Effect of environmental stress on clonal structure of Eucypris virens (Crustacea, Ostracoda)

Environmental stress imposes strong natural selection on clonal populations, promoting evolutionary change in clonal structure. Environmental stress may also lead to reduction in population size, which together with clonal selection may reduce genotypic diversity of the local populations. We examined how clonal structure in wild-collected samples of two parthenogenetic populations of the freshwater ostracod Eucypris virens responded to hypersalinity and starvation, and the combination of the two stressors. We applied the stress treatments in a factorial design for one generation. When 60% of the individuals per experimental unit had died, post-experimental clonal structure was compared to that of the start of the experiment, which reflected the field conditions. We used five polymorphic allozyme loci as genotype markers. All stress treatments reduced survival compared to the control treatment. In the population "Rivalazzetto”, we observed a reduction of clonal richness in the control treatment, with the initially dominant clone maintaining dominance. This may have resulted from interclonal competition and clone-specific survival under the different laboratory conditions. Clonal richness remained high in the salinity treatment while it was reduced in the combined stress and starvation treatments. In the population "Fornovo”, clonal richness reduced in all treatments including control, while the salinity and combined stress treatment reduced clonal evenness. The clone dominating at the start of the experiment increased in frequency in all treatments, but the change in clonal structure during the experiment was more pronounced in this population. These results suggest that in some conditions an intermediate level of environmental stress may lessen the decline in genetic diversity by strong inter-clonal competition. Moreover, the variation in clonal structure among the stress treatments and distinct genetic backgrounds indicates that more general predictions of stress effects on clonal structure may be difficul

Dynamics of sexual and parthenogenetic populations of Eucypris virens (Crustacea: Ostracoda) in three temporary ponds

Eucyprisvirens is a freshwater ostracod in which both sexual reproduction and parthenogenesis occur. Sympatric coexistence of both reproductive modes is known in zones of overlap. This renders the species a potentially valuable model organism to study the ‘queen of evolutionary problems', i.e. why sex is so successful despite its costs (paradox of sex). In order to maximally exploit this potential, a broad knowledge of the species' ecology is essential, including an understanding of its life history and population dynamics. Here, the phenology of the species was followed in three temporary ponds through monthly (Spain) or fortnightly (Poland) samplings, throughout an inundation period. This study confirms the wide ecological tolerances of E.virens. Although the species is generally assumed to be univoltine, two hatching periods were observed in the Spanish sites. Biotic interactions, especially predation, appear to be the important determinants of population dynamics in long-hydroperiod sites. Abiotic conditions may influence population dynamics through their impact on egg hatching. In the site with male presence, the initially female-biased sex ratio evolved towards a balanced sex ratio through the season. No consistent differences in limb morphology were observed between females originating from the three study sites. On the other hand, valve size of adult females varied among sites, possibly influenced by local environmental conditions (mainly salinity and pH) as well as the expected genetic diversit

Detection of bacterial endosymbionts in freshwater crustaceans: the applicability of non-degenerate primers to amplify the bacterial 16S rRNA gene

Bacterial endosymbionts of aquatic invertebrates remain poorly studied. This is at least partly due to a lack of suitable techniques and primers for their identification. We designed a pair of non-degenerate primers which enabled us to amplify a fragment of ca. 500 bp of the 16S rRNA gene from various known bacterial endosymbiont species. By using this approach, we identified four bacterial endosymbionts, two endoparasites and one uncultured bacterium in seven, taxonomically diverse, freshwater crustacean hosts from temporary waters across a wide geographical area. The overall efficiency of our new WOLBSL and WOLBSR primers for amplification of the bacterial 16S rRNA gene was 100%. However, if different bacterial species from one sample were amplified simultaneously, sequences were illegible, despite a good quality of PCR products. Therefore, we suggest using our primers at the first stage of bacterial endosymbiont identification. Subsequently, genus specific primers are recommended. Overall, in the era of next-generation sequencing our method can be used as a first simple and low-cost approach to identify potential microbial symbionts associated with freshwater crustaceans using simple Sanger sequencing. The potential to detected bacterial symbionts in various invertebrate hosts in such a way will facilitate studies on host-symbiont interactions and coevolution

Ostracoda of the Eemian Interglacial at Kruklanki in NE Poland

The assemblage of lacustrine ostracods found in the Eemian Interglacial sediments at Kruklanki (Masurian Lake Dis- s q trict, northeastern Poland) contains 18 species belonging to 13 genera. The most dominant species are Candona neglecta Sars, 1887, Limnocytherina sanctipatricii (Brady et Robertson, 1869), Limnocythere inopinala (Baird, 1843) and Candona candida (O.F. Muller, 1776). Cyclocypris serena (Koch, 1838), llyocypris decipiens Masi, 1905, Pseudocandona insculpta (G.W. Muller, 1900) and Leucocythere mirabilis Kaufmann, 1892 are recorded for the first time from the Eemian of Poland; the latter two species are also new for the Eemian lacustrine deposits of Europe. The ecological requirements of the recognised ostracod species as well as their geographic ranges in the Quaternary of Europe are summarised. Based on these data, past habitat type is estimated as a deeper littoral of a lake with reasonably cold, well-oxygenated and calcium-rich waters. The present state of knowledge of the Eemian ostracods from Poland is reviewed and their comparison with the Eemian ostracod assemblages from Europe is briefly given. Comparison of the ostracod fauna! assemblage from Kruklanki with those from other Eemian sites in Poland enables to establish and describe one general type of ostracod assemblages characteristic for lacustrine littoral in this interglacial

