Taxonomy of the sand bubbler crabs Scopimera globosa De Haan, 1835, and S. tuberculata Stimpson, 1858 (Crustacea: Decapoda: Dotillidae) in East Asia, with description of a new species from the Ryukyus, Japan

Sand bubbler crabs of the genus Scopimera are common on sandy shores in East Asia yet the taxonomy of the species remains unclear. Scopimera globosa De Haan, 1835, the type species, was described from Japanese specimens and also occurs in Korea and China. Scopimera tuberculata Stimpson, 1858, described from Japan, has been regarded a junior synonym of S. globosa, but the types had long been lost. Some workers have considered the two taxa distinct and S. tuberculata has been recorded from South China. In the present study, we confirm using male gonopod morphology and molecular analysis, that the early records of S. tuberculata from Hong Kong and S. globosa from Taiwan are in fact S. intermedia Balss, 1934. The present study regards S. tuberculata as a subjective junior synonym to S. globosa. A new species, Scopimera ryukyuensis sp. nov. from the Ryukyus, is identified and described herein. The new species is close to S. globosa but can be separated by carapace characters. The mitochondrial cytochrome oxidase I (COI) gene revealed basepair (bp) difference between the new species and other Scopimera spp. to be at the interspecific level, at least 28 bp (4.3\%).