How the Xiphophorus problem arrived in San Marcos, Texas.

The Genetic Stock Center can trace its origin to Myron Gordon’s doctoral research at Cornell University. He began his scientific work in 1924 while still an undergraduate student with 6 platyfish of a domesticated stock, and the following year he added some swordtails. Platyfish and swordtails were not new to him because already as a teenager he had kept many tropical fish. But a great enthusiasm for genetics was aroused by Professor A.C. Fraser in the Department of Plant Breeding. Other professors at Cornell who took a great interest in his work were H.D. Reed (Zoology), who was his official sponsor, and G.C. Embody (Limnology) and R.A. Emerson (Plant Breeding). Dr. Gordon concentrated first on platyfish, working out the genetics of various pigment patterns, and then on swordtails. He coined the terms micromelanophore and macromelanophore (Gordon, 1926). It is an incredible coincidence that at the same time, Dr. Curt Kosswig in Germany also started research on swordtails. Neither Gordon nor Kosswig knew of the other’s existence. But their initial contributions to the Xiphophorus melanoma problem were not the same (Atz, 1941). Kosswig (1928) pointed out that the melanoma was hereditary and in some way associated with melanophore patterns from the platyfish, while Gordon (1931) clearly identified the macromelanophore gene of X. maculatus as being responsible for the tumor. The complementary relationship between laboratory and field research that has made the study of Xiphophorus so exciting and successful was initiated early in Gordon’s career, and one hopes it will be continued in the future. Whereas the development of melanoma in certain platyfishswordtail hybrids was predictable, the sporadic appearance of such growths in some platyfish presented a problem. While working on his thesis at Cornell, Gordon reasoned that platyfish were known only from the hobby and had been bred for many years under domestication and hybridized with swordtails. He could not determine whether platyfish of natural populations also developed pigment cell abnormalities or whether the occurrence of melanoma in the domesticated platyfish was due to the introgression of helleri genes. The sample of 83 platyfish from Mexico in museum collections was too small to provide the answer. He also thought it possible that platyfish and swordtails might hybridize in nature, because Meek (1904) had found them together in one location. He must go to Mexico himself! None of the modern collecting paraphernalia were available to Gordon. There were no maps or rental cars, and only a few paved roads. He went in a model T Ford, loaded with camping equipment, shotguns, letters of introduction to every conceivable agency, and with milk and oil cans for shipping fish back to the United States. In 1930 only 6 of the 22 presently described species of Xiphophorus were known, and virtually nothing was known about their habitat and distribution. Platyfish were assigned to Platypoecilus and swordtails were known as Xiphophorus. Gordon knew that 3 scientific collections of platyfish had been made. The first consisted of 2 fish collected by La Salle prior to 1866 in “Central America,” a locality description utterly useless if you are trying to find the fish (Gordon, Received January 31, 2001; accepted March 30, 2001. E-mail Xiphkallman@aol.com Mar. Biotechnol. 3, S6–S16, 2001 DOI: 10.1007/s10126-001-0022-5