The Red-eyed Treefrog, Agalychnis callidryas, of Central America is a vibrant Neotropical frog that is used throughout the globe as a poster child for rainforest and amphibian conservation. Photo: Leah Jacobs.
Sex in the Lab: Using a New Technique to Facilitate Breeding in Tree Frogs
Over the past 30–100 years amphibians have experienced worldwide population declines. With a staggering 32% of the Earth’s amphibian species facing imminent decline, the use of captive breeding has emerged to prevent extinction. One method, assisted reproductive technologies (ART), uses hormones to stimulate egg and sperm production to aid in breeding and has been successfully used for years in mammals, fishes, and birds, with more recent applications in frogs. In light of the current amphibian extinction crisis, ART is recognized as an increasingly important avenue for rescuing the 100s of species of amphibians that are experiencing declines and face extinction.
The treefrogs of the Neotropical subfamily Phyllomedusinae, are a large group of colorful leaf frogs distributed throughout Central and South America. I will test two hormone doses to examine which is most effective at inducing spermiation (males) and ovulation (females) among Red-eyed Treefrogs. Previous research using ART indicates that hormone protocols are expected to be similar for closely related species. Although our focal species are not currently declining, making them ideal for large-scale, manipulative experiments, many of their closest relatives are listed on the International Union for the Conservation of Nature (IUCN) Red List as imperiled. Thus, my research will have a direct impact on informing captive breeding and management and the conservation and preservation of 8 imperiled species of leaf frog.
Each individual will be injected with either zero, two or four ug/g body weight GnRH. For males, I will examine the viability of each sperm sample by imaging sperm stained with sperm staining dye (propidium iodide and SYBR 14), under florescent microscopy, allowing for a count of live vs. dead sperm in each sample (see image). I will evaluate spermic urine from each individual every three, seven, 12, 24 hours to produce a sperm response curve for viability and production of each individual. Females will be injected via the same protocol. Comparison of the viability and production of sperm produced by each male, and egg clutch size by each female will be evaluated to compare for each individual dose.
Image of live vs. dead sperm under florescent microscopy. Live is green, dead is orange. Photo: Leah Jacobs
Amphibians are facing an extinction rate (32% of the 7,405 described species) that is greater than that of either birds (12%) or mammals (22%). Since 1980 it is estimated that almost 170 species of amphibians are extinct. Thus, with my research I hope to develop techniques on this species that will give us a clearer understanding of hormone doses and breeding techniques needed to conserve and breed other members of the group (a subfamily consisting of five genera and 59 species, 8 of which are listed as Endangered or Critically Endangered).
Leah Jacobs, Master’s student, California State University, Northridge, holding one of her Red-eyed Treefrogs.
With global warming, deforestation and the advent of a lethal disease that attacks their skin, amphibians are facing a mass extinction that some scientists compare with the extinction of the dinosaurs. For my research, I propose to develop a method using hormones to facilitate captive breeding in Red-eyed Treefrogs that can have direct benefit in the conservation of other endangered and threatened treefrog species.
Red-eyed Treefrog(Agalychnis callidryas)
California State University, Northridge
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