Studies on Stimulation of Feeding Behavior in Yellowtail Seriola Quinqueradiata

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The feeding-stimulatory effects of extracts of the jack mackerel Trachurus japonicus white muscle on the yellowtail Seriola quinqueradiata were studied by the extractive substances in starch.Their stimulatory effects on the gustatory and olfactory rece ptors were also studied by recording the electrical responses in the palatine taste and olfactory bulb.A. Feeding-stimulatory effectiveness of extracts(1) The feeding-stimulatory effects of a water extract of the jack mackerel muscle and a synthetic mixture containing amino acids, nucleotides and organic bases based on the reported analysis of the muscle were studied. The former was more effective than the latter, suggesting missing stimulants in the latter.(2) The lipid component fraction of the natural extract did not show any appreciable feeding-stimulatory effect when applied individually or enhance that of the synthetic mixture when added to it.(3) Lactic acid was not effective when applied individually at the concentration found in … More the natural extract. However, it enhanced the stimulatory effect of the synthetic mixture when added to it. The effectiveness of the synthetic mixture plus lactic acid was still lower than that of the natural extract, suggesting more stimulants in the natural extract.B. Gustatory and olfactory neural responses to extracts(4) Both gustatory and olfactory systems responded to the natural extract and synthetic mixture. The former showed a higher sensitivity to the natural extract than to the synthetic mixture. It also showed a high sensitivity to lactic acid. The latter showed a higher sensitivity to the natural extract and the synthetic mixture than the former. It had almost the same threshold for them. On the other hand, it showed only a low sensitivity to lactic acid. Thus, the present results suggest that taste system may be involved in food taking. Whereas, the high sensitivity of the olfactory system to the two mixtures suggests that olfactory system is important for detecting food at a distance. Less