Griffen Blaine D
Department of Biological Sciences and the School of the Earth, Ocean, and Environment University of South Carolina Columbia SC USA.
Ecol Evol. 2017 Mar 12;7(7):2423-2431. doi: 10.1002/ece3.2861. eCollection 2017 Apr.
Reproduction is energetically financed using strategies that fall along a continuum from animals that rely on stored energy acquired prior to reproduction (i.e., capital breeders) to those that rely on energy acquired during reproduction (i.e., income breeders). Energy storage incurs a metabolic cost. However, previous studies suggest that this cost may be minimal for small-bodied ectotherms. Here I test this assumption. I use a laboratory feeding experiment with the European green crab to establish individuals with different amounts of energy storage. I then demonstrate that differences in energy storage account for 26% of the variation in basal metabolic costs. The magnitudes of these costs for any individual crab vary through time depending on the amount of energy it has stored, as well as on temperature-dependent metabolism. I use previously established relationships between temperature- and mass-dependent metabolic rates, combined with a feasible annual pattern of energy storage in the Gulf of Maine and annual sea surface temperature patterns in this region, to estimate potential annual metabolic costs expected for mature female green crabs. Results indicate that energy storage should incur an ~8% increase in metabolic costs for female crabs, relative to a hypothetical crab that did not store any energy. Translated into feeding, for a medium-sized mature female (45 mm carapace width), this requires the consumption of an additional ~156 mussels annually to support the metabolic cost of energy storage. These results indicate, contrary to previous assumptions, that the cost of energy storage for small-bodied ectotherms may represent a considerable portion of their basic operating energy budget. An inability to meet these additional costs of energy storage may help explain the recent decline of green crabs in the Gulf of Maine where reduced prey availability and increased consumer competition have combined to hamper green crab foraging success in recent years.
繁殖所需的能量是通过一系列策略来提供的，这些策略分布在一个连续体上，从依赖繁殖前获取的储存能量的动物（即资本繁殖者）到依赖繁殖期间获取能量的动物（即收入繁殖者）。能量储存会产生代谢成本。然而，先前的研究表明，对于小型变温动物来说，这种成本可能最小。在此，我对这一假设进行检验。我利用对欧洲绿蟹进行的实验室饲养实验来建立具有不同能量储存量的个体。然后我证明，能量储存的差异占基础代谢成本变化的26%。任何一只螃蟹的这些成本大小会随时间而变化，这取决于它储存的能量数量以及与温度相关的代谢。我利用先前建立的温度和质量依赖的代谢率之间的关系，结合缅因湾可行的年度能量储存模式以及该地区的年度海表面温度模式，来估计成熟雌性绿蟹预期的潜在年度代谢成本。结果表明，相对于一只假设的没有储存任何能量的螃蟹，能量储存会使雌性螃蟹的代谢成本增加约8%。换算成摄食方面，对于一只中等大小的成熟雌性绿蟹（头胸甲宽度为45毫米），这需要每年额外消耗约156只贻贝来支持能量储存的代谢成本。这些结果表明，与先前的假设相反，小型变温动物的能量储存成本可能占其基本运行能量预算的相当一部分。无法满足这些额外的能量储存成本可能有助于解释缅因湾绿蟹数量最近的下降，近年来，猎物可获得性降低和消费者竞争加剧共同阻碍了绿蟹的觅食成功。
