; phylum Mollusca, class Gastropoda)
A relatively small order of opisthobranch gastropods in which individuals are small and may be primitively shelled, bivalved, or naked. They feed with a radula and suctorial mouth on the cell fluids of algae. Usually they feed on green algae, but some certainly feed on red algae and there are reports of sacoglossans feeding on large diatoms and on sea grasses. Some feed suctorially on eggs of other opisthobranchs. Several genera of sacoglossans are able to retain functional chloroplasts from their food algae, and benefit nutritionally from the photosynthetic activity of the chloroplasts. Gills are usually lacking, but rarely one may be present. They are named after the sac (‘ascus sac’) into which worn teeth normally pass (rather than being shed as are teeth in other opisthobranchs). Sacoglossa are not known in the fossil record.
Subjects: Zoology and Animal Sciences.