Season and testosterone affect contractile properties of fast calling muscles in the gray tree frog Hyla chrysoscelis
Season and testosterone affect contractile properties of fast calling muscles in the gray tree frog Hyla chrysoscelis
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DOI：
10.1152/ajpregu.00243.2002
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发表时间：
2003-06-01
影响因子：
2.8
通讯作者：
Marsh, RL
中科院分区：
文献类型：
--
作者：
Girgenrath, M;Marsh, RL
在无尾两栖动物中，循环中的雄激素水平会影响某些只在繁殖季节表现出来的第二性征。我们研究了繁殖季节北美灰树蛙Hyla chrysoscelis的外斜肌(用于发声)的收缩特性，以及繁殖季节后用睾酮处理的圈养雄性和雌性的收缩特性。与繁殖期雄鱼的肌肉相比，繁殖期后雄鱼的躯干肌肉质量减少了50%，抽动时间延长了60%，缩短速度慢了40%。雄性青蛙体内的睾酮水平与繁殖季节的雄性青蛙相似，可以恢复雄性躯干肌肉的收缩速度和质量，也可以将雌性缓慢的小躯干肌肉转化为更大的快速收缩肌肉。我们得出结论，雄激素可能在改变雄性这些肌肉在年度周期中的收缩特性方面发挥关键作用，使它们在繁殖季节以产生该物种特有的快速脉冲叫声所需的频率工作。雌性和非繁殖季节的雄性都不会发出广告叫声，因此在这些动物身上发现的较慢的肌肉可能会允许这些肌肉更经济地运作。睾酮对女性躯干肌肉的影响表明，这种激素有可能导致这些肌肉的大小和收缩特性的性别二型性，但这种二型性很可能是由于多种激素的相互作用。
In anurans, circulating levels of androgens influence certain secondary sexual characteristics that are expressed only during the breeding season. We studied the contractile properties of external oblique muscles ( used to power sound production) in a species of North American gray tree frog, Hyla chrysoscelis, during the breeding season and also in testosterone-treated captive males and females after the breeding season. Compared with the muscles of breeding-season males, the trunk muscles of postbreeding-season males have 50% less mass, 60% longer twitches, and 40% slower shortening velocities. Testosterone levels similar to those found in breeding-season male hylid frogs restore the contractile speed and mass of male trunk muscles and also convert the small slow trunk muscles of females into larger fast-contracting muscles. We conclude that androgens likely play a key role in altering the contractile properties of these muscles in males during the annual cycle, allowing them to operate in the breeding season at the frequencies required to produce the characteristic rapidly pulsed calls of this species. Females as well as nonbreeding-season males do not produce advertising calls, and therefore the slower muscles found in these animals may allow more economic operation of these muscles. The effects of testosterone on female trunk muscles indicate the potential of this hormone in contributing to the sexual dimorphism in size and contractile properties of these muscles, but this dimorphism is likely due to the interaction of more than one hormone.