Steroid levels in frog eggs: Manipulations, developmental changes, and implications for maternal steroid effects. Issue 4 (14th December 2021)

• Record Type: Journal Article
• Authors: Paitz, Ryan T.; Dugas, Matthew B.
• Is Part Of: Journal of experimental zoology. Volume 337:Issue 4(2022)
• Page Start: 293
• Page End: 302
• Publication Date: 2021-12-14
• Subjects: anura -- developmental endocrinology -- maternal effects -- poison frogs; Zoology -- Periodicals; Zoology; Animal Population Groups -- physiology; Zoology; Electronic journals; Periodical; Periodicals; 590
• DOI: 10.1002/jez.2566
• Languages: English
• ISSNs: 2471-5646

Abstract

Abstract: Exposure to maternally derived steroids during embryonic development can elicit phenotypic effects in the resulting offspring. Studies of maternal steroid effects, especially rich in mammals and birds, have offered exciting insights into the evolution of maternal effects in vertebrates. To extend this literature, we quantified levels of steroids in the eggs of four neotropical dendrobatid frogs that lay terrestrial clutches, a reproductive strategy that has evolved multiple times in amphibians. Building on our observational results, we then manipulated levels of pregnenolone and progesterone in eggs of one species and examined how this affected steroid levels during development. Eggs of all four species had detectable steroids levels, with progestogens being more abundant than androgens and glucocorticoids. Estrogens could not be detected. Immersion of frog eggs in a solution containing pregnenolone and progesterone resulted in elevated levels of both steroids early in development, but levels declined and were similar to those in unmanipulated eggs by the end of development. Treated eggs also exhibited a transient increase in levels of steroids that can be produced from pregnenolone and progesterone. Overall, our findings demonstrate that frog eggs contain steroids similar to what has been observed in other egg‐laying vertebrates. During development, steroid levels are dynamic, further suggesting developing embryos regulate exposure to maternal steroids. These results set the stage for investigating the causes and consequences of maternal steroid effects in frogs. Abstract : The eggs of poison dart frogs contain a variety of steroids and experimental manipulation of steroids levels demonstrate that steroid concentrations are dynamic across embryonic development. Highlights: Frog eggs contain a wide variety of steroids at the time they are laid Steroid levels within eggs can be manipulated by immersing eggs in water that contains steroids During embryonic development, steroid levels within eggs decline