Sexual dimorphism in species of Schistura (Teleostei: Nemacheilidae) from the Mae Khlong basin and peninsular Thailand

Abstract

Sexually dimorphic characteristics are described for four species of Schistura from the Mae Khlong basin and peninsular Thailand. Males of S. mahnerti have a suborbital flap and rows of unculi on the upper surfaces of the pectoral-fin rays. Females of S. mahnerti have a suborbital groove. None of the morphological measurements differ significantly between males and females of S. mahnerti. In the other three species, S. aurantiaca, S. cf. aurantiaca, and S. sexcauda, all indi-viduals lack the flap or groove, but most males have a conspicuous black botch on the procurrent rays of the upper lobe of the caudal fin, a feature absent in most females. Some morphometric characteristics vary between sexes of these spe-cies. Sexually dimorphic traits presumably have a function related to reproduction; however, little is known about repro-duction in Schistura, and variation in morphology in relation to habitat or other environmental factors has not been studied. Copyright © 2001-2012 Magnolia Press.