大沼螺的生物学研究

THE BIOLOGY OF THE FRESHWATER SNAIL PARAFOSSARULUS EXIMIUS (FRAUENFELD) IN POYANG LAKE, JIANGXI, CHINA

大沼螺在自然条件下的雌雄性比为1:0.69。交配期为10月底至次年6月。2、3月开始产卵,8月结束。5月初卵开始孵化。性腺一般当年成熟,次年螺可繁衍后代。幼螺经过4—5个月的生长,到10月份可达13—15毫米高。随后水温下降,螺停止生长,次年5、6月水温上升再继续长高。最大个体为18毫米左右。3个采集点的螺在繁殖、生长方面无明显差异。壳高与壳宽呈直线相关,而壳高、壳宽与湿重呈指数相关。本文首次报道了大沼螺是吸虫的中间宿主。

The biological investigation of Parafossarulus eximius was undertaken at Poyang Lake during February, 1985-January, 1986.The sex ratio (female: male) in nature is 1:0.69. The mating season is from late October to June of the next year and the period of ovulation is from February to August. Generally, eggs start hatching in early May and the juveniles attain sexual maturity in the same year, but ovulate and breed in the next year. Four- or five-month old juveniles attain to 13—15 mm in height. They stop growing in October owing to the lowering temperature and grow again in the next May or June when the climate becomes favourable. The biggest shell is about 18 mm high. The relationship between shell height and shell width is linear, while those between shell height, shell width and wet weight are exponential. P. eximius is recorded for the first time as an intermediate host of a trematode.