sites equally distributed among habitats were sampled within each region. 3. Stygobiotic species richness significantly varied across regions, probably as a result of important difference in physical and biogeographical characteristics among the regions. Only one species (Graeteriella unisetigera) occurred in all six regions, underlining the narrow geographic range and high degree of endemism of stygobiotic fauna. The low frequency of occurrence of stygobionts also points to the importance of rarity in ground waters and its relevance for drawing up sampling designs. 4. Rarefaction curves were calculated to determine sampling efficiencies within each region. Despite the high sampling effort, the curves did not reach saturation, especially in the Cantabria, Lessinia and Krim regions, which had the greatest numbers of rare species. 5. Species accumulation curves were also calculated by considering the main sources of environmental heterogeneity among basins, aquifer types and habitats captured by the sampling protocol. In two regions (Roussillon and Jura) sampling efficiency was improved
1. The Pleistocene glaciations during the Quaternary appear to have resulted in an impoverished g... more 1. The Pleistocene glaciations during the Quaternary appear to have resulted in an impoverished groundwater fauna in northern Europe. Re-colonisation may have occurred either through long-distance dispersal from unglaciated southern areas or from local refugia. 2. The Belgian groundwater fauna was sampled at multiple sites, and its habitats characterised, to assess whether the composition of present-day stygobiotic assemblages can be attributed to either of these mechanisms. 3. A total of 202 sampling sites were selected in four hydrogeographic units of the Meuse River catchment. Sites were equally divided among the saturated and unsaturated zones of fractured aquifers (karst) and within the hyporheic and phreatic zones of porous aquifers. Seventeen environmental parameters were determined in parallel. 4. More than 140 species were recorded, including representatives of the Amphipoda, Syncarida and Nematoda. Thirty stygobiont species were identified, of which 10 species were new to the Belgian fauna, raising the total number of stygobiotic species in Belgium to 41. 5. The frequency of occurrences of stygobiotic species was always low, with 37% of the sampled sites lacking stygobionts. A few species were exclusive to one hydrological zone, although no statistically significant differences were detected in species richness at any of the four hierarchial levels considered (Meuse catchment = region, hydrogeographic units, aquifer type and hydrological zone). 6. Overall, results suggest that the stygobiotic fauna of Belgium is species-poor and mostly comprises widely distributed species with broad ecological tolerances. This supports the view that eurytopic species re-colonised the area by long-distance dispersal from refugia in southern Europe. The virtual absence of endemic species further suggests that the scenario of an ancient fauna that survived in local refugia is of minor importance.
Patrick Martin1, Liba Granina2, Koen Martens1 & Boudewijn Goddeeris1 1 Royal Belgian Institute of... more Patrick Martin1, Liba Granina2, Koen Martens1 & Boudewijn Goddeeris1 1 Royal Belgian Institute of Natural Sciences, Freshwater Biology Section, rue Vautier 29, B-1000 Brussels, Belgium 2 Limnological Institute of the Siberian Division of the Russian Academy of Sciences, Ulan-...
... Worms were stained with alcoholic carmine and moun-ted in Canada balsam. ... n. (Fig. 1) Holo... more ... Worms were stained with alcoholic carmine and moun-ted in Canada balsam. ... n. (Fig. 1) Holotype. IRSc.NB, IG 28051, slide 95.065.9, mature specimen, incomplete (first 15 segments only), dissected, stained in alcoholic carmine and mounted in Canada balsam. Type locality. ...
There has been a significant body of literature on species flock definition but not so much about... more There has been a significant body of literature on species flock definition but not so much about practical means to appraise them. We here apply the five criteria of Eastman and McCune for detecting species flocks in four taxonomic components of the benthic fauna of the Antarctic shelf: teleost fishes, crinoids (feather stars), echinoids (sea urchins) and crustacean arthropods. Practical limitations led us to prioritize the three historical criteria (endemicity, monophyly, species richness) over the two ecological ones (ecological diversity and habitat dominance). We propose a new protocol which includes an iterative fine-tuning of the monophyly and endemicity criteria in order to discover unsuspected flocks. As a result nine « full » species flocks (fulfilling the five criteria) are briefly described. Eight other flocks fit the three historical criteria but need to be further investigated from the ecological point of view (here called « core flocks »). The approach also shows that some candidate taxonomic components are no species flocks at all. The present study contradicts the paradigm that marine species flocks are rare. The hypothesis according to which the Antarctic shelf acts as a species flocks generator is supported, and the approach indicates paths for further ecological studies and may serve as a starting point to investigate the processes leading to flock-like patterning of biodiversity.
Recent molecular analyses revealed that several so-called ''circum-Antarctic'' benthic crustacean... more Recent molecular analyses revealed that several so-called ''circum-Antarctic'' benthic crustacean species appeared to be complexes of cryptic species with restricted distributions. In this study we used a DNA barcoding approach based on mitochondrial cytochrome oxidase I gene sequences in order to detect possible cryptic diversity and to test the circumpolarity of some lysianassoid species. The orchomenid genus complex consists of the genera Abyssorchomene, Falklandia, Orchomenella, Orchomenyx and Pseudorchomene. Species of this genus complex are found throughout the Southern Ocean and show a high species richness and level of endemism. In the majority of the studied species, a genetic homogeneity was found even among specimens from remote sampling sites, which indicates a possible circum-Antarctic and eurybathic distribution. In four investigated species (Orchomenella (Orchomenopsis) acanthurus, Orchomenella (Orchomenopsis) cavimanus, Orchomenella (Orchomenella) franklini and Orchomenella (Orchomenella) pinguides), genetically divergent lineages and possible cryptic taxa were revealed. After a detailed morphological analysis, O. (O.) pinguides appeared to be composed of two distinct species, formerly synonymized under O. (O.) pinguides. The different genetic patterns observed in these orchomenid species might be explained by the evolutionary histories undergone by these species and by their different dispersal and gene flow capacities.
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