升温对铜锈环棱螺形态及春季个体增补影响的模拟实验研究

气候变暖已成为近几十年研究的热点,但是有关温度升高对螺类形态变化的研究还为数不多。利用中型室外模拟控制系统(Mesocosm)模拟百年之后长江中下游地区浅水湖泊水生态系统,实验设置对照组与升温组两个处理,以此探求水体温度升高对铜锈环棱螺(Bellamya aeruginosa)形态的影响。应用几何形态测量学得到铜锈环棱螺壳高、壳宽、轮廓面积与周长4个形态参数,并分别与质量进行回归分析。通过协方差分析比较两种处理回归方程的差异,发现螺类周长随温度升高发生显著变化,同时升温增加了螺类春季个体增补数量。升温对于螺类形态变化影响体现在以下3方面:升温显著增加了铜锈环棱螺的密度,加剧了种群个体间竞争,促使性成熟个体趋于小型化;升温改变铜锈环棱螺食物质量,通过影响螺类生长过程对螺类形态变化产生作用;升温改变了水体p H值,进而影响螺类外壳的钙化率和水体中钙可利用程度,对螺类外壳形成产生直接的影响,最终导致螺类形态变化。

EFFECTS OF TEMPERATURE ELEVATING ON MORPHOLOGY AND SPRING RECRUITMENT OF BELLAMYA AERUGINOSA IN AN OUTDOOR MESOCOSM EXPERIMENT

In recent decades temperature elevation has been the focus of many studies on climate change, but few studies have examined the effects on gastropod communities. We performed a mesocosm experiment to simulate temperature elevation in shallow lakes of the middle and lower reaches of the Yangtze River in 2100 with two treatments, i.e., control and heating, to explore the effects of temperature elevation on morphology of Bellamya aeruginosa. Snail shell dimensions (area, perimeter, height and width) were easily quantifiable morphological traits by geometric morphometric methods, and were correlated with weight. Then analysis of covariance was applied to contrast the difference of regression equations between the two treatments and we recognized that the perimeter was statistically significant different when the temperature elevated. Meanwhile, higher temperature increased the individuals of recruitment in spring. The effects of temperature elevation on morphology of Bellamya aeruginosa were reflected in the following three aspects. The density of Bellamya aeruginosa was significantly increased in heating tanks, and induced small juvenile shell size after maturation as a result of more intense intraspecific competition. Elevated temperature led to different food quality in the diet of Bellamya aeruginosa, morphological variation was indirectly affected in the process of growth due to different qualities of food. When the water temperature got warm, the change of pH value generated limited calcium availability and constrained calcification within the shell simultaneously which influenced the shell formation and induced shell plasticity consequently.