Abstract
A 7.12-kg, mature male Tasmanian king crab (Pseudocarcinus gigas) arrived from Japan in October of 2016 with an open defect in its carapace that progressed over time. This defect did not appear to be causing problems, as the animal was still active and eating; however, there were concerns regarding display aesthetics and the possibility of the defect further enlarging.
When the crab arrived at the hospital in January of 2019, there was a 5.5x9-cm irregular defect in the left caudal carapace. Black pigmented, translucent tissue and yellow fat surrounded the opening of the defect on the inside of the carapace. Cytology of the tissue revealed a large amount of gram-negative, highly motile bacteria. One of the gills under the defect was missing approximately 2 cm of the medial gill arch.
The crab was placed in a shallow tub containing several inches of enclosure water, and ketamine 0.1 mg/kg IM1 was administered in the right caudal leg (pereopod 5) with a needle inserted at a medial angle between the coxa and basi-ischium. Within 10 minutes, the animal was able to move slowly but was not reactive to surgical debridement. The black and yellow tissue surrounding the edges of the defect was debrided. The carapacial defect edges were then abraded using a 952 aluminum oxide Dremel™ grinding stone to remove decaying and infected chitin. The surface surrounding the defect was also abraded with the same bit to roughen the carapace and improve adhesion of the shell patch. Resultant debris was removed by rinsing the carapacial surface and gills with clean water from the animals’ enclosure. The carapace around the defect was prepared with Betadine-soaked gauze, followed by isopropyl alcohol. A plastic mesh patch was then applied and secured to the edge of the carapace surrounding the defect with coral glue (CorAffixPro® cyanoacrylate adhesive gel). Cotton-tipped applicators were used to hold the patch to the shell while it cured (approximately 1–3 minutes). To bridge across the mesh patch, coral epoxy putty (AquaStik™ epoxy putty in coralline red) was smoothed over it manually and thinned at the edges. The crab was then transferred back to its enclosure. The crab resumed eating fourteen days post sedation. Over time, algae regrew over the carapace and epoxy patch, creating a natural appearance. Recheck radiographs revealed no progression of the defect. Currently the epoxy remains intact, and the animal is on display.
Acknowledgments
The authors wish to thank Keoki Burton and Ernie Sawyer of the Shedd Fishes Department and Kristen Neria of the Shedd Fabrication Department for their contributions to this case.
*Presenting author
Literature Cited
1. Noga EJ, Hancock AL, Bullis RA. 2012. Crustaceans. In: Lewbart GA, editor. Invertebrate Medicine, 2nd edition. Ames (IA): John Wiley and Sons Press. Pp 235–254.