Weatherhead Patrick James, Kissner Kelley Joan, Sommerer Sophie Jane
Department of Biology, Carleton University, Ottawa, Ont., Canada K1S 5B6.
J Exp Zool A Comp Exp Biol. 2006 Aug 1;305(8):603-9. doi: 10.1002/jez.a.317.
Variation in intrauterine exposure to hormones associated with variation in the sex of litter mates has well-established and far-reaching effects on sexual development in some mammals. Research on this phenomenon in reptiles is scant, but suggests that lizards may follow the mammalian model whereas snakes may be affected differently. We examined sex-specific expression of four sexually dimorphic traits (tail length, head length, ventral scale count, swimming speed) in three species of snakes (Nerodia sipedon, Thamnophis sirtalis, T. sauritus) relative to litter sex ratios. We found little evidence that traits in either sex were masculinized or feminized in response to variation in litter sex ratio. The one significant result appeared best explained as a statistical artifact attributable to a single litter. Our results indicate that snakes are different from the one lizard studied to date. Unlike previous suggestions that prenatal hormonal mechanisms operate differently in snakes and lizards, however, the difference appears to be that development of sexually dimorphic traits in lizards is affected by litter sex ratios whereas in snakes it is not.
子宫内与同窝幼崽性别差异相关的激素暴露差异，对一些哺乳动物的性发育具有既定且深远的影响。对爬行动物这一现象的研究很少，但表明蜥蜴可能遵循哺乳动物模式，而蛇可能受到不同影响。我们研究了三种蛇（带纹水蛇、东部环颈蛇、细纹鞭尾蛇）中四个两性异形性状（尾长、头长、腹鳞数、游泳速度）相对于同窝性别比例的性别特异性表达。我们几乎没有发现证据表明，任何一种性别的性状会因同窝性别比例的变化而出现雄性化或雌性化。唯一显著的结果似乎最好解释为一个由单个窝所导致的统计假象。我们的结果表明，蛇与迄今为止研究过的一种蜥蜴不同。然而，与之前认为产前激素机制在蛇和蜥蜴中运作方式不同的观点不同，差异似乎在于蜥蜴两性异形性状的发育受同窝性别比例影响，而蛇则不受影响。
