SalpsThaliacea

Thaliaceans are pelagic tunicates that live with entirely free-floating life cycles. Most species exhibit largely transparent, gelatinous bodies, making them difficult to spot in the water column. Salps and doliolids typically present as barrel-shaped individuals, ranging from 1-10 cm (0.4-4 in) in length. Pyrosomes form hollow, cylindrical colonies, composed of numerous tiny zooids, which can extend to several meters (over 10 ft) long. They propel themselves through the water by rhythmic muscular contractions that pump water through their siphons.

These animals are obligate filter feeders, capturing phytoplankton and other microscopic plankton within a fine mucus net. Divers commonly encounter them in the upper 50 meters (165 ft) of open water, either as solitary individuals or in vast, sometimes iridescent, chains and swarms. Thaliaceans exhibit complex life cycles, alternating between solitary asexual individuals and colonial sexual generations. This rapid reproductive capability can lead to explosive population blooms in nutrient-rich waters.