Ostracod Species Research Articles

A comparison between active and passive communities of Ostracoda (Crustacea) in a tropical temporary lake

ABSTRACT Some microcrustaceans living in temporary waterbodies produce drought-resistant stages under adverse conditions. These structures accumulate in the sediment, forming an egg bank in which eggs can remain viable for many years. Here, we evaluate the contribution of ostracod resting eggs to the structure of the active ostracod community in a tropical temporary lake located in the Upper Paraná River floodplain, Brazil. The active ostracod communities were sampled by hand net, while sediment samples (egg banks) were collected using a core sampler. Sediments were oven-dried, then re-hydrated with filtered lake water and kept in hatching chambers. A total of 13 ostracod species were recorded, eight species in the passive community,and nine species in the active community, four species were recorded in both communities. The species composition between active and passive communities was significantly different. Five species of the active community could be of allochthonous origin and are most likely introduced by flooding or by other dispersal vectors. In conclusion, the egg bank adds species not necessarily found in the active community, thus acting in the maintenance and enrichment of the local and regional faunas.

Co-cultured non-marine ostracods from a temporary wetland harbor host-specific microbiota of different metabolic profiles

Rapid development of high-throughput sequencing methods and metagenomics revealed a diverse world of microbiota associated with multicellular organisms. Although recent discoveries indicate that freshwater invertebrates are hosts for specific bacteria, it is still unknown if this specificity is driven by host-derived factors or by the environment, especially in animals with diapause in ephemeral habitats, where parents and offspring are separated in time and space. In this work, using both low-throughput molecular approach and Next-generation sequencing of 16S ribosomal RNA gene, we present a taxonomic analysis of bacteria associated with two species of non-marine ostracods Sclerocypris tuberculata and Potamocypris mastigophora raised from diapausing eggs and co-cultured in laboratory conditions. Our analysis showed that despite sharing the same environment, each ostracod host developed distinct bacterial communities. The major difference was caused by the dominance of the family Comamonadaceae (Betaproteobacteria) in P. mastigophora and the Aeromonadaceae (Gammaproteobacteria) in S. tuberculata. Furthermore, prediction of metabolic pathways in metagenomes, revealed that microbiota of P. mastigophora exhibit higher number of sequences associated with the membrane transport and xenobiotics biodegradation and metabolism. Our study not only provides an insight into microbiota of non-marine ostracods but also shows that different ostracod species host functionally distinct bacterial communities.

Freshwater ostracods (Crustacea) from Hainan Island, southern China, with description of a new species.

In this study, 24 non-marine ostracod species were found in 142 samples collected from diverse water bodies from Hainan Island, south China. Among them, a new species Pseudocypretta lineata n. sp. is described and illustrated. Twelve species are new records for China. Among them, six species are identified: Microdarwinula zimmeri (Menzel, 1916), Pseudocypretta lineata n. sp., Pseudostrandesia mamarilorum (Victor Fernando, 1981c), Stenocypris malayica Victor Fernando, 1981b, Stenocypris orientalis Victor Fernando, 1981b and Strandesia freyi Victor Fernando, 1981c. Six species are left in open nomenclature: Batucypretta sp., Candonopsis? sp., Cypridoidea gen. et sp. indet. 1, Cypridoidea gen. et sp. indet. 2, Cyprinotus cf. kimberleyensis McKenzie, 1966 and Vestalenula sp. Additionally, a re-description of Strandesia freyi is provided.

A checklist of ciliates (Ciliophora) inhabiting on ostracods (Crustacea, Ostracoda).

A compilation of the ciliated species found on freshwater and marine ostracods as epibiont or parasite (endobiont) has been carried out based on published records. The checklist includes the taxonomic position of each species of epibiontic and endobiontic ciliate, the species of basibiont ostracodes, the geographic zones and the bibliographic references where they were recorded. Altogether 7 suctorian, 29 peritrich, one apostome and one scuticociliatid species were listed. Two of recorded suctorian species are possible specific to marine ostracodes, whereas only one, Tokophrya sibirica to freshwater hosts. Fourteen species of peritrichs are likely specific to freshwater ostracodes, while three possible specific to marine ostracode hosts. Other suctorian and peritrich ciliate species were found on a variety of host taxa. One species of scuticociliatid was recorded as endobiont in ostracod.

