The mysterious feeding ecology of leptocephali: a unique strategy of consuming marine snow materials
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The mysterious feeding ecology of leptocephali: a unique strategy of consuming marine snow materials Katsumi Tsukamoto1,2 · Michael J. Miller1,2 Received: 13 July 2020 / Accepted: 30 October 2020 © The Author(s) 2020
Abstract Leptocephalus larvae have transparent bodies with tubular intestines that usually lack identifiable food items when they are collected, so mystery has surrounded efforts to determine what they feed on. Artificially spawned and reared first-feeding larvae were found to be highly selective in what they would eat, but they would consume rotifers and eventually ate specially formulated diets that contained shark egg yolk. Gut content studies on wild-caught leptocephali in the Atlantic and Pacific observed marine snow-associated materials such as discarded appendicularian houses, zooplankton fecal pellets, protists, and amorphous materials, and DNA sequencing indicated that the gut contents contain materials originating from a wide range of microorganisms and food web zooplankton species that were likely consumed in marine snow. Isotopic studies found a low trophic position of leptocephali and inter-taxa and geographic signature differences. Behavioral studies with leptocephali and the characteristics and size-scaling of the teeth are also consistent with feeding on marine snow-related particles. The feeding strategy of leptocephali appears to be based on consuming types of marine snow that contain nutritious and easily assimilated carbohydrates, fatty acids, and other materials that facilitate rapid conversion to glycosaminoglycans and tissues for energy storage and growth. Keywords Anguilliformes · Leptocephali · Feeding ecology · Marine snow · Larval aquaculture
Introduction Leptocephali are a unique type of fish larvae that are present in the upper few hundred meters throughout the world’s oceans from tropical to temperate latitudes (Smith 1989; Miller 2009). They are the larvae of anguilliform fishes and their close relatives within the Elopomorpha, which live in Katsumi Tsukamoto and Michael J. Miller are equal coauthors. Published with support by the Japan Society for the Promotion of Science (JSPS) KAKENHI Grant no. JP19HP2002. * Michael J. Miller [email protected]‑tokyo.ac.jp Katsumi Tsukamoto [email protected]‑tokyo.ac.jp 1
Department of Marine Science and Resources, College of Bioresource Sciences, Nihon University, 1866 Kameino, Fujisawa‑shi, Kanagawa 252‑0880, Japan
Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1‑1‑1 Yayoi, Bunkyo, Tokyo 113‑8657, Japan
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a wide range of habitats from coastal areas to deep-benthic environments and in the meso- and bathypelagic zones (Miller and Tsukamoto 2004). The larvae, however, are all present together in the upper 300 m offshore, most are present in the upper 100 m at night, and some use diel vertical migration (see Miller and Tsukamoto 2020). They are specialized for extreme transparency and accumulation of energy storage compounds in an
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