Density‐dependent prophylaxis: evidence from Lepidoptera–baculovirus interactions?
Density‐dependent prophylaxis: evidence from Lepidoptera–baculovirus interactions?
复制标题
DOI：
10.1046/j.1365-2311.1998.00107.x
复制
发表时间：
1998-02
影响因子：
2.2
通讯作者：
K. Wilson;A. Reeson
中科院分区：
文献类型：
--
作者：
K. Wilson;A. Reeson
来自一系列分类群的昆虫使用早期幼虫密度作为其当前栖息地未来恶化的线索(Dingle，1996)。它们对这一提示的反应往往是将资源从有利于在出生地点立即繁殖的活动(例如卵子成熟)转向那些有利于在不同地点或不同时间繁殖的活动(例如翅膀和飞行肌肉的发育或脂肪储备的沉积)。除了预测幼虫食物资源的质量或数量下降外，早期幼虫密度还可能预测接触病原体的风险，这种风险通常随着种群密度的增加而以可预测的方式增加。在这种情况下，自然选择将有利于那些使用早期幼虫密度来预测在以后的生命中分配给病原体抗性的最佳资源水平的个体。这种对幼虫密度的适应性预防反应可以解释最近对蛾毛虫及其杆状病毒的几项研究结果。Kunimi&Yamada(1990)饲养粘虫幼虫(粘虫)的密度为每容器1-20条幼虫。然后，他们给新出现的四龄毛虫口服不同浓度的核多角体病毒(NPV)，并记录死亡人数。他们发现，NPV导致的死亡率逐渐下降，从单独饲养的昆虫的95%下降到每容器20只幼虫密度饲养的昆虫的37%。最高密度饲养毛虫的LC_(50)值约为单独饲养个体的10倍。在第二个实验中，kunimi&yamada(1990)允许二龄毛虫用被颗粒病病毒(GV)污染的人工饲料喂养2天，然后在单独或拥挤的条件下再饲养36天。他们发现，高密度饲养的幼虫(每个容器20只)对GV的抵抗力大约是单独饲养的幼虫的四倍。因此，至少在这个物种中，
Insects from a range of taxa use early larval density as a cue to the future deterioration of their current habitat (Dingle, 1996). Their response to this cue is often to redirect resources away from activities favouring immediate reproduction at the natal site (e.g. egg maturation) towards those that favour reproduction in a different location or at a different time (e.g. the development of wings and flight muscles or the deposition of lipid reserves). As well as predicting a decline in the quality or quantity of the larval food resource, early larval density may also predict the risk of exposure to pathogens, which often increases in a predictable manner with population density. Under such circumstances, natural selection will favour those individuals that use early larval density to predict the optimal level of resources to allocate to pathogen resistance later in life. Such an adaptive prophylactic response to larval density may explain the results of several recent studies of moth caterpillars and their baculoviruses. Kunimi & Yamada (1990) reared caterpillars of the Oriental armyworm moth ( Mythimna separata ) at densities ranging between one and twenty larvae per container. They then orally inoculated newly emerged fourth-instar caterpillars with various concentrations of nuclear polyhedrosis virus (NPV) and recorded the number of deaths. They found that NPV-induced mortality declined gradually from 95% for insects reared solitarily to 37% for those reared at a density of twenty larvae per container. The LC 50 value for caterpillars reared at the highest density was about tenfold that for individuals reared solitarily. In a second experiment, Kunimi & Yamada (1990) allowed second-instar caterpillars to feed for 2 days on artificial diet contaminated with a granulosis virus (GV) before rearing them for a further 36 days under either solitary or crowded conditions. They found that larvae reared at high densities (twenty per container) were about fourfold more resistant to GV than those reared singly. Thus, in this species at least,