Transglobal Spread of a Sea Urchin Parasite

Transglobal Spread of a Sea Urchin Parasite

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Researchers at the University of South Florida have made a concerning discovery: a marine parasite known for devastating sea urchins in the Caribbean and Florida in 2022 has now been found afflicting sea urchins in the Sea of Oman, over 7,000 miles away. This single-celled organism, identified as a ciliate, has caused alarm among scientists who fear it may lead to a pandemic for sea urchins.

Long-spined sea urchins
Long-spined sea urchins (National Marine Sanctuaries/CC BY 4.0)

The study identified the parasite that devastated 95 percent of long-spined sea urchins in affected areas in the Caribbean Sea two years ago. It burrows into the tissue of the sea urchins and triggers abnormal behaviour. The urchins droop and lose their ability to control their tube feet, which are crucial for movement. They lose their spines, then tissue necrosis sets in, leading to the death of the sea urchins.

Even for those individuals that manage to survive the parasite's attack, their weakened state makes them vulnerable to predation by other marine species. So far, the parasite has only been observed to affect sea urchins, as confirmed by genomic tests conducted at the USF lab. 

Vital to the coral reef community

The long-spined sea urchin (Diadema antillarum), has significant ecological importance on coral reefs. The animals contribute to reef resilience by grazing on algae, and thus providing space for corals to settle. Their dietary preferences, which include avoiding certain types of algae and cyanobacteria, contribute to the maintenance of a healthy ecosystem.  After disturbances like storms and bleaching events, sea urchins are vital for the recovery of coral communities. 

Additionally, the species' long spines serve as habitat for various reef fish species, so they are influential in the distribution of these fishes. They serve to provide protection for small species in reefs where structural complexity is lacking. 

Sea urchins face threats including overfishing and disease, so efforts to maintain this species have been a conservation priority.

The threat of the parasite's spread

For these reasons, any threat to the long-spined sea urchin poses a significant risk to the ecological balance of coral ecosystems, so the spread of the parasite has alarmed scientists.  Researchers are now looking into how the parasite might have spread so far, and how it is transported.

Transglobal spread of an ecologically relevant sea urchin parasite