Microthelphusa sucreensis, a new species of Pheudothelphusidae (Decapoda), with notes on abnormalities in the sexual appendages of fresh-water crabs

Malformations of the sexual appendages of Neotropical freshwater crabs are very rare. In two lots of specimens of a new species of the pseudothelphusid, Microthelphusa sucreensis, collected in 1930 and 1993, one male specimen from each lot has gonopodal malformations. In one case, the left first gonopod displays grass morphological deviations from the normal shape, and in the second case the right second gonopod has an additional rudimentary appendage resembling the first gonopod. In the Trichodactylidae, a specimen of Sylviocareinus pyriformis (Pretzmann, 1968) was observed to posses a bifid first left male gonopod. An intersexual specimen of Valdivia serrata White, 1847, had normal first and second male gonopods and three pairs of additional pleopods all similar to the second gonopod. The left appendage on the fifth pair was clearly a female pleopod.