冬眠對菊池氏龜殼花生殖行為及賀爾蒙之影響探討

Abstract

菊池氏龜殼花（Trimeresurus gracilis）為臺灣5種響尾蛇亞科蛇類，唯一侷限分布於2000公尺以上高海拔山區的物種；本研究主要探討冬眠的低溫刺激，是否會影響菊池氏龜殼花的生殖。傳統生殖生理常用生殖腺解剖及血清荷爾蒙週期進行研究，前者需犧牲大量成熟個體，不利動物族群維持。後者容易造成個體緊迫、拒食、細菌性感染等。非侵入式的糞便荷爾蒙經常被利用於其他類群的生殖週期研究，其優點在於不會造成個體的緊迫及大量犧牲，且可重複採樣。本研究將先以菊池氏龜殼花進行糞便及血清賀爾蒙的關係研究，並進一步利用糞便賀爾蒙，探討冬眠對其生殖行為及賀爾蒙週期的影響。 菊池氏龜殼花於2008及2009年進行冬眠（10℃）及未冬眠（20℃）處理。求偶交配實驗於2009年07月至11月及2010年04月至09月進行配對錄影；採血於2010年03月至08月進行，並僅對無緊迫反應的雌蛇進行採樣。糞便樣本於2008年03月至2010年08月每月收集一次，12月至隔年2月冬眠期間不收集。 實驗結果顯示菊池氏龜殼花雌蛇的糞便荷爾蒙能夠忠實反應體內血清雌二醇、助孕酮等荷爾蒙的濃度變化。雄蛇雖無進行血液收集，但其糞便睪固酮濃度具有週期性之變化，且其週期與近緣種相近，故應可應用於蛇類生殖研究。冬眠對菊池氏龜殼花的交配行為並無影響，交配行為僅與個體的體況有關。體況大的雄蛇交配成功率較高，而大多數雌蛇於體重達到80 g時，才會接受雄蛇的求偶並與之交配。糞便雌二醇濃度與雌蛇是否交配無關，但卻受到冬眠的影響。冬眠組雌蛇的糞便雌二醇於產後第二年春季有一高峰，無冬眠個體則無。此時的雌二醇濃度與次級卵黃生成作用有關，未冬眠雌蛇的雌二醇濃度較低，可能使濾泡無法正常發育影響生殖。糞便助孕酮與交配行為及冬季低溫刺激均無顯著相關，但與雌蛇是否懷孕有關，懷孕個體有較高濃度的糞便助孕酮濃度。菊池氏龜殼花雄蛇糞便睪固酮的週期不受冬眠與否的影響，但成功的交配雄蛇有較高濃度的糞便睪固酮。Trimeresurus gracilis is the only species limited to the altitude over 2000 m mountain area among the five Crotalinae snakes in Taiwan. The goal of my study is to clarify whether low temperature in hibernation influence the reproductive cycle of T. gracilis. In tradition, gonad anatomy and serum hormones were used in reproductive physiological studies, but the former requires sacrifice and the latter usually causes stress, antifeedant, or bacterial infections. Fecal hormone is a non-invasive technique that has been used in many researches of reproductive cycles of other animals. With this new technique, we don’t need to sacrifice animals, and there’s no stress problem. Furthermore, we are able to do repeat sampling. My study starts with linking serum hormones to fecal hormones of T. gracilis. Then I will probe the effect of hibernation on fecal hormones and on the reproductive behavior of T. gracilis. All T. gracilis were assigned to two treatments of different temperature, specifying hibernation group (10℃) and nonhibernation group (20℃) in winter of both 2008 and 2009. Courtship and mating behavior were recorded by video from July to November of 2009, and April to September of 2010. Blood samples were collected once a month, and were only from females that didn’t show sign of stress, in March to August of 2010. And fecal samples were also taken once a month, from March of 2008 to August of 2010, excluding winter times (October to February). The results showed that the concentrations of fecal estradiol (E2) and progesterone (P4) could reflect the serum ones of female snakes. Fecal testosterone (T) of male snakes showed periodicity and was similar to other Crotalinae males, hence would be able to apply to reproductive research of snakes. Mating behavior wasn’t affected by hibernation, but was associated with body condition. Males having larger body condition had higher mating rate. Most females with body weight over 80g mated. Concentration of fecal E2 was influenced by hibernation, yet didn’t affect mating behavior. Females of hibernation group which underwent parturition, had significant higher fecal E2 in the following second spring. The raised concentration of E2 in spring was associated with secondary vitellogenesis. Low concentration of E2 of non-hibernated females, may indicate obstructed growth of follicles, and thus made the females unable to produce. Pregnant females had higher concentration of fecal P4, but there was no significant correlation between fecal P4 and hibernation, nor between fecal P4 and mating behavior. Although hibernation didn’t affect the cycle of fecal T, those male who successfully mated had higher fecal T.