The Story Behind the Discovery of Hemigrapsus takanoi Asakura and Watanabe, 2005, a Cryptic Species of Crab, Previously Thought to be the Common Japanese Intertidal Crab H. penicillatus (Decapoda: Brachyura: Grapsoidea)

Abstract

In 1997, Masatsugu Takano and the applied population genetics research group at Tohoku University published a ground-breaking paper on biochemical and morphological evidence indicated that there were two sympatric forms, interpreted as sibling species, of the common crab Hemigrapsus penicillatus (De Haan). This species is very common in intertidal rocky shores, pebble beaches and mud flats in Japan, Korea and China, but prior to Takano et al., no one had noticed that the species comprised two different forms. A recent intensive study by Prof. Seiichi Watanabe, Tokyo University of Marine Science and Technology, and his research group revealed further differences between the two forms, including coloration, allometry, egg size and number, and geographical distribution. Watanabe and myself recognized these as two distinct species and described one of them as a new species Hemigrapsus takanoi in 2005.