AHMAD, Nina; COURSEY, Yvonne; STEIMEL, Nancy; KIMBLE, Mary: Blood Cell Production Begins at Stage 18 in the American Horseshoe Crab, Limulus Polyphemus.

The blood cells, or hemocytes of the American horseshoe crab, Limulus polyphemus, are used for production of Limulus Amebocyte Lysate (LAL). LAL is widely used in the medical field to test for the presence of endotoxins. Despite the fact that the blood cells of Limulus have been extensively studied since the 1950’s, the onset of blood cell production during embryogenesis has yet to be determined. Liang et al. (1990) reported that in the Asian horseshoe crab, Tachypleus tridentatus, blood cell production begins at stage 13. We hypothesized Limulus would begin blood cell production at about the same stage of development. Using a protocol developed in our lab and staging as described by Skiguchi et al. (1988), we analyzed stages 13 through 19 using a combination of histological and immunological stains to identify blood cells. Our results show that blood cell production begins at a latter stage (stage 18) in Limulus than in Tridentatus.