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.