Department of Biology, Miami University, Oxford, Ohio, USA.
Ecology. 2023 Dec;104(12):e4176. doi: 10.1002/ecy.4176. Epub 2023 Oct 20.
The chemical composition and stoichiometry of vertebrate bodies changes greatly during ontogeny as phosphorus-rich bones form, but we know little about the variation among species during early development. Such variation is important because element ratios in animal bodies influence which element limits growth and how animals contribute to nutrient cycling. We quantified ontogenetic variation from embryos through 2-3 months of age in 10 species of fish in six different families, ranging in adult size from 73 to 720 mm in length. We measured whole-body concentrations (percentage of dry mass) and ratios of carbon (C), nitrogen (N), and phosphorus (P) as fish developed. We also quantified whole-body concentrations of calcium (Ca), because Ca should reflect bone development, and RNA, which can be a major pool of body P. To account for interspecific differences in adult size, we also examined how trends changed with relative size, defined as body length divided by adult length. Ontogenetic changes in body composition and ratios were relatively similar among species and were more similar when expressed as a function of relative size compared to age. Body P increased rapidly in all species (likely because of bone development) from embryos until individuals were ~5%-8% of adult size. Body N also increased, while body C, C:N, C:P, and N:P all decreased over this period. Body Ca increased with development but was more variable among species. Body RNA was low in embryos, increased rapidly in young larvae, then decreased as fish reached 5%-8% of adult size. After fish were about 5%-8% of adult size, changes in body composition were relatively slight for all elements and ratios. These results reveal a consistency in the dynamics of body stoichiometry during early ontogeny, presumably because of similar constraints on the allocation of elements to bones and other body pools. Because most changes occur when individuals are <1 month old (<10% of adult size for that species), early ontogenetic variation in body stoichiometry may be especially important for growth limitation of individuals and ecosystem-level nutrient cycling.
脊椎动物的身体化学成分和化学计量在个体发育过程中会发生很大变化，因为富含磷的骨骼会形成，但我们对物种在早期发育过程中的变化知之甚少。这种变化很重要，因为动物体内的元素比例会影响哪些元素限制生长以及动物如何促进营养循环。我们在六个不同的鱼类科中，对 10 个物种的胚胎到 2-3 个月大的幼鱼进行了量化，这些物种的成年体长从 73 到 720 毫米不等。我们测量了鱼类发育过程中整个身体的浓度（干物质的百分比）和碳（C）、氮（N）和磷（P）的比例。我们还量化了整个身体的钙（Ca）浓度，因为 Ca 应该反映骨骼发育情况，以及 RNA，它可以是体内 P 的主要储存库。为了说明成年个体大小的种间差异，我们还研究了这些趋势如何随相对大小（定义为体长除以成年体长）而变化。与年龄相比，物种间的身体成分和比例的个体发育变化相对相似，而当以相对大小表示时则更为相似。所有物种的体内 P 都迅速增加（可能是由于骨骼发育），从胚胎到个体达到成年个体的 5%-8%。体内 N 也增加，而体内 C、C:N、C:P 和 N:P 在此期间均下降。体内 Ca 随着发育而增加，但在不同物种之间更为多变。胚胎中的 RNA 含量较低，在幼鱼中迅速增加，然后在鱼类达到成年个体的 5%-8%时减少。当鱼类达到成年个体的 5%-8%左右时，所有元素和比例的身体成分变化都相对较小。这些结果揭示了早期个体发育过程中身体化学计量动态的一致性，这可能是由于元素分配到骨骼和其他身体库的相似限制所致。由于大多数变化发生在个体<1 个月大（<该物种成年个体的 10%）时，因此，身体化学计量的早期个体发育变化可能对个体生长限制和生态系统水平的营养循环特别重要。
