Crown of thorns starfish can be eaten alone and at home

A world-first study of the Great Barrier Reef shows that crown-of-thorns starfish have the ability to find their way home – a previously undocumented behavior – but only if their neighborhood is stocked with their favorite food: corals.

Australian researchers watched starfish emerge from their shelters in the afternoon so they could feed on coral overnight before returning home at dawn.

“The crown of thorns starfish often feasted all night, slept and only those with a well-stocked pantry found their way home, so it’s a role model as a teenager,” said lead author Dr Scott Ling of the Institute for Marine and Antarctic Studies at the University of Tasmania.

‘Their favorite prey is Acropora corals,’ said co-author Professor Morgan Pratchett of the ARC Center of Excellence for Coral Reef Studies at James Cook University (CoralCoE at JCU). Acropora is an important species of coral: for the past two million years they have been the building blocks of coral reefs around the world.

“When Acropora populations declined, the starfish did not come home,” said Prof Pratchett. “Their behavior is directly related to the local abundance of Acropora.”

The study results show that healthy coral reefs with high coverage of these corals can encourage crown-of-thorn clusters and outbreaks. Epidemics cause extensive, widespread and sustained coral loss across the Indo-Pacific region.

Similar examples of predator infestations driving environmental devastation include sea urchins over-grazing in algae forests and reef fish munching on algae patches.

The researchers used in situ time-lapse photography to track the movements of 58 starfish in the northern and southern Great Barrier Reef during an outbreak in 2015. In the absence of their favorite Acropora coral prey, the starfish were typically homeless and instead they roamed up to 20 meters per day.

“Unlike sea urchins which can change their diets once they overgraze the kelp forests, the results of the time-lapse monitoring indicate that the starfish will consume available Acropora and will eventually eat outside and indoors before dispersing at home. search for new feeding grounds, “says Dr. Ling said.

Previous Great Barrier Reef epidemics were recorded in 1962, 1979, 1993 and 2009. Although mass coral bleaching due to global warming is now the greatest threat to coral reefs worldwide, the combined impact of bleaching mass and crown of thorns outbreaks is potentially catastrophic for coral reefs.

“By better understanding the behavior of these starfish, we can help prevent and control their outbreaks, which will help alleviate the pressures on coral reefs,” said prof. Pratchett.

Reference: “The return-home behavior of crown-of-thorn starfish is triggered by local availability of coral prey” by SD Ling, Z.-L. Cowan, J. Boada, EB Flukes and MS Pratchett, November 4, 2020, Proceedings of the Royal Society B.
DOI: 10.1098 / rspb.2020.1341