Out of around 380 species of marine damselfish, only three were known to exhibit brood care — until now. Scientists have discovered a new damselfish species, and it raises that number to four…
Most species of reef fish produce large numbers of young that disperse into the ocean as larvae, drifting with the currents before settling down on a reef.
Giacomo Bernardi is a professor of ecology and evolutionary biology at UC Santa Cruz, and he studies reef fish that buck this trend, protecting the young until they are big enough to fend for themselves.
On a recent trip to the Philippines, Bernardi and his team discovered a new species of damselfish that exhibits this unusual parental care behaviour. Only three brood-guarding damselfish species were known prior to this discovery. Bernardi's team had gone to the Philippines to study two of them, both in the genus Altrichthys, that live in shallow water off the small island of Busuanga. On the last day of the trip, the researchers went snorkeling in a remote area on the other side of the island from their study site.
"Immediately, as soon as we went in the water, we saw that this was a different species," Bernardi said. "It's very unusual to see a coral reef fish guarding its babies, so it's really cool when you see it."
Genetic tests on the specimens they collected confirmed that it is a new species, which the researchers named Altrichthys alelia (derived from the names of Bernardi's children, Alessio and Amalia, who helped with his field research).
According to Bernardi, less than one percent of larvae that disperse into the ocean survive to settle back on a reef, whereas survival rates can be as high as 35 percent for the offspring of the Altrichthys species.
One big disadvantage is that the young are unable to colonise new sites far from the home reef of their parents. As a result, brood-guarding species tend to occur in highly restricted areas, which leaves them more vulnerable to extinction.
"I suspect that species evolve this strategy regularly, and they are successful until there is some change to the local habitat, and then the whole population gets wiped out," Bernardi said. "These are very fragile species. The Banggai cardinalfish is one that was discovered just a few years ago in a small area in Indonesia, and it's already on the endangered species list."