The evolutionary pathway of light emission in myodocopid Ostracoda

The evolutionary history of bioluminescence and iridescence in myodocopid ostracods was estimated by phylogenetic analysis of mitochondrial 16S ribosomal RNA sequences. The inferred phylogeny of the myodocopids suggests that the common ancestor of Myodocopida evaluated in this study exhibits iridescence. This type of light emission was once lost and recaptured independently in the descendant lineages. Bioluminescent species also evolved from non-luminous ancestral species. In the suborder Myodocopina, all the bioluminescent species form a monophyletic group, suggesting that bioluminescence evolved only once. Structural differences between two bioluminescent groups in the order Myodocopida suggests independent origins for bioluminescence.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 87 , 449–455.     

Non-marine Ostracoda (Crustacea) of Banat district in Serbia

In order to enrich the knowledge on ostracods in Serbia, field work was carried out in the central and southern part of the Banat district during 2002 and 2003. Samples from the collection of the Institute of Zoology, Faculty of Biology in Belgrade were also examined. Altogether, 133 samples were investigated. In this research, 23 ostracod species were found. Most of them have a Palaearctic distribution. Ilyocypris decipiens, Bradleycypris obliqua and Tanycypris pellucida are new to the faunas of Serbia and Montenegro, as is the subfamily Cypricercinae. Three species were found again after several decades, including a new and stabile population of Candona natronophila Petkovski, 1969 . The most frequent species were Cypridopsis vidua and Physocypria kraepelini. Statistical analysis of ostracod communities and their relations to measured ecological variables is also given.     

Palaeozoogeography of Western European Lower Jurassic (Pliensbachian and Toarcian) Ostracoda

The palaeozoogeography of Lower Jurassic (Pliensbachian-Toarcian) Ostracoda is studied in terms of faunal similarity between 13 geographical areas. A list of 270 marine ostracod species from Europe, North Africa and North America has been compiled and subjected to quantitative analysis (using multivariate methods) in order to ascertain the degree of similarity between Spanish assemblages and those described from these areas. The cluster analysis demonstrates that degree of similarity generally reflects proximity in palaeogeographical position. The results indicate extensive intercommunication of taxa between the basins, and also the absence of clear differentiation between Tethyan and Boreal faunas.     

Marine Ostracoda of the Galapagos Islands and Ecuador

Marine algae collected from rock pools on Hood, Fernandina and Mosquera, in the Galapagos Islands, have provided a fauna of 26 ostracod species of which 14 are new. One genus, belonging to the Hemicytheridae, is also new and appears to be endemic to the Islands. From two littoral algal samples collected from Punta Canoa and San Pedro beach, Ecuador, an assemblage of some nine species, four of which are new, is also described. Two ostracods: Touroconcha lapidiscola and Loxoconcha (Lox-ocorniculum) lenticuloides , are the only species so far known to be present both in the Galapagos Islands and off the coast of Central and South America. One species: Cytherelloidea praecipua recorded from off Tobago and Clipperton Islands may be present in the Galapagos but this has not definitely been confirmed. The evolution in the Gulf Coast/Caribbean region of several ostracods and their subsequent dispersal westwards is discussed.     

Ostracoda and palaeo-oxygen levels, with particular reference to the Upper Cretaceous of East Anglia

It has been shown that the percentage of Platycopina (the sole remaining group of filter-feeding Ostracoda since the global extinction of the Metacopina in the Lower Toarcian) making up a fossil ostracod fauna can be used as a measure of dissolved oxygen in past oceans. High levels of platycopids indicate low oxygen and vice versa. A new scale is introduced here, based mainly on the environmental oxygen levels of modern oceans and their equivalent percentages of living platycopids, in order to evaluate the palaeo-oxygen levels of the Upper Chalk in East Anglia. The effects of varying oxygen concentrations on the overall simple species diversity of the Ostracoda is also shown to have important palaeoenvironmental implications. The study is based on 79 samples from the Santonian to Lower Maastrichtian of the Trunch Borehole and 126 samples from outcrops in Suffolk and Norfolk, ranging from the Coniacian to Lower Maastrichtian. The Coniacian is shown to have been a time of low to very low oxygen, except for its upper part that was much better ventilated. The Santonian and Lower Campanian were low to very low in their dissolved oxygen, while the Upper Campanian and particularly the Lower Maastrichtian had much higher oxygen levels. Notwithstanding these general trends, oxygen levels appear to have fluctuated rapidly throughout the interval, during times of both generally low and high oxygenation. These variations in oxygenation are thought to have been associated with the Oxygen Minimum Zone and its migrations onto the continental shelf and subsequent retreat to the continental slope. This in turn is related to sea-level fluctuations and this, together with the potential for the application of this technique to sequence stratigraphy are discussed.     

