| Autor: |
Valerie J. Paul, Chad R. Wylie |
| Rok vydání: |
1989 |
| Předmět: |
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| Zdroj: |
Journal of Experimental Marine Biology and Ecology. 129:141-160 |
| ISSN: |
0022-0981 |
| DOI: |
10.1016/0022-0981(89)90053-1 |
| Popis: |
Sinularia extracts and secondary metabolites were very effective at deterring natural populations of carnivorous fishes in field assays on Guam. These soft corals appear to be avoided by most fish predators; however, the butterflyfish Chaetodon unimaculatus Bloch fed almost exclusively on the soft corals Sinularia sp., Sinularia polydactyla (Ehrenberg) and Sinularia maxima Verseveldt on a Cocos Lagoon patch reef on Guam. C. unimaculatus generally fed from the tips of the soft corals where secondary metabolite concentrations are highest, likely because these are the most accessible portions of the colonies. Sinularia sp. was the most preferred while S. maxima was the least preferred soft coral by this predator. Secondary metabolites functioning as feeding deterrents were hypothesized as a major determinant of C. unimaculatus feeding preferences. Both types and concentrations of terpenoid secondary metabolites varied among the three species of Sinularia. Organic extracts were not deterrent toward C. unimaculatus at whole colony concentrations (3–7% dry wt); however, all extracts were feeding deterrents at concentrations of 20% dry wt and the S. polydactyla extract was deterrent at 10% dry wt. Extract concentration in the tips of Sinularia sp. (12% dry wt) was lower than the concentration which causes feeding deterrence while the extract concentration in S. maxima tips (28% dry wt) was higher. Chemical feeding deterrents may help to explain preferences for these two soft corals but not for S. polydactyla which is of intermediate preference. Comparisons between extracts of any two species showed no significant differences in deterrence when tested at the same concentrations. No significant differences in deterrence were found between extracts from grazed and ungrazed colonies. Nonpolar terpene hydrocarbon fractions of the extracts were also not deterrent at whole colony or tip concentrations. A major cembranoid diterpene isolated from S. maxima was deterrent only at the high concentration found in the soft coral tips (12% dry wt). Sclerites as structural defenses appear to be of little importance in determining the soft coral preferences of C. unimaculatus. Sclerites were found in highest amounts in the most preferred species Sinularia sp. and were small, powdery and least abundant in S. maxima. Thus, C. unimaculatus has an unusual tolerance for the secondary metabolites of Sinularia, enabling this fish to exploit a food source unavailable to most other marine organisms. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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