Shrimp are detritus feeders and ingest a wide variety of potential pathogens along with their food. The basal lamina is the last layer of defense against pathogens after it has penetrated the periotrophic membrane and epithelium of the midgut trunk. Being the only section of digestive track not lined with chitin, it is the spot where pathogens could enter into the body. Previous work in the lab has addressed the first two layers; my project focused on the permeability of the unusually thick basal lamina in the ridgeback prawn. Pieces of basal lamina were incubated with tracers of known size: India ink particles (500 nm), ferritin (10-20nm), and lanthanum nitrate (<2nm). Sections through these tissues examined by light and transmission electron microscopy suggest that only lanthanum was able to penetrate the basal lamina. Therein these projects will positively identify the composition of the basal lamina and certain sizes of pathogens that could be a significant risk.