Diazona violacea is a species of tunicate, an ascidian in the family Diazonidae. This genus is found in the renal sac of molgulid ascidian tunicates. Halocynthia is a genus of ascidian tunicates in the family Pyuridae. This species is a common shallow-water ascidian in Great Britain and Ireland. This colonial ascidian is translucent grey with transparent zooids. Bistramide A is a chemical compound originally found in the marine ascidian "Lissoclinum bistratum". Herdmania is a genus of ascidian tunicates in the family Pyuridae. Polycarpa is a genus of ascidian tunicates in the family Styelidae. Namiella is a genus of ascidian tunicates in the family Molgulidae. Boltenia is a genus of ascidian tunicates in the family Pyuridae. Botryllus schlosseri is a colonial ascidian tunicate. Lissoclinum patella is a species of ascidian in the family Didemnidae. Styela clava is a solitary, subtidal ascidian tunicate. Present information suggest that this nudibranch feeds exclusively on the stalked ascidian "Sigillina cyanea". In some species (for example, herring or the ascidian Ciona) activation of motility precedes chemotaxis.