Impacts of biomedical bleeding on locomotion and mating behavior in the horseshoe crab Limulus polyphemus

Abstract

Every year, more than 600000 horseshoe crabs are bled to produce Limulus amoebocyte lysate, which is used to detect Gram-negative bacteria in biomedical products. While numerous studies have shown that some horseshoe crabs die after being bled, less is known about what happens to those that are returned to their natural habitat. In this study, we used an array of VR2W acoustic receivers to track 10 bled and 10 control females during the mating season in the Great Bay Estuary, NH, USA. Animals were bled, or not, released where they had been initially captured, and tracked from 22 May to 26 June 2019. Bled and control females moved comparable distances at similar speeds during the weeks after they were released (controls: 90.3 m h-1; bled: 89.7 m h-1). The longer horseshoe crabs remained within the virtual positioning system array, the longer we were able to track them and the more beach approaches and mating attempts we were able to identify. When this relationship between the duration of time we were able to track a horseshoe crab and how many apparent mating attempts it expressed was taken into account, we found that bled females attempted to spawn half as often as control females, and this difference was significant. Overall, these data are consistent with previous findings indicating that females that are released back into their natural habitat after bleeding express similar levels of activity and seasonal movements but attempt to mate less than control animals, at least in the first few weeks after being bled.