Mucous Envelope Formation in Two Species of Hawaiian Parrotfishes (Genus Scarus)

Abstract

Some parrotfishes have developed a unique capacity to form a mucous envelope at night. Scarus dubius and S. perspicillatus are two Hawaiian species that exhibit envelope-building behavior. Laboratory experiments indicate that envelope formation is promoted by darkness, and is inhibited by constant light. The completed envelope is a transparent, mucous cocoon surrounding the fish. A mass of glandular tissue was found in the buccal cavity of S. dubius and S. perspicillatuS. It is suggested that this tissue is the envelope-producing gland.