Abstract Length measurements of sperms of 51 species of Cypridoidea ostracods were taken to supplement the paucity of ostracod sperm data in the published literature. The lengths of the posterior regions (carrying the mitochondria) and the thinner anterior regions were also measured when appropriate. Maximum lengths of sperms for individual species varied from 268 μm for Fabaeformiscandona velifera Smith and Janz, 2008 through to 11 787 μm for Australocypris robusta De Deckker, 1974; these lengths represent the shortest so far recorded for the superfamily and the longest ever recorded in ostracods, respectively. There appears to be only a loose relationship between taxonomy and sperm lengths. Species of the subfamily Candoninae generally have the shortest sperms compared with other subfamilies, but one Candoninae species, Candona altoides Petkovski, 1961, has sperms longer than some species of the families Cyprididae, Ilyocyprididae and Notodromadidae. The family Cyprididae showed the most variation, with sperms ranging from 1000 μm through to 11 787 μm in length. No hypothesis satisfactorily explains the origin of giant sperms in ostracods or the longevity of this trait through geological eras, and their existence remains enigmatic.
During the Eocene, Hahajima Island of the Ogasawara (Bonin) Islands of the Izu-Mariana Arc in the North Pacific was located near the present-day position of western Pacific Micronesia. We identified 17 Eocene ostracode species from the island, of which are new species and likely endemic to this island or to the West Pacific. These new species are systematically described herein and include: Costa matsumarui n. sp., Cytherelloidea ogasawaraensis n. sp., Havanardia ujiiei n. sp., Jugosocythereis nishii n. sp., Neonesidea boninensis n. sp., Schizocythere antiquimicronesiana n. sp., and Uroleberis hahajimaensis n. sp. The Eocene ostracode fauna has a higher rate of endemism than does the modern Micronesian fauna and contains Tethyan genera. These findings contradict a hypothesis that the Pacific fauna had a higher endemism rate after the Paleogene. The findings support another hypothesis that some genera invaded the Pacific from Tethys during the Paleogene. They suggest that West Pacific species did not disperse to the periphery of the Indo-West Pacific region during the Middle–Late Eocene. The “center of origin” hypothesis cannot be applied to Middle–Late Eocene marine ostracode biogeography.
The ostracod genus Sagmatocythere is known widely from marine environments on continental shelves and slopes and as fossils in the Upper Cenozoic strata. We describe S. sawa- nensis sp. nov., from the Lower Pleistocene Kawachi Formation on the coasts in Niigata Prefecture in the central Japan. Its geological and geographical distribution suggests that S. sawanensis sp. nov. is originated from the semi-isolated Sea of Japan and endemic during the Early Pleistocene, around 2.0 Ma. This is the first report on the genus Sagmatocythere in Japan and its adjacent areas.
Surveys of caves in South Korea yielded a new species of the ostracod genus Cavernocypris Hartmann, 1964, herein described as Cavernocypris danielopoli Smith & Kamiya n. sp. This is the fifth described species in this widely distributed genus, and can be discriminated from its congeners by the highly triangular shape of the carapace in lateral view, caused by a large dorsal protrusion on the left valve. A second triangular-shaped morphotype was also collected, differing from the first by a lower carapace and less pronounced dorsal protrusion. As it is not clear at present if this represents a separate species or intraspecific variation, it is left in open nomenclature. The lack of a pigmented eye, a highly triangular carapace and no carapace pigmentation suggests that Cavernocypris danielopoli Smith & Kamiya n. sp. is the most adapted species in the genus to a stygobiotic lifestyle. Another Korean species, Cavernocypris coreana (McKenzie, 1972), found in caves and spring discharges, has a reduced number of antennule segments, common for stygobiotic species, but this feature is lacking in the new species. This suggests that within the genus, species have followed different evolutionary pathways to adapt to the subterranean realm.
