Life-history theory predicts that animals adjust their resource allocation to somatic growth or to reproduction to maximize fitness. Resource allocation in Daphnia is known to respond to quantitative food limitation as well as to kairomones released from predators. Here we investigated in a full-factorial design how kairomone from larvae of Chaoborus flavicans, a gape-limited predator, and food quantity (0.5 mg C/L versus 1.5 mg C/L) affect the fatty acid allocation of D. pulex. Low food diminished somatic growth, clutch size and clutch biomass and increased neckteeth formation in response to the kairomone. Low food further led to increased fatty acid amounts per individual egg as well as to increased fatty acid content in eggs and to increased relative fatty acid allocation to reproduction. The latter effect was suppressed by kairomone of Chaoborus, whereas on high food the provision of eggs was further enhanced. We also found that more eicosapentaenoic acid was retained in the body of mothers in the presence of the predator at low food concentrations. These findings indicate that under food limitation and in the presence of kairomone from Chaoborus larvae, Daphnia switches from allocation into current reproduction to investment into future reproductive events.

中文翻译：

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食物限制下捕食的风险改变了水蚤的资源分配

生命历史理论预测，动物会根据躯体生长或繁殖来调整其资源分配，以最大程度地适应身体。众所周知，水蚤的资源分配对食物的定量限制以及从掠食者释放的海洛酮有反应。在这里，我们以全要素设计研究了潮虫黄Chao（Chaoborus flavicans）幼虫的海洛酮，有限的捕食者和食物量（0.5 mg C / L对1.5 mg C / L）如何影响D. pulex的脂肪酸分配。。低食物减少了对海洛酮的反应，使体细胞生长，离合器的大小和离合器的生物量减少，颈齿形成增加。食物不足会进一步增加每个鸡蛋的脂肪酸含量，并增加鸡蛋中的脂肪酸含量，并增加相对脂肪酸在生殖中的分配。Chaoborus的kairomone抑制了后者的作用，而在高食物中，鸡蛋的供应量进一步增加。我们还发现，在低食物浓度下存在捕食者的情况下，母亲体内会残留更多二十碳五烯酸。这些发现表明，在食物限制下，在水蚤中潮虫幼虫的海洛酮存在下 从分配到目前的繁殖，再到投资到未来的繁殖活动。