Tunicata/Ascidians
A tunicate is a marine invertebrate animal, a member of the subphylum Tunicata. It is part of the phylum Chordata, which includes all animals with dorsal nerve and notochords (including vertebrates). An Ascidiacea is a lower class within the subphylum tunicate.
Some tunicates live as solitary individuals, but others replicate by budding and become colonies, each unit being known as a zooid. They are marine filter feeders with a water-filled, sac-like body structure and two tubular openings, known as siphons, through which they draw in and expel water. During their respiration and feeding, they take in water through the incurrent (or inhalant) siphon and expel the filtered water through the excurrent (or exhalant) siphon. Most adult tunicates are immobile and permanently attached to rocks or other hard surfaces on the ocean floor; others, such as salps, and pyrosomes swim in the pelagic zone of the sea as adults.
Salpa
A salp or salpa is a barrel-shaped, planktic tunicate. It moves by contracting, thereby pumping water through its gelatinous body, one of the most efficient examples of jet propulsion in the animal kingdom. The salp strains the pumped water through its internal feeding filters, feeding on phytoplankton. Wikipedia
Pyrosoma
Pyrosomes, genus Pyrosoma, are free-floating colonial tunicates that usually live in the upper layers of the open ocean in warm seas, although some may be found at greater depths. Pyrosomes are cylindrical or cone-shaped colonies up to 18 m long, made up of hundreds to thousands of individuals, known as zooids.
