Vision has a role in Limulus mating behaviour

Abstract

In 1928 Hartline noted that the lateral eye of the horseshoe crab, Limulus polyphemus, was an admirable preparation for research in visual physiology. Since that time, extensive studies of Limulus have yielded fundamental understandings of visual processes and of sensory processes in general^1,2. However, except for demonstrations of primitive phototaxis^3–5, studies have not yet revealed a possible role of vision in the animal's behaviour. We have further investigated the problem by studying mating behaviour, the only known behaviour exhibited by Limulus in its natural habitat. We report here that horseshoe crabs discriminate form and contrast during mating: males are attracted to painted cement castings of the female carapace and other forms, the degree of attraction depending on the form and contrast of the castings, and on the time of day. The discrimination of form may result from information transmitted by several sensory systems but the discrimination of contrast requires vision.