TunicatesTunicata

Tunicates are marine invertebrates with a sac-like body protected by a thick, often leathery or gelatinous outer covering, known as a 'tunic' from which their name derives. They possess two prominent siphons and occur as either solitary individuals or as colonies formed from many small, connected zooids. Solitary forms, commonly called sea squirts, are typically globular, encrusting, or stalked, reaching from a few millimetres to over 10 cm (4 in) and often displaying vivid colours like red, orange, blue, or yellow. Colonial tunicates create extensive mats or large, amorphous masses.

Most sessile tunicates attach to hard substrates, including rock, coral rubble, or other organisms, on reef slopes, walls, and underhangs from the shallow subtidal down to at least 50 m (165 ft). All tunicates are filter feeders, drawing water through an incurrent siphon to capture plankton and organic detritus before expelling it through an excurrent siphon. Sessile species are common inhabitants of 🌊 Red Sea reefs, while pelagic forms, such as salps and pyrosomes, drift transparently in the water column. These pelagic forms often form long chains or bioluminescent colonies several meters in length and can appear seasonally in vast numbers.