Redescription of a 'rare' crab Hemigrapsus longitarsis (Miers, 1879) (Decapoda: Brachyura: Varunidae) based on the newly designated lectotype and recently collected material from Osaka Bay, central Japan, with some ecological notes

摘要

The varunid crab Hemigrapsus longitarsis (Miers, 1879) is widely distributed in East Asia; however, morphological characters of the crab have been poorly described. Herein we redescribe the species in detail, based on the newly designated lectotype and 149 recently collected specimens from Osaka Bay, central Japan. Comparison with 60 specimens from other localities showed close agreement with one another. The species is characterized by (1) subquadrate carapace with 3 distinct anterolateral teeth, (2) carapace covered with short setae, (3) relatively small chela with large patch of dense soft setae in males, and (4) long slender ambulatory legs, with dactyli longer than respective propodi. These characters correspond to the descriptions of Hemigrapsus longitarsis in previous papers, although Sakai (1935, 1939, 1976) had made no mention of the presence of the patch of setae on the male chela. Variation and some ecological notes of the species are also reported.