著者

斎藤 晋 百済 弘胤

出版者

日本生態学会

雑誌

日本生態学会誌 (ISSN:00215007)

巻号頁・発行日

vol.22, no.5, pp.213-221, 1972-10

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Life history, reproduction and population structure of an amphipod, Orchestia platensis (KROYER) were investigated in the forest of Kiyosumi, Chiba Prefecture. The breeding period of O. platensis in Kiyosumi was from May to October. Newborn animals appeared in May, and from June to August, clear growth of the new-born animal was found. Pregnant rate of the adult female of the amphipod was 40 per cent in September, and the average rate throughout the breeding period was 25.3 per cent. The relationship between the size of the female and number of eggs produced by the female is, Y=0.021X^<2.717> where Y is the estimated number of eggs produced, X is the size of the female in head and peraeon length. An adult female, 31 mg in body weight, of O. platensis had 10 eggs in her brood pouch, the percentage of these eggs to the mother was 18.7 per cent in terms of biomass, and 24.1 per cent in terms of energy. The reproduction efficiency of an individual (E_<rp>) in terms of energy is defined as, [numerical formula] Reproduction efficiency of an individual for O. platensis was 19.4 per cent, and those for three isopods were from 28 per cent to 33 per cent.