MEPS 502:157-167 (2014)  -  DOI: https://doi.org/10.3354/meps10703

ABSTRACT: In a series of laboratory Y-maze experiments, we investigated the directional response of juveniles of the muricid snail Concholepas concholepas, a rocky-shore keystone predator characteristic of the southeastern Pacific coast, in displaying prey detection and predator escape behaviour after 5 mo rearing under contrasting levels of pCO₂: 390 (present-day), 700 and 1000 µatm CO₂ (as expected in near-future scenarios of ocean acidification [OA]). Regardless of the experimental condition, juveniles significantly chose the Y-maze arm containing prey. In general terms, the directions of the displacement paths of the snails in the Y-maze were straight from the starting point to the final position, where the prey items were offered. Moreover, juveniles reared at present-day concentrations and 700 µatm CO₂ significantly avoided displacement in the Y-maze arm receiving predator odours. This predator-avoidance behaviour was disrupted in juveniles reared at 1000 µatm CO₂. In most cases, displacements recorded under such conditions were sinuous, and the trial individuals did not significantly choose the predator-free arm. In contrast, displacement paths recorded for snails reared at present-day concentrations and at 700 µatm CO₂ were straight from the initial to the final position, with displacements mostly ending near the prey and in the arm free of cues associated with predation. The loss of responses to a natural predator under high pCO₂ levels in the early ontogeny of C. concholepas may result in ecologically deleterious decisions by this keystone species. We conclude that the negative effects of OA on the chemosensory behaviour of keystone species could have negative consequences for community dynamics.

KEY WORDS: Y-maze · Chemoreception · Decision-making · Early ontogeny · Mucous trail · pH · Concholepas concholepas