KIMBLE, M.*; TREMBLAY, N.; HINSCH, G.W.; COURSEY, Y.; ARMSTRONG, P.B.; Northeastern Illinois University; University of South Florida; University of South Florida; University of Massachusetts, Dartmouth; University of California, Davis: Cyanocytes in Limulus polyphemus trilobite larvae.

The overall structure and function of hemocyanins, the primary oxygen transporting proteins in arthropods, is similar in different species, however, the site of protein synthesis varies substantially. In some species, hemocyanin is produced in glandular tissues and secreted into the hemolymph, while in others, including Limulus polyphemus, specialized cells (cyanocytes) are thought to be responsible for hemocyanin synthesis. In these species, the hemocyanin accumulates and assembles into intra-cytoplasmic crystals that eventually fill the extra-nuclear space of the cells. Release of the hemocyanin appears to be accomplished by cell lysis and crystal disassembly. Although the structure, composition and functions of L. polyphemus hemocyanin has been extensively studied, little is known about the location or origin of the cyanocytes, beyond Fahrenbach�s report of cyanocytes in the sinus spaces associated with the compound eyes. Using a polyclonal anti-hemocyanin antibody, we have identified clusters of cells that stain for hemocyanin in trilobite larvae. The largest clusters are located within the coxal regions of each pair of legs, while smaller clusters of cells are observed adjacent to the foregut. Electron microscopy of the coxal regions of the legs revealed cells containing hemocyanin-like crystals, suggesting that the antibody positive cells are immature cyanoblasts. Supported in part by the USF-RC (MK), and the NSF (PBA) grant #0344360.