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Scientists have warned that green crabs have long been known for their bad attitude, but a new variant of the species, mad about hell, is moving and destroying everything in its path.
Surprisingly, the crustaceans come from Canada famous and are better suited to the rink that the calm coast of Maine, on the east coast of the United States, where large clusters were discovered.
The green crabs of Nova Scotia are the same species as their Maine cousins, but infinitely worse, threatening to accelerate damage to the coastal ecosystem by engulfing soft-shelled clams and destroying them. grass to the native eel.
The docile green crabs are disappearing from a threat, while newcomers are more likely to shake their tongs and load.
"What we see is this level of insane aggression," said Professor Markus Frederich of the University of New England.
The variant of the angry crab, native to Northern Europe, is more resistant and better adapted to cooler waters than their soft cousins from Southern Europe.
Green crabs, even the most docile, are considered a plague that can devour soft-shell clams and juveniles. They can destroy the eelgrass that is a hiding place for juvenile sea creatures.
But Canadian crabs are taking a new step.
Louis Logan, a graduate student from the University of New England, had the unpleasant task of tagging crabs caught in Nova Scotia waters for research.
The crabs were not in the mood for games.
At a distance of 1.5 m, the pint-sized brutes, ranging from 10 to 12 cm in diameter, adopted a fighting posture. Those who caught it were not in a hurry to let go.
"Every time I went to get one, they came to take me instead," he wrote in an email.
One of them, in particular, would jump out of water in his attack frenzy.
In the lab, the researchers unleashed both types of crabs on an eelgrass bed in a saltwater pool, and the difference was striking. Canadian invaders have shredded eelgrass like Edward Scissorhands in their efforts to destroy marine organisms seeking refuge, said Professor Frederich.
The first series of studies focused on 200 crabs in Canada and will be published in the coming months.
Prof Frederich said that further studies will focus on whether a specific gene plays a role in aggressiveness or whether a factor called hybrid vigor is at stake.
Hybrid vigor theory suggests that crabs may be more aggressive as they become established, but will disappear later.
The quarrelsome newcomers currently only account for about 2 to 3 percent of the green crabs crawling on the bottom of the ocean off Maine, but these numbers will certainly increase, Frederich said.
"It will be a totally different ball game," he predicted. "It's just a question of when more crabs are competing with Maine's green crabs."
Docile green crabs have been around for more than a century in New England waters, but they have become a major problem during the warming of the Gulf of Maine.
The largest crabs arrived off Nova Scotia in the 1980s and currents brought their larvae south into New England waters.
Finally, newcomers will go further south. "We can not do anything about it," he says.
I said. "The only thing we can do is learn how to live with it".
With AP
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