Large sea squirt (Lat. Phallusia mammillata). It is found on rocky, sandy or muddy substrates in depths of about 200 m (656 ft). It is a solitary species of ascidian and can grow to a height of about 20 cm (8 in). The tunic is a translucent, bluish-white colour and is covered with irregular rounded lobes or mounds. It has a tough, leathery “tunic” that is milk-white in appearance. It feeds on the planktonic particles that it filters from the incoming seawater by passing it through a mucous net. Adult sea squirts have an unusual circulation system in which blood is pumped in one direction for several seconds and then in the opposite direction for the same length of time.