Microscale intertidal habitats modulate shell break resistance of the prey; Implications for prey selection

Intertidal microhabitats provide special conditions to the organisms that inhabit them and to some of their morpho-protective characteristics. Tidal pools, under the influence of acidified freshwater, may affect the characteristics of the protective shells of prey and have repercussions on predation. The shells of Perumytilus purpuratus from such tidepools are more fragile than those of their counterparts from the vertical intertidal walls of the same area. Those from the tidepools also have tissue content values intermediate between those from the lower and higher limits of the intertidal wall, possibly due to different feeding regimens of the bivalves. Also, the shells of tidepool individuals have a shell thickness that is intermediate between those from the lower and higher limits of their distribution. In a common garden, the predatory muricid Acanthina monodon prefers to attack individuals from the tide pool. This selection is not based on a higher energetic input from the prey, nor on the thickness of the prey's shell, but on the lower hardness of the shell that implies an easier and less-energetically expensive attack and possibly of shorter duration.