Cavaleiro Francisca I, Santos Maria J
Universidade do Porto, Faculdade de Ciências, Departamento de Biologia, Rua do Campo Alegre, s/n, Edifício FC4, 4169-007 Porto, Portugal; CIIMAR/CIMAR - Centro Interdisciplinar de Investigação Marinha e Ambiental, Universidade do Porto, Rua dos Bragas 289, 4050-123 Porto, Portugal.
Universidade do Porto, Faculdade de Ciências, Departamento de Biologia, Rua do Campo Alegre, s/n, Edifício FC4, 4169-007 Porto, Portugal; CIIMAR/CIMAR - Centro Interdisciplinar de Investigação Marinha e Ambiental, Universidade do Porto, Rua dos Bragas 289, 4050-123 Porto, Portugal.
Int J Parasitol. 2014 Mar;44(3-4):173-82. doi: 10.1016/j.ijpara.2013.10.009. Epub 2014 Jan 21.
Parasites produce from just a few to many eggs of variable size, but our understanding of the factors driving variation in these two life history traits at the intraspecific level is still very fragmentary. This study evaluates the importance of performing multilevel analyses on egg number and egg size, while characterising parasite life history strategies. A total of 120 ovigerous females of Octopicola superba (Copepoda: Octopicolidae) (one sample (n=30) per season) were characterised with respect to different body dimensions (total length; genital somite length) and measures of reproductive effort (fecundity; mean egg diameter; total reproductive effort; mean egg sac length). While endoparasites are suggested to follow both an r- and K-strategy simultaneously, the evidence found in this and other studies suggests that environmental conditions force ectoparasites into one of the two alternatives. The positive and negative skewness of the distributions of fecundity and mean egg diameter, respectively, suggest that O. superba is mainly a K-strategist (i.e. produces a relatively small number of large, well provisioned eggs). Significant sample differences were recorded concomitantly for all body dimensions and measures of reproductive effort, while a general linear model detected a significant influence of season*parasite total length in both egg number and size. This evidence suggests adaptive phenotypic plasticity in body dimensions and size-mediated changes in egg production. Seasonal changes in partitioning of resources between egg number and size resulted in significant differences in egg sac length but not in total reproductive effort. Evidence for a trade-off between egg number and size was found while controlling for a potential confounding effect of parasite total length. However, this trade-off became apparent only at high fecundity levels, suggesting a state of physiological exhaustion.
寄生虫产生的卵数量从几个到许多不等，大小也各不相同，但我们对种内水平上驱动这两个生活史特征变异的因素的理解仍然非常零散。本研究评估了在表征寄生虫生活史策略的同时，对卵数和卵大小进行多层次分析的重要性。总共对120只携带卵的超级八腕虱雌性个体（桡足类：八腕虱科）（每个季节一个样本（n = 30））进行了不同身体尺寸（全长；生殖节长度）和繁殖力指标（繁殖力；平均卵径；总繁殖力；平均卵囊长度）的表征。虽然内寄生虫被认为同时遵循r-策略和K-策略，但本研究及其他研究中发现的证据表明，环境条件迫使外寄生虫采取这两种策略中的一种。繁殖力分布的正偏态和平均卵径分布的负偏态分别表明，超级八腕虱主要是K-策略者（即产生相对较少数量的大且营养充足的卵）。所有身体尺寸和繁殖力指标均同时记录到显著的样本差异，而一个通用线性模型检测到季节*寄生虫全长对卵数和卵大小均有显著影响。这一证据表明身体尺寸存在适应性表型可塑性以及卵生产中大小介导的变化。卵数和卵大小之间资源分配的季节性变化导致卵囊长度存在显著差异，但总繁殖力没有差异。在控制寄生虫全长的潜在混杂效应时，发现了卵数和卵大小之间的权衡证据。然而，这种权衡仅在高繁殖力水平时才明显，表明存在生理耗竭状态。
