Didemnids

Didemnids are a family of sessile marine animals, comprising some 40 species of ascidians. These animals are commonly referred to as sea squirts due to the way they expel water from their siphons to breathe and feed. Didemnids are characterized by their flat, usually oval-shaped bodies, which can range from bright red to dark brown in color.

Didemnids are filter feeders, positioning themselves on rocks, reefs, and other surfaces in tropical and temperate waters around the world. They draw in water through a siphon and expel it through another opening, trapping small organisms such as plankton and algae for food. In doing so, they contribute significantly to the nutrient dynamics of marine ecosystems.

Some species of didemnids are bioluminescent, emitting light from specialized cells to communicate, attract prey, or defend against predators. Other characteristics include the production of antifeeding compounds, as well as aggregations of specific didemnid species on reefs during periods of reduced predation pressure.

Research on didemnids is focused on their ecological importance, immune system, and potential applications in the fields of materials science and tissue engineering. The study of ascidians' capacity for permission, regeneration, and self-organization has provided insights into the development of novel materials and medical devices.

The close genetic relationships between the several hundred species of marine animals make them an area of interest for studies of biodiversity and comparative evolutionary biology.