28th ANNUAL EASTERN FISH HEALTH WORKSHOP April 21-25, 2003 Investigations Into The Euthanasia Of Decapod Crustaceans Using The Green Crab Carcinus maenas As A Model Amy L. Hancock1 and Roxanna E. Smolowitz2 1 Harvard Medical School, Center for Animal Resources and Comparative Medicine, 665 Huntington Avenue, Boston, MA 02115; 2 Marine Biological Laboratory, Veterinary Services, 7 MBL Drive, Woods Hole, MA 02543 We investigated the use of Euthasol (Delmarva Laboratories), potassium chloride (KCl) solution (330 mg/ml solution), and eugenol (Sigma), for use in the humane euthanasia of decapod crustaceans using the green crab Carcinus maenas as a model.  Adult intermolt green crabs (average weight = 48.5 grams) were held in tanks receiving flow-through seawater at ambient temperature (21.9ºC – 23.4ºC).  Animals were acclimated for at least 24 hours prior to experiments.  Crabs were considered conscious if they were responsive to stimuli applied to the eyestalks and the third maxillipeds; these responses determine if the cerebral and thoracic ganglia, respectively, are still functioning.  Crabs were considered dead in the absence of these reflexes, and when respiration and movement of all appendages had ceased.  Euthasol (0.5 ml per crab) and KCl (1mg/g bodyweight) solutions were injected into the base of the second periopod and the eugenol was administered as a bath (1.2 ml/L seawater, dissolved first 1:10 in 95% ethanol). All three methods were effective in killing green crabs.  Euthasol resulted in the quickest time to death (1.3 – 1.8 minutes).  Injection with Euthasol caused a short period of distress (15-30 seconds) followed by loss of both the maxilliped and ocular responses, suggesting unconsciousness, until death.  The KCl solution caused death in 5.5 – 11 minutes.  Injection with KCl also caused distress for the first 15-30 seconds and was followed by severe muscle spasms until death. The crabs retained their ocular and maxilliped reactions for most of this time, suggesting retention of consciousness. Therefore the use of KCl should not be considered a humane method of killing in this species. The eugenol bath caused no apparent distress, however the time until death was much longer (25 – 80 minutes) than with the other two methods.  At necropsy, most animals displayed a weak heartbeat; we therefore recommend that euthanasia with eugenol be followed by physical disruption of the central nervous system (i.e. pithing). Return to 28th Annual Eastern Fish Health Workshop Return to Leetown Science Center Home Page