Outside Heat
Posted by Hayley on May 8, 2003
Q: are daphnia water fleas piokilothermic? if so, why?
A: Sorry for the delay in answering - somehow I missed your question until just today.
Yes, daphnia are also called water fleas (they are not insects, however). Biologists now prefer to call these animals ectotherms (heat from outside) rather than poikilotherms.
Only birds and mammals are not ectotherms, they're endotherms, although some fish and reptiles can and do regulate their body temperatures to some extent. All of the invertebrates (animals without backbones) are considered ectotherms but even some of them can modify their body temperature too. Butterflies, for instance, often sun themselves to raise their internal body temperature. I hope this helps.
John Wiessinger ( June 6, 2003)