FACTORS AFFECTING OXYGEN CONSUMPTION IN THE MARINE PULMONATE AMPHIBOLA CRENATA (GMELIN, 1791)

¹ Portobello Marine Laboratory, University of Otago, Dunedin, New Zealand

The rate of oxygen consumption by Amphibola crenata is unaffected by the salinity of the external medium in the range 0-125% sea water. There is no significant difference between the rates of oxygen consumption in air and water, oxygen consumption varying with the 0.45 power of body weight. During exposure to anaerobic conditions the snails showed an increase in the post-anaerobic:pre-anaerobic respiratory rate, this ratio reaching a maximum after 6 h anoxia over the range 0-125% sea water. Specimens of Amphibola crenata exposed to declining oxygen tensions at full salinity show almost no ability to regulate their rate of oxygen consumption. The ratio K₁/K₂, (see text) plotted against the weight specific oxygen consumption yields the following equation: K₁/K₂ = 527.7 QO₂^1.610. As salinity decreases, the ratio K₁/K₂ also decreases, indicating an increase of oxygen independence with decreasing salinities. As salinity decreases, the zone of critical pressure decreases, i.e. the snails become more oxygen independent; the maximum decrease in the zone of critical pressure coming in animals exposed to 0 and 25% sea water. When exposed to both salinity and anoxic stress, the animals reach their maximum degree of oxygen independence.