EXOLYSOSOMES, ENZYME-CONTAINING VESICLES IN THE ECDYSIAL SPACE OF MOLTING CRABS

Free vesicle-like bodies (VLBs) present in the ecdysial space of cutic le regions undergoing degradation during preecdysis of the Atlantic sh ore crab Carcinus maenas have been interpreted either as infectious or ganisms or as secretion structures associated with degradation of the old cuticle, Ultrastructural, cytochemical, and immunocytological inve stigations were performed to test these hypotheses and to see whether VLBs are peculiar to this crab species. Similar VLBs were systematical ly found in two other preecdysial crabs, Cancer pagurus and Macropipus puber. In Car, maenas, they originate during early premolt inside Gol gi buddings and are often gathered into large vacuoles in epidermal ce lls, The histochemical ate-dye technique and a cerium-based cytochemic al method revealed acid phosphatase activity in both the ecdysial spac e and the VLBs, while Feulgen's method and immunocytological labelling always failed to reveal any DNA or RNA in either the ecdysial space o r the VLBs. We conclude that VLBs are not infectious organisms but ''e xtracellular'' cuticle-degrading organelles of lysosomal origin and pr opose to coin them ''exolysosomes.'' (C) 1997 Academic Press.