Density-dependent prophylaxis and condition-dependent immune function in Lepidopteran larvae: a multivariate approach
Density-dependent prophylaxis and condition-dependent immune function in Lepidopteran larvae: a multivariate approach
复制标题
DOI：
10.1111/j.0021-8790.2004.00806.x
复制
发表时间：
2004-03-01
影响因子：
4.8
通讯作者：
Wilson, K
中科院分区：
文献类型：
--
作者：
Cotter, SC;Hails, RS;Wilson, K
1.寄生虫和传染病的风险预计会随着人口密度的增加而增加，因为正的密度依赖性传播率。因此，预计遇到种群密度大幅波动的物种将在其免疫系统中表现出可塑性，从而调整对昂贵的免疫防御的投资，以匹配接触寄生虫和病原体的可能性（即密度依赖性预防）。尽管有越来越多的证据表明，高密度种群中的昆虫对某些病原体的抵抗力会有所提高，但很少有研究探讨免疫功能的潜在变化。由于许多这些物种在高密度下表现出增加的表皮黑化，本研究的目的是使用多变量方法来量化与饲养密度（孤立与拥挤）和表皮颜色（苍白与黑暗）相关联的免疫资源分配的相对变化，多相鳞翅目物种（Spodoptera littoralis Boisduval）。相对于苍白的个人，黑暗的幼虫（高密度表型）表现出更高的血淋巴和表皮酚氧化酶（PO）的活性和更强的黑色素封装反应的人工寄生虫插入血腔。然而，他们也表现出较低的抗菌（溶菌酶样）活性比苍白的幼虫。幼虫密度本身对大多数免疫参数的影响不大，但单独饲养的幼虫被膜黑化和抗菌活性显著高于拥挤饲养的幼虫.根据体重和血淋巴蛋白水平估计，校正幼虫身体状况的变化对这些结果几乎没有影响，表明处理组间免疫功能的变化不能用条件依赖性来解释。这些结果进行检查有关的病原体抗性，并讨论了免疫系统内的权衡的可能性。
1. The risk of parasitism and infectious disease is expected to increase with population density as a consequence of positive density-dependent transmission rates. Therefore, species that encounter large fluctuations in population density are predicted to exhibit plasticity in their immune system, such that investment in costly immune defences is adjusted to match the probability of exposure to parasites and pathogens (i.e. density-dependent prophylaxis).2. Despite growing evidence that insects in high-density populations show the predicted increase in resistance to certain pathogens, few studies have examined the underlying alteration in immune function. As many of these species show increased cuticular melanism at high densities, the aim of this study was to use a multivariate approach to quantify relative variation in the allocation of resources to immunity associated with both rearing density (solitary vs. crowded) and cuticular colour (pale vs. dark) in a phase-polyphenic Lepidopteran species (Spodoptera littoralis Boisduval).3. Relative to pale individuals, dark larvae (the high-density phenotype) exhibited higher haemolymph and cuticular phenoloxidase (PO) activity and a stronger melanotic encapsulation response to an artificial parasite inserted into the haemocoel. However, they also exhibited lower antibacterial (lysozyme-like) activity than pale larvae. Larval density per se had little effect on most of the immune parameters measured, though capsule melanization and antibacterial activity were significantly higher in solitary-reared than crowded larvae.4. Correcting for variation in larval body condition, as estimated by weight and haemolymph protein levels, had little effect on these results, suggesting that variation in immune function across treatment groups cannot be explained by condition-dependence. These results are examined in relation to pathogen resistance, and the possibility of a trade-off within the immune system is discussed.