Respiration of Air by the Primitive Fish Polypterus senegalus

Abstract

THE primitive aetinopterygian fish Polypterus senegalus Cuvier inhabits shallow and swampy waters throughout tropical Africa, often in conditions of severe oxygen deficiency, and its adaptation to this type of habitat includes the possession of spiracles and a double swim bladder or lung which has long been assumed to act as an accessory respiratory organ. Conflicting views have, however, been expressed regarding the use of spiracles in connexion with the respiration of air. Budgett¹ stated that the spiracles are used to take in and expire air from the swim bladders; but Boulenger² concluded that there was little evidence to show that Polypterus comes to the surface to breathe. More recently, it has been shown that the spiracles are used to inhale air which is passed to the lungs³. Air is inspired both in conditions of low oxygen concentration and during periods of excessive activity.