AB 23:129-137 (2015)  -  DOI: https://doi.org/10.3354/ab00614

Chemical versus structural defense against fish predation in two dominant soft coral species (Xeniidae) in the Red Sea

Ben Xuan Hoang1,2,*, Yvonne Sawall1, Abdulmohsin Al-Sofyani3, Martin Wahl1

1Helmholtz Centre for Ocean Research, GEOMAR, Wischhofstrasse 1-3, 24148 Kiel, Germany
2Institute of Oceanography, Vietnam Academy of Science and Technology, 01 Cada, Nha Trang, Vietnam
3Faculty of Marine Science, King Abdulaziz University, PO Box 80207, Jeddah 21589, Saudi Arabia
*Corresponding author:

ABSTRACT: Soft corals of the family Xeniidae are particularly abundant in Red Sea coral reefs. Their success may be partly due to a strong defense mechanism against fish predation. To test this, we conducted field and aquarium experiments in which we assessed the anti-feeding effect of secondary metabolites of 2 common xeniid species, Ovabunda crenata and Heteroxenia ghardaqensis. In the field experiment, the metabolites of both investigated species reduced feeding on experimental food pellets in the natural population of Red Sea reef fishes by 86 and 92% for O. crenata and H. ghardaqensis, respectively. In the aquarium experiment, natural concentration of soft coral crude extract reduced feeding on experimental food pellets in the moon wrasse Thalassoma lunare (a common reef fish) by 83 and 85% for O. crenata and H. ghardaqensis, respectively. Moon wrasse feeding was even reduced at extract concentrations as low as 12.5% of the natural crude extract concentration in living soft coral tissues. To assess the potential of a structural anti-feeding defense, sclerites of O. crenata (H. ghardaqensis lacks sclerites) were extracted and mixed into food pellets at natural, doubled and reduced concentration without and in combination with crude extract at 25% of natural concentration, and tested in an aquarium experiment. The sclerites did not show any effect on the feeding behavior of the moon wrasse, indicating that sclerites provide structural support rather than anti-feeding defense. We conclude that the conspicuous abundance of xeniid soft coral species in the Red Sea is likely a consequence of a strong chemical defense, rather than physical defenses, against potential predators.


KEY WORDS: Chemical defense · Feeding deterrence · Sclerites · Soft coral · Xeniidae · Ovabunda · Heteroxenia · Red Sea


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Cite this article as: Hoang BX, Sawall Y, Al-Sofyani A, Wahl M (2015) Chemical versus structural defense against fish predation in two dominant soft coral species (Xeniidae) in the Red Sea. Aquat Biol 23:129-137. https://doi.org/10.3354/ab00614

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