Chemical and structural defenses of Caribbean gorgonians (Pseudopterogorgia spp.): Intercolony localization of defense

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Abstract
We have adopted an integrated approach to assessing the function of gorgonian defenses by analyzing within‐colony patterns in the distribution of both structural elements and chemical compounds in two morphologically similar species of Pseudopterogorgia. In both species, crude extract concentrations are higher in polyp‐bearing regions of colonies than in more proximal, nonpolyp‐bearing regions of colonies. The concentration of the ichthyodeterrent terpene from Pseudopterogorgia acerosa (pseudopterolide) is also higher in polyps than in axial tissue. In Pseudopterogorgia rigida, an ichthyodeterrent terpene (curcuhydroquinone) occurs almost exclusively in the polyps and is undetectable in most samples from the axial coenenchyme. The distribution of the calcium carbonate structural elements (sclerites) within colonies is negatively correlated with the concentration of extract. Sclerites comprise the largest percent composition in the axial tissue and a very small proportion of branch tissue. Geographic variation in the negative within‐colony correlation between chemical and structural components indicates the range of variation possible in these defensive traits.