Taxonomy, morphology and speciation of the Semicytherura henryhowei group (Crustacea, Ostracoda)

Abstract

The genus Semicytherura belongs to the family Cytheruridae, and was distinguished from Cytherura on the basis of carapace features. Species of Semicytherura from Japan and adjacent seas can be divided into two groups. One is represented by Semicytherura miurensis Hanai, 1957, characterized by a thin, oval carapace covered with fine reticulation. The other is represented by Semicytherura henryhowei Hanai & Ikeya, 1977, characterized by a thick sub-rectangular carapace in lateral view. Semicytherura henryhowei, which is distributed from Hokkaido to Okinawa in Japan, has been regarded as having several morphotypes distinguishable on outline and reticulation of carapace. However, as a result of detailed observations on the copulatory organ, carapace outline and distributional pattern of pore systems, remarkable differences are shown to exist between the two most frequently occurring morphotypes. In order to recognize S. henryhowei sensu stricto, the carapace of the holotype was re-examined. Consequently, neither of the two morphotypes are considered to belong to S. henryhowei due to differences of carapace outline and distribution of pore systems. The two morphotypes are here regarded as independent taxa, described as new: S. kazahana n. sp. and S. sasameyuki n. sp. The geographical distributions of the two new species overlap, but their micro-habitats differ from each other; the former lives on calcareous algae on rocky shores, the latter lives on silty sand bottom within the inner bay. A third new species, S. slipperi sp. nov., is also described. In view of their present geographical distributions and fossil records, the origin of this group of species would appear to be the Japanese islands or adjacent areas in and after the Miocene. This group then migrated to the Arctic Ocean and East Pacific Ocean during or before the middle Pliocene.

A New Species of <i>Semicytherura</i> (Crustacea: Ostracoda: Cytheroidea) from Obitsu River Estuary (Central Japan) and Its Microhabitat

“…Yamada et al (2005) and Yamada and Tsukagoshi (2010) has reported 4 benthic Semicytherura species. Semicytherura sasameyuki Yamada et al, 2005 was collected from the sediment samples of Maizuru Bay, and the other three species, S. slipperi Yamada et al, 2005, S. maxima Yamada and Tsukagoshi, 2010, and S. ikeyai Yamada and Tsukagoshi, 2010 were collected from the dredged samples of Akkeshi Bay. Based on the kind of the samples, it is possible that these species are infaunal.…”

First Report of an Interstitial Semicytherura (Crustacea: Ostracoda: Cytheruridae: Cytherurinae) : a New Species from Central Japan

“…The carapace of S. sagittijbrnzts (O.34 mm in length and O.15mm in height on average) is smaller than those of other epibenthic Semiaytherura (O.44mm in lengtli and e.23mm in height on average) and is comparable with those of some large interstitial ostracods (e.g., Microtoxo- tijbrntis. Data compiled from Sars (1866), Hanai (1957), Ishizaki (1966Ishizaki ( , 1981, Hazel and Valentine (1969), Schorriikev (1975), , Hanai et al, (1977), ), Frydl (1982, Yajima (1982), Tabuki (1986), Nohara (1987), Hiruta (1989Hiruta ( , 1991, lkeya et al <1992), Irizuki et al (2004), Yamada et al (2005), Hir'uta et al, (2007)…”

A morphological reappraisal of Tubifex blanchardi Vejdovský, 1891 (Clitellata: Tubificidae)

“…In any case, in many taxa the morphology of the copulatory organs is considered as a helpful tool in the identification of different species and in distinguishing sibling taxa, since even closely related species with similar morphology have strikingly different genitalia (Curini‐Galletti and Puccinelli 1998; Šimková et al . 2002; Yamada et al . 2005; Pastorino and Cohen 2006).…”