Migration is common for animals living in the intertidal zone, between the ocean and dry land. We studied two intertidal snails (Cerithidea californica and Cerithidea montagnei) of the same genus to determine how these two snails, which share habitat and have similar life histories, are affected by their different migration behaviors.

While C. californica and C. montagnei both live on the sediment beneath mangrove trees on the Pacific coast of Panama, their use of that habitat differs markedly. C. montagnei is partially arboreal and climbs extensively up mangrove roots, trunks, and branches. They secure themselves to mangroves using a mucous thread, which allows them to enter a hibernation-like state and remain in the trees for days at a time. These snails do leave the trees to eat on the ground but are much less abundant there than C. californica. While C. californica is capable of vertical climbing, it is very rarely found only on mangrove pneumatophores (pencil roots usually not more than about 20 cm high).

Our research indicates that these Cerithidea snails are prey for just one main predator— the whelk Thais kiosquiformis. We evaluated how differences in climbing behavior influence predation, a key community interaction, in Panama’s mangrove forests. Specifically, we hypothesized that climbing by C. montagnei reduces contact with T. kiosquiformis. Thus, we expected that C. montagnei would be preyed upon less than C. californica as a direct result of its pronounced vertical use of mangrove structure.

We used field experiments to investigate this hypothesis in 2014 in Panama’s mangrove forests. We found that T. kiosquiformis eats significantly more C. montagnei than C. californica when the two snails were prevented from climbing (using monofilament tethers). When these two prey snails were put into cages with T. kiosquiformis, more C. californica were eaten when structure was present, but we need larger sample sizes to elaborate on the details of this interaction.

C. californica were rarely seen climbing mangrove structures (and then they were only seen very close to the ground) in field observations and in our experiments. In contrast, C. montagnei were consistently seen climbing mangrove structures and cages, often more than 2 m above the ground. While climbing behavior may have once been optional for C. montagnei, an additional experiment we performed suggests that they currently cannot physiologically tolerate the tidal inundation frequency and duration that C. californica can. This means that too much submersion is lethal for them and they at some point must climb above the water during high tides. While T. kiosquiformis is capable of climbing short distances, they were only observed attacking prey Cerithidea when the tide was high and they were underneath the water. So C. montagnei’s forced climbing also takes them out of reach of predatory T. kiosquiformis.

In addition to addressing our key research objective, we also collected preliminary data to determine how climbing behavior influences contact with other water-borne enemies, like trematode parasites.

Data from this project are publically available at the Biological and Chemical Oceanography Data Management Office (BCO-DMO):  http://www.bco-dmo.org/project/643602 This project is the beginning of a collaboration between U.S. and Panamanian scientists anticipated to result in further grant proposals and experiments. We sponsored 1 po...

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