Growth promoting effect of hyaluronan synthesis promoting substances on Japanese eel leptocephali.

Yutaka Kawakami,Kazuharu Nomura,Hideki Tanaka,Ted S Acott

doi:10.1371/journal.pone.0098688

Abstract

Hyaluronans (HAs) are glycosaminoglycans produced in the bodies of Anguilliform and Elopiform leptocephali, and play a role in metabolic energy. In mammals, HA synthesis-promoting substances (HASPS) up-regulate the expression of HA synthase (HAS) and increase the amount of HA in the body. In this study, Japanese eel leptocephali were fed a HASPS containing diet. We analyzed HAS1s and HAS2 expression, HA content, and their influence on growth. HASPS extracted from Grifola frondosa promoted HAS1s and HAS2 mRNA and HA content. Other than mammals, these results are first reported in vertebrate. Moreover, HASPS extracted from G. frondosa promoted leptocephalus growth. The relationship between growth and HA in the leptocephali is not yet clear. However, based on our results we hypothesize that HA is involved in the storage of energy, which is metabolized to sugars when needed for metabolic energy.

Highlights

The Japanese eel (Anguilla japonica) is an important commercial species in Japan owing to its high market value as a food source
HA is synthesized by integral plasma membrane glycosyltransferases and is exported directly into the extracellular space
The eel hyaluronan synthase 1 (eHAS1) and eHAS2 nucleotide and deduced amino acid sequences are shown in Figures 1 and 2

Summary

Introduction

The Japanese eel (Anguilla japonica) is an important commercial species in Japan owing to its high market value as a food source. In 2010, successful closed-cycle breeding of the Japanese eel was reported [1]. Kawakami et al [2], [3] reported that wild Japanese eel larvae, leptocephali, start metamorphosing at 4- to 5-months-old using otolith daily increment analysis. The average duration from hatched larvae to glasseel is about 299 days (minimum to maximum: 153–754 days) [6]; this is longer in cultured than in wild leptocephali. Japanese leptocephali feed on readily available particulate material originating from various sources closely linked to ocean primary production [7]. For largescale glass-eel production, shortening of the breeding duration is desirable; to do this, development of a new breeding system and/ or upgrading the present breeding system is necessary

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