Publication Abstract

The effects of chronic radiation exposure on the testes of a marine fish, the plaice

L.N. Greenwood and J.F. Knowles

Continuous whole body irradiation at a dose rate as low as 1.3 mGy h^-1 has been shown to cause significant effects on the testis of a marine flatfish, the plaice. This indicates that plaice testes are at least as radiosensitive as those of any fish so far examined. Young adult male plaice were exposed to continuous y-radiation at dose rates of 2.4 mGy h^-1, 1.3 mGy h^-1 or 0 mGy h^-1 (controls) for a period of 168 days. The doses accumulated by the irradiated fish during this time were 9.9 Gy or 5.1 Gy. There were significant radiation-induced reductions in testis weight at both dose rates used with the higher dose rate producing significantly greater reductions. These were accompanied by radiation dose-dependent reductions in the proportion of testis occupied by sperm and concommittant increases in that occupied by nongerminal tissue, indicating that radiation-induced reductions in testis weight occured mainly as a result of reduction in sperm. Effects on the proportions of other germinal cell stages (spermatogonia, spermatocytes) were uncertain. However, fish were killed at a time in the sexual cycle when these stages are present only in low numbers and further investigation is required at times when they are normally present in greater numbers.