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Marine Turtle Newsletter 69:10-11, © 1995

Marine Turtle Newsletter-Online

COMMENT ON ALBINO SEA TURTLE HATCHLINGS IN BRAZIL

While many of us here in Canada were dreaming of a white Christmas, a loggerhead turtle (Caretta caretta) in Brazil was making sure it happened. Twenty-two albino loggerheads hatched on 25 December 1994 at Atafona Beach near Sao Joao da Barra, north of Rio de Janeiro. The ratio of albino to normal hatchlings found within this nest is relevant to the matter of multiple paternity in sea turtle clutches. If albinism in sea turtles is the phenotype of a single locus homozygous recessive allele (as is the case in some snakes; Bechtel and Bechtel 1989), then following a cross between two heterozygous parents, one would expect roughly 25% of the offspring to be albinos. As reported by Marcovaldi et al. (this issue), 22.4% of the total number of hatchlings (22 of 98) that emerged from the nest were albinos. Assuming equal mortality for all genotypes in the nest, the percentage of surviving albinos in this clutch is consistent with the suggestion that there was only one father. Previous studies have indicated that multiple paternity is a major feature of reproduction in sea turtle populations (Harry and Briscoe 1988; Peare et al. 1994). Perhaps populations differ in their patterns of reproductive behaviour.

Another issue concerns the pleiotropic effects of albinism. Pathways from the retina to the brain are known to be abnormally routed in albinos of some species (Guillery 1986). Seafinding by turtles is thought by some to depend on a complex phototropotactic system involving differential stimulation of various parts of the visual system (Mrosovsky et al. 1979). The albino hatchlings may appear normal, but it would be interesting to test whether or not their seafinding ability is compromised. Tests with unilaterally blindfolded albino hatchlings might be instructive.

Bechtel, H. B. and E. Bechtel. 1989. Color mutations in the corn snake (Elaphe guttata guttata): review and additional breeding data. J. Heredity 80:272-276.

Guillery, R. W. 1986. Neural abnormalities of albinos. Trends in Neurosciences 9:364-367.

Harry, J. L. and D. A. Briscoe. 1988. Multiple paternity in the loggerhead turtle (Caretta caretta). J. Heredity 79:96-99.

Mrosovsky, N., A. M. Granda and T. Hay. 1979. Seaward orientation of hatchling turtles: turning systems in the optic tectum. Brain, Behavior and Evolution 16:203-221.

Peare, T., P. G. Parker and T. A. Waite. 1994. Multiple paternity in green turtles (Chelonia mydas): conservation implications, p. 115-118. In: Bjorndal, K. A., A. B. Bolten, D. A. Johnson and P. J. Eliazar (Compilers), Proc. 14th Annual Symposium on Sea Turtle Biology and Conservation. NOAA Tech. Memo. NMFS-SEFSC-351. U. S. Dept. Commerce.

MATTHEW H. GODFREY and N. MROSOVSKY, Department of Zoology, University of Toronto, 25 Harbord Street, Toronto, Ontario MS5 1A1, CANADA.