This family consists of clavanin proteins from the haemocytes of the invertebrate Styela clava (Sea squirt), a solitary tunicate. The family is made up of four alpha-helical antimicrobial peptides, clavanins A, B, C and D. The tunicate peptides resemble magainins in size, primary sequence and antibacterial activity. Synthetic clavanin A displays comparable antimicrobial activity to magainins and cecropins. The presence of alpha-helical antimicrobial peptides in the haemocytes of a urochordate suggests that such peptides are primeval effectors of innate immunity in the vertebrate lineage [PMID: 9001389].