ORDER SACOGLOSSA -- Sap-sucking slugs
Most of sacoglossans are herbivorous, their teeth are used for piercing
the algal cells. The fluid contents of the algal cells are sucked out
for their nutrition. A few of sacoglossans do not feed on algae but feed
on the eggs of other opisthobranchs. Some species of the family Elysiidae
have been discovered in Hong Kong.