EVALUATION OF INTRACARDIAC ADMINISTRATION OF POTASSIUM CHLORIDE, IVERMECTIN, OR LIDOCAINE HYDROCHLORIDE FOR EUTHANASIA OF ANESTHETIZED BLUE CRABS ( CALLINECTES SAPIDUS ).

Methods to anesthetize and euthanize aquatic invertebrates have proven unreliable in decapods; thus studies to optimize euthanasia techniques for crustaceans are needed. Study objectives were to evaluate efficacy of intracardiac potassium chloride (KCl), ivermectin, or lidocaine hydrochloride (HCl) for euthanasia of anesthetized blue crabs (). Twenty adult male crabs ( = 5/group) were immersed in 500 mg/L eugenol for 5 min beyond loss of the righting reflex and then randomly administered intracardiac 10 mEq/kg KCl (333 mg/mL), 5 mg/kg ivermectin (10 mg/ml), 100 mg/kg lidocaine hydrochloride (HCl) (20 mg/ml), or 5 ml/kg saline (0.9%). Serial heart rate assessments were made using a Doppler probe placed over the dorsum, and times to loss of righting reflex, Doppler sound cessation, and/or recovery were recorded. Median (range) time to loss of righting reflex was 32 (17-57) min. One crab in all groups, except lidocaine HCl, had no detectable Doppler sounds prior to injection. In the remaining crabs, Doppler sound cessation occurred in 4/4, 4/4, 4/5, and 0/4 crabs administered KCl, ivermectin, lidocaine HCl, and saline, respectively. Median (range) time to Doppler sound cessation was 30 (0-55), 18 (16-28), and 50 (0-90) s in KCl, ivermectin, and lidocaine HCl groups, respectively. Tonic limb movements were observed in 5/5 KCl-treated crabs. Median (range) time to recovery was 180 (115-345) and 300 m in four saline-treated crabs and one lidocaine HCl-treated crab, respectively. Intracardiac KCl at 10 mEq/kg and ivermectin at 5 mg/kg were effective, rapid methods for euthanasia of anesthetized blue crabs.