Serum steroid concentrations and development of reproductive organs during puberty in male bonnethead sharks, Sphyrna tiburo |
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Authors: | J Gelsleichter LEL Rasmussen CA Manire J Tyminski B Chang L Lombardi-Carlson |
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Institution: | (1) Elasmobranch Physiology and Environmental Biology Program, Center for Shark Research, Mote Marine Laboratory, Sarasota, FL 34236, USA;(2) Department of Chemistry, Biochemistry, and Molecular Biology, Oregon Graduate Institute, P.O. Box 91000, Portland, OR 97291, USA;(3) Stanford University, Stanford, CA 94305, USA;(4) National Marine Fisheries Service, Southeastern Fisheries Science Center, 3500 Delwood Beach Road, Panama City, FL 32408, USA |
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Abstract: | Puberty is a critical, hormone-mediated event during which an animal acquires the ability to breed and propagate. Despite
the importance of this stage in animal reproduction, little is known regarding the physiological factors that regulate and/or
accompany puberty in several vertebrate groups including elasmobranchs. To address the need for such information, the present
study investigated morphological and hormonal changes that occur during puberty in male bonnethead sharks (Sphyrna tiburo). Serial changes in development of claspers, paired copulatory organs in male elasmobranchs, and serum steroid concentrations
during puberty were evaluated in captive-held male S. tiburo. Captive-animal studies were supplemented by observations on gonadal development, gonaduct morphology, and serum steroid
concentrations in feral, peripubertal male S. tiburo. Changes in size and histological architecture of testes and gonaducts of peripubertal sharks mirrored the seasonal progression
of events that occur in these structures in mature males. Claspers grew in length continuously during puberty, but sharks
did not reach functional maturity until a short period before mating activity commences in the mature population. Clasper
growth appeared to be strictly regulated in S. tiburo, perhaps to ensure growth of these organs to sizes deemed critical for reproductive success. Serum concentrations of testosterone,
dihydrotestosterone, progesterone, and 17β-estradiol increased in both captive and feral sharks during pubertal development,
and may be associated with development of the gonads and gonaducts. Differences in hormone profiles of captive and feral sharks
were observed at certain periods during puberty, but their origin remains unclear.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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Keywords: | bonnethead shark puberty spermatogenesis steroid hormones |
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