BIOL 2325 Lecture Notes - Lecture 4: Acoelomorpha, Monogenea, Platyzoa
Document Summary
Have a saclike gut without anus or lack digestive cavity. Have radial arrangement of nerves and lack ganglia of a true brain. Most are free living but some are symbionts or parasites. Ciliated cellular epidermis resting on a basement membrane. Digestion-pharynx opens posteriorly inside mouth through which it extends. Clamp onto external surfaces using a hooked opisthaptor. Simple life cycle-egg hatches a ciliated larva that attaches to host. Often have 2 hosts, first is invertebrate and second is vertebrate. No digestion system-absorbs small molecules through tegument. Asexual reproduction-bud of thousands of juveniles in intermediate host. Long flat bodies with scolex for attachment. Entire surface is covered with minute projections(microtrix) similar to microvilli in vertebrate small intestine. Move by gliding on ventral cilia or via adhesive gland(leech like) Feed on bacteria, diatoms, and unicellular eukaryotes. Hermaphroditic- male system in freshwater species not functional so females reproduce parthenogenetically. Jaw bearing-have small cuticular jaws with homologous microstructure(not acanthocephala)
