Use of injectable potassium chloride for euthanasia of American lobsters (Homarus americanus)

Potassium chloride (KCI: 330 mg/ml) was assessed as an euthanasia agent in American lobsters (Homarus americanus). Two groups of 10 lobsters (408.2 to 849.9 g) were maintained at 11.9 to 12.1 degreesC ('warm') and 1.5 to 2,5 degreesC ('cold') to evaluate the possible effect of ambient temperature on response to KCl. Death was defined as time of cardiac arrest, as viewed an d measured by use of ultrasound. The KCl solution was injected (100 mg of K Cl/100 g of body weight) at the base of the second walking leg to flood the hemolymph sinus containing the ventral nerve cord with potassium. Disrupti on of this 'central nervous system' was immediate, followed by cardiac arre st within 60 to 90 seconds. Group median (+/- SD) baseline heart rate was 4 2 +/- 14 'warm and 36 +/- 5('cold') beats per minute. Time until cardiac ar rest ranged from 35 to 90 (57 +/- 18) seconds in the 'warm' group and from 40 to 132 (53 +/- 34) seconds in the 'cold' group. There was no significant difference between group medians for either parameter. Histologic lesions were limited to mild to moderate acute degeneration, characterized by cell swelling, loss of contraction bands, and occasional mild cytoplasmic vacuol ation of skeletal muscle at the injection site. Injectable KCl solution was an effective, reliable method for euthanasia of H. americanus.