Two Visual Systems in One Brain

Abstract

Although so far we know very little about visually controlled behavior of Cupiennius (see Chapter XXIII), the capabilities of the eyes (see Chapter XI) provide the foundation for a well-developed sense of vision and we might well expect the animals to exploit this potential. Our expectation is strengthened when we look at the size and structure of the centers in the brain that receive input from the eyes and process this visual information. The situation is quite different from that in insects: in spiders the actual brain is almost completely devoted to vision, receiving only the optic nerves and containing only the optic ganglia and some association centers. A few years ago we examined the anatomy of these ganglia and discovered a number of interesting things (Babu and Barth 1984, 1989; Weltzien and Barth 1991; Strausfeld and Barth 1993; Strausfeld et al. 1993).