Tiny killer threatens giant clam, aquatic emblem of the Med

phys.org | 1/25/2019 | Staff
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With wing-shaped shells lined with iridescent mother-of-pearl and producing the fibres of rare and delicate sea silk, the noble pen shell clam is one of the most emblematic species in the Mediterranean and a bellwether for marine environmental health.

But the giant mollusc, the world's second biggest, is under mortal threat from a parasite that has ravaged populations since it was identified along Spanish coasts in 2016.

Scientists - Climate - Change - Waters - Devastation

Scientists fear that climate change and warming waters will intensify the devastation, which they now class as an emergency.

The noble pen shells, or Pinna nobilis, can live for up to 45 years and grow to about 1.2 metres (four feet).

Mediterranean - Sea - Ships - Sails - Tips

They are only found in the Mediterranean Sea, standing proudly upright like ships' sails, their tips anchored in sandy seagrass meadows by sinewy fibres.

On the tranquil surface of the water at Villefranche-sur-Mer, near Nice in southern France, there is little evidence of the carnage below.

Seafloor - Graveyard - Shells

But dive down and the seafloor is a graveyard of noble pen shells.

Death has shrivelled the flesh of the molluscs and dulled the mother-of-pearl to a rusted brown inside the shells, in an area abandoned by the usual myriad of tiny cohabitors—little crabs, shrimps and orange sea fans.

Living - Olivier - Jude - Camera - Hand

"We cannot find a living one," said diver Olivier Jude, emerging, camera in hand, from the bay after an unsuccessful attempt to photograph the Pinna nobilis for his Phoctopus website.

Map of the Mediterranean showing zones where populations of noble pen shell clams have been decimated by a tiny parasite, thriving in warmer sea water.

Riviera - Site - Die-off - Relentless - Assault

The French Riviera is the latest site of the die-off, caused by the relentless assault of a new parasite that weakens the clam, quickly starving it to death.

The pathogen has almost eradicated the noble pen shell population off the Spanish coast, where it is now listed as critically endangered, and has spread...
(Excerpt) Read more at: phys.org
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