1. Blinded goldfish behave in a centrifuge as if they were orienting to absolute rotation by means of a Foucault pendulum. That is, they swim so as to compensate the rate of imposed rotation about the apparent vertical.
2. Blinded goldfish swim in the centrifuge in a plane essentially orthogonal to the apparent vertical at low accelerations and low rates of rotation. With higher rates of rotation the axis about which the fish swims leans away from the apparent vertical and towards the axis of rotation of the centrifuge.
3. Analysis of the physics of the centrifuge shows that if the fish rotates about any axis relative to the cab of the moving centrifuge with a rate of rotation within the physiological range of its semicircular canals it will receive signals from its otocysts and its semicircular canals which would reflect contradictory information in a nonrotating environment. This fact, together with the fish's response to absolute rotation, affords a method for quantitatively assessing the relative roles of the otocysts and the semicircular canals in orienting the free-swimming fish.
Max Planck Institut für Verhaltensphysiologie, Abteilung H. Mittlestaedt, Seewiesen, Germany.
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