抄録
Abstract: Growth patterns in the shell and soft parts of the dogwhelk Nucella freycineti were examined. Growth rings in the shells were investigated by X-ray photography and were shown to form annually. In snails that hatched in summer, the first rings formed in the first winter. The shell growth equation was determined based on the age character, population age structure, seasonal growth rate and size frequency distribution of the population. The maximum shell growth occurred in summer. The life span was estimated to be>11 years. Low physiological activity and/or starvation induced by low temperature might be main factor(s) causing the formation of annual rings, although age might also influence ring formation. Total body weight increased in late summer in males and from late summer to winter in females. Gonad weight showed a similar trend in each sex. After the reproductive season, shell growth occurred in summer, and body weight increased from summer to winter. These growth characteristics might promote higher survival and fitness.
