Meeting Abstract
Arthropods are most notably differentiated by their open circulatory system, where vessels extend from the heart but eventually end, allowing hemolymph to flow into sinuses. The organs in the body of arthropods are directly bathed with hemolymph until the fluid returns to the heart. In crustaceans, the lining of the vessels and hemal spaces is often coined a basal lamina, despite obvious differences from the acellular layers more thoroughly studied in vertebrate systems. In the latter, the basal lamina lies beneath the epithelium and is composed of type IV collagen and a collection of proteoglycans such as laminin. Exposure of the basal lamina is one trigger for blood coagulation. Previous studies have demonstrated fibrillin in the acellular layer lining major vessels in the lobster and have begun to address the extracellular matrix in several invertebrates. Our study has used electron microscopy to characterize the basal lamina of large and small vessels as well as the lining of hemal spaces within and on the outside of the heart, muscles, and gut of the shrimp Sicyonia ingentis and a variety of other crustaceans. Immunofluorescent staining of these areas with antibodies to type IV collagen and fibrillin identified the materials “seen” by circulating hemocytes and show that exposure to the “basal lamina” is an important step in identifying what these organisms consider self vs non-self.
