The mysterious food source of anguilliform leptocephali has been difficult to understand, so this review evaluates potential interrelationships among recent discoveries on this subject. There are typically few identifiable gut-content objects in leptocephalus intestines, which usually contain amorphous materials. Gut content observation studies and stable isotope research have suggested that marine snow detrital-type particles are a food source, but this was difficult to validate. Recent gut-content DNA-sequence analyses indicated that small 4–25 mm Sargasso Sea European eel larvae, Anguilla anguilla, frequently ingest calycophoran siphonophore tissues as well as other taxa not likely to be ingested individually. A high-magnification photographic study of Sargasso Sea leptocephalus gut contents recently detected possible hydrozoan tentacles and apparent fatty acid-rich single-celled, heterotrophic thraustochytrid protists (class Labyrinthulomycetes), which have been found in marine snow in previous studies, but are not amplified by some DNA primers. Calycophoran siphonophores are abundant in the Sargasso Sea and have extensive tentacle arrays and short-lived eudoxid reproductive stages that might be appropriate sizes to be eaten directly or contribute to marine snow aggregates. The two groups may be interrelated because thraustochytrids are ubiquitously present decomposers that colonize detrital materials in oceanic and coastal ecosystems, so both siphonophore tissues and thraustochytrids may be present in marine snow consumed by European eel and other leptocephali. Therefore, future research on what leptocephali consume as food should be approached from a size-scaling perspective using systematic direct gut-content observations in combination with appropriate primers for next-generation DNA sequencing.

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马尾藻的食物来源

鳗鲡的神秘食物来源一直难以理解，因此本综述评估了有关该主题的最新发现之间的潜在相互关系。细头鱼肠道中通常很少有可识别的肠道内容物，这些物体通常包含无定形材料。肠道内容观察研究和稳定同位素研究表明，海洋雪碎屑型颗粒是一种食物来源，但这很难验证。最近的肠道内容 DNA 序列分析表明，小型 4-25 毫米马尾藻海欧洲鳗幼虫 Anguilla anguilla 经常摄取花萼虹吸管组织以及其他不太可能单独摄取的分类群。一项对马尾藻的高倍率摄影研究最近检测到可能的水螅触手和明显富含脂肪酸的单细胞、异养破囊壶菌原生生物（Labyrinthulomycetes 类），它们在之前的研究中已在海雪中发现，但没有被放大通过一些 DNA 引物。Calycophoran siphonophores 在马尾藻海中很丰富，具有广泛的触手阵列和短命的 eudoxid 生殖阶段，它们的大小可能适合直接食用或有助于海洋积雪。这两组可能是相互关联的，因为破囊壶菌是无处不在的分解者，它们定植于海洋和沿海生态系统中的碎屑材料，因此，虹吸管组织和破囊壶菌可能存在于欧洲鳗鱼和其他细头鱼食用的海洋雪中。因此，未来关于细头虫作为食物消耗的内容的研究应该从大小尺度的角度进行，使用系统的直接肠道内容观察结合适当的引物进行下一代 DNA 测序。