Global diversity of ostracods (Ostracoda,Crustacea) in freshwater

There are close to 2,000 subjective species and about 200 genera of Recent non-marine Ostracoda. Together, Cyprididae (1,000 spp.) and Candonidae (c. 550 spp.) represent more than 75% of the extant specific diversity; the remaining 11 families comprise the other 25% of the species. The Palaearctic region has the highest absolute non-marine ostracod diversity, followed by the Afrotropical. The Australian region has the highest relative endemicity. About 90% of the species and 60% of the genera occur in one zoogeographical region only. This means that all the biological mechanisms which lead up to efficient dispersal and which are present in at least part of the non-marine Ostracoda (e.g. brooding, drought-resistant eggs, parthenogenesis) have not induced common cosmopolitan distributions in ostracods. Several habitats are hotspots for ostracod diversity and endemicity. For example, it appears that the ancient lakes hold up to 25% of the total ostracod diversity. Other speciation-prone habitats are groundwater, temporary pools and Australian salt lakes; in the latter two instances, cladogenesis has often been paralleled by gigantism. The present ostracod diversity results from 9 to 12 separate invasions of the non-marine habitat, starting about 400 Myr ago. Genetic diversity can be very different in different species, mostly, but not always, related to reproductive mode. Guest editors: E. V. Balian, C. Lévêque, H. Segers & K. Martens Freshwater Animal Diversity Assessment     

Freshwater ostracods (Crustacea: Ostracoda) of the subfamily Dolerocypridinae Triebel, 1961 from Southeast Asia

The systematics of the freshwater ostracods of the subfamily Dolerocypridinae in Southeast Asia is reviewed: A total of five species are known and they are assigned to three genera. Astenocypris papyracea (Sars) 1903 and Dolerocypris sinensis Sars, 1903 are redescribed. Dolerocypris fasciata (Müller) 1776, from Indonesia is figured and the hitherto observed variations are discussed. Dolerocypris pellucida Klie, 1932 is transferred to the genus Tanycypris Triebel, 1959.     

Body‐size distribution and biogeographical patterns in non‐marine ostracods (Crustacea: Ostracoda)

The idea that free‐living minute organisms have ubiquitous distributions has been recently revitalized, causing significant controversy. The ubiquitous model predicts that a threshold where ubiquity leaves room to biogeography might exist somewhere along the animal body‐size range. In the present study, such a prediction is tested by analysing body‐size frequency distribution, species distribution, and local‐to‐global species ratio at the scale of biogeographical realms in cypridoidean non‐marine ostracods, a group with a body‐size range in the ubiquity–biogeography (U‐B) boundary. Data were gathered for all described extant cypridoidean ostracod species (N = 1761), with body‐size recorded for 1134 of them. Although local‐to‐global species ratios show significant over‐dispersal of small‐body ostracods for the Palaearctic and the Australasian regions, there are explanations alternative to the ‘Everything is Everywhere’ model that can account for such a result. Indicators of taxonomic structure do not support the hypothesis of a random distribution of cypridoidean species among realms. Nevertheless, the strong biogeography signal occurring at a large scale vanishes at the local scale (country‐level within the Palaearctic), and suggests wide dispersion within biogeographical realms. Additional factors, including inconsistent taxonomic criteria for species recognition, uneven sampling effort, and an excess of ‘single‐report’ occurrences, have been identified too as potential distorters of the observed patterns. Taxonomic harmonization, open databases of biogeographical data, and better ecological information are suggested as critical goals that need to be achieved for further understanding of ostracod global distribution patterns. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 109 , 409–423.     

The distribution and habitat preference of ostracods (Crustacea: Ostracoda) in a coastal sand-dune lake, Loch of Strathbeg, north-east Scotland

