Taste receptor stimulation and feeding behaviour in the puffer, Fugu pardalis. II. Effects produced by mixtures of constituents of clam extracts

The effects of extracts of short-necked clam, Tapes japonica,as feeding stimulants on the puffer, Fugu pardalis, were studiedby applying the constituents of the extracts in starch pellets.As observed elsewhere (Hidaka et al., 1978), the starch pelletcontaining all the constituents found in the clam extracts (Konosuet al., 1965), except homarine and choline, at the same concentrationratios as in the clam tissue was taken up by the fish. Omissiontests on the chemical constituents suggested that the palatabilityof the clam pellet might be largely produced by some amino acidsand betaine: Pellets containing alanine, glycine, proline, serineplus betaine were nearly as effective as those containing allthe extractive compounds except homarine and choline. Mixturesfree of either the above amino acids or betaine tested wereall less effective. The nucleotides and related substances andorganic acids detected in the clam extracts had no appreciableeffect except that a mixture of all of them was weakly acceptedby adding betaine to it. The other amino acids found in theextracts appear to be ineffective.