Defaecation strategies of two freshwater gastropods, Ancylus fluviatilis Müll. and Planorbis contortus Linn. (Pulmonata) with a comparsion of field and laboratory estimates of food absorption rate
Defaecation strategies of two freshwater gastropods, Ancylus fluviatilis Müll. and Planorbis contortus Linn. (Pulmonata) with a comparsion of field and laboratory estimates of food absorption rate
复制标题
两种淡水腹足动物 Ancylus Fluviatilis Müll 和 Planorbis contortus Linn (Pulmonata) 的排便策略以及对食物吸收率的现场和实验室估计的比较。
作者：
Peter Calow
应用~(51)Cr放射性示踪技术监测钉螺和螺旋藻的排泄率。当钉螺被饥饿时，无论是在接触标签食物之前或之后，肠道排空率都会降低。对粪便成分的检查表明，这是由于食物通过肝胰腺的速度降低。由于后者是腹足动物消化和吸收的主要场所，这种策略被解释为蜗牛试图从扰乱的食物供应中提取更多的营养。其他影响排泄率的因素还有温度、食物质量和蜗牛大小。螺旋藻的体重比河豚的体重排出更快，这是有害动物和草食动物之间的典型差异。有关排便策略的信息使人们能够估计河豚的田间吸收和摄取率。后者与根据实验室观察预测的估计值之间有很好的一致性。然而，现场确定的吸收效率更恒定，通常比实验室测量预测的要高。
SummaryA radiotracer technique involving 51Cr was used to monitor the egestion rates of A. fluviatilis and P. contortus.When snails were starved, either before or after exposure to labelled food, gut emptying rate reduced. Examination of faecal components suggested that this was due to reductions in the rate of passage of food through the hepatopancreas. Since the latter is the major site of digestion and absorption in the Gastropoda this strategy was explained as an attempt by the snails to extract more nutrient from the disturbed food supply. Other factors affecting egestion rate were, temperature, food quality and snail size. Weight for weight egestion was more rapid in P. contortus than in A. fluviatilis and this difference is typical between detrivores and herbivores.Information on defaecation strategy enabled an estimation of field absorption and ingestion rates in A. fluviatilis. There was good agreement between the latter and estimates predicted on the basis of laboratory observation. However, field determined absorption efficiencies were more constant and generally higher than those predicted on the basis of laboratory measurements.