Sexual dimorphism in Australian Echiniscus (Tardigrada, Echiniscidae) with descriptions of three new species

The presence of males in species of Echiniscus has been reported only as recently as 1987 and is still considered to be rare. However, males have been found to be common in a disproportionately large number of species of this genus found in Australia. Evidence of sexual dimorphism is presented for five species (three of which are new to science), females and males of which are differentiated on the basis of distinctive gonopores. In all five species males are shorter with longer clavae. Males of Echiniscus jamesi sp. nov., Echiniscus rodnae sp. nov. and Echiniscus curiosus sp. nov. have significantly longer claws. In E. rodnae sp. nov. and E. curiosus sp. nov. males have significantly longer lateral trunk appendages and the dorsal trunk appendage combinations of males of the latter are different from those of females. The widespread distribution of bisexual species of Echiniscus in xeric habitats in Australia does not support the current theory that parthenogenetic species are favoured in such environments.