Costasiella

Costasiella is a genus of sacoglossan sea slugs, a shell-less marine opisthobranchid gastropod mollusk in the family Costasiellidae. The Costasiella is defined by some specific characteristics such as smooth rhinophores which are usually simple with dull tips and flattened at their base. Other features include rounded, tentacular anterior foot corners that exhibit their spatulate shape to enhance mobility and blade-shaped radular teeth with substantially short bases. Most of the genus could be found within the tropical and subtropical regions of the Western Pacific oceans. Their preferred habitats include areas of soft, muddy sediments around intertidal zones. Their diets vary from species to species but generally consume various types of green algae, more commonly the Vaucheria and Avrainvillea.

The most recent diagnosis of the genus Costasiella is by the Dutch malacologist Cornelis Kees Swennen (2007).