Regeneration and growth control in Nereis III. Separation of wound healing and segment regeneration by experimental endocrine manipulation.

Loss of posterior segments from immature Nereis is followed by the associated processes of wound healing and segment regeneration. In the absence of a hormone secreted by the brain, wound healing alone ensues. However, proliferation of segments can be initiated by intracoelomic implantation of a living brain (removed from a donor) during the course of wound healing or subsequent to its completion. In this way, wound healing and regenerative growth can be separated experimentally. Wound hormones may have a role in wound healing, but are probably not involved in the initiation of segment regeneration in Nereis. However, developments at the site of the wound which follow loss of posterior segments in the absence of regeneration progressively reduce the regenerative activity which follows subsequent brain implantation. The nature of the changes is unknown. Maintenance in a decerebrate condition also reduces regenerative capacity. This effect is independent of changes at the wound and may be due to accelerated maturation.