Morphology and evolution of respiratory structures in the pleopod exopodites of terrestrial Isopoda (Crustacea, Isopoda, Oniscidea)

Abstract

Abstract The morphology of the respiratory structures located in the pleopod exopodites of terrestrial Isopoda is described for representative species of different genera. Special emphasis is set on the evolution of these lungs in the context of phylogenetic relationships as revealed by other morphological characters. In the most primitive species of the Oniscidea, and still of subordinate taxa of the Crinocheta, respiration takes place in the thin ventral integument of the exopodites. The evolution of dorsal respiratory fields with a weakly wrinkled surface occurred at least six times within the Crinocheta. In five of these cases, a further development can be observed. The evolution of a partly covered respiratory field with strongly wrinkled surface may have taken place six times. It is assumed that completely internalized lungs with spiracles surrounded by a water‐repellent surface microsculpture, evolved at least six times independently within the Oniscidea: in the Tylidae, Actaecia , Aphiloscia , the Eubelidae, the Armadillidae and in a taxon probably comprising Porcellionidae plus Armadillidiidae.