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Spontaneous Thyroidal Tumors in the Swordtail Xiphophorus montezumae^*

Aubrey Gorbman and Myron Gordon

(From the Departments of Zoölogy, Barnard College and Columbia University, and the New York Zoölogical Society, N.Y.)

In a laboratory population of swordtails (Xiphophorus montezumae) obtained originally in 1939 from the Rio Axtla in Mexico, a high incidence of spontaneous thyroidal tumors has been observed. In two other species of Xiphophorus, four species of Platypoecilus, and in Lebistes reticulatus, kept under identical conditions, thyroidal tumors are very rare or are never seen.

The thyroidal tumor is not uniform in microscopic structure, consisting of areas of normal follicles, very small follicles, nonfollicular cell masses, and a few cystic follicles. It has the property of invading bone. By gradually filling the visceral arches it apparently interferes with respiration, contributing finally to the death of the fish.

In radioautographs of thyroidal tumors of swordtails given radioactive iodine it appears that the few normal follicles are normally functional in respect to iodine metabolism. The remaining areas of the tumor, on the other hand, seem to lack this ability to a large extent.

^* Aided by grants to the New York Zoölogical Society and Barnard College, Columbia University, from the National Cancer Institute, National Institutes of Health, Public Health Service. We acknowledge the use of facilities of the Department of Birds of the American Museum of Natural History.

Appreciation is gratefully acknowledged to Dr. Ross F. Nigrelli and to Mr. S. C. Dunton of the New York Zoölogical Society for Figure 1 and to Dr. Balduin Lucké of the University of Pennsylvania for Figure 2.

Received 10/30/50.