[Ultrastructural aspects of Carcinus maenas L. hemocytes (Crustacea, Decapoda), parasitized by Sacculina carcini Thompson (Crustacea, Cirripeda) : reactive activity, collagen genesis].

The collagen embedding Sacculina roots is synthesized by hemocytes of Carcinus maenas and is described. Hemocytes engaged in the secretion of collagen as a reaction against a parasite constitute a defensive mechanism still largely unknown within Crustacea.