Internal defenses of the snail Biomphalaria glabrata

Injection of foreign particles (zymosan, latex beads, living bacteria) and substances (ferritine, horseradish peroxidase) in Biomphalaria glabrata induces the rapid appearance of tubular double-helical filaments in the hemolymph. This rapid induction may be due to the polymerization of precursor proteins of the hemolymph. Tubular helical filaments are also observed in normal snails, especially in the hemal spaces of the proximal kidney; they seem to belong to the extracellular matrix and form bundles of a few parallel units associated with fine fibrils. Hemocytes adhere to these bundles by means of the filopodia tip or by small areas of the cell surface; consequently, they may become temporarily sedentary in the hemal spaces. The deposition of helical filaments seems increased in ageing snails and in snails parasitized by Echinostoma caproni.