Spatial variation of ostracod (Crustacea, Ostracoda) egg banks in temporary lakes of a tropical flood plain

Ostracods are microcrustaceans that produce resting eggs under adverse conditions. In this study we evaluated the spatial variation of ostracod resting eggs in different regions of temporary lakes in a Brazilian flood plain. Based on the homogenisation effect of flood pulses on aquatic communities in flood plains, we hypothesised that the composition and abundance of ostracod eggs in the centre of temporary lakes would be similar to those in edge regions. Samples were collected from the centre and edge regions of five temporary lakes. Sediment was oven dried, rehydrated and hatching was monitored in germinating chambers. Twelve ostracod species hatched from the egg banks during our experiments. The abundance and species composition were similar between the two regions of the lakes. Flood events may be responsible for the homogenisation of the egg banks as a result of the connection of lakes with principal river channels. During flooding, water masses powerfully enter lakes and can redistribute sediments. This study shows that egg banks have the potential to contribute to the maintenance of local biodiversity and the resilience of biodiversity of temporary lake ecosystems.

Ecological interactions and the distribution, abundance, and diversity of ostracod species associated with some coastal brackish karstic springs in southwest Turkey

Ostracod species obtained from five coastal karstic brackish water springs on the Aegean Sea coastline were evaluated using multivariate statistical methods. Information on the diversity and distribution of ostracod fauna associated with coastal brackish karstic springs and on the ecological factors affecting them was obtained. A total of eight ostracod species were identified in five karstic brackish springs (southwest Aegean region, Turkey) in May, July, October, and December 2016. Cyprideis torosa (Jones, 1850) and Loxoconcha elliptica (Brady, 1868) were the most abundant species. The three main clustering groups in an unweighted pair group mean averages (UPGMA) dendrogram created by Jaccard’s coefficient test provided an understanding of the faunal similarity among the sampling stations. Canonical correspondence analysis (CCA) was used to explain the relationships between the species and environmental variables. Results revealed that salinity, water-flow velocity, and distance to the sea were the most significant factors in species diversity and composition in the five coastal karstic brackish springs. Results of the Spearman correlation analysis showed significant correlations between ostracod species and environmental variables. Protection should be put in place for the five karstic brackish springs for their long-term preservation.

New Material on the Ordovician Ostracodes of the Siberian Platform

Twelve new species of Ordovician ostracodes are described from the sections on the Moyero, Angara and Nizhnyaya Chunku rivers. They belong to six previously described genera (Laccochilina, Kiesowia, Disulcina, Foramenella, Hallatina, and Pseudulrichia) and four new genera (Direigina, Korolyukina, Angarallina, and Tesakovites). The taxonomic assignment of Novoglanditesvarius Melnikova, 2003 and Dudinkites cavatus Abushik, 2003 has been revised.

Non-marine Ostracoda (Crustacea) as indicator species group of habitat types

To understand interactions between ecological properties of ostracod species and the habitat types, 89 different aquatic bodies with nine different habitat types were randomly visited in Artvin province, Turkey. A total of 24 taxa, all new for the province, were found from 62 sites. Shannon–Weaver alpha diversity of the numbers of species value was higher (3.972) than the mean index value of all samples (2.945) with relatively low standard error (0.264). Six species (Psychrodromus olivaceus, P. fontinalis, Heterocypris incongruens, Potamocypris fulva, P. fallax and Ilyocypris bradyi) encountered most frequently contributed more than 90% of diversity in four different habitat types (lake, creek, trough and canal) of 11 sampling sites. Two positive co-occurrences (p < 0.05) were found for P. olivaceus–I. bradyi, and P. olivaceus–I. inermis. Canonical correspondence analyses explained 60.5% of the variance between 12 asexual species and environmental variables. Water temperature, dissolved oxygen and elevation were the most predictive variables for species found in five different habitats (lake, creek, trough, canal and ditch). Ordination on the first axis of the species negative filter method characterized the sites (samples) by the presence of rare (negative indicators) and common (positive indicator) species in opposite ends. According to TWINSPAN analysis, these species as the key members (indicators) of that particular habitat(s) can be used to distinguish characteristics of habitats. Overall, multiple regression models suggested that rather than focusing on one particular species, two or more ostracod species or the so-called indicator species group can also be used for habitat type(s) and/or aquatic condition(s).

