Observations on the Compound Eyes of the Deep-Sea Ostracod Macrocypridina Castanea

Macrocypridina lives at depths of 800 m, where residual daylight is very weak. It has a pair of mobile apposition compound eyes with large lenses, wide rhabdoms and high acceptance angles, all of which contribute to a calculated sensitivity comparable with the superposition eyes of deep-water decapod crustaceans. The axes of the 27 ommatidia in each eye are not uniformly distributed in space, with a modest acute zone in the anteroventral region. Here the interommatidial angles are about 6°, compared with 20° at the rear of the eye. The eyes make two kinds of spontaneous movements: large slow rotations of up to 50° around a transverse axis, and a superimposed 2 Hz tremor with an amplitude of 5 °.