Marine Science

Marine Science

Senior Theses 2008

Grant Olson (2008)  Adaptations of juvenile mangrove littorinid snails to predation by the puffer Sphoeroides rosenblatti

Faculty Advisor: Bill Szelistowski

The adults of two species of mangrove littorinid snails, Littoraria varia and L. variegata, use vertical migration and growth as a size refuge to avoid intense predation by the puffer Sphoeroides rosenblatti in the Gulf of Nicoya, Costa Rica. Juveniles of both species, however, are unable to stay above the jumping range of puffers for long periods, which can reach up to 13 cm above the water surface, and are too small to attain the size refuge observed in adults. It was hypothesized that juveniles of both species have mechanisms that reduce predation during this period of high vulnerability. Data from field surveys and predation experiments revealed that juveniles exhibit several anti-predator adaptations: 1) Increasing vertical distribution above the water surface within the jumping range of puffers, 2) Concealment in submerged root junctures, 3) Fast growth rates minimizing the time spent in the vulnerable size range, and 4) Vertical migration behaviors that minimized the time spent in the jumping range of puffers. The capacity to retain water differed between species and may account for differences in whether they vertically migrated or utilized protected microhabitats to avoid predation. These results suggest that S. rosenblatti plays an important role in the ecology and life histories of juvenile L. varia and L. variegata.

Student Research