Horseshoe crabs are harvested in large numbers for their blood, which is essential for testing medical equipment safety, raising novel welfare questions about an ancient species.
Horseshoe crab welfare presents a genuinely novel challenge at the intersection of medical necessity, ancient biology, and emerging invertebrate welfare science. The LAL test derived from horseshoe crab blood is currently essential for ensuring that medical equipment, vaccines, and injectable drugs are free from dangerous bacterial endotoxins - it is, in a very practical sense, saving human lives. Yet the harvest process is welfare-relevant: crabs are collected, transported, bled at industrial scale, and returned to the sea in a physiologically compromised state. Mortality rates from the process are disputed but significant, and surviving crabs show behavioural and physiological abnormalities that persist for weeks after return. Whether horseshoe crabs can experience pain or distress in a morally relevant sense is uncertain - their nervous systems differ substantially from vertebrates - but the precautionary principle argues for minimising harm. The existence of a validated synthetic alternative (rFC) that does not require horseshoe crab blood makes the welfare equation clearer: continued use of animal-derived LAL when rFC is available requires regulatory and industrial justification beyond technical necessity.