SUMMARY. 1. Ostracods were a numerically abundant component of the benthos >0.1 mm in size (up to 20% of the total) in the Loch of Strathbeg.
2. Distinct assemblages of species were associated with some habitats: Cypridopsis vidua (Müller) and Herpetocypris reptans (Baird) with Eleocharis palustris (L.) beds; Cypria uphtalmica (Jurine), Candona Candida Müller and Cypria exsculpta (Fischer) with Phragmites communis Trin. beds; and Limnocythere inopinata (Baird) with open sand. In contrast, no distinct ostracod assemblage was associated with submerged beds of Chara aspera Detharding, or Myriophyllum spicatum (L.).
3. The number of ostracod species and ostracod diversity increased from open sand through macroalgal and submerged macrophytes to emergent macrophyte habitats and was associated with increasing number of types of detritus.
4. Laboratory experiments suggested that substratum particle size played a dominant role in determining the distribution of L. inopinata. This species preferred sandy sediments. The distributions of both H. reptans and C. vidua were affected by food supply and H. reptans also preferred fine-grained sediments. The absence of these taxa from some habitats where food supply and sediment particle size conditions were suitable suggested that unmeasured factors played a role. A possible predatory exclusion of H. reptans from such habitats was indicated by a negative association of this species with a predatory mite.     

Association of body size and behavior of freshwater ostracods (Crustacea,Ostracoda) with aquatic macrophytes

Aquatic Ecology - In aquatic systems, macrophytes play an important role in habitat structuring and can be relevant for the establishment and/or mobility of the organisms and might thus influence...     

Structure and distribution of pelagic ostracods (Ostracoda: Myodocopa) in the Arctic Ocean

The study of the pelagic ostracod fauna of the Arctic Ocean based on materials collected by numerous Russian expeditions (1929–1993) and data from the literature showed the extreme poorness of the Arctic pelagic ostracod fauna, its mainly North Atlantic genesis and complete isolation from the Pacific fauna. Maximum ostracod abundance was observed in the epipelagic zone, and the greatest species diversity occurred in the relatively warm deep Atlantic layer throughout the year. To the north, east, and west of Franz Josef Land and Spitsbergen, the number of species and abundance indices of pelagic ostracods were decreased. In superficial water layers of the Central Arctic, maximum ostracod density and biomass were recorded in June and September. The best bioindicator of warm Atlantic water in the Arctic basin is Obtusoecia obtusata; and of cold polar water in the North Atlantic, Boroecia maxima.     

The species composition and distribution of ostracods (Crustacea,Ostracoda) in rockpools on islands in the Kandalaksha Bay of the White Sea

A total of 15 species of ostracods of 7 genera and 3 families of the suborder Podocopa Sars have been recorded in rockpools of the Kandalaksha Bay in the White Sea. Among them, Potamocypris pallida Alm is a new species for the fauna of Russia. Data on species composition and the dominant complex and ecological features of ostracods which inhabit waters of rockpools are presented.     

Redescription of two freshwater ostracods (Crustacea,Ostracoda) of the genus Eucypris Vavra, 1891 from the Philippines

The type specimens of the freshwater ostracodsEucypris bayensis Tressler, 1937 andEucypris orca Tressler, 1937, from the Philippines are redescribed and their valves and appendages are figured.     

Recent ostracods (Crustacea,Ostracoda) found in lowland springs of the provinces of Piacenza and Parma (Northern Italy)

The “fontanili” are artificial aquatic ecosystems, typical of the lowland plains of Northern Italy, exploiting natural resurgences of deep groundwater. These habitats are characterized by low variation in hydrologic, hydrochemical and thermal conditions throughout the year. Proper management is required to prevent the spring clogging by biomass accumulation. In spite of their importance as refugia for endangered species, many springs were completely abandoned in the last years and several of them will disappear. We report the results of a study carried out in 2001 on 31 springs of the provinces of Piacenza and Parma, distributed in seven areas defined on hydrological and geological considerations. Physical and chemical variables and parameters of waters were measured and ostracod samples were collected. Most of the springs showed high nitrate concentration, due to a diffuse pollution of agricultural origin. Twelve ostracod species in four families were identified. Ostracod valves were analysed by scanning electron microscopy. Cypria ophtalmica was found in all the springs; other relatively common species were Cyclocypris laevis,Notodromas persica, and Prionocypris zenkeri.The maximum number of species per site was four. Cypridopsis vidua,P. zenkeri, and N. persicashowed a very localized distribution in the study area. The ostracod fauna of the “fontanili” was compared to other species assemblages found in spring habitats and to the available information on recent freshwater ostracods reported for Italy.     

