Morphological and molecular investigation of polymorphism and cryptic species in tanaid crustaceans: implications for tanaid systematics and biodiversity estimates

A combination of traditional taxonomic procedures and molecular techniques has provided new insight into the problems of cryptic species and sexual an d ontogenetic polymorphism in the Tanaidacea. Using polymerase chain reacti on and DNA markers, three cryptic species of Paratanais were identified. PC R primers were used to amplify the divergent internal transcribed spacers ( ITS) of these species. Restriction digestion of the amplified rDNA generate d species specific DNA banding. Male and five female stages of Paratanais m aleficus sp. nov. and two other new species, P. malignus and P. perturbatiu s, are described. Morphological variation, both sexual and ontogenetic, was found in several generic characters of Paranais and required the diagnosis to be modified. The identification of three undescribed cryptic species fr om a single microhabitat in a well studied, shallow water and easily access ible locality, demonstrate that the biodiversity of tanaid crustacean is si gnificantly underestimated. (C) 2001 The Linnean Society of London.