Gill Morphology and Formulae of European Astacidae

We examined gills (podobranchs, arthrobranchs and pleurobranchs) from five European Astacidae (Austropotamobius pallipes, Austropotamobius torrentium, Astacus astacus, Pontastacus leptodactylus and Pontastacus pachypus) to assess the relationships between their phylogeny and gill morphology and formulae. In addition, we checked for the presence or absence of pleurocoxal lappets. The morphology of the gills and associated structures was similar in all examined European astacid species except for three rudimentary pleurobranchs found in P. pachypus. In European Astacidae and Cambaroididae, the pleurocoxal lappets are absent but are present in the American Astacidae, Cambaridae and Parastacidae. The number of pleurobranchs decreases from the most primitive Parastacidae to the most advanced Cambaridae. Nevertheless, although the most primitive parastacid crayfish and the most advanced Cambaridae all have pleurocoxal lappets, they are absent in European Astacidae and Cambaroididae, which suggests that a reversible gill morphology has occurred in crayfish evolution.