Data from: Trade-offs between personal immunity and reproduction in the burying beetle, N. vespilloides

We know that parental investment and immune investment are costly processes, but it is unclear which trait will be prioritized when both may be required. Here, we address this question using the burying beetle Nicrophorus vespilloides, carrion breeders that exhibit biparental care of young. Our results show that immunosuppression occurs during provision of parental care. We measured phenoloxidase (PO) on Days 1–8 of the breeding bout and results show a clear decrease in PO immediately from presentation of the breeding resource onward. Having established baseline immune investment during breeding we then manipulated immune investment at different times by applying a wounding challenge. Beetles were wounded prior to and during the parental care period and reproductive investment quantified. Different effects on reproductive output occur depending on the timing of wounding. Challenging the immune system with wounding prior to breeding does not affect reproductive output and subsequent lifetime reproductive success (LRS). LRS is also unaffected by applying an immune elicitor prior to breeding, though different arms of the immune system are up/downregulated, perhaps indicating a trade-off between cellular and humoral immunity. In contrast, wounding during breeding reduces reproductive output and to the greatest extent if the challenge is applied early in the breeding bout. Despite being immunosuppressed, breeding beetles can still respond to wounding by increasing PO, albeit not to prebreeding levels. This upregulation of PO during breeding may affect parental investment, resulting in a reduction in reproductive output. The potential role of juvenile hormone in controlling this trade-off is discussed.

已知亲本投资（parental investment）与免疫投资（immune investment）均为高成本生命过程，但当二者均为生存所需时，生物体如何权衡二者的资源分配优先级仍未明确。本研究以展现出双亲抚育（biparental care）幼崽行为的食腐昆虫埋葬甲（Nicrophorus vespilloides）为实验对象，探讨上述科学问题。研究结果表明，亲本抚育阶段会出现免疫抑制现象。我们在繁育周期的第1至8天检测了酚氧化酶（phenoloxidase, PO）活性，结果显示，自繁殖资源被引入繁育体系起，PO活性即出现显著下降。在明确繁殖期免疫投资的基线水平后，我们通过施加创伤刺激（wounding challenge），在不同时间节点对甲虫的免疫投资水平进行了人为调控。我们分别在亲本抚育开始前与抚育期间对甲虫实施创伤处理，并量化其繁殖投资情况。实验结果显示，创伤处理的时间不同，对繁殖产出的影响存在显著差异：繁殖前通过创伤刺激激活免疫系统，并不会影响甲虫的繁殖产出及其后续的终生繁殖成功率（lifetime reproductive success, LRS）。尽管此时甲虫的不同免疫分支会出现上调或下调，这或许暗示了细胞免疫与体液免疫间存在资源权衡，但繁殖前施加免疫激活剂同样不会对LRS造成影响。与之相反，繁殖期间施加创伤刺激会降低繁殖产出，且在繁育周期早期进行刺激时，该抑制效果最为显著。尽管处于免疫抑制状态，抚育中的甲虫仍可通过提升PO活性应对创伤刺激，尽管其活性无法恢复至繁殖前水平。繁殖期间PO活性的上调可能会干扰亲本投资，进而导致繁殖产出下降。本研究最后讨论了保幼激素（juvenile hormone）在调控该权衡过程中的潜在作用。