ANOXIC DEPRESSION OF SPONTANEOUS LOCOMOTOR-ACTIVITY IN CRUCIAN CARP QUANTIFIED BY A COMPUTERIZED IMAGING TECHNIQUE

The crucian carp (Carassius carassius L.) is one of the most anoxia-to lerant fishes. An important strategy used by the crucian carp to survi ve anoxia is to lower its rate of energy consumption. Anoxia-tolerant fish are known to utilize simultaneously two different strategies for reducing energy consumption during anoxia, the first being a reduction in locomotor activity and the second being a depression of cellular e nergy demands. Nevertheless, the reduction in locomotor activity durin g anoxia has never been measured quantitatively. This lack of informat ion is apparently because technical problems have prevented the measur ement of spontaneous locomotor activity in fish. It is now possible to use computerized video-imaging techniques to record the movement of a n animal continuously. By the use of such a technique, we show that cr ucian carp respond to anoxia (330 min at 9-degrees-C) by rapidly decre asing their locomotor activity (spontaneous swimming distance) to abou t 50% of that displayed during normoxia. Frequency diagrams of spontan eous swimming speed showed no bimodality and indicated a general decre ase in swimming speed from a median value of 1.82 m min-1 during normo xia to 0.82m min-1 during anoxia. It is tentatively estimated that the anoxic depression of locomotor activity corresponds to a 35-40% reduc tion in total energy consumption. The role of locomotor activity in fi sh energy budgets is discussed.