室内飼育におけるナカセコカワニナの成長と産仔数

概要

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Growth and number of newborns in Semisulcospira nakasekoae reared during 48-61 months under the laboratory conditions were studied. The newborns, which were produced in June 1990, Oct. 1990 and May 1992, grew up to 8.0-8.4 mm in mean shell diameter at age 1, 9.2-9.3 mm at age 2, 10.2-10.8 mm at age 3, and 10.3-10.9 mm at age 4. The maximum size of S. nakasekoae was 13.4 mm in shell diameter, 29.1 mm in shell height, 3.3 g in wet weight with shell at age 4+. The production of newborns has begun in snails grown up over 8 mm in mean shell diameter at the 10-12th months after the birth. Birth of newborns occurred at a water temperature between 8 and 32℃. Large number of newborns were produced at a water temperature over 20℃. Number of newborns produced during a month per female was estimated 3-10 individuals at a water temperature between 20 and 32℃. Large number of newborns during one year were produced by mature females larger than 9 mm in shell diameter at age 1 to 4+. Mean number of newborns produced during a year per female at age 1 to 4+ was estimated 26-33 individuals.
1998-10-31