Feeding of the Cymatiid Gastropod,Argobuccinum argus, in Relation to the Structure of the Proboscis and Secretions of the Proboscis Gland

Abstract

Several gastropod families belonging to the superfamily Tonnacea are known to bore into the calcareous shells of echinoids and bivalves, but little work has been done on the family Cymatiidae. New observations show that the cymatiid, Argobuccinum argus , which feeds on the tubicolous polychaete, Gunnarea capensis , possesses large proboscis glands which secrete 0.4 to 0.5N H2SO4; further, the secretion dissolves greater amounts of pure CaCO3 than does O.47N H2SO4, alone. A toxin is also present, which abolishes responses to light and touch in several invertebrates. The proboscis is atypically pleurembolic, having a permanent proboscis sheath. Retraction is due to the muscles ot the proboscis wall, and the contracted proboscis is not inverted. Unlike other mesogastropods, the Tonnacea have three pairs ofglands associated with the foregut: proboscis glands, true salivary glands, and a small, partly paired gland of unknown function immediately posterior to the buccal mass. It is concluded that because of an abundance of readily available food in the form of Gunnarea, A. argus does not drillinto animals protected by a calcareous shell. The presence of a CaCO3 dissolving mechanism indicates that the Cymatiidae ingeneral may be able to employ this method of feeding.