Infertility Observed in Wild Bonnethead Sharks, Sphyrna tiburo, may be Due to Anthropogenic Effects
Charles A. Manire1; James Gelsleichter1; L.E.L. Rasmussen2; Enric Cortes3
Several studies have shown a high incidence of infertile ova present in the uterus of pregnant bonnet-head sharks captured along the central Gulf coast of Florida.1,2 The current study was undertaken to determine if the observed infertility was due to endocrinological changes in either the mature males or mature females and to determine if the infertility could be correlated with elevated serum or tissue concentrations of organ chlorine environmental contaminants. To accomplish this, serum and tissues were collected from sharks from three different areas. These areas were Tampa Bay (a highly contaminated area), Florida Bay in the Florida Keys (an area of very low organ chlorine contamination), and Apalachicola Bay in the Florida Panhandle (an area of intermediate organ chlorine contamination. Differences were found in serum concentrations of reproductive steroid hormones, sperm counts and sperm viability, concentrations of various organ chlorines, growth and reproductive parameters, and resultant population intrinsic rates of increase. Estradiol concentrations in mature females from Tampa Bay were found to be one half the concentrations found in the Florida Bay (control) females. There were also significant differences in serum concentrations of estradiol and testosterone from immature females (Tampa Bay << Florida Bay). It is likely that these differences in hormone concentrations are caused by the presence of endocrine-disrupting organ chlorine compounds present in the marine environment inhabited by these sharks.
Although the research described in this abstract has been funded wholly or in part by the United States Environmental Protection Agency through R826128-01-0 to CAM, it has not been subjected to the Agency's required peer and policy review and therefore does not necessarily reflect the views of the Agency and no official endorsement should be inferred.
1. Manire, C.A., L.E.L. Rasmussen, D.L. Hess, and R.E. Hueter. 1995. Serum steroid hormones and the reproductive cycle of the female bonnethead shark, Sphyrna tiburo. Gen. Comp. Endocrino 1.97" 3 66-3 76.