Annelids - Regeneration in Invertebrates

Between the segmented worms both the polychaetes and oligochaetes have remarkable powers of regeneration. Leeches totally lack this capability. In polychaetes tentacles, palps, and even heads ripped off by predators are soon replaced. This is of common occurrence in burrowers and tube dwellers. Some worms as well display self-amputation or autotomy. For example, the posterior segments are detached while the worm is disturbed and they are regenerated soon thereafter. Earthworms (oligochaeta) can as well regenerate both anterior and posterior segments. If an earthworm is cut into two halves the posterior half regenerates the anterior segments involving the mouth, and the anterior half regenerates from its posterior cut end, the new posterior segments. Two new individuals so rise from the original one.