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The chemical composition of the skeletons of two black coral species, Antipathes fiordensis from New Zealand and A. salix from the Caribbean, was examined to compare elemental and protein composition, and the chitin content both between species and between colonial tip and base. Of all elements surveyed, iodine and bromine were dominant in the skeleton. In A. fiordensis these halogens constituted 2–3% of the skeletal weight, with different proportions occurring in tip and base. In contrast, the halogen content of A. salix constituted about 5% of the skeletal weight and consisted primarily of iodine in both tip and base. The chitin content of A. salix skeleton was about twice that of A. fiordensis based on 13 C NMR analysis, but the glucosamine content was more significantly different between tip to base of A. fiordensis than between species, and suggests that the chitin content of both is about 10–15% of the skeletal weight. The protein content of the two species was similar, constituting about 50% of the skeletal weight and varying by as much as 10% between the branch tip and base. Tip-to-base protein differences varied inversely with the chitin content. The skeletal proteins were rich in histidine, which constituted ca 11–14% of the amino acids. Both species also contained a tyrosine-rich fraction associated with chitin. The most distinctive difference between the skeletal proteins of the two species was the disparity in the levels and types of diphenol as shown by 13 C NMR and chemical analyses. In A. fiordensis , the skeleton contained about four and 12 times as much hydrolyzable DOPA in tip and base, respectively, compared to A. salix . Small amounts of 3,4-dihydroxybenzaldehyde were also present in A. fiordensis skeleton, but none was found in A. salix . |
