Coral larvae feed on their baby fat

For corals, baby fat is food. Coral mothers send their offspring into the world with a balanced meal of fat and algae, but baby corals mainly chew the fat, new research finds.

Adult corals of the species Pocillopora damicornis get most of their nutrition from symbiotic algae that live inside them, providing metabolic energy by photosynthesis. But coral larvae, researchers report online March 25 in Science Advances, rely instead on their “baby fat.”

The finding sheds light on corals’ metabolism during their most vulnerable developmental stage, says biological geochemist Anders Meibom of École Polytechnique Fédérale de Lausanne in Switzerland. Baby fat “is a good thing,” he says. “It gives the coral some time to find a good home without running out of juice.” Larvae’s dependence on fat may make them less sensitive to bleaching — a process in which stressed corals jettison their algal tenants and eventually starve to death. So understanding larval nutrition could help scientists better understand the effects of ocean warming and acidification on bleaching, Meibom says.

Meibom and colleagues fed isotope-tagged nutrients to larvae of P. damicornis, commonly called cauliflower coral, and tracked how the larvae’s symbiotic algae used the nutrients over time. Algae are less abundant in larvae compared with adult corals and provide very little energy, the researchers found.

The next step is to pinpoint exactly when and how larvae switch from feeding on fat to algae as they transition into adulthood, Meibom says, as well as exploring how Earth’s changing oceans might impact the process.