Lake Balkhash (Kazakhstan): Recent human impact and natural variability in the last 2900 years

Lake Balkhash is a large and relatively shallow closed-basin lake in the arid part of Central Asia. The lake experienced an ecological crisis in the 1970s and 1980s when the filling of the Kapchagay Reservoir in the middle reaches of its main tributary caused a significant lake-level decline and salinity rise, and resulting biodiversity loss. A sediment core representing 2900 years of lake history was obtained to assess man-made alterations of the lake in the last decades in comparison to the natural status of Lake Balkhash. Analyses of sediments and of ostracod (micro-crustacean) species assemblages and shell chemistry revealed that the lake was probably relatively shallow and more brackish ca. 2900–2200 calibrated years before present (cal a BP) in comparison to the period when the Kapchagay Reservoir was filled. A relatively high lake level and lower salinity prevail since ca. 2200 cal a BP.The uppermost sediments of the obtained core and nearby surface-sediment samples provide evidence for the establishment of hypoxic conditions in Lake Balkhash since the middle of the 1970s. The lake-level decline during the filling of the Kapchagay Reservoir probably caused the redistribution of organic-matter rich littoral sediments to greater depth in the lake where dissolved oxygen became consumed due to the decomposition of organic remains. The spatial and temporal distribution of hypoxia in Lake Balkhash is not known, and systematic studies are required to assess the status of the benthic life and potential impacts of future lake-level, nutrient influx and temperature changes.

Paleoecology of the middle Eocene ostracods of Egypt

Data on one hundred and three ostracod species belonging to forty-one genera from the middle Eocene sediments of Egypt have been subjected to appropriate multivariate data analyses techniques in order to reconstruct the paleoenvironment. The most common ostracod species of the studied regions belong to the genera: Cytherella, Paracosta, Bairdia and Reticulina (these species represent more than 32% of the total number of the studied ostracod species). Cluster analysis based on the neighbour joining clustering method (Jukes-Cantor similarity measure) of eleven rock units and fifty ostracod species suggested the separation of these rock units according to their ages under the control of their geographical distribution within the studied regions. On the other hand, Factor Analysis (based on the varimax rotation technique) of the same data matrix aided to detect four paleoenvironmental factors affected the distribution of the ostracod assemblages. The first factor discloses the turbulence of water; the second factor corresponds to the degree of salinity of water; the third factor signifies the water depth associated with oscillation in the oxygen content; the fourth factor demonstrates the temperature of water in the euphotic zone exposure to water depth. Moreover, ten ostracod biofacies with specific paleoenvironmental conditions were recognized. Outstandingly, it seems prominently that paleoenvironmental changes had shaped the distribution of the middle Eocene ostracods of Egypt rather than origination or extinction.

Influence of late Quaternary climate on the biogeography of Neotropical aquatic species as reflected by non-marine ostracodes

Abstract. We evaluated how ranges of four endemic and non-endemic aquatic ostracode species changed in response to long-term (glacial–interglacial cycles) and abrupt climate fluctuations during the last 155 kyr in the northern Neotropical region. We employed two complementary approaches, fossil records and species distribution models (SDMs). Fossil assemblages were obtained from sediment cores PI-1, PI-2, PI-6 and Petén-Itzá 22-VIII-99 from the Petén Itzá Scientific Drilling Project, Lake Petén Itzá, Guatemala. To obtain a spatially resolved pattern of (past) species distribution, a downscaling cascade is employed. SDMs were reconstructed for the last interglacial (∼120 ka), the last glacial maximum (∼22 ka) and the middle Holocene (∼6 ka). During glacial and interglacial cycles and marine isotope stages (MISs), modelled paleo-distributions and paleo-records show the nearly continuous presence of endemic and non-endemic species in the region, suggesting negligible effects of long-term climate variations on aquatic niche stability. During periods of abrupt ecological disruption such as Heinrich Stadial 1 (HS1), endemic species were resilient, remaining within their current areas of distribution. Non-endemic species, however, proved to be more sensitive. Modelled paleo-distributions suggest that the geographic range of non-endemic species changed, moving southward into Central America. Due to the uncertainties involved in the downscaling from the global numerical to the highly resolved regional geospatial statistical modelling, results can be seen as a benchmark for future studies using similar approaches. Given relatively moderate temperature decreases in Lake Petén Itzá waters (∼5 ∘C) and the persistence of some aquatic ecosystems even during periods of severe drying in HS1, our data suggest (1) the existence of micro-refugia and/or (2) continuous interaction between central metapopulations and surrounding populations, enabling aquatic taxa to survive climate fluctuations in the northern Neotropical region.

