Visual interneurons of the crab Chasmagnathus studied by intracellular recordings in vivo

Abstract.

Comparative physiology of visual systems has become an important field of investigation. However, despite the fact that Crustacea represents a major phylogenetic group, research on the physiology of vision of these animals is scant and almost limited to the crayfish. We developed a preparation to study in vivo the visual nervous system of a semiterrestrial crab through intracellular recordings. The response to a pulse of light was investigated in 206 interneurons from 38 animals. Seventy-eight of these neurons could be classified by functional criteria as sustaining cells, dimming cells, nonspiking hyperpolarizing cells and nonspiking depolarizing cells. Quantitative description is provided for the first two groups and qualitative description is given for the last two. The remaining neurons presented a broad range of different types of phasic responses to light. Although semiterrestrial crabs are behaviorally more reactive to visual stimuli than the crayfish, the general physiological properties of identified lamina and medullary neurons of Chasmagnathus resemble those of the crayfish. The results described here represent the first attempt to study the visual system of crabs with intracellular recordings and constitute the beginning of a project aimed to investigate the neuronal functions underlying behavioral responses elicited by visual stimuli.