Morphological aspects of the Hyalella Smith, 1874 (Crustacea: Amphipoda: Hyalellidae) genus

Abstract

Hyalella is the only genus of crustacean amphipods found on the surface waters of the Brazilian territory. When we move to the underground, however, Hyalella shares the space with other amphipods. It seems to be, to this day, the less adapted genus of amphipods to the underground medium. The morphology within the genus, especially amongst the Brazilian epigean and hypogean species, is extremely preserved. There isn’t, to this day, any research that demonstrated the influence of the environment on the morphology of Hyalella. This thesis has four chapters. On the first one, we found that, among other variables, the minimum annual temperature is the environmental variable that affects more morphological variables, followed by the life habit (epigean or hypogean). On the second chapter we present the description of a new species of Hyalella found at “Gruta da Água Sumida” and the reconstructed phylogeny of Brazilian Hyalella based on two genes. On the third chapter we describe two new parapatric species of the genus and redescribe another, all of them found on the same river. Finally, we present another two new species of Hyalella together with a pictorial key of identification for cave related Brazilian Hyalella (troglobiotic and troglophile species).