Evolution Characteristics and Stratigraphic Division of Quaternary Sedimentary in the South Wing of Yangtze River Delta, East China

This paper discusses the sporo pollen assemblage, evolution of sedimentary environment, sedimentary facies and the lithotope characteristics revealed by boreholes since pliocene epoch by carrying out 14C dating, sporo pollen and micro-paleontological analysis of sediments in borehole BK01 (depth 237.80 m) in the southern flank of the Yangtze River Delta Plain. According to the results of this study, there are 17 species of foraminifera that have been identified as 11 genera, including 16 benthic foraminifera and 1 planktonic foraminifera；8 species of Ostracoda that have been identified as 8 genera; sporo pollen analysis shows that there are 37 types, including 18 species of woody plant pollen, 11 species of herbaceous plant pollen, 8 species of fern spores, of which, in the sporo pollen assemblage, woody plants have the highest content (about 85.1%), ferns spores have about 8.7%, and herbaceous plants have only 6.3%. Sedimentary environment records can be divided into 18 sporo pollen assemblage zones according to borehole lithology, sporo pollen assemblage and micropaleontology analysis. The results show that the BK01 bore strata from bottom to top can be divided into carbonaceous mudstone (Ech), Jiaxing Formation (N-Qp1j), Qiangang Formation (Qp2q) Dongpu Formation (Qp3d), Ningbo Formation (Qp3n) and Zhenhai Formation (Qhzh).

Ordovician Ostracods from the Chunya River Basin (A Right Tributary of the Podkamennaya Tunguska River, Siberian Platform)

The ostracod assemblages of the Baksian and Dolborian horizons of the Chunya River basin (a right tributary of the Podkamennaya Tunguska River) have been studied. They add essentially the paleontological characteristics of Upper Ordovician deposits of the Siberian Platform. The age of deposits was verified and the studied sections were correlated with the Gaindinskaya 3 reference borehole. Two new genera and 9 new species were described. Images for known ostracod species are given.

Cosmopolitan myodocope ostracods from the Silurian of Uzbekistan, Central Asia

Four species of myodocope ostracod are documented from the Silurian Ludlow Series of the Aburtkan gorge on the southern slope of Dzhalpak Mountain, Uzbekistan: namely,Parabolbozoe bohemica(Barrande, 1872),Bolbozoe anomalaBarrande, 1872,Silurocypridina calvaPerrier, Vannier and Siveter, 2011 andRichteria migrans(Barrande, 1872). These species have a palaeogeographically widespread trans-oceanic distribution, which supports the notion that Silurian myodocopes signify the earliest zooplanktonic ostracods.Richteria migrans(Barrande, 1872), in particular, provides a precise intercontinental biostratigraphic marker that identifies rocks of the upper Gorstian to upper Ludfordian stages.

Habitat factors differentiating the occurrence of Ostracoda (Crustacea) in the floodplain of a small lowland River Krąpiel (N-W Poland)

We analysed the occurrence of ostracods in a small river, taking into account all the types of water bodies in the floodplain − these included helocrenes, oxbow lakes, and ponds, as well as the main river channel. The objective of the study was to investigate the variation in ostracod communities and identify those factors determining species distribution. The environmental factors considered were the type of water body, responsible for 17% of the variance, the physical and chemical water properties (29%), and the biotic and abiotic factors associated with the substrate type (23%). Among the factors associated with the substrate, sediment sorting, plant coverage and insolation were the most important. The ostracod fauna of the helocrenes differed from that of the other water bodies in the floodplain. In the water bodies of the Krąpiel valley and in the main river channel, 33 ostracod species were recorded, of which 26 were found in the main river channel. Refugia in the floodplain were the main source of the diversity and abundance of ostracods in the main river channel. The mean density in the main river channel was very low, at 330 indiv. m−2, while in the water bodies of the floodplain it was the greatest, reaching up to 5568 indiv. m−2.

Towards objectivity in Ostracoda species definition

The problem of consistent identification of unornamented fossil ostracod taxa, especially species, is reviewed in an historical context. The solution lies in modern imaging and image storage and handling technologies combined with a careful but pragmatic (heuristic) approach to identification and taxonomy.

Late Glacial to mid Holocene lacustrine ostracods from southern Anatolia, Turkey: A palaeoenvironmental study with pollen and stable isotopes

This study investigates the ostracod assemblages obtained from a sediment core from a paleolake in the Sağlık plain in south-central Anatolia (Turkey). In addition to ostracods, oxygen and carbon stable isotopes of ostracod shells were analysed and pollen analysis of the core undertaken. The sediments comprise the Late Glacial and early Holocene interval with an approximate 14C age from 18,000 to 6700 14C years ago, after applying a correction for reservoir effects. Eight podocopid ostracod species were recorded, among them Cyprideis torosa and Candona sp. which were used for stable oxygen and carbon isotope analyses. C. torosa dominated during the Late Glacial while Candona sp. dominated most of the early Holocene assemblages. Both forms of C. torosa disappear abruptly close to the onset of the Holocene. Around this time, ostracod preservation was dominated by many black coloured valves and carapaces.Based on ostracod assemblage data and isotope analyses, relatively wet phases were identified for the Older Dryas, Younger Dryas, and during the mid-Holocene at around 7500 14C years ago. Relatively dry phases were identified during the Allerød interstadial, at the end of YD, and at about 6700 14C years ago. An oligotrophic and brackish lake persisted until shortly before the end of the YD, when, according to the δ 13C values, conditions gradually became more eutrophic. The sudden disappearance of C. torosa at the end of the YD seems the consequence of anoxic bottom water conditions and/or eutrophication.Alternating wet and dry phases characterize the early Holocene, with a longer period of wet and oligotrophic conditions around 7500 14C years ago (ca. 8300 calBP). Ostracod assemblages and isotope records indicate a dry and more productive lake around 6700 14C years ago (ca. 7550 calBP).

