Why Rescue Earthworms after Rain?

In heavy rain, many earthworms (and fellow invertebrates) migrate to the surface. They do this for one reason: to breathe. Earthworms follow a diurnal rhythm (this is an extension of the circadian rhythm), and essentially their night rhythm involves getting more oxygen (and moving to the surface enables this). Now, not all earthworms are the same- <a href="https://s3.amazonaws.com/academia.edu.documents/34021026/22.pdf?AWSAccessKeyId=AKIAIWOWYYGZ2Y53UL3A&Expires=1512697752&Signature=afLrR6bZUQ61CNWSRBgNdSkybKY%3D&response-content-disposition=inline%3B+filename%3DRole_of_diurnal_rhythm_of_oxygen_consump.pdf" rel="noopener ugc nofollow" target="_blank">research</a> shows that the Amynthas gracilis worm is more likely to come to the surface in rain than the Pontoscolex corethrurus worm. Earthworms need oxygen just like we do. The difference? They breathe in the oxygen through their skin by a process of <a href="https://en.wikipedia.org/wiki/Diffusion" rel="noopener ugc nofollow" target="_blank">diffusion</a>. For diffusion to occur, worms need to have moist skin. This allows oxygen to be absorbed and carbon-dioxide to be released. Without damp conditions, earthworms suffer. <a href="https://medium.com/@autumnaspie/why-rescue-earthworms-after-rain-7f9fa04dc4d8">Website</a>