P2.42 Thursday, Jan. 5 The hormonal response to fasting in an amphibious fish LEE, EA*; EARLEY, RL; HANNINEN , AF; The University of Alabama; The University of Alabama; The University of Alabama email@example.com
The mangrove rivulus (Kryptolebias marmoratus), is a self-fertilizing hermaphroditic vertebrate capable of producing lineages of genetically identically animals, making it an exceptional model organism to study plasticity in hormonal responses to variable feeding regimes. In its natural environment of mangroves, the mangrove rivulus is exposed to periods of time where it is in the water and when it is out of the water, due to the tides. These fish are known to be able to survive out of water for an extended period of time, but little is known about the availability of food while this fish is out of water. We investigated variation in progesterone, estradiol, testosterone, and 11-ketotestosterone (KT) of fed versus fasted individuals within and between genotypes. We used a total of 38 fish, half fed and half fasted from two different isogenic lineages, DAN2K and RHL derived from Belize and the Bahamas, respectively. Water borne hormones were taken before and after exposure to the feeding regiment and then were assayed using enzyme immunoassay. We also harvested gonadal and digestive tissues to later explore changes in reproductive investment, gonad and gut morphology using histological techniques. Initial analyses illustrated that there were no differences in the endocrine profiles of fed and fasted individuals; however, gonad size was significantly smaller in individuals that were fasted compared to those that were fed. These results suggest that limited food availability could be a cause for a reduction in reproductive investment.