Similar distribution pattern of different phenotypes of Limnocythere inopinata (Baird) in a brackish-water lake in Inner Mongolia

Abstract

It has been recognized long ago that Limnocythere inopinata is a widely distributed ostracod and comprises various phenotypes. The taxonomy of the different phenotypes and their ecological differences, however, are still under debate. In this study, we investigated the relationships between ostracod distribution, water depth, and the substrate based on the analyses of species composition, abundance, and age structure of ostracods in 51 surface-sediment samples from Dali Lake in Inner Mongolia in order to reveal the distribution pattern and habitat characteristics of the ostracods. The identification of a total of 32,182 valves indicates that the dominant ostracod in Dali Lake is L. inopinata, which includes unnoded, 1-, 2-and 3-node and 1-carina phenotypes. The distribution of L. inopinata is affected both by the water depth and by the sand content of the substrate, and the phenotypes show their maximum abundances in the intermediate zone of the lake. All the phenotypes of L. inopinata display a similar preference for water depth and substrate, implying that the occurrence of different phenotypes is controlled by other factors. The age structure of L. inopinata is mainly related to the sand content, with the percentage of adults increasing and that of early juveniles decreasing with increasing sand content. Our data suggest that the occurrence of L. inopinata is closely related to water depth and substrate grain size, and different phenotypes of L. inopinata respond in a similar pattern to water depth and substrate.

Differential transport and preservation of the instars of Limnocythere inopinata (Crustacea, Ostracoda) in three large brackish lakes in northern China

“…We did not sample the deepest part of Lake Dali (ca. 10 m depth, in the southwest of the lake), but an earlier investigation (Zhai et al, 2010) revealed that this area contain sparse populations of L. inopinata that are very rich in early juveniles and are deprived of adults. So it is likely that downslope contamination has influenced the whole profundal area of Lake Dali.…”

“…These 1-cm samples may cover the past one to three decades as estimated from the age-depth models of the sediment cores retrieved from these lakes (Xiao et al, 2004(Xiao et al, , 2008(Xiao et al, , 2009). In the laboratory, ostracod valves were extracted from freeze-dried samples following the method described by Zhai et al (2010Zhai et al ( , 2013, which used Na 2 CO 3 -buffered H 2 O 2 solution (pH 9-10) to disaggregate the sample before it was sieved and then pipetted onto some glass plates for microscopic examination. No distinction was made between the valves of 'living' and 'dead' specimens.…”

“…Limnocythere inopinata is the dominant ostracod in the three lakes (Zhai et al, 2010. In Lakes Daihai and Dali, usually 50-100 randomly selected valves of L. inopinata from each sample were scored.…”

Freshwater ostracods as environmental tracers

“…Cytherissa lacustris, Limnocythere inopinata or Cyprideis torosa show smooth, punctuated, reticulated or noded carapaces (Fig. 4) depending on salinity range (Vesper 1975;Zhai et al 2010) and have rounded pores in freshwater environments, whereas irregular pores are present mainly in oligohaline to hypersaline waters. Rosenfeld and Vesper (1977) proposed a graphic diagram to calculate palaeosalinities based on percentages of round, elongate and irregular sieve pores of this species, which have been used in the palaeoenvironmental reconstruction of sediment cores (Gliozzi and Mazzini 1998).…”

Synchronous drying and cooling in central Asia during late Oligocene

“…The extraction of fossil ostracod valves followed the peroxide method described by Zhai et al [15]. We identified ostracods in the samples according to the taxonomy of Jiang et al [16], Meisch [17] and Hou et al [18].…”