Juvenile Crown-of-Thorns Switch Diets to Enhance Growth Rates

It is hard to imagine the destruction that crown-of-thorns starfish can do in their lifetime. The sea creatures are renowned for eating the coral and destroying the coral reefs in the process.

Young crown-of-thorns typically settle in reef environments where they start by eating rock-hard coralline algae. However, researchers tried to raise some juvenile crown-of-thorns starfish in the lab and discovered a worrying new findings of its growth into adulthood.

Juvenile Crown-of-Thorns Shifts Its Diet

Jennifer Wilmes and her colleagues compared the growth of two groups of crown-of-thorns starfish, which has different types of diet. One group switched its diet early after settlement, within six months, and the other group continues to feed on coralline algae for one year.

The research published on July 21 from the University of Sydney and Southern Cross University's National Marine Science Centre in Coffs Harbour, found that juvenile crown-of-thorns starfish that start eating corals at an earlier age exhibit enhanced growth rates for longer and will get much bigger than those who continues to feed on corals.

The study confirms that the starfish will eat a much more varied diet as juveniles than scientists previously thought.

The authors noted that larger crown-of-thorns starfish are more likely to reproduce and consume the corals at higher rates. The variation of the diet of juvenile crown-of-thorns starfish can have important implications on the population dynamics of the starfish and can have grave impacts on coral reef ecosystems.

"We initially thought that they only ate crustose coralline algae but we found that they can also eat biofilm, which is a mixture of diatoms, bacteria, and other microorganisms that grow pretty much everywhere in the ocean," says Dr. Benjamin Mos, one of the study authors.

The findings suggest that a significant change can affect the life cycle of the crown-of-thorns starfish and raises the threat it can cause to the coral reefs, ABC News reports.

"Juvenile crown-of-thorns starfish appear to be the cockroach of the ocean - highly resilient and able to survive for months on food that we initially thought they would not eat," Dr. Mos added.

Crown-of-Thorns Starfish and the Coral Reef Ecosystem

The crown-of-thorns starfish is named for the spikes that cover its body and arms. These spikes are flexible to help them move and to act as their defense mechanism from potential predators. These starfish are known coral predator, outbreaks of tens of thousands of these can cause serious harm to the coral reefs in the area.

They are known to prey on large swaths of coral reefs when these corals are already stressed, such as on times of coral bleaching or stresses caused by human activities. They feed by inverting their entire stomachs through the mouth and digesting the thin layer of the soft tissue of a coral's skeleton and sucks its nutrients.

Fishers and conservationists who feared the starfish would permanently damage coral reefs in the past to control the population of the starfish. In some places, people would chop them in half or into smaller pieces.

However, that method could backfire as crown-of-thorns starfish can regenerate their arms and sometimes be able to regenerate from only half of an animal. Currently, methods to control the starfish population include complete removal from the reef or poisoning with a substance that kills the crown-of-thorns starfish but not other species on the reef, especially the corals.

The recent study may help scientists develop ways of effective early management intervention.