Biodiversity of Non-Marine Ostracoda (Crustacea) of Botswana: An Annotated Checklist with Notes on Distribution

Botswana constitutes a major gap in our knowledge of the distribution of Ostracoda in the region of Southern Africa, restraining thorough biogeographic interpretations. We combine records from previously published surveys along with our own field collections to provide a collation of living and fossil (Late Pleistocene to Holocene) Ostracoda recorded in Botswana. Our survey yielded 17 species, of which nine species have not been recorded before in the country. Including the present update, 54 species (45 living and nine fossil or subfossil) belonging to 22 genera of five families (with 76% species belonging to the family Cyprididae) are currently reported from Botswana. Yet, 23 taxa are left in open nomenclature, indicating the urgent need for sound systematic studies on harmonizing taxonomy of Southern African ostracods, especially of those inhabiting small temporary waterbodies, considered as threatened with extinction before being properly described or discovered. This updated checklist provides detailed information about the distribution and habitat of each recorded species. Species richness, distribution patterns, and diversity of ostracod species regionally and in different freshwater ecoregions are also discussed. We found low alpha (site) diversity (mean 3.3 species per site) and a significant difference in species composition and beta diversity of the Okavango ecoregion versus the Kalahari and Zambezian Lowveld ecoregions

Freshwater Ostracoda (Crustacea) of Inari Lapland in northern Finland

Collections of ostracods from various habitats in and around Lake Inari, Finnish Lapland, provide the first record of these crustaceans from Finland north of the Arctic Circle. From a total of 35 sites visited, 14 species were collected, out of which four appeared to be new to Finland: Fabaeformiscandona lapponica, Pseudocandona pratensis, Eucypris pigra and Paralimnocythere relicta. Two major assemblage groups were recognised by clustering classification and multi-dimensional scaling ordination, one dominated by Cyclocypris ovum, the second by Candona candida. Taxonomic diversity of the most assemblages was of expected range based on the inventory of 53 freshwater species of Finland

Biodiversity of Non-Marine Ostracoda (Crustacea) of Botswana: An Annotated Checklist with Notes on Distribution

Botswana constitutes a major gap in our knowledge of the distribution of Ostracoda in the region of Southern Africa, restraining thorough biogeographic interpretations. We combine records from previously published surveys along with our own field collections to provide a collation of living and fossil (Late Pleistocene to Holocene) Ostracoda recorded in Botswana. Our survey yielded 17 species, of which nine species have not been recorded before in the country. Including the present update, 54 species (45 living and nine fossil or subfossil) belonging to 22 genera of five families (with 76% species belonging to the family Cyprididae) are currently reported from Botswana. Yet, 23 taxa are left in open nomenclature, indicating the urgent need for sound systematic studies on harmonizing taxonomy of Southern African ostracods, especially of those inhabiting small temporary waterbodies, considered as threatened with extinction before being properly described or discovered. This updated checklist provides detailed information about the distribution and habitat of each recorded species. Species richness, distribution patterns, and diversity of ostracod species regionally and in different freshwater ecoregions are also discussed. We found low alpha (site) diversity (mean 3.3 species per site) and a significant difference in species composition and beta diversity of the Okavango ecoregion versus the Kalahari and Zambezian Lowveld ecoregions

The non-marine Ostracoda of Lapland: changes over the past century

Novel faunistic data are presented from the poorly explored area of northern Lapland and comparisons are made between the present day ostracod diversity and historical records from a century ago. Twenty sites were sampled across Norwegian, Swedish and Finnish Lapland: eight to the west of the Scandinavian Mountain range, where the climate is milder under the influence of the Gulfstream, and 12 sites in the slope area east of these mountains, where the impact of the continental climate is stronger. The sample sites were mainly peat bogs fed by springs (the dominant habitat type in the study area), but also included helocrene springs, ditches, ponds and the littoral zone of lakes. In total 4376 individuals belonging to 16 species were collected. The most widespread and abundant species were Cyclocypris ovum, Candona candida and Pseudocandona rostrata, whereas Cyclocypris serena, Cryptocandona vavrai and Eucypris pigra were least abundant. The diversity of the ostracod assemblages to the west and to the east of the Scandinavian Mountains was significantly different, as measured by the Shannon diversity index. Mean values were 0.36 (western slopes) and 0.84 (eastern slopes). Three assemblage types were distinguished using UPGMA cluster analysis, with C. ovum, C. candida and P. rostrata as the three characteristic species. However, no statistically significant differences were revealed between the ostracod site assemblages when grouped geographically into west and east of the Scandinavian Mountains. Our results did not show any significant correlation between the Bray-Curtis similarity of the ostracod assemblages and the geographical separation between sites. The most marked difference in ostracod diversity between the present data and the records from the beginning of the 20th century seems to be a retreat of some Arctic species from the Lapland area and a shift of a few eurytopic species further to the north of Lapland. Possible factors influencing this shift are discussed

Crustacean species new to Spitsbergen with notes on the polymorphism and the subfossil preservation of Cytherissa lacustris (G. O. Sars)

The copepods Limnocalanus macrurus G. O. Sars and Eucyclops serrulatus (Fisch.) and the ostracode Cytherissa lacustris (G. O. Sars), hitherto unknown on Spitsbergen, were found in Lake Rewatnet, the last species also in Lake Svartvatnet. Samples from parthenogenetic populations of C. lacustris showed a complete lack of electrophoretically detectable variability at four enzyme-encoding loci, two of which are highly variable in mainland populations. However, morphological variation in the carapace length and nodation was no less than in the mainland populations. The carapace valves of C. lacustris do not preserve well in the sediments of Rewatnet