BIOLOGICAL NOTES
darkness, to feed in safety. A basketstar climbs up the gorgonian at whose foot it dwells. It deploys hundreds of finely ramified arms to snatch the tiny particles of nutrients floating in the currents, like the other ophiuroids and comatulida or feather stars. During the day, most of these invertebrates which feed through filtration stay curled up, to prevent parrotfish from nibbling their arms. Crabs, shrimp, and small cardinalfish also take advantage of the darkness to emerge from their hiding places, and venomous sea urchins with menacing stings gnaw at the corals while formidable mollusks hunt them. Soldierfish are everywhere, opening their oversized eyes to spot minuscule shrimp and krill. The flickering lights are those of lanternfish, which use bioluminescent pouches below their eyes to communicate with one another, particularly during the mating season or when they chance upon a particularly appetizing prey. They simply lift or lower a flap of skin to turn their lanterns “on” or “off”. An octopus makes its way along the foot of the reef, pausing to examine its new backyard. On spotting a half-buried bivalve, it emits a series of pulses. Finally, the coral polyps emerge from their calcium skeleton to join the party, and the whole appearance of the reef is transformed. In the blackness of night, a manta ray passes through the reef illuminated by the light of the ophiuroids and shrimp, leaving a phosphorescent trail in its wake.
Reefs develop in tropical waters with little in the way of food resources, each forming a sort of aquatic oasis in which each inhabitant recycles the elements available in a perfectly economical system. The activity of the coral reef provides a striking example of the living world’s ability to recycle and reuse. Everyone can take part. The rich minerals obtained from a decomposing angelshark carcass, the last prey of the moray eel, have not yet been swept away by the current. They feed the symbiotic algae that will make nutrients in the mantle of the giant clam or will embed themselves into the corals’ skeleton. Finally, by grazing on the coral in the search for algae and ejecting its ground up skeleton like grains of sand, the parrotfish will recycle the last traces of the angelshark.
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