K. Kita-Tsukamoto, H. Urakawa, T. Otake, K. Ohwada
Little is known of a life cycle, especially early life history of Japanese eel, Anguilla japonica. Food source for eel leptocephali is not clarified. The particulate organic matter (marine snow) are thought to be a food source for leptocephali. Marine snow is known as localized microhabitats and highly enriched assemblages including various marine microorganisms. We examined a microbial diversity in the gut of eel leptocephalus for inferring their food source.
An Anguilla japonica leptocephalus, nearly 50 days of age, was collected at the middle of the Philippine Sea in 1995. A gut of the leptocephalus was aseptically dissected on board and stored at -85 C until DNA extraction. The amplified bacterial 16S rRNA genes were cloned into a plasmid vector. RFLP patterns showed twenty-three genotypes from a total of 50 clones. Eight genotypes were detected from 3-10 clones and other 15 clones showed single genotype. Almost 1000 bases of 16S RNA were sequenced from each genotypes. A similar sequences to the gamma subgroup of Proteobacteria, the genera Halomonas, Pseudomonas and Pseudoalteromonas, were detected. Our result suggests that marine snow can be a food source of eel leptocephali.
Glass eel catch decreases drastically in East Asia in these decades. We hope our result may be helpful for eel culture and for the catch of eel in East Asia.
(Ocean Research Institute, University of Tokyo, Minamidai, Nakano, Tokyo 164-8639, Japan)