Date of Award

Spring 1997

Project Type

Dissertation

Program or Major

Zoology

Degree Name

Doctor of Philosophy

First Advisor

Larry Harris

Abstract

Prey preference and recognition by individuals of Nucella lapillus from 13 different populations from New England were studied, to determine if individuals of this species kept on a single prey diet develops a preference for this prey, and if prey availability affects prey recognition in this predator. Individuals from all 13 populations showed a preference for Mytilus edulis over Littorina obtusata in laboratory experiments, including those from a population that prey only on L. obtusata in the field. Individuals from another population were not able to recognize L. obtusata as a prey. N. lapillus kept in a diet of M. edulis in the laboratory had its preference for this prey reinforced, but those kept in a diet of L. obtusata, did not develop a preference for this prey.

Adults and juveniles of Nucella lapillus showed higher feeding rates on both M. edulis and L. obtusata, in treatments with higher prey density than in those with lower prey density. Nucella lapillus showed a higher growth rate feeding on Mytilus edulis than on Littorina obtusata during a 8 months laboratory experiment. The results indicate that M. edulis presented a greater "food value" for N. lapillus than L. obtusata.

Carcinus maenas appeared for the first time in obvious numbers in Pembroke, Maine in the summer of 1995. C. maenas is a predator of N. lapillus, and experiments were conducted to determine if Nucella lapillus from Pembroke, showed different predation rates on Littorina obtusata in the presence and absence of the green crab Carcinus maenas. Parallel experiments were also done using N. lapillus from Little Harbor, NH population, where the crab has been well established for at least 25 years. In another experiment, the preference of C. maenas between N. lapillus, high spire L. obtusata and low spire L. obtusata was investigated.

The predation on L. obtusata was significantly higher in the treatments with N. lapillus from Pembroke than in those with N. lapillus from Little Harbor, in both times the experiment was performed. Small C. maenas were just able to prey on L. obtusata with high spires. Large crabs were able to prey on all three food items, and high spire L. obtusata were successfully attacked most often.

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