Konuma Junji, Chiba Satoshi
Department of Ecology and Evolutionary Biology, Graduate School of Life Sciences, University of Tohoku, Aobayama, Sendai, Japan.
Am Nat. 2007 Jul;170(1):90-100. doi: 10.1086/518182. Epub 2007 May 22.
We explored how functional trade-offs in resource handling strategies are associated with the divergent morphology of predators. The malacophagous carabid Damaster blaptoides shows two extreme morphologies in the forebody; there is an elongate small-headed type and a stout large-headed type. A feeding experiment showed that the small-headed type obtained a high feeding performance on snails with a thick shell and a large aperture by penetrating the shell with its head. In contrast, the large-headed type showed a high feeding performance on snails that had a thin shell and a small aperture, and they ate these prey by crushing the shell. The large-headed, strong-jawed beetles are efficient at shell crushing but are ineffective at shell entry; the large mandibles and musculature that allow for shell crushing make the beetle's head too wide to penetrate shell apertures. On the other hand, small-headed, weak-jawed beetles crush poorly but can reach into shells for direct predation on snail bodies. These findings are hypothesized to be functional trade-offs between force and fit due to morphological constraints. This trade-off would be a primary mechanism affecting both resource handling ability in animals and phenotypic diversity in predators and prey.
我们探究了资源处理策略中的功能权衡如何与捕食者的不同形态相关联。食软体动物的步甲Damaster blaptoides在前体呈现出两种极端形态；一种是细长小头型，另一种是粗壮大头型。一项喂食实验表明，小头型通过用头部穿透外壳，在具有厚壳和大开口的蜗牛上获得了较高的进食性能。相比之下，大头型在具有薄壳和小开口的蜗牛上表现出较高的进食性能，它们通过压碎外壳来吃掉这些猎物。大头、下颚强壮的甲虫在压碎外壳方面效率很高，但在穿透外壳方面效率低下；用于压碎外壳的大下颚和肌肉组织使甲虫的头部太宽而无法穿透外壳开口。另一方面，小头、下颚较弱的甲虫压碎能力差，但可以伸进壳内直接捕食蜗牛身体。这些发现被假设为由于形态限制导致的力量与适配性之间的功能权衡。这种权衡将是影响动物资源处理能力以及捕食者和猎物表型多样性的主要机制。
