Seasonal Distribution and Growth of Sphaerium (Musculium) japonicum (Bivalvia ; Sphaeriidae) in Lake Suwa, Japan

概要

論文の詳細を見る
seasonal changes in the distribution and the growing characteristics of Sphaerium (Musculium) japonicum were investigated in Lake suwa from June 20 to November 11, 1993. The main distribution area of S. (Musculium) Japonicum transfered from the littoral zone to the lake center with increasing water temperature, and began to retransfer to the littoral zone with decreasing dissolved oxygen content of bottom water. Thereafter, their distribution in the lake was at random. The organic contents of bottom mud in Lake Suwa were 13.5-15.6%, but they were no influence on the movement of S. (Musculium) Japonicum. In vitro, their migration speed was 50 cm per hour at 16.9℃ water temperature (D. O. 7.52 mg/l), and their movement distance per minute corresponded to their shell length. All adults of S. (Musculium) japonicum were taken from June 21 to September 24 held juveniles inside them. The maximum size of the inside juveniles was 1.71 mm, and the minimum size of the outside adult was 1.59 mm. The young taken from the lake grew up to 1.92-2.12 mm in nature and to 2.25-2.55 mm in vitro after 100 days. The growth rate was 0.1 mm in one month in natural conditions, against 2 weeks in vitro. The living shells of juvenile decreased to 50% during 50 days in vitro, and after that remained stable for 50-100 days.
信州大学理学部の論文
1994-10-31