Molecular and morphological diversity of Heterodesmus Brady and its phylogenetic position within Cypridinidae (Ostracoda)

Ostracod genus HeterodesmusBrady, 1866 is known thus far to contain only three species: H. adamsiiBrady, 1866; H. apriculusHiruta, 1992; and H. naviformis (Poulsen, 1962). This genus has been recorded from the Sea of Japan, and the coastal areas of Thailand and Vietnam. The main generic character is the presence of antero-dorsal and postero-dorsal tube-like processes on the rostrum on both valves. The three species mostly differ in the shell lateral projections. Their relationship and the position of Heterodesmus within family Cypridinidae are poorly understood, partly due to the lack of publication of DNA data so far. We study Heterodesmus collected from several localities in the Northwest Pacific, namely Tsushima and Iki Islands in Japan and Maemul Island in Korea. Besides morphological characters, we also use two mitochondrial markers (16S rRNA and mtCOI) and three nuclear regions (18S rRNA, 28S rRNA, and internal transcribed spacer - ITS) in the samples to detect the biodiversity of this genus. Our phylogenetic tree based on molecular data coupled with morphology reveals the presence of two species, H. adamsii and H. apriculus. We report on their morphological variability, molecular diversity, and phylogenetic position within Cypridinidae based on 16S, 28S and 18S rRNAs, and provide a taxonomic key for all living genera of this family. For the first time, we give an overview of the intrageneric and intrafamily DNA distances of the above markers for the entire subclass Myodocopa.</p

Phylogenetic position of Xenoleberis Kornicker, 1994 within Cylindroleberidinae (Ostracoda: Myodocopa) with descriptions of three new species and one new genus from the Northwestern Pacific Ocean

Cylindroleberididae is a peculiar ostracod myodocopid family, characterized by the presence of gills. It accounts for over 200 species described from all bathymetric ranges and from all the world’s oceans. Nevertheless, its biodiversity is still underestimated, with each study brining new taxa to the list. As a result of recent sampling effort in seas around Korea and Japan, we report five cylindroleberid taxa. One of those is described as a new genus (Toyoshioleberis gen. nov.), and four belong to Xenoleberis Kornicker, 1994. Of the latter, three are described as new species, and one has already been reported from Japan, but is the first record for Korea. In fact, our study is also the first record of the family from this country. Having fresh samples provided an opportunity to obtain sequences of three gene markers (16S, 28S, and 18S rRNA), and, by combining those with the ones belonging to Cylindroleberididae available in GenBank, we reconstruct a molecular phylogeny with the aim to assess the position of the new taxa within the family and try to resolve the currently polyphyletic nature of some cylindroleberid taxa. The results of the phylogenetic analyses indicate the monophyly of Xenoleberis and its deep separation from Toyoshioleberis, along with distinct morphological features genetics to support our taxonomic decision. In addition, the phylogenetic results confirm that the general systematic of Cylindroleberididae should be reassessed, in particular the tribes of the subfamily Cyclasteropinae should be given a higher systematic ranking, as suggested previously based on morphology alone.</p

Two new xylophile cytheroid ostracods (Crustacea) from Kuril-Kamchatka Trench, with remarks on the systematics and phylogeny of the family Keysercytheridae, Limnocytheridae, and Paradoxostomatidae

Keysercythere reticulata sp. nov. and Redekea abyssalis sp. nov., collected from the wood fall submerged in the Kuril-Kamchatka Trench (Northwestern Pacific), are only the second records of the naturally occurring, wood-associated ostracod fauna from a depth of over 5000 m. At the same time, K. reticulata is the second and R. abyssalis is the third representative of their respective genera. While Keysercythere Karanovic and Brandão, 2015 species are free-living, deep-sea taxa, all Redekea de Vos, 1953 live symbiotically on the body surface of wood-boring isopods, Limnoria spp. Since R. abyssalis is the only genus representative found in the deep sea, we hypothesize that its ancestor colonized this ecosystem as a result of the symbiotic relationship. Newly collected material enabled us to update molecular phylogeny of Cythreoidea based on 18S rRNA gene sequences, especially to clarify the current systematics of the families Keysercytheridae, Limnocytheridae, and Paradoxostomatidae. The resulting phylogenetic tree supports a close relationship between Keysercythere and Redekea and a distant relationship between two Limnocytheridae lineages, Timiriaseviinae and Limnocytherinae. Consequently, we propose a transfer of Redekea from Paradoxostomatidae to Keysercytheridae, and erecting of the two limnocytherid subfamilies onto the family level. The phylogenetic analysis also implies a close relationship between the nominal Limnocytherinae genus and Keysercythere+Redekea clade, albeit with a low posterior probability, requiring further studies to clarify this.</p