Meeting Abstract

P1.15  Jan. 4  Multimodal Cues for Defense in Aposematic Nudibranchs (Opisthobranchia: Phyllidiidae) RITSON-WILLIAMS, R.*; PAUL, V.J.; Smithsonian Marine Station at Fort Pierce; Smithsonian Marine Station at Fort Pierce williams@sms.si.edu

The use of bright coloration to warn predators of toxic prey, termed aposematism, is a defensive strategy well studied in terrestrial ecosystems. Some marine animals have contrasting color patterns and chemical defenses but few studies have tested the behavior of marine predators in response to aposematic coloration. In this study we tested the deterrent role of phyllidiid nudibranch color patterns and chemical extracts independently and together against natural assemblages of fishes at two reefs on Guam. Using agar-based food to keep food quality consistent, chemical extracts and two out of five phyllidiid color patterns reduced fish feeding at both reefs. Feeding assays with crude extracts from the nudibranchs Phyllidia varicosa, Phyllidia elegans and Phyllidiella pustulosa showed that they were chemically defended except for Phyllidiella pustulosa from Guam. To determine if a chemical extract can act as an olfactory defense we videotaped fish behavior as they approached food containing nonpolar extracts of Acanthella cavernosa, the dietary sponge of Phyllidiella granulatus. Fish approached and then tasted the food with the chemical extract significantly less than the control and the crude extract of another sponge Stylissa massa. In feeding assays with a phyllidiid color pattern combined with the chemical extract at natural concentrations, fish were deterred by the extract regardless of the color pattern. At half natural concentration only the chemical extract and the phyllidiid color pattern together significantly decreased fish feeding. Phyllidiid spp. use a multimodal defense strategy including visual, taste and olfactory cues to deter fish predators.