Ask A Scientist© Biology Archive

name        Jeffrey
status       other
grade        other
location     CA

Question -   Do earthworms come to the surface to utilize the rain for
fertilization of the eggs?
---------------------------------------
I think that earthworms surface after rain to escape saturation of the soil.

J. Elliott 
====================================================================
Jeff,

The moiture found within the mucus secreted by the earthworm is used to 
facilitate the transfer of sperm between mating earthworms.  This is the same
secretion many people find when handling these animals.  Rain is not a part of
this process.

However, earthworms surface during a heavy or prolong rain because the transfer of 
oxygen between their soil environment and their blood stream is greatly reduced
when their surroundings is primarily water.  Water holds much less oxygen than
air and earthworms rely on the air in the soil for diffusing adequate oxygen
through their skin.  Hence, they come to the surface to increase the oxygen uptake when rain
water saturates the soil and displaces the air in the soil.

Steve Sample
====================================================================