March 2003 Lab Animal Volume 32, No. 3 WHAT’S YOUR DIAGNOSIS

Thomas M. Donnelly, DVM, Column Editor What’s your diagnosis? Dermal Lesions, Hemorrhage, and Limb Swelling in Laboratory Axolotls

Submitted by Elizabeth W. Davidson, PhD, James K. Jancovich, MS, Sandra Borland, BA, Meg Newberry, BS, and Jill Gresens, ALAT, BS

The axolotl (Ambystoma mexicanum) is a eggs, juveniles have unsurpassed regenera- large salamander native to Lake tive capabilities, adults have large nerves, Xochimilco, Mexico. It belongs to the and genetically defined mutants are avail- group of salamanders known as mole sala- able. All axolotls used in research come manders. Other members of this group from the Indiana University Axolotl include the tiger salamander (Ambystoma Colony (IUAC; http://www.indiana.edu/ tigrinum) and the spotted salamander ~axolotl/), which was founded in 1957. (Ambystoma maculatum). Axolotls exhibit There we breed axolotls ~10 months of the neoteny, which is the retention of juvenile year and distribute tens of thousands of FIGURE 1. Dermal pustules with diffuse petechial hemorrhaging on the vent of a characteristics in adult stages of life. Adult embryos, larvae, and adult axolotls. white axolotl. axolotls display arrested transformation of We house adult axolotls individually in selected features such as gills, despite the 1 gallon bowls or in groups of three or four colony had undergone a similar disease sexual maturation of their gonads. They in plastic tubs, ~10 inches x 18 inches x 6 outbreak in the summer of 1995. Not only keep their feathery external gills and tailfin inches deep (25 cm x 46 cm x 15 cm). Adult did our colony have similar high-density their entire lives, and they maintain their males live in individual bowls when they conditions, but we were also housing tiger aquatic lifestyle. are not being mated, and adult females live salamanders. The disease moved through Developmental biologists, neurobiolo- singly or in groups. We maintain the the entire colony in a four- to five-month gists, and amphibian research scientists axolotls at 15–18 °C (60–65 °F) in 1/2 gal- period, and then the incidence tapered off. find the axolotl an excellent animal model lon (2 L) of water per animal, and change Careful husbandry and immediate removal for their research. Not only are axolotls the water daily using Holtfreter’s solution of animals showing clinical signs eventual- easy to handle, but females produce large (http://www.indiana.edu/~axolotl/). We ly extinguished the disease. feed larval axolotls brine shrimp, and juve- Considering the epizootic history and niles and adults pelleted food. clinical signs, what do you think is the From October 2001 through February cause of the two outbreaks? Is there any 2002, we had a larger than normal number potential problem in housing tiger sala- Davidson and Jancovich are affiliated of axolotls and had to house some animals manders with axolotls or introducing wild with the Department of Biology, Arizona in unusually crowded conditions. During axolotls to the colony? Could other State University, Tempe, AZ 85287-1501. this period, a colony-wide disease outbreak amphibians or reptiles housed in close Borland, Newberry, and Gresens are occurred. Juvenile and adult axolotls proximity be affected? affiliated with the Indiana University showed skin pustules, reddening and Axolotl Colony, Department of Biology, swelling of the vent, limbs, and neck, and Jordan Hall 142, 1001 East Third Street, occasional bleeding from the gills (Fig. 1). Bloomington, IN 47405-3700. Please All animals that exhibited these signs died send reprint requests to Davidson at the within one to five days. above address, or email: Following the introduction in late 1994 [email protected]. of wild axolotls from Lake Xochimilco, our What’s your diagnosis?

23