生息場所のことなるフナの低酸素に対する呼吸反応

抄録

Adult fish of Gengorobuna (Carassius auratus cuvieri) inhabit the upper or middle layer of offshore waters where they are seldom confronted with hypoxic conditions in the natural environment. On the other hand, Hiwara (C. auratus gibelio) occupy lagoon and bays bottoms, where they are often confronted with hypoxic conditions. Oxygen consumption and opercular rate were measured in the laboratory in crucian carp found living in different habitat, under various oxygen concentrations.
A marked differences in critical concentration of oxygen consumption (P_C) was not detected between Gengorobuna and Hiwara. In Gengorobuna, a decrease in dissolved oxygen concentration first evoked an increase in opercular movement at a dissolved oxygen concentration of 3ml/l, and maximum opercular movement (1.5 fold increase) appeared at 0.75ml/l. The first disruption in the periodicity of the opercular rhythm occurred at 0.5ml/l. In Hiwara the initial rapid increase in opercular movement occurred at a lower oxygen concentration than that of Gengorobuna (2ml/l), and disruption in the opercular rhythm was not detected within the range of oxygen concentrations employed in our experiments.
These results show that opercular movements of Gengorobuna must be more sensitive to lower oxygen tension. Thus, it is considered that Hiwara are more adaptive to hypoxic conditions than Gengorobuna.