MadSci Network: General Biology

Re: What does mineral oil do the heart rate of daphnia and why?

Date: Mon Mar 24 15:32:35 2003
Posted By: David Hubble, Consultant/Owner
Area of science: General Biology
ID: 1044720677.Gb

Hi Katherine,

Daphnia absorb any chemicals in the water surrounding them straight into 
their bodies. This means that any chemical with a physiological effect 
affects the Daphnia extremely quickly and for this reason, Daphnia are 
actually used as an indicator to find out how toxic a liquid is by 
measuring its effect on the organism's heart rate.

Some chemicals (such as caffeine) increase Daphnia heart rate. Others such 
as oil or ethanol (ethyl alcohol) show their toxicity by a general 
depressive effect on nerve transmissions which causes a slowing of the 
heart rate. This occurs through action on enzymes which control heart rate 
by either slowing or raising it, and these enzymes may be activated or 
suppressed by different chemicals.

The precise details would be complex as oils often contain many chemicals 
with different specific effects, but I hope this explains the basic ideas.


Dr David Hubble, UK

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