Reproductive Endocrinology of the Ozark Hellbender, Cryptobranchus Alleganiensis Bishopi
Seasonal changes in steroid concentrations in the serum of adult Ozark hellbenders, Cryptobranchus alleganiensis bishopi, were investigated from June 1993 to December, 1993. These dates included the periods before, during and after the breeding season. Radioimmunoassays were performed to measure the concentrations of estradiol, progesterone, and testosterone. Estradiol concentrations in females increased throughout July, when gonadal changes were first observed, and remained high during the time when oocytes were maturing and breeding took place. In males, estradiol levels were constant between June and December and had values one hundred times lower than the values of female estradiol. Progesterone concentrations in females peaked when gonadal changes were first observed and again just after the breeding season. Similar peaks in progesterone concentrations were seen in males. Testosterone concentrations in females peaked during the last two weeks of September when breeding was taking place; levels were low at all other times. Testosterone concentrations in males started increasing in July, when cloacal gland enlargement was first observed; levels further increased and remained high throughout the breeding season then decreased shortly thereafter. This study suggested that estradiol played an important role in oocyte maturation, that progesterone may have initiated gamete maturation and have terminated breeding processes in both females and males, and that testosterone functioned in mating behavior and in the development of secondary sexual characteristics, the reproductive tract, and spermatozoa.
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