Molecular evidence of sexual polymorphism in the rare deep-sea lobster genus Thaumastocheles Wood-Mason, 1874 (Crustacea: Decapoda: Nephropidae)

Abstract

The rare deep-sea lobsters of the genus ThaumastochelesWood-Mason, 1874 are characterized by having conspicuously unequal first chelipeds, with the right cheliped greatly elongated and pectinate. The five species of Thaumastocheles are mainly separated by the shape of the teeth in the major chelae. Molecular analysis using four genetic markers (three mitochondrial: COI, 12S rDNA, 16S rDNA; one nuclear: ITS-1) on an extensive series of the species of Thaumastocheles from different localities reveals that there is sexual dimorphism and even male polymorphism in the major chelae in at least half of the species, with T. dochmiodonChan & de Saint Laurent, 1999 being the male form in T. japonicusCalman, 1913. Thaumastocheles dochmiodon is therefore considered a junior synonym of T. japonicus. The other species confirmed as showing sexual dimorphism and male polymorphism is T. massonktenosChang, Chan & Ahyong, 2014. A revised key is provided for the species of Thaumastocheles. Whether sexual dimorphism and male polymorphism are common phenomena in Thaumastocheles or even all thaumastocheliforms still awaits the collection and discovery of additional material of both sexes.