Unfortunately, this process may have backfired, as crown-of-thorns starfish can regenerate arms and in extreme cases may be able to regenerate from only half of an animal. Current efforts to control crown-of-thorns starfish include complete removal from the reef or poisoning with substances that kill the starfish but not other species on the reef particularly corals. At least one group of animals associated with specific corals is known to attack the crown-of-thorns starfish in order to protect their homes.
The guard crabs genus Trapezia live amongst the branches of cauliflower corals and other branching corals and are known to defend their home colonies from crown-of-thorns starfish that are trying to feed on them.
Through this symbiosis, the crabs protect the coral colony from potential predators and in return, they receive a safe place to live and to avoid their own predators. These starfish reproduce through a behavior known as broadcast spawning, where several females release eggs and several males release sperm into the water column above the reef, all at the same time. This method increases the likelihood that eggs will become successfully fertilized and that fertilized eggs will not be eaten by egg predators on the reef surface.
The team identified 30 fish from 18 species that had chowed down on a crown-of-thorns starfish in recent days, according to their paper published on May 18 in the journal Scientific Reports. The only well-known predator of adult crown-of-thorns starfish was the Pacific triton, a giant sea snail that hunts by injecting venom.
The new study sheds light on new possibilities in crown-of-thorns starfish management. So far, experts have tried to cull wild populations by injecting them with vinegar or bile salts, or by removing and destroying the starfish one at a time. In , crews killed , starfish, but somewhere between 4 to 12 million in total live in the Great Barrier Reef, per the Washington Post. Then, the team gathered the fish poop left behind in the tank and used a new genetic analysis technology to scan for DNA evidence of the crown-of-thorns starfish.
Living Oceans Foundation. The telltale white skeletons of recently eaten branch coral pointed to the culprit — Acanthaster planci , or Crown of Thorns Starfish, named for its helmet of venomous spines. For reefs in the Pacific and Indian Oceans, only cyclones and bleaching events cause more destruction than the voracious Crown of Thorns.
They move fast for starfish — 20 meters an hour. Each night the nocturnal COTS can eat its own body area in coral, and they can grow up to a meter in diameter. That means on average one COTS can consume 13 square meters of reef per year.
During population spikes, clusters of COTS eat living coral polyps faster than the coral can grow and reproduce. And the COTS menace is growing even worse. Once COTS ate only the fast-growing corals that thrive in shallow water.
After a COTS outbreak, these coral can grow back in a few years. Now, Crown of Thorns Starfish also go after deeper, slower-growing corals, like the reef-building species, Porites.
To fight the outbreak around Aitutaki, science divers from our research team collected COTS from ten different sites, by hand.
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