Regeneration in sabellid annelids

Abstract

Sabellid regeneration and the expression of polarity are known to be under direct neural control. During regeneration nerves exhibit both neurotrophic and neurosecretory capacities. Indeed, it is proposed that the basic neurotrophic control mechanism is neurosecretory in nature, involving the synthesis, packaging and transport of neurosecretory granules to the wound site. The expression of polarity is envisioned as a cellular differentiating response to a threshold increase in neurohormone. Under maximal stimulus, anterior regeneration involves the sequential synthesis and assembly of a rich hyaluronate matrix followed by the deposition of chondroitin sulfate and collagen to form the normal adult crown. Posterior regeneration, according to the model, is under minimal stimulation and does not progress beyond the hyaluronate stage. The relationship between neural control and the assembly of extracellular macromolecules during regeneration is discussed in relation to the proposed model. © 1976 by the American Society of Zoologists.