Visual Accommodation System in the Eyes of a Berycid Deep-Sea Fish Beryx splendens

Abstract

Efferent arrangements of the accommodation system are examined in the eyes of a berycid deep-sea fish, Beryx splendens. A large rectangular lens muscle and its associated ligaments and nerves are described for the first time. The relative size of the lens muscle to the lens muscle to the lens is almost three times that of the mackerel. B. splendens may have almost the same wide accommodative range as the shallow-water sea bass. The lens muscle nerve contains about 300 large myelinated fibres. Mean fiber diameter is about 10 μm. The present study shows that the visual axis of B. splendens is directed up and forward. The ecological significance of the well-developed accommodation system in this berycid fish is discussed in connection with its feeding behavior in a deep-sea environment.