Phylogeny and evolution of Loxoconcha (Ostracoda, Crustacea) species around Japan

The pore-systems of 17 extant species of Loxoconcha around Japan were studied in order to understand their phylogeny and evolution. The phylogeny was estimated by two steps. First, the 17 species were divided into two groups, Group A (12 species) and Group B (five species) by Pore pattern Below Eye tubercle (PBE) analysis. Then, intragroup relationships were estimated by Differentiation of Distributional pattern of Pore-system (DDP) analysis. PBE analysis reveals that species of Groups A and B have on average different ecological preferences. Species of Group A, which appeared in the late Pliocene, are more diverse, have both phytal and bottom-dwelling modes of life, possess fewer pore-systems in the ventral area, and inhabit normal marine environments. Species of Group B, whose oldest fossil record is the lower Miocene, are less diverse, have only bottom-dwelling species, possess more pore-systems in the ventral area, and tend to inhabit brackish water environments. The results of this study suggest that the differences in ecology may have had an impact on the late Cenozoic diversification around Japan. The primary invasion of Group B occurred before the lower Miocene,with no subsequent diversification. Group A invaded after the late Pliocene and immediately diversified, which created the present abundance of Loxoconcha species around Japan in both species diversity and variety of modes of life.     

Marine Ostracoda from Pitcairn, Oeno and Henderson Islands

All of the samples yielded podocopid ostracods. Most of the faunas from Pitcairn and Oeno were poorly preserved and sparse; those from Henderson were much more abundant, more diverse and better preserved. Only 33 species are recorded from the joint fauna and this may reflect the limited number of environments sampled or the remote geographical situation of the islands. At least 20 species (and a new genus) are restricted to the islands. Other species are known from the Solomon Islands, Australia and Indonesia. Of a considerable number of Indo-Pacific pandemic species, only three Kotoracythere inconspicua (Brady), Tenedocythere transoceanica (Teeter) and Triebelina sertata (Triebel) have been identified to date. The fauna is not, however, nearly so endemic as that of Easter Island on which the two authors are currently working.     

Distribution and community structure of Ostracoda (Crustacea) in shallow waterbodies of southern Kenya

The current study presents the ostracod communities recovered from 26 shallow waterbodies in southern Kenya, combined with an ecological assessment of habitat characteristics. A total of 37 waterbodies were sampled in 2001 and 2003, ranging from small ephemeral pools to large permanent lakes along broad gradients in altitude (700–2 800 m) and salinity (37–67 200 µS cm^?1). Between 0 and 12 species were recorded per site. Lack of ostracods was associated with either hypersaline waters, or the presence of fish in fresh waters. Three of the 32 recovered ostracod taxa, Physocypria sp., Sarscypridopsis cf. elizabethae and Oncocypris mulleri, combined a wide distribution with frequent local dominance. Canonical correspondence analysis on species–environment relationships indicated that littoral vegetation, altitude, surface water temperature and pH best explain the variation in ostracod communities. Presence of fish and water depth also influence species occurrence, with the larger species being more common in shallow waterbodies lacking fish. Based on Chao’s estimator of total regional species richness, this survey recovered about two-thirds (60–68%) of the regional ostracod species pool. Scanning electron micrographs (SEM) of the valve morphology of 14 ostracod taxa are provided, in order to facilitate their application in biodiversity and water-quality assessments and in palaeoenvironmental reconstruction.     

Biostratigraphy and palaeobiogeography of the Cambrian genusHipponicharion (Ostracoda)

The bradoriid genusHipponicharion Matthew, 1886 is one of the oldest known Cambrian ostracods. Until now, five species have been documented and another three taxa have been tentatively assigned to one or another species.Hipponicharion has been recorded from Poland, Germany, Morocco as well as from Canada and Great Britain.Hipponicharion hispanicum n. sp. represents the first Cambrian ostracod documented from Spain.Hipponicharion taidaltensis n. sp., formerlyH. aff.geyeri Hinz-Schallreuter, 1993 andH. elickii n. sp., formerlyH. cf.eos sensuElicki, 1994 have also been restudied in this paper.Hipponicharion seems to be restricted to the Acadobaltic Province sensuSdzuy (1972). The systematic relationships of the Bradoriida, which is controverse, is briefly outlined, emphasizing close affinities to the Ostracoda.      

