Search

A new species of the genus Polycopetta Chavtur, 1981, Polycopetta quadrispinata sp. n. is described from the interstitial environment of Mihomasaki Beach in Japan. These observations showed some morphological peculiarities of Polycopetta quadrispinata sp. n. compared with its congeners; P. monneroni Chavtur, 1979, P. curva Chavtur, 1979, P. bransfieldensis (Hartmann, 1987), and P. pax Kornicker and Harrison-Nelson, 2005. Three characteristics are described for the first time: (1) a seta with serrated tip on the male antennula, (2) the endopodite of the fifth limb consisting of two podomeres, (3) the long spermatozoa in the male posterior body. More detailed observations of the type species are needed in order to update the generic diagnosis.

Two new species of the interstitial ostracod genus Parvocythere, P. gottwaldi sp. n. and P. gracilis sp. n., are herein described. Although these two new species are clearly distinguishable by certain morphological differences in elements of the male copulatory organ, and the carapace, they share the following simplified characters of the appendages and male copulatory organ: antennular fourth podomere with no suture; reduced claws on the distal end of antenna; and asymmetric male copulatory organ. The morphological differences among known and new Parvocythere species suggest that the species of this genus can be classified into two groups by the presence/absence of the suture on the antennular fourth podomere. The “Group S” is characterised by the presence of the antennular suture, and all species of this group have a two-clawed antenna and symmetric male copulatory organ, characters which are generally seen in cytheroid ostracods. The species belonging to “Group N” are characterised by the absence of the suture, regarded as a pedomorphic character, show the following characters: two clawed or one clawed antenna, and symmetric or asymmetric male copulatory organ. The morphological variation within Group N includes reductive characters regarded as an adaptation to the narrow spaces of the interstitial environment of a sandy beach. These intrageneric morphological variations of the exclusively interstitial genus Parvocythere suggest the possibilities that Group N might be derived from Group S, and that some adaptive characters to an interstitial environment could have developed after the colonisation of these environments.

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. [ABSTRACT FROM AUTHOR]

One survey was done with SCUBA diving in Ha Long Bay and Cat Ba Island, Northern Vietnam (December 2013) and another one at Nha Trang Bay Marine Protected Area, Nha Trang city, Central Vietnam and Phu Quoc Marine Protected Area, Kien Giang Province, Southern Vietnam (November 2014). Sixteen species of the genus Loxoconcha and fourteen species of the genus Xestoleberis were found and identified. Eight species of the genus Loxoconcha were identified in group A, three species in group B, two in group C and three unidentified. Meanwhile, twelve species of the genus Xestoleberis were classified in group A and two in group B according to phylogenetic groups. From geographical distribution of the pore groups of the species in two genera Loxoconcha and Xestoleberis showed that the fauna of these genera in Vietnam is close to those of southern part of Japanese Island Arc, i.e., from Amami Island to the Philippines and Australia rather than Japanese Island Arc faunas. [ABSTRACT FROM AUTHOR]

The ostracod genera Parapolycope Klie, 1939 and Kliecope Tanaka, Tsukagoshi & Karanovic, 2014 have a sexually dimorphic upper lip, and males use their lip during courtship. Here we study the male upper lip of 14 species in order to find homologous structures. For this purpose, the lip is divided into six homologous parts, determined by their relative position on the lip and the lip's position in relation to other body parts. We found that the distal part ('c') is the most variable across taxa, probably due to high sexual selection. Six characters of the male upper lip are used in our cladistic analysis, along with another 12, in order to study phylogenetic relationships between Parapolycope species from East Asia. In addition, 18S rRNA is used to reconstruct molecular phylogeny and test the congruence between morphological and molecular data. The recovered topology on all obtained trees is almost identical, emphasising the importance of the male upper lip morphology in interpreting phylogenetic relationships in this peculiar ostracod group. Parapolycope viriosa, sp. nov. and P. widoensis, sp. nov. from marine interstitial habitats in South Korea are described here. To aid further identification of the 12 East Asian Parapolycope species we provide a taxonomic key. [ABSTRACT FROM AUTHOR]

The ontogenetic changes of the maxillula in Loxoconcha noharai Le and Tsukagoshi, 2014 from the second instar (A-7) through to the adult are described. The general development and number of setae on the maxillula of L. noharai are the same as L. japonica Ishizaki, 1968 from the second (A-7) to the fourth instars (A-5), but differences in these characters are found between the two species in and after the fifth instar (A-4). The number of setae on the endites and endopodite of the maxillula of L. noharai reaches a maximum in the pre-adult stage A-1, whereas in other species, it continuously increases throughout all ontogenetic stages. The maxillula of L. noharai bears fewer setae and claws throughout ontogeny compared with other species in different superfamilies. This tendency reflects possible paedomorphic evolution in L. noharai . In addition, the new species Loxoconcha yoshidai sp. nov., from the Okinawa Islands, southern Japan, is described herein. The distribution pattern of pore systems below the eye tubercle, which is used to divide the genus Loxoconcha into groups, shows that this new species has an unstable intermediate state between Groups B and C. [ABSTRACT FROM AUTHOR]

This study is a first report of an interstitial ostracod from Southeast Asia. The ostracod species, Paracobanocythere vietnamensis sp. n., was found in the marine interstitial environment of Phu Quoc Island, Vietnam. Thus far, three species of this genus have been described. The morphology of the carapace as well as the appendages of this new species are quite similar to P. hawaiiensis and P. watanabei. However, we found that they could be easily distinguished according to the morphology of the male copulatory organ. Additionally, we estimated the evolutionary distances among these three species based on nucleotide and amino acid sequences of the mitochondrial CO1 gene. Similar morphologies of carapaces and appendages, and relatively small evolutionary distances according to CO1 between P. vietnamensis sp. n. and P. watanabei suggest that these two species are very closely related. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]