Aplidium californicum

Aplidium californicum is a compound tunicate forming sheets, mounds or slabs on rocks and other hard substrates. The tunic is jelly-like in consistency, 1 to 3 cm thick and a shiny yellow, orange, reddish-brown or a translucent white colour. The individual zooids are brown or buff, 6 mm long and arranged in oval or elongate systems. Each one is subdivided into a thorax, an abdomen and a postabdomen. There are usually 10 to 12 rows of perforations.[2][3]

Aplidium californicum is common on the west coast of North America from British Columbia south to Baja California, Mexico and the Galapagos Islands.[2] It is found in the intertidal zone and at depths down to 85 metres.[3]

Aplidium californicum is a filter feeder. Water is sucked into the interior of the organism through a siphon and then expelled through another one. Phytoplankton and other small organisms get trapped in mucus threads secreted by the endostyle. The tunicate seems to form a symbiotic relationship with the bryozoan Bugula neritina.[4]

Certain antineoplastic agents, bryostatins 4 and 5, have been extracted from Aplidium californicum and are being evaluated.[4]