Aral Sea Ostracoda as environmental indicators

Fluctuations in the level and chemistry during its history have played a major part in shaping the floral and faunal communities of the Aral Sea. Of the eleven species of Ostracoda (Crustacea) known to have been living in the Aral Sea in 1960, only one survives today due to the anthropogenically induced salinity increase of the past three decades. The origins of a mixed fresh- and brackish-water ostracod fauna are discussed, and it is concluded that some of the major faunal elements must have reached the Aral Sea Basin during a past high water level phase when connection existed with the Caspian Sea. The taxonomic position of key taxa is clarified, and the major elements of the pre-1960 Aral Sea ostracod fauna are illustrated from Holocene sequences. Aral Sea, Ostracoda, Holocene, palaeolimnology.     

Taxonomy, morphology and speciation of the Semicytherura henryhowei group (Crustacea, Ostracoda)

The genus Semicytherura belongs to the family Cytheruridae, and was distinguished from Cytherura on the basis of carapace features. Species of Semicytherura from Japan and adjacent seas can be divided into two groups. One is represented by Semicytherura miurensis Hanai, 1957, characterized by a thin, oval carapace covered with fine reticulation. The other is represented by Semicytherura henryhowei Hanai & Ikeya, 1977, characterized by a thick sub-rectangular carapace in lateral view. Semicytherura henryhowei, which is distributed from Hokkaido to Okinawa in Japan, has been regarded as having several morphotypes distinguishable on outline and reticulation of carapace. However, as a result of detailed observations on the copulatory organ, carapace outline and distributional pattern of pore systems, remarkable differences are shown to exist between the two most frequently occurring morphotypes. In order to recognize S. henryhowei sensu stricto, the carapace of the holotype was re-examined. Consequently, neither of the two morphotypes are considered to belong to S. henryhowei due to differences of carapace outline and distribution of pore systems. The two morphotypes are here regarded as independent taxa, described as new: S. kazahanan. sp. and S. sasameyukin. sp. The geographical distributions of the two new species overlap, but their micro-habitats differ from each other; the former lives on calcareous algae on rocky shores, the latter lives on silty sand bottom within the inner bay. A third new species, S. slipperi sp. nov., is also described. In view of their present geographical distributions and fossil records, the origin of this group of species would appear to be the Japanese islands or adjacent areas in and after the Miocene. This group then migrated to the Arctic Ocean and East Pacific Ocean during or before the middle Pliocene.     

Evidence of brooding in Permian non-marine Ostracoda

The discovery of some exceptional non-marine fossil Ostracoda, showing larval stages within the carapaces of females, demonstrates that incubation was an ontogenetical adaptation which appeared at least as early as the Permian. Thus, it seems, the superfamilies Danvinulacea and Cytheracea diversified in Permian lakes where the Carbonitacea had flourished in the Carboniferous. The Cypridacea accomplished an evolutionary radiation in continental environments after a permanent invasion from the sea in the Middle Jurassic, thanks to the resistance of their eggs to dessication and heezing and the evolution of parthenogenetic reproduction.     

Origin of the Ostracoda and their maxillopodan and hexapodan affinities

There are Cambrian fossils attributed to the Ostracoda but the extant subclasses Podocopa and Myodocopa do not appear until the Ordovician. At this time the morphologically similar, free-living ancestors of the now sedentary Thecostraca (Ascothoracida, Acrothoracica and Cirripedia) may have still been extant, and from an ecological point of view it seems likely that, by and large, ostracods replaced them. However, living ostracods have an abbreviated, direct development, and some key aspects of their morphology, such as the nature of the maxillary segment and abdomen, are conjectural. Thus the affinities between these and related taxa remain uncertain; e.g., while some contemporary carcinologists place Ostracoda as a taxon coordinate with the Branchiopoda, Remipedia, Cephalocarida, Maxillopoda, Malacostraca, others tentatively or unequivocally ally them with the Maxillopoda (generally Mystacocarida, Copepoda, Tantulocarida and Thecostraca, and sometimes Branchiura and Pentastomida). Others, largely involved with fossils, have stretched the definition of the Maxillopoda even further, to the point where it seems even less likely a monophyletic taxon. Until recently cladistic analyses utilizing genetic (largely 18S rDNA) as well traditional morphological characteristics have given confusing results regarding the affinities between these taxa, and an important one suggested the Ostracoda might even be diphyletic. Furthermore, a very recent genetic study utilizing protein encoding genes places a podocopine ostracod among the most primitive of the extant crustaceans (Branchiopoda, Cephalocarida Remipedia and Mystacocarida), and then generally at the base of a lineage leading to the Malacostraca, a lineage giving rise to copepods and cirripeds along the way. This indicates these so-called maxillopodan taxa evolved independently from a malacostracan-like ancestor, and if so they are convergent. And finally, from genetic studies it is not only becoming well documented the Crustacea rather than Myriapoda gave rise to the Hexapoda, but it appears the Hexapoda stem from among the lower rather than the higher crustaceans, possibly even from the Ostracoda. Whether there were terrestrial ostracods at the time hexapods appeared in the Lower Ordovician is unknown, but the modest diversity of terrestrial ostracods today are podocopines which also first appeared in the Lower Ordovician. Thus, if current interpretations of living ostracodan and fossil hexapodan body plans are largely correct, it can be hypothesized the Ostracoda are close to the ancestor of the Hexapoda.     

