The behavioural and sensory ecology of Agaronia propatula (Caenogastropoda: Olividae), a swash-surfing predator on sandy beaches of the Panamic faunal province

The genus Agaronia includes dominant predators in the eulittoral zone of dissipative sandy beaches of the tropical Eastern Pacific, which show specific adaptations to this environment such as swashsurfing locomotion. We studied A. propatula in its natural habitat in El Salvador and Costa Rica, and performed field experiments to obtain insights into its ecology, behaviour and sensory physiology. Agaronia propatula is not attracted by carrion and preys mostly on the ubiquitous beach snail Olivella semistriata. This, however, reflects community composition rather than prey specialization; A. propatula is an investigative hunter and will, quite literally, attack everything that moves (with the notable exception of echinoids). Prey is identified at short range by tactile and, to a lesser degree, by chemosensation located in the propodium. We found no evidence for long-distance sensory capabilities; A. propatula rather seems to rely on the regular physical structure of its wave-dominated environment when it moves between its shallow subtidal resting zone and its upper intertidal hunting grounds where potential prey predictably congregates. On the other hand, behavioural patterns such as the rapid yet haphazard cruising of foraging individuals, or the complex prey capture sequence in which the prey is transferred to a metapodial pouch, are similar in A. propatula and Oliva. Thus, our results lead us to speculate that the development of behavioural features that proved adaptive in the intertidal environment was essential in the evolution of Agaronia from Oliva-like ancestors.