September 2012 - March 2013
Maned wolves are a threatened species found in South America. The largest population in the USA is kept at the Smithsonian Conservation Biology Institute, I worked with Dr. Nucharin Songsasen and graduate student Amy Johnson to research methods of optimizing and supporting maned wolf reproduction in captivity. We used non invasive hormone sampling to study the management conditions necessary for stimulating ovulation in single and paired wolves.
I processed fecal samples, extracted hormones, and ran progesterone and estrogen conjugate enzyme immuno assays.From the hormone profiles we were able to determine that paired wolves only needed a deslorelin implant to induce ovulation, while single wolves needed both deslorelin and lutenizing hormone.
I also conducted an independent project comparing methods of in vitro follicle culture. I tested 2D (agar block) and 3D (alginate and collagen encapsulation) methods on follicle and oocyte growth as well as oocyte development. I found that the although there was variation based on the size of the follicle, overall the 3D methods were much more effective.
Southern White Rhinoceroses were on the brink of extinction in the 19th century, their numbers were estimated to be as low as 20 - 200. Luckily through intensive conservation efforts the current wild population is approximately 20,000 and the IUCN classification is 'near threatened'. However, these rhinoceroses are still in danger because of low genetic diversity and threats of poaching and habitat loss. Thus, Southern White Rhinoceroses in captivity serve as a valuable insurance population. Unfortunately, numbers in captivity are decreasing; captive born females have low reproductive rates and a high incidence of reproductive abnormalities.
Previous research determined that the low reproduction rate in Southern White Rhinoceroses, as compared to Greater One Horned Rhinoceroses, is because of differences in the sensitivity of their estrogen receptors. They concluded that zoo diets rich in soy products with high phytoestrogen content was differentially effecting rhinoceros species, and Southern White Rhinoceros are more susceptible to endocrine disruption. However, the method used was artificial and far removed from a rhinoceros estrogen response in vivo.
As a Sefton Summer Fellow, I worked with Dr. Tubbs to develop a new experimental method with fibroblast cells to more accurately represent rhinoceros response to phytoestrogens. With this method we were able to observe estrogen sensitivities that were undetected using the previous method. These findings were included in a review of molecular techniques that can be used in conservation by zoos.
Memphis Zoo Conservation & Research
Amphibians are facing a global extinction crisis. They are threatened by global warming, loss of habitat and the spreading incidence of the chytrid fungus. The implementation of captive insurance populations and reintroduction programs is imperative to prevent further loss of species.
Amphibian reintroduction efforts need to maximize tadpole production in a small window of optimal release time. A common method to achieve this goal is to use hormone injections to stimulate the release of gametes and collect from the same individual multiple times. However, little is known about the effect frequent hormone-induced spermiation may have on the quantity and quality of sperm.
We tested the effect of frequency of collection on sperm characteristics among four different treatments (twice a week, once a week, every other week, and every three weeks) on sperm concentration, motility, and forward progressive movement in Fowler's toads as a model for endangered Bufonids. We observed a significant decrease in sperm concentration and forward progressive movement in the most frequent treatment group. This group also experienced the greatest weight decrease over the study period as a result of the hormone treatments and not stress from the collection methodology. We concluded that management protocols should not induce spermiation more frequently than every other week.