Dr. Walter and The Molecular Biosciences Research Group and Xiphophorus Genetic Stock Center are renowned for their work with Xiphophorus, a freshwater fish genus comprised of 23 species. These fishes live in eastern drainages in Mexico, Guatemala, Belize, and Honduras. The taxa make up three groups, the Northern Swordtails, the Southern Swordtails, and the Platyfish. If these names are familiar to you, there is a good chance that you have seen them at pet stores, as they are very popular with hobbyists.

It was realized as early as the 1920's that one could make hybrids between the different species. In many situations, the resulting hybrid fish that were produced would show traits from both parent species and were intermediate in appearance. It was also realized by scientists in Germany and the United States that hybrid fish sometimes also developed melanoma, one of the deadliest skin cancers. These melanomas were derived from improperly regulated melanistic pigment patterns. Scientists immediately began to study Xiphophorus hybrids, since they realized that they had discovered an animal model that could be useful in the study of cancer.

Dr. Walter’s Group continues the work that was begun by the scientists in the 1920's. Their work focuses on studying melanoma and other cancers that form in hybrid fish.