Reproductive Techniques for Ovarian Monitoring and Control in Amphibians

Abstract

Ovarian control and monitoring in amphibians require a multi-faceted approach. There are several applications that can successfully induce reproductive behaviors and the acquisition of gametes and embryos for physiological or molecular research. Amphibians contribute to onequarter to one-third of vertebrate research, and of interest in this context is their contribution to the scientific community's knowledge of reproductive processes and embryological development. However, most of this knowledge is derived from a small number of species. In recent times, the decimation of amphibians across the globe has required increasing intervention by conservationists. The captive recovery and assurance colonies that continue to emerge in response to the extinction risk make existing research and clinical applications invaluable to the survival and reproduction of amphibians held under human care. The success of any captive population is founded on its health and reproduction and the ability to develop viable offspring that carry forward the most diverse genetic representation of their species. For researchers and veterinarians, the ability to monitor and control ovarian development and health is, therefore, imperative. The focus of this article is to highlight the different assisted reproductive techniques that can be used to monitor and, where appropriate or necessary, control ovarian function in amphibians. Ideally, any reproductive and health issues should be reduced through proper captive husbandry, but, as with any animal, issues of health and reproductive pathologies are inevitable. Non-invasive techniques include behavioral assessments, visual inspection and palpation and morphometric measurements for the calculation of body condition indices and ultrasound. Invasive techniques include hormonal injections, blood sampling, and surgery. Ovarian control can be exercised in a number of ways depending on the application required and species of interest.

Non-invasive methods to measure inter-renal function in aquatic salamanders—correlating fecal corticosterone to the environmental and physiologic conditions of captive Necturus

“…A similar f CM decline was also noted in two breeding pairs where the female did not go on to oviposit eggs. Oviposition timing matched that previously observed in this and two other captive Necturus species (Calatayud et al ., 2019, Stoops et al ., 2014). As this study did not employ ultrasound technology, it remains unknown if the two females that failed to deposit eggs did so because of lack of egg development versus having matured eggs that failed to ovulate and/or oviposit (Calatayud et al ., 2018, 2019).…”

“…In this study, f CM concentrations were excreted during the breeding season, a time of marked water temperature decline and when males from each breeding pair deposited spermatophores. This is also when Necturus egg development and growth take place (Calatayud et al ., 2019, Stoops et al ., 2014). A sharp decline in f CM in April was concomitant with warming water temperatures, a cessation of breeding activity and the oviposition of eggs by four of six paired females.…”

“…Nitrile gloves were worn throughout all waterborne collection processes. Three separate anaesthetic procedures were conducted (Calatayud et al ., 2019, Stoops et al ., 2014) on N. maculosus at 3- to 5-week intervals; two procedures were associated with a single i.p. injection (27G, 125 μL) of 10.7 IU ACTH (A6303; Sigma-Aldrich, St. Louis, MO, USA) dissolved in sterile water, and one control procedure consisted of i.p.…”

Sex Determination in Two Species of Anuran Amphibians by Magnetic Resonance Imaging and Ultrasound Techniques

“…Ultrasonographic visualization of reproductive organs in anurans has been considered difficult, especially in males [13][14][15][16][17]. However, in our study, ultrasound examination allowed an easy identification of testes and ovaries in both anuran species (Figures 5-7).…”

“…Several articles describe the use of ultrasonography in amphibians for medical purposes [11][12][13], assessment of reproductive status and sex identification in frogs with better specificity for female identification [14][15][16][17]. Magnetic resonance imaging (MRI) has been previously used in frogs focusing on different functional aspects of the Central Nervous System (CNS) [18,19].…”