Development of external sexual characters in the deep-sea sponge-associated shrimp Spongicola japonica Kubo (Crustacea: Decapoda: Spongicolidae)

Abstract

Development of external sexual characters in the deep-sea sponge-associated shrimp, Spongicola japonica Kubo is investigated. Sexual dimorphism is observed in the gonopore, pereopod 3, abdominal width, pleuron and pleopods, and the size difference between paired shrimps is apparent. The external appearance of the gonopore is the first evidence of sexual dimorphism, opening on the coxa of pereopod 3 of females, while on the coxa of pereopod 5 of males. In females a slower growth rate for the pereopod 3 chela length and a positive growth rate for the abdominal width is recognized when both sexes are compared. The morphological changes in abdominal appendages during the formative period of the brooding chamber are illustrated.