Accumulation of hyaluronan in reared Japanese eel Anguilla japonica during early ontogeny

Abstract

Hyaluronan (HA) is a main component of the highly hydrated extracellular body matrix of the larval stage of eels (leptocephalus). To determine the physiological and nutritional significance of HA in artificially reared larvae of the Japanese eel Anguilla japonica, HA and water content were measured at various larval stages in captivity. HA accumulated in the larval body with growth and water content also increased in parallel with HA. Almost all the accumulated HA was consumed during metamorphosis, suggesting HA plays a significant role in eel growth and metamorphosis. However, the amounts of HA and water were significantly lower in reared than in wild-caught larvae at the young stage, indicating a poorer nutritional condition of reared larvae, probably due to the deficient performance of currently used artificial diets. HA accumulation in reared larvae, however, eventually attained a level sufficient for metamorphosis by 250 days or more, and the glass eels of reared larvae had the same nutritional condition as that of wild glass eels. These findings are discussed with respect to the development of more effective artificial diets for rearing eel larvae.