Amino acid metabolism in scleractinian corals

Date of Award




Degree Name

Doctor of Philosophy (Ph.D.)

First Committee Member

Alina M. Szmant, Committee Chair


Scleractinian corals have attained their greatest numbers and diversity in shallow, tropical locales characterized by low concentrations of particulate and dissolved nutrients. Corals are also found in temperate and/or near-shore environments richer in nutrients. Zooxanthellate corals depend energetically on translocated photosynthate, but may depend on external sources for essential nutrients. Nonzooxanthellate corals depend entirely on capture of particles and absorption of dissolved material. This study examined the hypothesis that zooxanthellate corals have more pathways for amino acid synthesis and conserve more amino acids than nonzooxanthellate corals.Three species of zooxanthellate corals, Montastrea annularis, Acropora cervicornis, and Porites porites, and two nonzooxanthellate corals, Astrangia poculata and Tubastrea coccinea, were selected for study. The two nonzooxanthellate species are assumed to have diets relatively enriched in amino acids in comparison to those of the zooxanthellate species.Corals were incubated with (U-$\sp $C) D-glucose, amino acids ($\sp3$H or $\sp $C: glu, lys, val), or $\sp $C-sodium bicarbonate and the radiolabel was followed into general biochemical compounds, or individual protein amino acids. Radiolabel retention was also ascertained.All five species of coral synthesized the same amino acids, many of which are essential in other metazoa (val, met, leu, ile, phe, lys, and his). Zooxanthellate corals retained a greater percentage of the absorbed amino-acids (82 $\pm$ 25% vs. 55 $\pm$ 23%) and assimilated more into protein (37 to 76% vs. 19 to 30%) in comparison to nonzooxanthellate corals. No such differences were found among zooxanthellate corals from different nutrient environments. Overall, the results suggest that observed differences in amino acid utilization between corals with and without zooxanthellate may be the result of genetic adaptation rather than environmental acclimation. The abilities of scleractinian corals to synthesize most of the protein amino acids may reduce their dependance on diet for these compounds, and may explain the general lack of differences in amino acid metabolism among corals with different diets and from different habitats.No clear differences in bicarbonate metabolism by the zooxanthellate species were attributable to differences in nutritional regime. However, exposure of Montastrea annularis to high concentrations of ammonium increased its synthesis of amino acids from photosynthate.


Biology, Ecology; Biology, Oceanography; Biology, Animal Physiology

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