Evolution in the slow lane: molecular rates of evolution in sexual and asexual ostracods (Crustacea: Ostracoda)

Parthenogenetic lineages within non-marine ostracods can occur either in mixed (with sexual and asexual females) or exclusively asexual taxa. The former mode of reproduction is associated with a high intraspecific diversity at all levels (genetic, morphological, ecological) and, at least in the Cypridoidea, with geographical parthenogenesis. Obligate asexuality is restricted to the Darwinuloidea, the strongest candidate for an ancient asexual animal group after the bdelloid rotifers, and is characterized by low diversity. We have compared rates of molecular evolution for the nuclear ITS1 region and the mitochondrial COI gene amongst the three major lineages of non-marine ostracods with sexual, mixed and asexual reproduction. Absolute rates of molecular evolution are low for both regions in the darwinulids. The slow-down of evolution in ITS1 that has been observed for Darwinula stevensoni (Brady & Robertson) apparently does not occur in other darwinulid species. ITS1 evolves more slowly than COI within non-marine ostracod families, including the darwinulids, but not between superfamilies. The ancient asexuals might have a higher relative substitution rate in ITS1, as would be expected from hypotheses that predict the accumulation of mutations in asexuals. However, the speed-up of ITS could also be ancient, for example through the stochastic loss of most lineages within the superfamily after the Permian–Triassic mass extinction. In this case, the difference in rate would have occurred independently from any effects of asexual reproduction.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 79 , 93–100.     

Ultrastructure of the light organ and immunocytochemical localization of luciferase in luminescent marine ostracods (Crustacea: Ostracoda: Cypridinidae)

The ultrastructure of the upper lip, which is the location of the light organ in luminescent ostracods, is described for two species of marine ostracods (Vargula graminicola, and V. tsujii). The light organ contains four primary cell types (here designated A–D) readily identified both by the types of vesicles that they contain and their location. Cell type A, restricted to the center of the light organ, has vesicles that are homogeneous throughout. Cell type B has vesicles with a single electron-dense central area. This cell is most common in the lateral regions but is also found in the tusks. Immunocytochemical experiments revealed that luciferase is found in B cells, but not in any other cells or in control specimens. Cell type C has vesicles containing many electrondense microstructures; this cell type is the least common and is found along with B cells within the lateral margins of the light organ. Cell type D has granulated vesicles and is restricted to the tusks. Metachromatic staining with toluidine blue suggests that the vesicles contain acidic mucosubstances. The cells of the light organ are very long (360–460 μm) and extend through its entire length. The cells found exclusively in the tusks are shorter (ea. 150 μm). All cells possess similar polarity: proximal synthesis, middle transitional, and distal secretory regions. These cells terminate ventrally at nozzles on the anterior portion of the upper lip, and on the tusks. The upper lip and light organ possess two large longitudinal muscles, a central muscle, and several smaller “bridle” muscles that attach onto sclerotized ridges. Various hypotheses for the storage and secretion of light organ materials are suggested relative to these morphological data. © 1993 Wiley-Liss, Inc.     

Tanganyikacypridopsis gen.n. (Crustacea, Ostracoda) from Lake Tanganyika

A new genus of freshwater ostracods, Tanganyikacypridopsis gen.n., is established to include the species Potamocypris depressa Kiss, 1959, Cypridopsis calcarata Rome, 1962 and Cypridopsis anomala Rome, 1962, all from Lake Tanganyika. The genus is related to Sarscypridopsis McKenzie, 1977 and Plesiocypridopsis (Rome, 1965), mainly because of its hemipenis anatomy, and is believed to be endemic to Lake Tanganyika.     

A taxonomic reevaluation of freshwater ostracods (Crustacea,Ostracoda) referred to the genus Cypridopsis Brady, 1868 from Southeast Asia

A taxonomic reevaluation of five species of Southeast Asian freshwater ostracods formerly assigned to the genus Cypridopsis Brady, 1868 has resulted in the retention of Cypridopsis adusta Sars, 1903, Cypridopsis exigua Sars, 1903 and Cypridopsis dubia Sars, 1903 in Cypridopsis and transfer of Cypridopsis albida (Vavra) 1898 and Cypridopsis arsenia Tressler, 1937 to the genus Plesiocypridopsis Rome, 1965.     

