Photoreactivation in two closely related marine fishes having different longevities

The tautog, Tautoga onitis, and cunner, Tautogolabrus adspersus, are marine fishes which are closely related taxonomically (family Labridae), have similar habits, the same ecological requirements and are found in the same areas. However, they differ markedly in their longevity. The tautog is longer-lived, reaching an estimated average age of 34 years. It attains sexual maturity at 3--4 years of age. The cunner, on the other hand, lives to about 5--6 years of age and is sexually mature at about one year. An examination of their respective capacities for photoreactivation using cells in tissue culture derived from these fishes revealed marked differences in the rate of monomerization of ultraviolet-induced pyrimidine dimers from their DNA. Radiochromatographic analysis of dimers in the tautog showed that half the dimers were removed within a period of 10 min of exposure to photoreactivating light whereas a 50-min exposure was required to photoreactivate dimers to this same level in the cunner. Dark repair of dimers was measured by radiochromatography and by endonuclease assay. The two methods showed similar low levels of excision repair in both species.