Figure 1 A–C

Life cycle stages of Aspidogastrea (seen from ventral side). A, B. Aspidogaster conchicola . A. Adult worm (2–3 mm long) from kidney of clams (Lamellibranchiata, Unionidae) or from the intestine of snails, fish, and reptiles. Excreted operculated eggs are embryonated and contain a creeping, nonciliated larva (B), which grows to the adult stage by gradual transformation. C. Multicotyle purvisi , ciliated free-swimming larva; adults reach 10 mm in length and occur inside the pallial complex of snails ( Pila) or in the intestine of snail-eating turtles. CF, ciliated field; CI, cilia; DO, development of opisthaptor; IN, intestine; LA, lateral larval glands; LS, larval anterior sucker; M, mouth; NE, nephridioporus (seen from ventral side since it opens dorsally); S, ventral sucker (= Baer's disc).