Insulin-related peptide cDNA was characterized in the Pacific oyster Crassostrea gigas. It was determined that three transcripts with differing lengths of 3 -untranslated region (3 -UTR) were expressed in the visceral ganglia. The insulin-related peptide cDNA contained a number of AUUUA motifs that were typical of adenylate/uridylaterich elements in the 3 -UTR. The deduced preprohormone was a polypeptide of 161 residues and showed a conformation typical of preprohormones of the insulin superfamily, which included conserved amino acids necessary to adopt the globular insulin structure. The expression of the three different transcripts was variable throughout the year, with the highest expression observed in March and lower expression in November and July.

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Abstract(!) Underwater observations and experiments on pair formation in Apogon notatus were conducted almost every morning in June to July, 1976 in a rocky region north of the Seto Marine Biological Laboratory. (2) Experiments manifested that homing of this fish at least in the rocky region can be referred to the "pharotaxis". But homing in the sandy area remains still unexplained. (3) The usual sex recognition of this fish is thought to be based primarily on the differences in behavioural patterns between the sexes, while the mate identification in paired fish is supposed to be closely related to their determined attitude at the nest site. (4) Defended space, or individual space of paired fish is regarded as territory from the viewpoints of territory definition and its functional significance. (5) The smaller aggregations formed mostly in the season of pair formation is comparable with "the club" of the herring gull, Larus argentatus, from the viewpoint of animal sociology. As the aggregated fish maintain their restricted area for the time, the term "home site" may be used in explaining the behaviours of this fish. This seemingly accords with the results of studies on other fishes.