Gustatory responses in Pacific bluefin tuna Thunnus orientalis (Temminck and Schlegel)

Abstract

Gustatory neural responses of the Paci¢c blue¢n tuna Thunnus orientalis (Temminck and Schlegel) to extracted compounds of prey organisms, such as amino acids, nucleotide-related substances, organic acids and organic bases, were electrophysiologically recorded from the facial nerve supplying the anterior palate. Of the17 amino acids tested, L-proline was the most potent amino acid at 10 À2 M, and its threshold was the lowest at around 10 À 6 M. L-leucine, Lmethionine, L-alanine, L-valine and L-isoleucine were also highly stimulatory at 10 À2 M; however, the other 11 amino acids examined were not as e¡ective or were ine¡ective. Thus, the gustatory receptors for amino acids of the Paci¢c blue¢n tuna show a narrowly tuned response pro¢le. Among the seven nucleotide-related substances tested, uridine-5 0 -monophosphate, inosine-5 0 -monophosphate and adenosine-5 0 -diphosphate were highly stimulatory, and their thresholds were 10 À 4^1 0 À5 M. Inosine elicited a positive response at10 À2 M but its response magnitude was not so high. Organic acids L-lactic and pyruvic acids were e¡ective at 10 À2 M, but no response was elicited at 10 À3 M. Among organic bases, betaine was highly stimulatory, and its response magnitude at 10 À2 M is almost equal to that of L-proline at the same concentration. The threshold for betaine was determined to be at around 10 À5 M. Trimethylamine oxide and ammonium chloride were ine¡ective.

Tuna Nutrition and Feeds: Current Status and Future Perspectives

“…Betaine was highly stimulatory, but trimethylamine oxide and ammonium chloride were 22 ineffective, and lactic and pyruvic acids were only effective at higher concentrations (Kohbara et al, 2006).…”

“…IMP, inosine monophosphate) (Rust, 2002). Neural gustatory responses of PBT to compounds extracted from prey organisms were studied by electrophysiological recording from the facial nerve supplying the anterior palate (Kohbara et al, 2006). Of the 17 amino acids tested, L-proline was the most potent, followed by L-leucine, L-methionine, L-alanine, L-valine and L-isoleucine.…”

Effects of postharvest processes on quality of Australian sardines (Sardinops sagax) and redbait (Emmelichthys nitidus nitidus) for feeding aquacultured southern bluefin tuna (Thunnus maccoyii)

“…Scombrids (i.e. mackerels and tunas) such as jack mackerel ( Trachurus japonicus ) and chub mackerel ( Scomber japonicus ; Ishida & Hidaka 1987) and Pacific bluefin tuna ( Thunnus orientalis ; Kohbara et al. 2006) also show feeding responses to IMP.…”

“…Scombrids (i.e. mackerels and tunas) such as jack mackerel (Trachurus japonicus) and chub mackerel (Scomber japonicus; Ishida & Hidaka 1987) and Pacific bluefin tuna (Thunnus orientalis; Kohbara et al 2006) also show feeding responses to IMP. These studies indicate that many scombrids are not just visual predators, but rely upon other cues when foraging for prey beyond the line of sight, as suggested by Atema et al (1980).…”

Improvement in the feeding activity, early growth and survival of Pacific bluefin tuna Thunnus orientalis larvae fed a casein peptide-based microdiet supplemented with inosine monophosphate

“…Several feed attractants were reported to improve the palatability of the MD to marine fish larvae [8,9]. It is well documented that inosine monophosphate (IMP) exhibits the highest potency as a feed attractant for fishes, including PBT [9][10][11][12][13][14][15]. However, no study has been previously conducted to investigate the effect of IMP on the feed performance of a casein-based MD for PBT.…”