Life history theory suggests that maximum size and growth evolve to maximize fitness. In contrast, the Gill Oxygen Limitation Theory (GOLT) suggests that growth and maximum size in fishes and other aquatic, water-breathing organisms is constrained by the body mass-scaling of gill surface area. Here, we use new data and a novel phylogenetic Bayesian multilevel modelling framework to test this idea by asking the three questions posed by the GOLT regarding maximum size, growth and gills. Across fishes, we ask whether the body mass-scaling of gill surface area explains (1) variation in the von Bertalanffy growth coefficient (k) above and beyond that explained by asymptomatic size (W_∞), (2) variation in growth performance (a trait that integrates the tradeoff between k and W_∞) and (3) more variation in growth performance compared to activity (as approximated by caudal fin aspect ratio). Overall, we find that there is only a weak relationship among maximum size, growth and gill surface area across species. Indeed, the body mass-scaling of gill surface area does not explain much variation in k (especially for those species that reach the same W_∞) or growth performance. Activity explained three to five times more variation in growth performance compared to gill surface area. Our results suggest that in fishes, gill surface area is not the only factor that explains variation in maximum size and growth, and that other covariates (e.g. activity) are likely important in understanding how growth, maximum size and other life history traits vary across species.

中文翻译：

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鱼类的鳃、生长和活动

生命史理论表明，最大尺寸和生长的进化是为了最大化适应性。相比之下，鳃氧限制理论（GOLT）表明，鱼类和其他水生、水呼吸生物的生长和最大尺寸受到鳃表面积的体重缩放的限制。在这里，我们使用新数据和新颖的系统发育贝叶斯多级建模框架，通过询问 GOLT 提出的关于最大尺寸、生长和鳃的三个问题来测试这一想法。在鱼类中，我们询问鳃表面积的体重缩放是否解释了（1）冯·贝塔朗菲生长系数（k）的变化超出了无症状大小（W _∞）所解释的变化，（2）生长性能的变化（整合了之间权衡的特征k和W _∞）和（3）与活动相比，生长性能的变化更大（通过尾鳍长宽比近似）。总的来说，我们发现不同物种的最大尺寸、生长和鳃表面积之间的关系很弱。事实上，鳃表面积的体重缩放并不能解释k的太大变化（特别是对于那些达到相同W _{∞的物种）}）或增长绩效。与鳃表面积相比，活动解释了生长性能变化的三到五倍。我们的结果表明，在鱼类中，鳃表面积并不是解释最大尺寸和生长变化的唯一因素，其他协变量（例如活动）对于理解生长、最大尺寸和其他生活史特征如何因物种而异可能很重要。