Measuring millimetres, this juvenile crown-of-thorns starfish can devastate coral reefs as an adult.

It’s hard to comprehend the destruction this ethereal creature could do in its lifetime — a juvenile crown-of-thorns starfish, raised in a lab where researchers have discovered worrying new findings about its progression into adulthood.

Research published today from the University of Sydney and Southern Cross University’s National Marine Science Centre in Coffs Harbour has found the crown-of-thorns starfish will eat a much more varied diet as juveniles than previously thought, making them worryingly resilient.

“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,” Dr Mos said.

The surprising findings followed research earlier this year that showed baby starfish can survive on algae for up to six and a half years instead of switching to a coral diet at four months of age — the point at which they can cause devastation to coral reefs.

“This could be a problem in that it might allow numbers of these juveniles to build up over a number of years and then move out in one mass onto the reef and cause an outbreak,” Dr Mos said.

https://www.abc.net.au/news/2020-07-21/crown-of-thorns-starfish-are-more-resilient-than-thought/12472656

> the crown-of-thorns starfish will eat a much more varied diet as juveniles than previously thought, making them worryingly resilient.
> baby starfish can survive on algae for up to six and a half years instead of switching to a coral diet at four months of age — the point at which they can cause devastation to coral reefs.

OK. Noted.

Has crown of thorns been found in large numbers of other reefs, such as in the Red Sea or Caribbean?

Are there many echinoderms without pentameral symmetry?

mollwollfumble said:

> the crown-of-thorns starfish will eat a much more varied diet as juveniles than previously thought, making them worryingly resilient.
> baby starfish can survive on algae for up to six and a half years instead of switching to a coral diet at four months of age — the point at which they can cause devastation to coral reefs.

OK. Noted.

Has crown of thorns been found in large numbers of other reefs, such as in the Red Sea or Caribbean?

https://www.reefresilience.org/pdf/COTS_Nov2003.pdf provides as much information currently available. The Sea Star’s distribution is in the western Pacific region, so not in the Red Sea or Caribbean.

>>Outbreaks of crown-of-thorns starfish Acanthaster plancihave been a major issue on the Great Barrier Reef and other Indo-Pacific reefs for nearly 40 years. The outbreaks have generated great concern among the community and considerable debate among scientists.

While there have been many theories on the causes of outbreaks of the crown-of-thorns starfish,there are three theories that are supported by scientists.These theories have neither been proved nor disproved.The theories are:

Fluctuations in crown-of-thorns starfish population are a natural phenomenon.

Removal of natural predators of the crown-of-thorns starfish has allowed populations to expand.

Human use of the coastal zone has increased the nutrients flowing to the sea and resulted in an increase in planktonic food for larvae of crown-of-thorns starfish.The improved survival of larvae has led to an increase in the number of adult starfish which results in outbreak.<<

As there are/were plenty of corals spanning hundreds of years, it strongly suggests the Crown-of-Thorns plagues are recent.

dv said:

Are there many echinoderms without pentameral symmetry?

The larval forms show bilateral symmetry and adult forms show radial symmetry. They do not need to be five armed.

dv said:

Are there many echinoderms without pentameral symmetry?

Not a lot.

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