Abstract

Humans and other primates exhibit a consensual pupillary light reflex, i.e., when a light is presented to one eye, the pupils of both eyes constrict equally. Rodents and birds, however, do not have a consensual pupillary light reflex, i.e., the pupil of one eye is not affected by light presented to the other eye. We have simultaneously imaged the pupils of both eyes of two dolphins (Tursiops truncatus) with two independent infrared-sensitive videotape systems. When a light is presented to one eye, the pupil of the stimulated eye constricts more than the pupil of the contralateral eye. This partially-consensual pupillary light reflex has never been reported in other animals. We correlate this reflex with the unusual anatomy of the dolphin midbrain (Jacobs, M.S., Morgane, P.J., and McFarland, W.L., Degeneration of visual pathways in the bottlenose dolphin. Brain Research, 1975, 88: 346-352). This research was supported by NSF grant no. BNS 75-20147-A0l and NIH training grants 1 T32 EY 07012 and 1 F32 EY 05180.

Notes

The optic nerve fibers of the bottlenose dolphin cross completely at the optic chiasm, indicating that it should not have a consensual eye reflex. However, tests showed a partially-consensual pupillary light reflex.

The route of the optic pathways in the dolphin brain remains highly speculative.