Localization and electrical activity of the distance chemoreceptors that mediate predator avoidance behaviour in Acmaea limatula and Acmaea scutum (gastropoda, prosobranchia).

1. The marine gastropods Acmaea (Collisella) limatula and Acmaea (Notoacmea) scutum respond to distant predatory starfish (i.e. to starfish scent) by moving up a vertical surface. 2. The distance chemoreceptors that mediate this avoidance behaviour are located on the mantle margin. Heat cauterization of the limpets' mantle margin eliminates their responsiveness to Pisaster ochraceus scent, while a similar cauterization of the ctenidium and the osphradia does not diminish the avoidance behaviour. 3. Primary afferent electrical activity can be recorded from the chemoreceptors on the mantle margin that are responsive to starfish scent and also from other physiologically distinct receptors that are responsive to contact with starfish tube feet.