稚魚期の攻撃性に性差はあるか。 : サクラマス(Oncorhynchus masou)の場合

概要

論文の詳細を見る
An experiment was carried out in order to determine whether sexual differences in aggressiveness exist in masu salmon fry (Oncorhynchus masou). Eighteen groups, each consistihg of four even-sized fish aged 37-57 days after hatching, were used. Agressive behavior in individual fish of each group was recorded for 3 days. After the experiment, all the fry were examined histologically to determine their sexes. Females were judged by the appearance of auxocytes with young oocytes and males by blood vessels and sperm ducts in the stroma in the proximal region of the gonad. The 72 fry used consised of 38 females and 34 males and of the present 18 groups, only one group consisted of individuals of all the same sex (male). Chasing, nipping, lateral display, wigwag display, fighting and territorial defense were taken as expressions of aggressiveness. A dominance order of the nip-dominance type was recognized in most of the goups. No significant difference due to sex was noted in the number of dominant fish either in the 9 groups consisting of the same numbers of both sexes or in the 2 groups consisting of one female and three males, whereas all the dominant fish were females in the 6 grousp consisting of three females and one male.
1983-03-25