COREXPLORE

The first, core technical objective of the project was the implementation of new experimental equipment in a marine invertebrate facility, ANTIAGE. Overcoming the technical challenges of controlling temperature conditions in various large-volume marine aquariums that share the same water circuit was a primary goal of the project.
The second, scientific objective was to perform controlled heat-stress experiments on corals to assess their effects on telomere length (TL). Telomeres are the extremities of linear chromosomes that are essential to maintain genome stability, control cellular homeostasis and determine disease susceptibility. While telomere-length variation has been mostly associated with the aging process in humans, a few studies in mammalian animals have shown that deviations from the optimal temperature can also change telomere length. It is well known that heat waves can have major consequences for corals, inducing a bleaching event during which photo-symbiotic algae are expulsed by the animal, eventually leading to its death. Interestingly, our analyses of the reef coral sampled across the Pacific Ocean during the Tara-Pacific expedition suggest that the way telomeres are regulated by seasonal temperature is different between two coral species that share the same habitat but diverge in their longevity and stress resistance: the short-lived, stress-sensitive branched coral Pocillopora spp and the long-lived, stress-resistant massive coral Porites spp. While the TL appears longer in higher temperatures for Pocillopora spp, no correlation between TL and temperature was observed in Porites ssp.

In order to test the effects of thermal variations on TL under laboratory conditions, we acclimatized Porites and Pocillopora coral colonies in the maintenance system of the facility for several weeks, then transferred them into the experimental system. The conditions used were defined by the range of temperatures measured during the Tara-Pacific expedition and mimicking cold (20˚C, 23˚C), normal (26˚C) and warm (30˚C) conditions. The first results obtained from this experiment show a trend towards longer TL after one month in the high temperature aquarium (30°C) for Pocillopora colonies as was observed across the Pacific for this type of coral.