The Optokinetic Responses of the Mysid Shrimp Praunus Flexuosus

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Abstract
The optokinetic responses of the mysid shrimp Praunus flexuosus in the horizontal and vertical-transverse planes have been studied. The horizontal optokinetic nystagmus is fragmented, and eyestalk following speed is a function of stimulus speed. The vertical optokinetic response is not a nystagmus, but involves maintained eyestalk deviations. These deviations, and eyestalk following speed are both functions of stimulus speed. The velocity gain (eye speed/slip speed) of the responses in both dimensions has a constant value between drum speed 2°/sec and 40°/sec, which suggests that they subserve a simple rheotactic function. The vertical optokinetic response is modulated by statocyst input, and possible mechanisms underlying this effect are discussed.