Evaluation of parenteral drugs for anesthesia in the blue crab (Callinectes sapidus)

The objective of this study was to evaluate the efficacy and safety of several parenteral anesthetics in blue crabs (Callinectes sapidus). Thirty-one animals were administered one or more of the following drugs by injection into the hemolymph (i.v.) through an arthrodial membrane: etomidate, ketamine, lidocaine, pentobarbital, propofol, tiletamine-zolazepam, xylazine, and ketamine-xylazine. A subset of crabs received intracardiac ketamine. Etomidate had no effect. Lidocaine effects were ultrashort (<3 min). Pentobarbital had prolonged inductions (2 min) and often caused violent excitement and poor anesthesia. Propofol induced light anesthesia accompanied by distress and limb autotomy. Inductions with ketamine, xylazine, tiletamine-zolazepam, and ketamine-xylazine were usually fast (<60 sec). Their anesthetic effects were generally very short (5-10 min) but predictable, smooth, and with good muscle relaxation. The latter two protocols induced a deep plane of anesthesia more consistently but also more significant bradycardia. Intracardiac ketamine injection was fatal in four of five crabs. In conclusion, the anesthetic protocols were considered unsuitable for prolonged anesthesia. However, if very short-term anesthesia is desired, then tiletamine-zolazepam or ketamine-xylazine is recommended. Further studies are indicated to identify a safe anesthetic protocol of longer duration in C. sapidus as well as in other crab species.