Tadeusz Namiotko

Exceptional cryptic diversity and multiple origins of parthenogenesis in a freshwater ostracod.

The persistence of asexual reproduction in many taxa depends on a balance between the origin of new asexual lineages and the extinction of old ones. This turnover determines the diversity of extant asexual populations and so influences the interaction between sexual and asexual modes of reproduction. Species with mixed reproduction, like the freshwater ostracod (Crustacea) morphospecies Eucypris virens, are a good model to examine these dynamics. This species is also a geographic parthenogen, in which sexual females and males co-exist with asexual females in the circum-Mediterranean area only, whereas asexual females occur all over Europe. A molecular phylogeny of E. virens based on the mitochondrial COI and 16S fragments is presented. It is characterised by many distinct clusters of haplotypes which are either exclusively sexual or asexual, with only one exception, and are often separated by deep branches. Analysis of the phylogeny reveals an astonishing cryptic diversity, which indicates the existence of a species complex with more than 40 cryptic taxa. We therefore suggest a revision of the single species status of E. virens. The phylogeny indicates multiple transitions from diverse sexual ancestor populations to asexuality. Although many transitions appear to be ancient, we argue that this may be an artefact of the existence of unsampled or extinct sexual lineages.

Developmental trajectories in geographically separated populations of non-marine ostracods: morphometric applications for palaeoecological studies

Developmental trajectories refer here to patterns of size and shape changes in ostracod valves during the sequence of post-embryonic growth stages. The information obtained from the study of such patterns has significant applications for evolutionary biology and/or (palaeo) ecology. Using geometric morphometrics methods, we describe the developmental trajectories of three ostracod species with valves retrieved from the sediments of lakes Mondsee (Austria), Hańcza (Poland) and Iseo (Italy). Size and shape data result in distinct developmental trajectories. Ontogenetic changes agree with predictions of Prizbram’s and Brooks’ laws. Patterns of valve shape change provide information which might be of use to the taxonomic definition of evolutionary lineages and to the development of studies of allometry and heterochrony in non-marine ostracods.

Evolutionary and taxonomic aspects within the species group Pseudocandona eremita (Vejdovsky ´ ) (Ostracoda, Candonidae)

The contribution deals with evolutionary and taxonomic aspects of the stygobitic ostracod lineage Pseudocandona eremita (Ostracoda, Candonidae). It is based on a comparative study of the morphology of both the carapace and limbs of individuals belonging to eight populations from Romania (three reproducing bisexually, the others by parthenogenesis). Left valves display various outline shapes, classified in two morphotypes, the “dorsally rounded shape” and the “triangular shape”. The intra- and interpopulation shape variability of these valves is described using geometric morphometrics and multivariate statistics. It is shown that the more flat carapace occurs frequently in populations living in gravel-sand habitats. Moreover, variability of 12 morphological limb characters taken on females is quantitatively evaluated by discriminant analysis. The character state of the m process of the male copulatory organ gives the most reliable information for the separation of the three bisexual populations in different species: P. serbani Danielopol, P. danubialis sp. nov. and P. transylvanica sp. nov. Short descriptions of the latter two species are presented. For the five parthenogenetic populations where no particular discriminant trait could be found, a solution of compromise is adopted, i.e. they are temporary assigned to Pseudocandona eremita (Vejdovský, 1882, Thierische Organismen der Brunnenwasser von Prag. Prag) sensu lato.

On the origin and evolution of a new anchialine stygobitic Microceratina species (Crustacea, Ostracoda) from Christmas Island (Indian Ocean)

Marine species of the ostracod genus Microceratina Swanson (Cytheruridae, Eucytherurinae) were until now known only from their hard parts, the valves and carapaces, as no living animals have been described. Here we report the first living population, from a tropical anchialine cave. The description of the limbs and hard parts of this new taxon, M. martensi sp. nov., enhances our understanding of the origin and evolution of the cave-dwelling Microceratina – the new species and M. pseudoamfibola (Barbeito-Gonzalez) from an anchialine cave in Southern Italy – and clarifies their affinities with other Eucytherurinae species. Microceratina is known from both Recent and fossil species (Quaternary, Tertiary and Late Cretaceous) from shelf and deep-sea habitats and/or sedimentary facies, located in the Pacific Ocean (along the Australian and New Zealand coasts), the Mediterranean (Greece and Italy), the North Atlantic (British Isles) and the Baltic Sea (Rügen Island). This suggests that the Microceratina group spread through the expanding Tethys Ocean. The morphological traits of the two cave-dwelling species reflect their ecological conditions. Cave-dwelling Microceratina species appear to have originated from epigean shallow water species predisposed to colonize subterranean habitats.

