Institute of Ecology and Evolution, University of Bern, Bern, Switzerland.
PLoS One. 2013 Nov 29;8(11):e82637. doi: 10.1371/journal.pone.0082637. eCollection 2013.
Orb-weaving spiders (Araneidae) are commonly regarded as generalist insect predators but resources provided by plants such as pollen may be an important dietary supplementation. Their webs snare insect prey, but can also trap aerial plankton like pollen and fungal spores. When recycling their orb webs, the spiders may therefore also feed on adhering pollen grains or fungal spores via extraoral digestion. In this study we measured stable isotope ratios in the bodies of two araneid species (Aculepeira ceropegia and Araneus diadematus), their potential prey and pollen to determine the relative contribution of pollen to their diet. We found that about 25% of juvenile orb-weaving spiders' diet consisted of pollen, the other 75% of flying insects, mainly small dipterans and hymenopterans. The pollen grains in our study were too large to be taken up accidentally by the spiders and had first to be digested extraorally by enzymes in an active act of consumption. Therefore, pollen can be seen as a substantial component of the spiders' diet. This finding suggests that these spiders need to be classified as omnivores rather than pure carnivores.
结网蜘蛛（Araneidae）通常被认为是昆虫的全能捕食者，但植物（如花粉）提供的资源可能是其重要的饮食补充。它们的蛛网可以捕捉昆虫猎物，但也可以捕获空气中的浮游生物，如花粉和真菌孢子。因此，当蜘蛛回收它们的蛛网时，它们可能会通过体外消化来食用附着的花粉粒或真菌孢子。在这项研究中，我们测量了两种结网蜘蛛（Aculepeira ceropegia 和 Araneus diadematus）、它们的潜在猎物和花粉的稳定同位素比值，以确定花粉对它们饮食的相对贡献。我们发现，大约 25%的幼年结网蜘蛛的饮食由花粉组成，其余 75%由飞行昆虫组成，主要是小型双翅目和膜翅目昆虫。我们研究中的花粉粒太大，不能被蜘蛛偶然吸收，必须首先通过酶在积极的消耗行为中进行体外消化。因此，花粉可以被视为蜘蛛饮食的重要组成部分。这一发现表明，这些蜘蛛需要被归类为杂食动物，而不是纯粹的肉食动物。
