Data from: Among-sibling differences in the phenotypes of juvenile fish depend on their location within the egg mass and maternal dominance rank

We investigated whether among-sibling differences in the phenotypes of juvenile fish were systematically related to the position in the egg mass where each individual developed during oogenesis. We sampled eggs from the front, middle and rear thirds of the egg mass in female brown trout of known dominance rank. In the resulting juveniles, we then measured traits that are related to individual fitness: body size, social status and standard metabolic rate (SMR). When controlling for differences among females in mean egg size, siblings from dominant mothers were initially larger (and had a lower mass-corrected SMR) if they developed from eggs at the rear of the egg mass. However, heterogeneity in the size of siblings from different positions in the egg mass diminished in lower ranking females. Location of the egg within the egg mass also affected the social dominance of the resulting juvenile fish, although the direction of this effect varied with developmental age. This study provides the first evidence of a systematic basis for among-sibling differences in the phenotypes of offspring in a highly fecund organism.

本研究旨在探究幼鱼同胞间的表型差异，是否与其在卵子发生阶段所处卵团中的位置存在系统性关联。我们从已知社会支配等级的褐鳟雌鱼的卵团前、中、后三分之一区段采集卵子，随后对孵化得到的幼鱼开展与个体适合度相关的性状测定，涵盖体型大小、社会地位以及标准代谢率（standard metabolic rate, SMR）。在控制雌鱼平均卵径差异的条件下，若幼鱼源自卵团后部的卵子，则其来自支配型母本的同胞个体初始体型更大（且经体重校正后的标准代谢率更低）。然而，在社会等级较低的雌鱼后代中，卵团不同位置来源的同胞个体间体型异质性会显著减弱。卵在卵团中的位置同样会影响孵化幼鱼的社会支配等级，不过该效应的方向会随发育年龄发生变化。本研究首次在高繁殖力生物类群中，为子代同胞间表型差异的系统性成因提供了实证依据。