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Toward a physiological explanation of juvenile growth curves
Journal of Zoology ( IF 1.9 ) Pub Date : 2020-02-20 , DOI: 10.1111/jzo.12770 R. M. Sibly 1 , J. H. Brown 2
Journal of Zoology ( IF 1.9 ) Pub Date : 2020-02-20 , DOI: 10.1111/jzo.12770 R. M. Sibly 1 , J. H. Brown 2
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Juvenile growth curves are generally sigmoid in shape: Growth is initially nearly exponential, but it slows to near zero as the animal approaches maturity. The drop‐off in growth rate is puzzling because, everything else being equal, selection favors growing as fast as possible. Existing theory posits sublinear scaling of resource acquisition with juvenile body mass and linear scaling of the requirement for maintenance, so the difference, fuel for growth, decreases as the juvenile increases in size. Experimental evidence, however, suggests that maintenance metabolism increases sublinearly not linearly with size. Here, we develop a new theory consistent with the experimental evidence. Our theory is based on the plausible assumption that there is a trade‐off in the capacity of capillaries to supply growing and developed cells. As the proportion of non‐growing cells increases, they take up more macromolecules from the capillaries, leaving fewer to support growing cells. The predicted growth curves are realistic and similar to those of previous models (Bertalanffy, Gompertz, and Logistic) but have the advantage of being derived from a plausible physiological model. We hope that our focus on resource delivery in capillaries will encourage new experimental work to identify the detailed physiological basis of the trade‐off underlying juvenile growth curves.
中文翻译：
对幼年生长曲线的生理解释
幼年生长曲线通常呈 S 形：生长最初几乎呈指数增长，但随着动物接近成熟，它会减慢至接近零。增长率的下降令人费解，因为在其他条件相同的情况下，选择有利于尽可能快地增长。现有理论假设资源获取与幼鱼体重呈亚线性比例，而维持需求呈线性比例，因此差异，即生长燃料，随着幼鱼体型的增加而减小。然而，实验证据表明，维持代谢随大小呈亚线性而非线性增加。在这里，我们开发了一个与实验证据一致的新理论。我们的理论基于一个合理的假设，即毛细血管供应生长和发育细胞的能力存在权衡。随着非生长细胞比例的增加，它们从毛细血管中吸收更多的大分子，留下更少的用于支持生长的细胞。预测的生长曲线是现实的，与以前的模型（Bertalanffy、Gompertz 和 Logistic）相似，但具有从合理的生理模型中推导出来的优势。我们希望我们对毛细血管资源输送的关注将鼓励新的实验工作，以确定幼年生长曲线权衡的详细生理基础。
更新日期：2020-02-20
中文翻译：
对幼年生长曲线的生理解释
幼年生长曲线通常呈 S 形：生长最初几乎呈指数增长，但随着动物接近成熟，它会减慢至接近零。增长率的下降令人费解，因为在其他条件相同的情况下，选择有利于尽可能快地增长。现有理论假设资源获取与幼鱼体重呈亚线性比例，而维持需求呈线性比例，因此差异，即生长燃料，随着幼鱼体型的增加而减小。然而，实验证据表明，维持代谢随大小呈亚线性而非线性增加。在这里，我们开发了一个与实验证据一致的新理论。我们的理论基于一个合理的假设，即毛细血管供应生长和发育细胞的能力存在权衡。随着非生长细胞比例的增加，它们从毛细血管中吸收更多的大分子，留下更少的用于支持生长的细胞。预测的生长曲线是现实的，与以前的模型（Bertalanffy、Gompertz 和 Logistic）相似，但具有从合理的生理模型中推导出来的优势。我们希望我们对毛细血管资源输送的关注将鼓励新的实验工作，以确定幼年生长曲线权衡的详细生理基础。
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