“…Despite the diversity within the Crustacea the paired excretory organs always consist of three regions -the end sac, excretory canal and short exit duct which opens to the exterior via a pore (Goodrich, 1945). In the branchiopod Anemia salina (Tyson, 1968(Tyson, , 1969 and the amphipod Corophium volutator (Icely & Nott, 1979) the excretory canal is simply a coiled or looped tubular structure, but in decapods the distal region is formed into a large, thin-walled bladder (Marchal, 1892;Peters, 1935;Maluf, 1939;Schmidt-Nielsen, Gertz & Davis, 1968). Further specialization of the excretory canal in freshwater crayfish has resulted in the loss of the tubular form of the proximal part by anastomization of the wall forming a labyrinthine region (Peters, 1935;Maluf, 1939;Peterson & Loizzi, 1973).…”