Practice question

Excretory organs in Mollusca are metanephridial kidneys commonly called nephridia, historically Keber's organ or organ of Bojanus in bivalves. Typically one or two large sac-like kidneys connect at one end to pericardial coelom via renopericardial duct and at other open into mantle cavity via nephridiopore, filtering hemolymph removing ammonia in aquatic forms. They perform ionic, acid-base and volume regulation, resorbing glucose. Unlike Malpighian tubules of insects, green glands of crustaceans or solitary renette cells of nematodes, molluscan nephridia represent true coelomoduct derivatives linked to vascular system and pericardium for ultrafiltration.