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Reproductive Maturation of the Tropical Clawed Frog, Xenopus tropicalis
Citation:
OLMSTEAD, A. W., J. J. KORTE, K. K. WOODIS, B. A. BENNETT, S. OSTAZESKI, AND S. J. DEGITZ. Reproductive Maturation of the Tropical Clawed Frog, Xenopus tropicalis. GENERAL AND COMPARATIVE ENDOCRINOLOGY. Academic Press Incorporated, Orlando, FL, 160(2):117-123, (2009).
Impact/Purpose:
Results from this study can be used in the design of amphibian toxicology assays and increase our understanding of the reproductive biology of this relatively new model species.
Description:
The model species Xenopus tropicalis is being widely used in developmental biology and amphibian toxicology studies. In order to increase our understanding of the role of steroid hormones in maturation in this species, we collected baseline reproductive data from metamorphosis to adulthood. One cohort of frogs was maintained for 42 weeks post-metamorphosis (PM) with endpoints representative of important reproductive parameters collected at one or two week intervals. These endpoints were then correlated to titers of either estradiol or testosterone. Male frogs exhibited nuptial pads, starting at 8 weeks (PM) when measureable concentrations of circulating testosterone (5.3 ng/mL serum) first appear. Testosterone concentrations remained above this level at all later time points, but was highly variable among individuals. Testes sizes in males reached their peak at 22 weeks PM (21 mg) with sperm counts peaking at the same time (25 million sperm/male). In females, estradiol becomes elevated in the blood at 16 weeks PM (1.5 ng/mL serum) which corresponds with the presences of vitellogenin (4.4 mg/mL serum), vitellogenic oocytes in the ovary, ovarian growth, and oviduct growth. Vitellogenic oocytes increase in number up to 15,000 per female at 30 weeks PM and account for 75% of the total number of oocytes present in the ovary. The ovary and oviducts continue to grow in mass until 30 weeks PM where they have reached sizes of 3.6 g and 0.8 g respectively. These data indicate that male and female X. tropicalis reach reproductive maturation at 22 and 30 weeks PM respectively Results from this study can be used in the design of amphibian toxicology assays and increase our understanding of the reproductive biology of this relatively new model species.
