Microloxoconcha, Hartmann, 1954

Smith, Robin James & Chang, Cheon Young, 2022, Two new species of non-marine Ostracoda (Crustacea) of the genera Vestalenula Rossetti & Martens, 1998 (Darwinuloidea) and Microloxoconcha Hartmann, 1954 (Cytheroidea) from Tsushima, Japan, and a summary of the non-marine ostracod fauna of the island, Zootaxa 5150 (4), pp. 529-555 : 547

Microloxoconcha

The genus Microloxoconcha consists of 13 species, reported from Japan, Hawaii, Ecuador, Tanzania, the Black Sea and France (see summary in Tanaka & Ohtsuka 2019). Eight are now known from Japan, but it is unclear if this is a result of a natural higher diversity of this taxon in Japan, or due to sampling bias. With the exception of Microloxoconcha semicircularis sp. nov., species are from sublittoral (up to 52 m depth) through to intertidal habitats, with seven of the species reported from beaches. Thus, Microloxoconcha semicircularis sp. nov. is the first species of the genus to be found in low salinity brackish waters of a tidal part of a river, but as the sample was collected at low tide, at other times of the tidal cycle the salinity may be higher. Microloxoconcha ikeyai Watanabe et al., 2008 was collected from interstitial habitats with a range of 1–33‰ salinity ( Watanabe et al. 2008), and other marine interstitial ostracods demonstrate high tolerance to a wide range of salinities (e.g. Tanaka & Tsukagoshi 2010). Thus, the presence of Microloxoconcha semicircularis sp. nov. from a tidal part of a river is not necessarily unexpected; other species may be found in similar habitats, and conversely, Microloxoconcha semicircularis sp. nov. may be found in other types of habitats. Although ostracods can be collected in habitats with wide-ranging salinities, it is often unknown if they are active throughout the tidal cycle (but see Tanaka & Tsukagoshi 2010). A strategy for dealing with such variable conditions may be to close the carapace and wait until salinities become agreeable. Thus, tolerance could be attained via behavioural changes rather than physiological adaptations.