Schwabl H
Rockefeller University Field Research Center for Ecology and Ethology, Millbrook, NY 12545, USA.
Comp Biochem Physiol A Physiol. 1996 Jul;114(3):271-6. doi: 10.1016/0300-9629(96)00009-6.
The eggs of the canary (Serinus canaria) contain variable doses of maternal testosterone. The reported experiments investigated whether testosterone influences nestling growth and how this interacts with differences of the growth of nest mates that are caused by asynchronous hatching. Injections of testosterone into the yolk of unincubated eggs enhanced the growth after hatching compared to nestlings that had hatched simultaneously from control eggs. These differences were established within 22 hr of hatching. Exogenous testosterone promoted growth in both sexes and there was no sexual difference in the growth of control birds. Testoster-one-treated chicks also begged more often for food. Previous studies have shown that the content of maternal testosterone increases in each subsequently laid egg in a clutch. Consistent with the results obtained by testosterone injections nestlings that hatched from eggs with higher concentrations of maternal testosterone grew faster compared to chicks that hatched synchronously from eggs with lower testosterone concentrations. However, more testosterone did not compensate for reduced growth that was caused by later hatching due to asynchronous incubation of clutches. This direct effect of maternal testosterone on growth in combination with a flexible onset of incubation allows to selectively enhance the growth and fitness of individual offspring of a brood.
金丝雀（Serinus canaria）的卵含有不同剂量的母体睾酮。所报道的实验研究了睾酮是否会影响雏鸟的生长，以及它如何与因孵化不同步导致的同窝雏鸟生长差异相互作用。与从对照卵同时孵化出的雏鸟相比，向未孵化卵的卵黄中注射睾酮可促进孵化后的生长。这些差异在孵化后的22小时内就已显现。外源性睾酮促进了两性的生长，对照鸟的生长没有性别差异。经睾酮处理的雏鸟也更频繁地乞食。先前的研究表明，一窝中随后产下的每枚卵中母体睾酮的含量都会增加。与注射睾酮获得的结果一致，与从睾酮浓度较低的卵中同步孵化出的雏鸟相比，从母体睾酮浓度较高的卵中孵化出的雏鸟生长得更快。然而，更多的睾酮并不能弥补由于一窝卵孵化不同步导致的晚孵化所造成的生长减缓。母体睾酮对生长的这种直接影响与灵活的孵化开始时间相结合，使得一窝雏鸟中个别后代的生长和适应性能够得到选择性增强。
