Subject: Will detergent have an effect on the heartrates of Daphnia and Why?

As part of my A-level Biology I am currently planning an experiment to test 
whether detergent (Washing-up Liquid) has an effect on the heartrate of Daphnia 
Pulex, however, explaining the principle theory as to why any change in 
heartrate would occur is giving me difficulty and I would most appreciate any 
help you could give me. Could any change that might occur in heartrate be due 
to the phospholipid membranes of the Daphnia being tampered with by the 
detergent? As I do not study Chemistry to the same level as Biology I am having 
trouble explaining the principle theory and hence my writing to you. I would be 
most appreciative if you could help me out with answering this question. 
Thankyou. Laura Bradley

Re: Will detergent have an effect on the heartrates of Daphnia and Why?