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.
A new ostracod species, Semicytherura obitsuensis sp. nov., is described from the intertidal zone of the Obitsu River estuary, Chiba Prefecture, central Japan. As S. obitsuensis sp. nov. individuals were collected from muddy sand bottoms in tidal creeks, possess some carapace-features comparable to those of interstitial and infaunal ostracods, and were observed to crawl in detritus rich fine-grained sediment in the laboratory, we concluded that this new species is an infaunal species.
Herein, two new bairdiid ostracod species in the western Pacific Coast of Japan, namely Neonesidea kamiyai sp. nov. and Bairdoppilata japonica sp. nov. are described. They are the fourth and first species described in their respective genus in Japan within the Recent Bairdiidae. The description of the two new species is based on scanning electron microscopic investigation of carapaces and on the analysis of anatomy and chaetotaxy of appendages. Scanning electron microscopy of the carapace and soft-part anatomy of appendages of the two new species provided the complete species description. An asymmetric brush-shaped organ, with the right part considerably larger than the left part, is found in both species; this characteristic is suggested to be synapomorphic for some taxa in the family Bairdiidae.
Species of the genus Spinileberis (Crustacea: Ostracoda: PodDcopida:Cytheridae) have been recorded frequently from brackish waters around the North Pacific Ocean and as fossils from sedimentary deposits of and after the Neogene of East Asia. A new species of this genus, S. endoi, is heretn described from the Philippines. In having a thick and ragged carapaee and merodont hingement, the new species substantially differs from the type species of the genus, S, quadriaculeata
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