ONE OF THE WONDERS OF TROPICAL REEFS IS THE DAZZLING ARRAY OF COLORS EXHIBITED BY THE CORALS that constitute the foundation of reefs. Coralheads sitting side by side on a reef can display different colors and different shades and intensities of the same colors.
New research has indicated that, rather than random phenomena for dramatic effect, corals’ variations in color involve genetic factors that help protect the symbiotic algae – zooxanthellae – embedded in coral polyp tissues.
ACROPORA MILLEPORA, A BRANCHING CORAL The team of researchers from universities in the United Kingdom, Germany and Australia studied three colonies of Acropora millepora, a branching coral found throughout the Pacific basin. The study by was published in the journal Molecular Ecology in January.
The scientists found that the corals contained not just one gene to control pigmentation but multiple copies of that gene. While algae requires access to sunlight to produce nutrients that benefit the corals, too much light can damage, and possibly kill, the algae. With multiple copies of the gene available, corals exposed to too much sun can activate more copies of the gene to intensify the pigmentation – and protect the algae (New research has indicated a different approach to fostering coral growth in deep-water corals that receive little solar energy; see “In Deep Waters, Corals Glow to Grow“).
GENETIC OPTIONS “The cluster of light regulated pigment genes,” the authors write, can enable the corals to invest either in expensive high-level pigmentation, offering benefits under light stress, or to rely on low tissue pigment concentrations and used the conserved resources for other purposes, which is preferable in less light-exposed environments.”
They also noted that the study, revealing the genomic process that enables individual corals to adjust to changing light levels, provides “a roadmap to further our understanding of stress resistance in corals, an important prerequisite to predict the capacity of coral reefs to survive under the pressure of a changing environment.”
PRINCIPAL SOURCE: Fluorescent protein-mediated colour polymorphism in reef corals: multicopy genes extend the adaptation/acclimatization potential to variable light environments, John R. Gittins, Cecilia D’Angelo, Franz Oswald, Richard J. Edwards, Jörg Wiedenmann, Molecular Ecology, Volume 24, Issue 2, pages 453–465, January 2015