Jennings Scott, Varsani Arvind, Dugger Katie M, Ballard Grant, Ainley David G
Oregon Cooperative Fish and Wildlife Research Unit, Department of Fisheries and Wildlife, Oregon State University, Corvallis, OR, United States of America.
School of Biological Sciences and Biomolecular Interaction Centre, University of Canterbury, Private Bag 4800, Christchurch, 8140, New Zealand.
PLoS One. 2016 Mar 2;11(3):e0149090. doi: 10.1371/journal.pone.0149090. eCollection 2016.
Sexually size-dimorphic species must show some difference between the sexes in growth rate and/or length of growing period. Such differences in growth parameters can cause the sexes to be impacted by environmental variability in different ways, and understanding these differences allows a better understanding of patterns in productivity between individuals and populations. We investigated differences in growth rate and diet between male and female Adélie Penguin (Pygoscelis adeliae) chicks during two breeding seasons at Cape Crozier, Ross Island, Antarctica. Adélie Penguins are a slightly dimorphic species, with adult males averaging larger than adult females in mass (11%) as well as bill (8%) and flipper length (~3%). We measured mass and length of flipper, bill, tibiotarsus, and foot at 5-day intervals for 45 male and 40 female individually-marked chicks. Chick sex was molecularly determined from feathers. We used linear mixed effects models to estimate daily growth rate as a function of chick sex, while controlling for hatching order, brood size, year, and potential variation in breeding quality between pairs of parents. Accounting for season and hatching order, male chicks gained mass an average of 15.6 g d(-1) faster than females. Similarly, growth in bill length was faster for males, and the calculated bill size difference at fledging was similar to that observed in adults. There was no evidence for sex-based differences in growth of other morphological features. Adélie diet at Ross Island is composed almost entirely of two species--one krill (Euphausia crystallorophias) and one fish (Pleuragramma antarctica), with fish having a higher caloric value. Using isotopic analyses of feather samples, we also determined that male chicks were fed a higher proportion of fish than female chicks. The related differences in provisioning and growth rates of male and female offspring provides a greater understanding of the ways in which ecological factors may impact the two sexes differently.
两性在体型大小上存在差异的物种，其雌雄个体在生长速率和/或生长期长度方面必然存在某些差异。生长参数的这些差异会导致雌雄个体以不同方式受到环境变化的影响，了解这些差异有助于更好地理解个体和种群之间的生产力模式。我们在南极洲罗斯岛克罗泽角的两个繁殖季节，对阿德利企鹅（Pygoscelis adeliae）雏鸟的雌雄生长速率和饮食差异进行了调查。阿德利企鹅是一种略有体型差异的物种，成年雄性在体重（约11%）、喙长（约8%）和鳍肢长度（约3%）方面平均比成年雌性大。我们对45只雄性和40只雌性单独标记的雏鸟，每隔5天测量一次体重以及鳍肢、喙、胫跗骨和脚的长度。雏鸟的性别通过羽毛进行分子鉴定。我们使用线性混合效应模型来估计日生长速率与雏鸟性别的函数关系，同时控制孵化顺序、育雏规模、年份以及双亲对之间繁殖质量的潜在差异。考虑到季节和孵化顺序，雄性雏鸟的体重增加平均比雌性快15.6克/天。同样，雄性雏鸟的喙长生长更快，计算得出的出飞时喙大小差异与成年个体中观察到的相似。没有证据表明其他形态特征的生长存在基于性别的差异。罗斯岛阿德利企鹅的食物几乎完全由两种物种组成——一种磷虾（晶磷虾Euphausia crystallorophias）和一种鱼类（南极冰鱼Pleuragramma antarctica），鱼类的热量值更高。通过对羽毛样本的同位素分析，我们还确定雄性雏鸟比雌性雏鸟摄入了更高比例的鱼类。雌雄后代在食物供应和生长速率方面的相关差异，让我们对生态因素可能以不同方式影响两性的方式有了更深入的理解。
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