Étude ultrastructurale des bourgeons de régénération mis en place après amputation de la ventouse postérieure chez l'hirudinée rhynchobdelle adulte Helobdella stagnalis

Abstract

Tissue behaviour in the rhynchobdellid hirudinean, Helobdella stagnalis, was studied at the ultrastructural level between 8 and 18 days after amputation of the posterior sucker. Ultrastructural transformations of the regenerative buds progress in a sequential mode. They are successively characterized by nerve fiber regeneration, differentiation of the adhesive sole, and muscular and conjonctive tissues reconstitution with cells provided by the stump. Adhesive sole differentiation involves, first, the basal cells, which occurs without previous dedifferentiation, then the sensory receptors and, lastly, the glandular cells. Some basal epidermal cells are at the origin of the mucus glandular cells. The piriform and tubular phenotypes must be considered as successive maturation stages of the same clone. The conjunctive extracellular matrix probably plays a primordial role in the differentiation of the specific tubular glands of the adhesive sole.