Regeneration in the earthworm, Eisenia foetida, Savigny, 1826; posterior regeneration.

Abstract

Posterior substrates of E. foetida, cut exactly at intersegmental furrows, regenerated homomorphic heads at levels 1/2-23/24, with equimery at 1/2-8/9 and hypermery (+ 1) at 4/5 and 8/9. Heteromorphic tails regenerated at 20/21 and from 23/24 to 54/55. Behind 54/55, regeneration of heteromorphic tails was obtained only from tail regenerates and substrates conditioned by a previous regeneration. Gradient of segment number in heteromorphic tails appears to be of an inverted V-shape.Starvation for 70 + days did not inhibit regeneration at 5/6 and 6/7 but all regenerates were hypomeric.Hypermery and hypomery provide an adequate explanation of the origin of symmetrical homoeosis.Regenerative capacity in a region from 20/21 to 23/24 is characterized as bipotential since an anterior regenerate, in that region, may be a homomorphic head or a heteromorphic tail.Review of previous work on E. foetida provides indications that the region of bipotential regenerative capacity is even more extensive, with anterior limit...