Evaluation of the pigmentation stages and body pro

Authors: Nobuto Fukuda Michael J Miller Jun Aoyama Akira Shinoda Katsumi Tsukamoto

Publish Date: 2013/04/24

Volume: 79, Issue: 3, Pages: 425-438

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Abstract

The pigmentation stages of Anguilla japonica were classified from the glass eel to yellow eel stage using 412 wildcaught eels from Hamana Lake and detailed developmental observations of 10 laboratoryreared eels The sequential appearance of pigment was similar to that in A anguilla except for delayed pigment formation on the nerve cord of A japonica The general classification of pigmentation stages VA–VIB in A anguilla was applicable to A japonica but the VB stage could be separated into two stages VB1 VB2 in A japonica The completion of guanine deposition on the intraabdominal membrane may be a trait to discriminate the yellow eel stage VII from the VIB stage In natural conditions wildcaught 0age eels n = 3298 did not increase in size and retained a slender body form until VIA4 and then became thicker during VIB The transition between body forms and growth may correspond to their ecological change from using passive transport in glass eels with tidal flow into rivers to their settlement and further movements of elvers upstream Considering this behavioral transition and pigmentation progression it is proposed that the terms glass eel and elver could be defined as stages VA–VIA4 and VIB respectivelyWe thank K Yokouchi and R Sudo for helping our eel sampling and the Fisheries Laboratory of the University of Tokyo the Fisheries Cooperatives of Hamana Lake and the Fisheries Division of Shizuoka Prefecture for cooperation This study was supported by Grantinaid for Scientific Research to K Tsukamoto from the Japan Society for the Promotion of Science and Ministry of Education Culture Sports Science and Technology of Japan and the research funds from Toyo Suisan Ltd and the Eel Research Foundation Noborikai

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