Serum steroid hormones and the reproductive cycle of the female bonnethead shark, Sphyrna tiburo

Charles A. Manire, L. E.L. Rasmussen, David L. Hess, Robert E. Hueter

    Research output: Contribution to journalArticlepeer-review

    32 Scopus citations


    The bonnethead shark Sphyrna tiburo reproduces by placental viviparity with one of the shortest gestation periods (4.5-5 months) known in sharks. In southwest Florida, mating in this species occurs in November, sperm is stored until ovulation/fertilization the following March-April, and parturition occurs in August. Serum concentrations of four steroid hormones (17β- estradiol, progesterone, testosterone, and dihydrotestosterone) were determined by radioimmunoassay over a complete reproductive cycle in mature females from a wild population. Serum 17β-estradiol and testosterone levels are high during mating and preovulatory stages. Preovulatory concentrations of testosterone are greater in female S. tiburo than in any other female elasmobranch previously studied. Progesterone levels are significantly elevated during preovulatory, ovulatory, and postovulatory stages, while serum dihydrotestosterone levels increase significantly during the preovulatory stage. Our study is the first to demonstrate a sustained rise in progesterone during gestation in a placental shark and suggests a regulatory role for this hormone during the period prior to implantation of the embryos in the uterus.

    Original languageEnglish (US)
    Pages (from-to)366-376
    Number of pages11
    JournalGeneral and Comparative Endocrinology
    Issue number3
    StatePublished - Mar 1995

    ASJC Scopus subject areas

    • Animal Science and Zoology
    • Endocrinology


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