Global Courant 2023-04-19 23:19:51
NEW YORK (AP) — Sea urchins hit the Caribbean last year started to get sick – shedding their spines, dying off and throwing reef ecosystems into chaos. Now scientists think they’ve caught the killer in this marine murder mystery.
A tiny single-celled parasite is responsible for the mass die-off, researchers reported Wednesday in the journal Scientific progress.
“The case is closed,” said study author Mya Breitbart, a marine microbiologist at the University of South Florida.
These long-spine sea urchins, or Diadema antillarum, are spiny black creatures that hide in reefs in the Caribbean. They play a key role as “lawnmowers” of the reef, Breitbart said, as they eat the algae that grow on corals.
But in January 2022, these animals began showing strange symptoms — their sharp spines droop and fall off, their suction cups lose their grip — before dying en masse, from the Virgin Islands to Puerto Rico to Florida.
For marine scientists, it was deja vu: In the 1980s, another die-off swept through the region and reduced sea urchin populations by about 98%.
That case was never solved. But this time, an international team of researchers sprang into action, taking samples from sick hedgehogs and healthy hedgehogs in the Caribbean to search for genetic clues.
They saw no signs of viruses or bacteria, said study co-author Ian Hewson, who researches marine diseases at Cornell University. But they did see traces of tiny single-celled organisms called ciliates that only showed up in the sick hedgehogs.
While most ciliates don’t cause disease, this species has been linked to other aquatic outbreaks, making it a prime suspect, Hewson said.
To confirm they had caught the killer, scientists placed the parasites in tanks of healthy hedgehogs bred in captivity to see how they would react. Of the 10 hedgehogs that took on the tiny creatures, 60% died – after displaying the same symptoms researchers saw in the wild.
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It’s possible that the same parasite also caused the extinction in the 1980s, but scientists aren’t sure, Breitbart said.
And they haven’t found a way to treat the sick hedgehogs yet. But they’re hopeful that knowing the source of the die-off will help preserve the reefs, especially as they learn more about how the parasites spread, Breitbart said.
This death of sea urchins and other stresses have already transformed the reefs, added Don Levitan, a marine scientist at Florida State University who was not involved in the study.
Before the first sea urchin became extinct, Levitan recalled seeing reefs in the US Virgin Islands covered in spiny creatures. Now those reefs look very different – choked with algae, affected by coral disease and stressed by rising temperatures.
“Coral reefs in the Caribbean are in trouble,” Levitan said. “We’re in a different place than we were 30, 40 years ago.”
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