Inertial Guidance System in the Orientation of the Goldfish (Carassius auratus)

Abstract

WHILE investigating orientation mechanisms in fish we are making a detailed analysis of “spontaneous” locomotor behaviour of naive animals in controlled conditions. Movements are monitored in a tank measuring 5.0 × 5.0 × 0.5 m in the bottom of which is embedded a matrix of 1,936 photoconductive cells on 10 cm centres. The linear resolution for the smallest target (3 mm diameter) which ocan elicit an adequate response by a photocell is 10 cm. The angular resolution for a fish 30 cm long, the size used in the experiments reported here, is not less than 4°. Provisions in the circuitry and the computer programs discard the effects of consecutive targets on a same photocell so that minor movements of parts of the body (tail, fins), which do not result in locomotion, are not computed. The cells are uniformly illuminated at a colour temperature of 2,300–2,400 K by a collimated light field from a suspended ceiling above the tank (Fig. 1). The electrical effect in a photocell of the interception of light by the fish forms the input of an electronic logic interface. The address of the photocell in the x, y matrix and the time of the event is then established by a computer on line. The latter is programmed to process information on various parameters of the locomotion of individual fish and to put out this information on a teletypewriter, as a visual display on a cathode ray tube and plotter and/or magnetic tape for additional processing.