Departamento de Ecología, Facultad de Ciencias, Universidad de Granada, 18071, Granada, Spain.
Departamento de Zoología, Facultad de Ciencias, Universidad de Granada, 18071, Granada, Spain.
Sci Rep. 2021 May 13;11(1):10313. doi: 10.1038/s41598-021-89736-w.
Nucleic acids help clarify variation in species richness of insects having different metamorphosis modes, a biological conundrum. Here we analyse nucleic acid contents of 639 specimens of aquatic insects collected from four high mountain streams of Sierra Nevada in southern Spain to test whether the allocation to RNA or DNA content differs during ontogeny between juvenile insects undergoing direct (hemimetabolous) or indirect (holometabolous) metamorphosis. The results show that RNA content as a function of body mass was negatively correlated to insect body length in four out of six and three out of six of the holometabolan and hemimetabolan taxa, respectively. Although no significant differences in RNA content were found between holometabolans and hemimetabolans, the significant interaction between body length and metamorphosis mode for RNA and RNA:DNA indicates a strong ontogenetic component to RNA allocation. In addition, our finding of lower DNA content in holometabolans relative to hemimetabolans agree with the analysis of empirical genome data in aquatic and terrestrial insects, and extend to this class of arthropods the "growth rate-genome size-nutrient limitation" hypothesis that differences in allocation between RNA and DNA may reflect fundamental evolutionary trade-off of life-history strategies associated with high growth rates (and RNA content) in holometabolans at the expense of diminished genome sizes.
核酸有助于阐明具有不同变态模式的昆虫物种丰富度的变化，这是一个生物学难题。在这里，我们分析了从西班牙南部内华达山脉的四条高山溪流中采集的 639 个水生昆虫标本的核酸含量，以测试在直接（半变态）或间接（全变态）变态过程中，RNA 或 DNA 含量在幼体发育过程中的分配是否不同。结果表明，在六个半变态昆虫中，有四个的 RNA 含量与体重呈负相关，在六个全变态昆虫中，有三个的 RNA 含量与体重呈负相关。尽管在 RNA 含量方面，全变态昆虫和半变态昆虫之间没有显著差异，但 RNA 和 RNA:DNA 之间的体长和变态模式的显著相互作用表明，RNA 的分配具有强烈的个体发育成分。此外，我们发现全变态昆虫的 DNA 含量相对较低，这与水生和陆生昆虫的经验基因组数据分析结果一致，并将“生长速率-基因组大小-营养限制”假说扩展到这类节肢动物，即 RNA 和 DNA 之间的分配差异可能反映了与全变态昆虫高生长速率（和 RNA 含量）相关的生活史策略的基本进化权衡，而代价是基因组大小的减小。
