The effect of heavy bleeding on mortality of the horseshoe crab, Limulus polyphemus, in the natural environment

The goal of this study was to ascertain the impact of bleeding such as is done to produce Limulus lysate (LAL) on a horseshoe crab population after animals are returned to the natural environment. Techniques used to evaluate the impact of bleeding on subsequent survival included a field tagging experiment and an analysis of survival in the laboratory after bleeding. Approximately 10,000 mature Limulus polyphemus were collected, described, and individually tagged. Half were bled and half were handled as controls. All were released into the field. An analysis of the rate of tag recovery for the two groups indicates that bleeding increases mortality by 10% during the first year after bleeding. Crabs rebled after 4 weeks at large had recovered their blood volume. Animals recovered during the second year showed an 11% increase in mortality of bled over control animals. Animals held in the laboratory showed no significant differences in activity after bleeding as compared to unbled controls. Lysate bleeding followed by release of the animals does not appear to constitute a threat to current population levels of L. polyphemus.