| Abstrakt: |
A description is given of variations found in the life-cycles and local differences in weight of the leech E. octoculatafrom five different reaches of the River Trent which were subjected to different levels of pollution, mainly in the form of domestic sewage, and to different temperature regimes produced by the condenser effluents from four Power Stations. In reaches receiving high levels of sewage pollution the mean weights of leeches were higher than in relatively unpolluted reaches (P < 0.001). This increase could have been produced by the abundance of tubificid worms present in the polluted reaches, the worms providing a ready food supply for the leeches. Earlier emergence of newly hatched leeches which occurred at some of the sampling points was probably caused by the combined or separate effects of the increased temperatures below condenser effluents and the earlier production of cocoons induced by the greater availability of food organisms in the more polluted reaches. |
Full text from SpringerLink