Meekan M G, Virtue P, Marcus L, Clements K D, Nichols P D, Revill A T
Australian Institute of Marine Science, c/o UWA Indian Ocean Marine Research Centre (MO96), Crawley, Western Australia, Australia.
Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania, Australia.
Ecology. 2022 Dec;103(12):e3818. doi: 10.1002/ecy.3818. Epub 2022 Sep 19.
The evolution of very large body size requires a ubiquitous and abundant source of food. In marine environments, the largest animals such as whale sharks are secondary consumers that filter feed on nekton, which is plentiful, although patchy. Consequently, feeding in coastal environments requires cost-efficient foraging that focuses on oceanographic features that aggregate both nektonic prey and marine debris such as floating macroalgae. Consumption of this algae could present an energetic challenge for these animals, unless some component can be digested. Here, we use a multi-technique approach involving amino acid compound-specific stable isotope analysis (CSIA) and fatty acid analysis to determine the trophic level of whale sharks and to identify likely items in the diet. CSIA analyses showed that the species has a trophic level consistent with omnivory. Fatty acid profiles of whale shark tissues, feces and potential prey items suggest that the floating macroalgae, Sargassum, and its associated epibionts is a significant source of food. Although this overcomes the energetic challenge of consumption of floating algae, this mode of feeding and the need to focus on oceanographic features that aggregate prey also increases the threat to the species posed by pollutants such as plastic.
超大体型的进化需要无处不在且丰富的食物来源。在海洋环境中，像鲸鲨这样的大型动物是二级消费者，它们以浮游生物为食，浮游生物数量众多，尽管分布不均。因此，在沿海环境中觅食需要高效觅食，重点关注能聚集浮游生物猎物和海洋垃圾（如漂浮的大型藻类）的海洋学特征。食用这种藻类可能给这些动物带来能量挑战，除非其中某些成分能够被消化。在此，我们采用了一种多技术方法，包括氨基酸化合物特异性稳定同位素分析（CSIA）和脂肪酸分析，以确定鲸鲨的营养级，并识别其饮食中可能的食物种类。CSIA分析表明，该物种的营养级与杂食性相符。鲸鲨组织、粪便和潜在猎物的脂肪酸谱表明，漂浮的大型藻类马尾藻及其相关附生生物是重要的食物来源。虽然这克服了食用漂浮藻类带来的能量挑战，但这种觅食方式以及聚焦于聚集猎物的海洋学特征的需求，也增加了塑料等污染物对该物种构成的威胁。
