Meeting Abstract

P2.84  Sunday, Jan. 5 15:30  Does chitin line the open circulatory systems of crustaceans and mollusk? MARTIN, G.G.; Occidental College, Los Angeles gmartin@oxy.edu

Chitin is the second most abundant organic compound in nature, behind cellulose and billions of tons sink from molted crustacean exoskeletons to the ocean floor every year. More piles up as waste at culture facilities. In addition to exoskeletons, chitin is found in egg coverings of nematodes, radulae of mollusks, peritrophic membranes, nudibranch epidermal cells, tubes of the hydrothermal vent worm Riftia, and the squid pen. A rather surprising location is its recent description in vesicles and granules in circulating hemocytes of mollusks and crustaceans. The identification of chitin is typically based on its insolubility in concentrated potassium hydroxide and its selective staining with the lectin wheat germ agglutinin, especially its succinylated form. WGA binds to N-acetyl –D-glucosamine the precursor of chitin. Although it is possible that hemocytes migrate to and deposit chitin on the tissues listed above, we have asked if the hemocytes may be involved in producing the intima that lines blood vessels and sinuses in animals with open circulatory systems. This poster presents results showing the staining of the lining of some blood spaces with fluorescently labeled WGA and complementary TEM images of a variety of tissues including heart, gills, and blood vessels, in the shrimp Sicyonia ingentis and the giant keyhole limpet , Megathura crenulata. Our results suggest that the N-acetyl –D-glucosamine contained within hemocytes from these two phyla may indeed participate in producing the boundary layer between hemolymph and tissues which is relevant to circulation and immune responses. Future work will ask if hemocytes may also deposit chitin in the nodules they form around encapsulated foreign materials.