宍道湖産ヤマトシジミ殻体の微細成長縞の観察

　 A vital marking experiment was carried out to examine the process of micro-growth striations of Corbicula japonica Prime from Lake Shinji. Samples were cultured in aquarium and in Lake Shinji for about one month. During culturing they were marked two to three times by tetracycline hydrochloride solution. The fluorescent lines showing the time of marking are observed remarkably well, especially in the samples marked during day time. In addition to these lines, strong stress bands are observed in whole samples in concurrence with the markings. This fact suggests that the process of marking experiment itself arrested the growth of shell. The pattern of micro-growth striations in between the marked lines of each sample show neither cyclicity nor regularity.
　On the other hand, the micro-growth striations in the samples cultured in Lake Shinji show tendency of higher frequency per day than those in aquarium. From these results, the formation of micro-growth striations is assumed to be influenced by complex changes in the brackish-water environments as well as by their physiological rhythm and its individual variation.