Gill ventilation in the sturgeon, Acipenser transmontanus: Unusual adaptations for bottom dwelling

Abstract

Measurement of branchial cavity water pressure and flow patterns, arterial blood P O 2 and pH, and oxygen utilization and uptake have been made in undisturbed, free swimming sturgeon, Acipenser transmontanus. Although the jaws are degenerate and the oral apparatus is highly modified for feeding, gill ventilation in nonetheless powered by a buccal force pump and an opercular suction pump common to most bony fishes. The reduced spiracles play little or no role in gill ventilation. In sturgeon in which water intake through the ventrally located mouth was experimentaly eliminated, a condition which may often develop when these fish forage in mud and sand on river substrates, effective ventilation of the gills was maintained with water drawn into the branchial cavities in a retrograde fashion solely through permanent openings in the regions of the opecular slits. O 2 uptake and transport also remained at control levels. It is suggested that this unusual alternative mode of gill ventilation in the sturgeon represents and important respiratory adaptation to bottom dwelling and feeding.