miracidium of Megalodiscus temperatus, the rectal fluke of Rana
pipiens. This is a section through the apical papilla which attaches to its
specific ram horn snail host, Helisoma trivolvis during the
penetration act. There are four different glands, each carrying different secretory
vesicles, depositing secretions on the surface of the snail, aiding in
penetration. The four types of glands are penetration glands (PG), secretory sac (SS), and accessory penetration glands (AC). The
fourth type, the apical gland is not seen here. The open spaces are
the pores of three of the different types of secretory glands. 30,000x.