Shell and appendages variability in two allopatric ostracod species seen through the light of molecular data

Ostracod crustaceans are among the most abundant microfossil animals. Understanding intra- and interspecific variability of their shell is of pivotal importance for the interpretation of paleontological data. In comparison to appendages, ostracod shell displays more intraspecific variability (in shape, size, and ornamentation), often as a response to environmental conditions. Shell variability has been studied with sophisticated methods, such as geometric morphometrics (GM), but the conspecificity of examined specimens and populations was never tested. In addition, there are no GM studies of appendages. We build on previously published high cytochrome c oxidase subunit I (COI) divergence rates among populations of a brackish water species, Ishizakiella miurensis (Hanai, 1957). With landmark-based GM analyses of its shell and appendages, and additional genetic markers (ITS, 28S, 18S), we test if the genetic variability is structured in morphospace. This approach is the core of integrative taxonomy paradigm which has been proposed to bring the gap between traditional taxonomy and other disciplines such as evolutionary biology. The results show that it is the shell shape, and not the shape of appendages, that mirrors the molecular phylogeny, and we describe a new species. Our results suggest that the landmark-based GM studies may be useful in paleontological datasets for closely related species delineation. We implement molecular clock and population statistics to discuss speciation processes and phylogeography of the two congeners in Korea and Japan.

Mapping the observed and modelled intracontinental distribution of non-marine ostracods from South America

Ecological niche modelling (ENM) has been used to quantify the potential occurrence of species, by identifying the main environmental factors that determine the presence of species across geographical space. We provide a large-scale survey of the distribution of ostracod species in South America, by using the domains of 25 river basins. From 221 known ostracod species, we estimate the potential distribution of 61 species, using ENM. Ten clusters of potential distribution patterns were found. Clusters 8 and 9 grouped most of the species, which presented high similarity of niche between them. Heterocypris paningi Brehm, 1934 (group 1) obtained higher niche variability. The minimum temperatures of the coldest month and the mean elevation of the river basin were most important to predict the potential distribution of ostracods of most groups. South America has a complex pattern of elevation, which affects species distributions indirectly through changes in local factors. For instance, the Andes mountains might impose a barrier for ostracod distribution in the southern part of South America because of the low temperatures and precipitation. The ENM indicated that some regions and/or basins of South America might be susceptible to the entry of several ostracod species, presently absent, including non-native species.

Do Reproductive Modes and Swimming Ability Influence Occurrence of Non-Marine Ostracod (Crustacea) Species among Aquatic Habitats?

To gain a better understanding of the effect of reproductive modes and swimming ability on ostracod distribution, we visited 111 randomly selected aquatic sites in Kırşehir province. A total of 35 ostracods were newly reported for the area. The number of species with and without swimming setae was not statistically different, but numbers of sexual species was significantly lower than parthenogenetics. Species without setae did not show a significant difference between sexual and parthenogenetic forms. Numbers of species with (out) setae were not significant among different elevational ranges. Distribution of parthenogenetic species was common in all 11 habitat types when sexual species were only found from three different types located from 690 to ca. 1400 m of elevational ranges. Numbers of parthenogenetic species with or without setae did not show a difference among the ranges, but sexual species without setae exhibited wider distributional ranges (690-1289 m) than species with swimming setae (690-1089 m). Species' co-occurrence revealed two positive, five negative, and 44 random pairs of co-occurrences. Wards cluster analyses portrayed three main clustering groups. While group I includes parthenogenetic and sexual species, group II covers mostly parthenogenetic species with and without setae. Group III consists of species without setae. CCA results displayed three environmental variables (water temperature, pH and elevation) effective on species distribution. Species distributed in all elevational ranges tend to show lower optimum and wider ecological tolerances. Parthenogenetic species with swimming setae and with relatively higher tolerance ranges were dominant over sexual species. The present results suggest that swimming mode has a greater effect on species distribution among the habitats than reproductive modes.