Jantz B, Neumann D
Department of Zoology, Physiological Ecology, University of Köln, Weyertal 119, D-50931 Köln, Germany fax: 0221/470-5932; e-mail:
Oecologia. 1998 Apr;114(2):213-225. doi: 10.1007/s004420050439.
In a Rhine River bypass built at a water pollution control station, the growth and reproductive cycle of the zebra mussel (Dreissena polymorpha) were studied over a period of nearly 3 years. The experimental setup offered the possibility to manipulate the temperature of the continuously passing river water and to calculate influences of temperature and food on the growth of individually marked mussels. Shell growth rates were a function of algal density (measured as chlorophyll a). This function followed saturation curves with temperature-dependent plateau levels, and saturation occurred at values above 40 μg/l chlorophyll a. The relationship between shell growth rate and temperature followed the courses of bell-shaped curves with algal-food-dependent heights. No clear correlations could be found between shell growth and other environmental factors such as dissolved organic matter, total organic content, seston, and turbidity. Two spawning periods per year characterized the reproductive cycle of the zebra mussels at the study site. The first one covered nearly 3 months (April to July) comprising several spawning events. The second shorter one occurred in August. Young mussels of the first spawning period settled at the end of May, and they were able to reproduce a few months later (end of August) when their shell length exceeded 9 mm. This first spawning period of the young-of-the-years coincided with the second spawning period of the older generations. Through the combined analysis of the results of both body weight determinations and shell growth experiments, it was possible to model mussel growth over a period of nearly 3 successive years, and to suggest the presence of an endogenous factor that might be involved in determining the start of the annual shell growth period.
在一个建在水污染控制站的莱茵河旁路中，对斑马贻贝（多形饰贝）的生长和繁殖周期进行了近3年的研究。该实验装置提供了控制连续流过的河水温度的可能性，并能计算温度和食物对个体标记贻贝生长的影响。贝壳生长速率是藻类密度（以叶绿素a衡量）的函数。该函数遵循具有温度依赖性平稳水平的饱和曲线，当叶绿素a值高于40μg/l时出现饱和。贝壳生长速率与温度之间的关系遵循具有藻类食物依赖性高度的钟形曲线。在贝壳生长与其他环境因素（如溶解有机物、总有机含量、悬浮颗粒和浊度）之间未发现明显的相关性。研究地点的斑马贻贝繁殖周期每年有两个产卵期。第一个产卵期持续近3个月（4月至7月），包括几次产卵事件。第二个较短的产卵期发生在8月。第一个产卵期的幼贝在5月底定居，当它们的壳长超过9毫米时，几个月后（8月底）就能繁殖。当年幼贝的第一个产卵期与老一代的第二个产卵期重合。通过对体重测定结果和贝壳生长实验结果的综合分析，有可能对贻贝近3年连续时间内的生长进行建模，并表明可能存在一个内源性因素参与确定年度贝壳生长周期的开始。
