尖膀胱螺的生物学特征及光照对其生长繁殖影响的初步研究

尖膀胱螺Physa acuta是世界广泛分布的淡水螺类,在我国属外来入侵种.本文着重对该螺的形态特征、繁殖、发育及光照对螺生长和繁殖发育的影响等进行了实验观察和研究.尖膀胱螺个体中等,左旋,壳口无厣.喜聚居于水生植物较多、营养丰富的淡水区域.尖膀胱螺为雌雄同体,异体受精,有时也可自体受精.性成熟个体在条件适宜的情况下(温度、食物和光照)每天都可产卵,卵孵化率近100％.尖膀胱螺胚胎发育共经历卵裂期、囊胚期、原肠期、担轮幼虫期、面盆幼虫期、仔螺形成及出膜期7个时期.一般情况下,螺卵7～10 d可孵化,60 d即可性成熟.25℃、24 h连续光照条件下,尖膀胱螺体重明显增加,40 d就可以性成熟并产卵.

Biological Characteristics of Physa acuta and the Effects of Light ontheir Growth and Development

The freshwater snail Physa acuta(Draparnaud,1805) are widely distributed in the world and are believed to be an invasive species in China.The morphological characteristics,reproduction,development and the effects of light on the growth of Physa acuta were studied in this paper.The results showed that the shell of Physa acuta was medium in size,sinistral,without epiphragm.Most of them inhabited in freshwater regions with abundance of nutrition and aquatic plants.Physa acuta were hermaphroditic and cross-fertilization,sometimes self-fertilization.In suitable conditions,maturity individual is able to spawn daily and the rate of hatching could reach 100%.The embryonic development went through the following seven stages:cleavage,gastrula,trochophore larva,basin larva,aberdeen spiral formation and the hatching,which mainly finished within 7 to 10 days.The larva grew to sexual maturity after 60 days of hatching.The snail grew fast with light 24 hours a day at 25℃,and the larva became mature after 40 days of hatching under these conditions.