Morphology of the pleopodal lungs in the Eubelidae (Crustacea, Oniscidea)

The morphology of the respiratory organs of pleopodal exopods has been investigated in the family Eubelidae (Crustacea, Oniscidea). This family, considered here as a monophyletic unit, includes 39 genera and 216 species, which, with the exception of the genus Saidjahus, all live in tropical Africa and Arabian Peninsula. Only two genera, Elumoides (two species) and Parelumoides (one species), have no pleopodal lungs, most probably due to secondary reduction. All the other genera possess lungs, which, however, vary in number and structure. In the Eubelidae, pleopodal lungs are present on exopods 1 (two genera), 1-2 (11 genera), 1-3 (one genus) or 1-5 (23 genera). All the intermediate morphological steps are represented, from the Atracheodillo-type (Oniscus-like) lung consisting of a folded, uncovered respiratory surface, to the highly specialized Periscyphis-type (Hemilepistus-like), where extarnally the tubuliform lung terminates in an extremely narrow cleft, and internally its branches penetrate the body cavity. Correlations with ecological adaptations are discussed in brief.