School of Agriculture and Biology, Shanghai Jiao Tong University, Minhang, Shanghai, China.
Shanghai Urban Forest Ecosystem Research Station, State Forestry Administration, Minhang, Shanghai, China.
J Insect Sci. 2021 Jan 1;21(1). doi: 10.1093/jisesa/ieaa139.
Parasites obtain energy and nutrients from the host, and their body size is also usually limited by host size. However, the regulatory mechanisms that control the plasticity of parasite body sizes and the stoichiometric relationships with their hosts remain unclear. Here we investigated the concentrations of 14 elements (C, H, O, N, P, S, K, Na, Ca, Mg, Al, Fe, Mn, and Zn) in the acorns of three oak species (Quercus spp.), in their endoparasitic weevil (Curculio davidi Fairmaire) (Coleoptera: Curculionidae) larvae and in the larval feces, and the weight of weevil larvae within different hosts in a warm-temperate zone of China. Our results showed that the three acorn species exhibited significant differences in C, H, O, P, K, Mg, and Mn concentrations. However, in the weevil larvae, only P, Mn, and C:P ratio revealed significant differences. Weevil larvae preferentially absorbed and retained N, Zn, Na, and P, whereas Mn, K, Ca, and O were passively absorbed and transported. The weevil larvae weight was associated with acorn stoichiometry, and positively correlated with acorn size. Weevil larvae P decreased, but Mn and C:P increased with their weight, implying highly variable in somatic stoichiometry are coupled with the plasticity of body size. Interestingly, weevil larvae weight was negatively correlated with acorn infection rate, indicating small-size parasitic insects might have higher fitness level in parasite-host systems than larger-size ones. Our results suggest that variation in P, Mn, and C:P in parasites may play critical roles in shaping their body size and in improving their fitness.
寄生虫从宿主那里获取能量和营养，其体型通常也受到宿主体型的限制。然而，控制寄生虫体型可塑性和与宿主之间化学计量关系的调节机制仍不清楚。在这里，我们研究了中国暖温带三种栎属树种（Quercus spp.）的橡实中的 14 种元素（C、H、O、N、P、S、K、Na、Ca、Mg、Al、Fe、Mn 和 Zn）的浓度、其体内的内寄生象甲（Curculio davidi Fairmaire）（鞘翅目：象甲科）幼虫以及幼虫粪便中的浓度，以及在不同宿主中象甲幼虫的体重。我们的结果表明，三种橡实的 C、H、O、P、K、Mg 和 Mn 浓度存在显著差异。然而，在象甲幼虫中，只有 P、Mn 和 C:P 比显示出显著差异。象甲幼虫优先吸收和保留 N、Zn、Na 和 P，而 Mn、K、Ca 和 O 则是被动吸收和转运。象甲幼虫的体重与橡实的化学计量有关，与橡实的大小呈正相关。象甲幼虫的 P 减少，但 Mn 和 C:P 增加，表明其体型的可塑性与身体化学计量的高度可变性相关。有趣的是，象甲幼虫的体重与橡实的感染率呈负相关，这表明在寄生虫-宿主系统中，体型较小的寄生昆虫可能比体型较大的寄生昆虫具有更高的适应度水平。我们的研究结果表明，寄生虫中 P、Mn 和 C:P 的变化可能在塑造其体型和提高其适应度方面起着关键作用。