Four new species of Gomphocythere (Crustacea, Ostracoda) from Lake Tanganyika, East Africa

Four new species of the ostracod genus Gomphocythere are described from Lake Tanganyika (East Africa): Gomphocythere downingi n. sp. G. coheni n. sp., G. wilsoni n. sp., and G. woutersi n. sp. All species are endemic to the lake and are found within a variety of substrates and depths. The addition of these four new species brings the total number of endemic Gomphocythere species in Lake Tanganyika to nine. Other Gomphocythere species are known from water bodies throughout East and South Africa and in the Levant. Brooding is an important, but not a unique, preadaptation for the persistence and taxic prolific speciation of this lineage in Lake Tanganyika.     

Distribution and population dynamics of ostracodes (Crustacea,Ostracoda) in a karstic lake: Lake Banyoles (Catalonia,Spain)

Qualitative and quantitative benthic samples were collected monthly between December 1986 and December 1987 from several stations at various depths and basins in the karstic Lake Banyoles (Catalonia, Spain), to study the spatial distribution and seasonality of ostracodes. A total of eight ostracode species were found in the lake. Of these, Candona neglecta Sars, Isocypris beauchampi Paris and Cypria ophtalmica Jurine were the most common ostracodes at all depth stations. Darwinula stevensoni Brady & Robertson, Ilyocypris species (I. bradyi Sars and I. gibba (Ramdohr)), Cyprideis torosa (Jones) and Cyclocypris ovum Jurine, on the other hand, were confined to sublittoral and littoral areas of the lake.Substrate and organic matter content appeared to be relevant factors determining the distribution of ostracode species at the different stations. The highest abundance of ostracodes were in the sublittoral (Basin IV–7 m and Basin I-5 m) where the substrate was coarse and sediment had a high organic matter content (>35% LOI). Low oxygen levels in the hypolimnetic waters (i.e. < 1 mg l^–1) may explain the absence of ostracodes at deeper zones in stations where the anoxic period lasts more than four months. On the other hand, low temperatures seem to favour the development of C. neglecta and D. stevensoni, while with higher temperatures I. beauchampi, C. torosa and C. ovum increased their abundances. However, no clear pattern can be observed, so ostracode species in Lake Banyoles, apparently, have non-seasonal life histories.     

The life-cycle of Cyprideis torosa (Crustacea,Ostracoda)

Summary The life-cycle of the dominant brackish water ostracod Cyprideis torosa (Jones, 1850) has been studied during 4 years. The species has only one generation anually. Reproduction is fairly similar throughout the years and appears to be tuned in to temperature. The number of adults has one peak every year and can be described by two exponential functions, one for the increase and one for the decrease. Mortality is very similar every year and approximately constant for months. Cyprideis torosa is on top of the food chain: regulation of numbers is probably not external and may be a function of the past of the habitat. A model is described which permits the evaluation of the duration of development from field data only. Predicted values are in good agreement with observed values.This paper was given as a lecture on the Second International Conference on Meiofauna, York, September 1973     

The female reproductive organ in podocopid ostracods is homologous to five appendages: histological evidence from Liocypris grandis (Crustacea,Ostracoda)

The giant ostracod, Liocypris grandis, found in South African temporary pools, has five pairs of additional appendage-like structures, seemingly associated with the Female Reproductive Organ (FRO). Original investigations of these structures by light and scanning electron microscopy could not unequivocally determine whether or not these structures are homologous to genuine appendages and if so, to how many. The present paper investigates morphology and attachment of these structures by frontal and transversal micro-sectioning (thickness = 1 μ m) of the caudal soft parts of mature females of L. grandis. It is found that all five appendages (R1–R5) have one individual attachment point where they enter into the FRO. Also R3(I) and R3(II) have a single attachment only, these two parts thus represent one single appendage. Whereas R1–R4 have clear lateral insertions, R5 is caudally positioned. The fusion of this latter appendage with the FRO occurs internally, at the posterior edge of the bulge of the FRO and is not externally visible. It is herewith thus accepted that R1–R5 are genuinely endogenous structures (and not, for example, exogenous parasites), that the five structures are homologous to five appendages, and not for example to parts of biramous appendages. It follows from this that the female reproductive organ is homologous to at least five, not to one segment. This would bring the number of (original) thoracic segments in podocopid ostracods to at least 8. An additional pair of triangular structures, inserted in between the two FRO is here described as structures ‘X’. Their homology and function remain unknown.