The giant keyhole limpet, Megathura crenulata , is an archaeogastropod characterized by a strong muscular foot that is able to attach to various substrates. This animal resides in the intertidal and subtidal zones ranging from Monterey, California down to Baja, California. M. crenulata has recently become an animal of interest because of its respiratory pigment, Keyhole Limpet Hemocyanin (KLH). KLH has been shown to be effective in the clinical treatment of cancer. Stellar Labs in Oxnard is developing ways to culture these limpets and to non-lethally extract their blood (and KLH). Our goal is to understand the function and structure of each region of the gut in order to learn more about the nutritional needs of these limpets and also to screen for possible gut-associated pathogens. The main parts of the gut include the pharynx, esophagus, intestine, and digestive gland. Using various histological stains, different cell types were identified. Light and electron microscopy suggest that several regions of the gut have secretory cells. The possibility that these secretions are involved with food digestion is the next topic we wish to address. The diet of these limpets is not yet known.