The composition,structure, and distribution of benthic ostracod fauna (Ostracoda,Myodocopa) in Antarctic waters

The benthic fauna of ostracods of the order Myodocopida of Antarctic waters is characterized by high diversity, relative species abundance, and a complicated taxonomic and ecological structure, with a simplified biogeographical structure. This fauna, which is distinguished by a high level of endemicity, although at a low taxonomic rank, includes a great share of deep-sea and subtidal elements. Ostracod populations of High and Low-Antarctic subzones differ qualitatively and quantitatively. A distinct impoverishment of fauna is observed in the region of the Antarctic divergence compared to the more northern areas. The number of species increases with depth to reach its maximum in the lower subtidal zone and on the upper continental slope at depths of 200–500 m. The number of species decreases with increasing depth. Myodocopida have not been yet found in the Antarctic waters deeper than 5000 m.     

Megalocypris ingens Delorme (Ostracoda) in Saskatchewan saline lakes: osmoregulation and abundance

Results of freezing point depression determinations show that the haemolymph of the ostracod, Megalocypris ingens Delorme, remains hyperosmotic to the medium as the concentration of the medium increases. Even though M. ingens is poikilosmotic, the median lethal concentration (LC50) for this species exceeds the LC50 for an insect species living in the same lakes that is capable of hyposmotic regulation. The LC50 for M. ingens occurred in sulphate-saline lake water with a specific conductance of 48 000 µS cm^-1 (at 25 °C). The absence of vegetation may be more important than salinity in limiting the distribution of M. ingens in Saskatchewan saline lakes.     

Preface: Ostracoda and the four pillars of evolutionary wisdom

Morphology, palaeontology, genetics and ecology are the main scientific domains contributing theories, concepts and new data to evolutionary biology. Ostracods are potentially very good model organisms for evolutionary studies because they combine an excellent fossil record with a wide extant distribution and, therefore, allow studies on both patterns and processes leading to extant diversity. This preface provides an overview of the 15 contributions to the present volume and concludes that this set of papers supports the claim that ostracod studies are situated in all main evolutionary domains.     

The osmoregulatory capacity of the Ostracoda

All ostracods that inhabit inland waters are osmoregulators. Freshwater ostracods must be hyperosmotic regulators while ostracods that live in hyperhaline water are hypoosmotic regulators. Some euryhaline species are hypoosmotic regulators in salinities above 8 g·l^-1 and hyperosmotic below. Hyperosmotic regulation in ostracods is partly dependent on salt consumed in the food but hypoosmotic regulation is dependent on the excretion of salt brought about by special cells located on the inside of the carapace.     

Growth and respiration of Cyprideis torosa Jones 1850 (Crustacea Ostracoda)

Summary The ostracod Cyprideis torosa Jones 1850 is a dominant species in brackish water habitats. To assess its importance, growth and respiration were measured. The shells form an increasing part of total weight as the animals grow but there is no correlation between shell weight and soft parts weight in the adults, indicating that tissue growth is a continuous process in these ostracods.Respiration was measured at 20° C. The slope of the log-log regression of respiration on dry weight was 0.746, showing that Cyprideis torosa follows the general rule for this relationship. The respiration rate per unit biomass was 0.246 nl O₂ g^-1 h^-1, which is low but well within the range of observed meiobenthic respiration rates.The Q₁₀, expressing the temperature dependence of respiration, was 2.15. The general validity of Price and Warwick's (1980) hypothesis relating Q₁₀ to stability of food supply is questioned.