Underwater long spiny sea urchin on the Caribbean sea floor
Sea Photo Art / Alamy
The mystery killer behind the recent mass deaths of the once common sea urchin species has been identified as a parasitic microbe called a ciliate.
Spiny sea urchin (Crown of the Antilles) once attacked millions of Caribbean reefs, but in 1983 the sea urchins began to lose their spines and within days died and disappeared from the reefs. 98% of the disappeared.
The sea urchins have been slowly recovering for 40 years until the mystery killer strikes again in January 2022. “We are probably looking at millions [of urchin deaths] Ian Hewson of Cornell University in New York said:
To study, Hughson’s collaborators in the Caribbean collected both healthy and diseased sea urchins from 23 different reef locations. They sent sea urchin tissue samples to Hewson’s lab in New York, where he and his colleagues looked for evidence of viruses and pathogens — common culprits of mass death — at the molecular level.
Nothing stood out at first. We then looked for genetic signals in microorganisms such as fungi and ciliates. These are tiny creatures covered in hair-like structures that help them move and eat.Hughson said that ciliates philaster apodigitiformis It was abundant in diseased sea urchins and absent in healthy sea urchins.
The researchers then added live ciliates to tanks of healthy sea urchins in the lab. “After a few days, he 60% of the sea urchins had lost their spines and looked just like the sea urchins that had died in the fields,” Hewson suggests. P. apodigitiformis was the cause.
The result was “a bit of a surprise,” Hewson said, because ciliates are usually thought of as simple decomposers that devour bacteria and decaying tissue. Although related ciliates are known to infect sharks, this is the first time they have been found to kill sea urchins.
“the cause of [long-spined sea urchin] Mass deaths in the Caribbean have long been a mystery,” says Michael Sweet of the University of Derby, UK. “What this group has done is absolutely amazing.”
Researchers don’t yet know what triggers it. P. apodigitiformis But we hope this study will be a first step toward developing ways to control its spread, a task that would be very difficult in an aquatic environment, Hewson said.
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