Meeting Abstract

P3.138  Wednesday, Jan. 6  Journey through the digestive system of Megathura crenulata, the giant keyhole limpet: morphology and enzyme activity. MARTIN, Gary G.*; MARTIN, Alanna M.; TSAI, Whitney; Occidental College, Los Angeles; Occidental College, Los Angeles; Occidental College, Los Angeles gmartin@oxy.edu

The morphology of the prosobranch gut has been examined at the anatomical and light microscope levels by early researchers and reviewed by Voltzow (1994). The role of each region of the gut is poorly understood. The first goal of this study was to provide a complete view of the ultrastructure of the digestive tract, identifying regions secreting materials into the gut lumen. We found that in addition to the salivary glands, a common cell type makes up the epithelium of the esophagus, style sac, and intestine, and shows apocrine secretion. The digestive gland is composed of two cell types described in other mollusks that are involved with the digestive process. Our second goal was to test each region for the presence of digestive enzymes. API ZYM results for 17 hydrolases are presented and compared with results from the abalone. Kits from Molecular Probes were used to test for protease, α-amylase, lipase, lysozyme and cellulase. Our results show the morphology of the gut as food passes along its entire length and the levels of digestive enzymes released from the secretory epithelium at each region. Unlike some reports, the esophagus and intestine seem capable of secreting enzymes that may work on food trapped within the mucus strands carried through the gut. The style sac and crystalline style show high levels of cellulase and lysozyme and the interplay of these enzymes require further investigation. M. crenulata is commercially important as the source of KLH, its respiratory pigment, which shows promise in the treatment of cancer and allergy. Information on its digestive physiology should help with the health of this animal in aquaculture settings.