Redefinition of the genus Typhlocypris Vejdovský, 1882 (Ostracoda, Candonidae)

The taxonomy of the genus Typhlocypris Vejdovský, 1882 is reviewed. New morphological information on Typhlocypris eremita (Vejdovský, 1882), the type species of the genus, is provided, and a new reference material is presented. The generic diagnosis is emended with details derived from the developmental trajectory of the valves, from the juvenile stage A-3 to the adult. Those criteria clearly differentiate Typhlocypris from the related genus Pseudocandona Kaufmann, 1900. As here redefined, Typhlocypris is a phylogentic lineage of the subfamily Candoninae containing extant species presently living in aquatic subterranean habitats and fossil species recovered from non-marine Late Palaeogene to Neogene and Quaternary deposits in Europe and western Asia. The type species of Typhlocypris is considered a metaspecies, taxonomically treated as T. eremita (sensu lato), which includes populations resembling the newly designated reference material. The homeomorphic triangular valve shape of the Candoninae is discussed. Careful examination of the valve morphology of Typhlocypris combined with the analysis of limb traits helps to distinguish representatives of this genus from unrelated phylogenetic groups presenting similar triangularly shaped valves. It is emphasised that for a useful description of Typhlocypris taxa both transmitted light and scanning electron microscopy are necessary.

REDESCRIPTION OF TWO RARE HYPOGEAN SPECIES OF THE GENUS CRYPTOCANDONA KAUFMANN (OSTRACODA)

Cryptocandona phreaticola(Kiefer & Klie, 1927) and C. leruthi (Klie, 1936) are redecribed on the basis of type specimens, which allows (1) to present their morphology in detail, (2) to compare both species, and (3) to emphasize differential diagnostic characters of these species within the genus. They appear to be similar to each other and to come close to C. kieferi (Klie, 1938). Known data on the distribution and ecology of both redescribed species are also briefly summarized.

Ostracod Assemblages in the Frasassi Caves and Adjacent Sulfidic Spring and Sentino River in the Northeastern Apennines of Italy

Rich, diverse assemblages comprising a total (live + dead) of twenty-one ostracod species belonging to fifteen genera were recovered from phreatic waters of the hypogenic Frasassi Cave system and the adjacent Frasassi sulfidic spring and Sentino River in the Marche region of the northeastern Apennines of Italy. Specimens were recovered from ten sites, eight of which were in the phreatic waters of the cave system and sampled at different times of the year over a period of five years. Approximately 6900 specimens were recovered, the vast majority of which were disarticulated valves; live ostracods were also collected. The most abundant species in the sulfidic spring and Sentino River were Prionocypris zenkeri, Herpetocypris chevreuxi, and Cypridopsis vidua, while the phreatic waters of the cave system were dominated by two putatively new stygobitic species of Mixtacandona and Pseudolimnocythere and a species that was also abundant in the sulfidic spring, Fabaeformiscandona ex gr. F. fabaeformis. Pseudocandona ex gr. P. eremita, likely another new stygobitic species, is recorded for the first time in Italy. The relatively high diversity of the ostracod assemblages at Frasassi could be attributed to the heterogeneity of groundwater and associated habitats or to niche partitioning promoted by the creation of a chemoautotrophic ecosystem based on sulfur-oxidizing bacteria. Other possible factors are the geologic age and hydrologic conditions of the cave and karst aquifer system that possibly originated in the early– middle Pleistocene when topographic uplift and incision enabled deep sulfidic waters to reach the local carbonate aquifer. Flooding or active migration would have introduced the invertebrates that now inhabit the Frasassi Cave system.

The Impact of Environmental Factors on Diversity of Ostracoda in Freshwater Habitats of Subarctic and Temperate Europe

In this study, we compared the ostracod species diversity in selected inland-water habitats of Lapland and Poland, and assessed the relationships between ostracod occurrence and abiotic environmental variables. In total, 41 species were collected, of which only 15 species were found in Lapland, as compared with 35 in Poland. Almost all species collected from the Lapland sites were eurybiontic and no clear differences were found between ostracod assemblages inhabiting different habitat types. We hypothesize that this homogeneity might be a consequence of the raised water level during the springtime snow melt, temporarily connecting various waterbodies. The main factors limiting distribution of ostracod species in Lapland appeared to be low pH and low ionic content of water. In Poland,predominantly stenobiontic species were observed. In temporary waters and peat-bogs of this area useful indicator species were identified.

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 difficult.

Pseudocandona Sywulai Sp. Nov., a New Stygobitic Ostracode (Ostracoda, Candonidae) from Croatia

Pseudocandona sywulai sp. nov. (Ostracoda, Candonidae) collected in the cave Ðuderina, Croatia, is described and illustrated. The new species belongs to the eremita-species group of the genus Pseudocandona Kaufmann and can be distinguished from its congeners belonging to this group mainly by the shape and size of the carapace as well as by the chaetotaxy of the second antenna. It resembles P. eremita (Vejdovský, 1880) sensu lato very closely. A comparative morphological analysis of the species belonging to this group is presented also.