Chemoreception as a factor in food location ofElysia cauzeMarcus (Opisthobranchia, Ascoglossa)

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Abstract
When encountering stimulatory substances, the ascoglossan ( = sacoglossan) Elysia cauze Marcus displays a headlifting response, i.e. lifts its head and anterior part of its body and turns it in the direction of the stimulus. This response was used to identify food attractants. Proteins isolated from food algae by precipitation with (NH4)2SO4 had as much stimulatory effect as the filtered algal homogenate. Gel‐separation on Sephadex G‐25 of algal homogenates showed that a small protein or large polypeptide (approximate molecular weight 2000–3500) had almost as much stimulatory effect as the proteins isolated by precipitation. A few low molecular weight substances, i.e. betaine and cysteine, had some stimulatory effect at relatively high concentrations (10‐3‐10‐4 M). Thus, proteins seem to be most important in food location and recognition in E. cauze. Ablation of the rhinophores showed that these structures play a significant role in food location in E. cauze.