Parasite is wiping out rare species of giant clam
A MYSTERIOUS microscopic parasite is seeking out and killing a giant species of clam found only in the Mediterranean Sea.
Unless scientists can find a way of stopping it soon, they say the mollusc could go extinct.
For thousands of years the noble pen shell has been intrinsically connected to humans.
The largest bivalve in the Mediterranean can grow to more than a metre long and provides food and one of the world’s rarest materials: sea silk, spun from fibres it uses to secure itself to the seabed.
The Pinna nobilis, which can grow up to four feet long, has been a protected species for decades. So the rapid spread of the parasite, which first appeared in the western Mediterranean in late 2016 and was identified just this year, has alarmed experts.
The mollusc also contributes to clear water by filtering out organic particulates.
The pen shell has been on the European Union’s protected species list for decades because of overfishing, pollution and the destruction of its natural habitat, meaning any fishing is banned. But the ban is often poorly enforced, with the animal harvested for food or for its shell, which is used for decorative purposes.
The pen shells, which have a life span of several decades and take years to reach reproductive age, were already dying faster than they could be replaced.
Exactly how the parasite kills is not clear, although scientists have found it attacks the pen shell’s digestive system. The infected animal is also unable to close its shell, incapacitating its defence against predators. Once infected, death is almost certain.
“In less than a year it wiped out [the pen shell population of] the Spanish coast,” said Maria del Mar Otero of the International Union for Conservation of Nature.
Soon parts of France, Malta, Tunisia and Italy were affected. In recent weeks, tests confirmed the same parasite, Haplosporidium pinnae, is responsible for pen shell die-offs in parts of Greece, and researchers have reported mass mortality as far east as Turkey and Cyprus.
Scientists are now racing to understand how the parasite spreads and its life cycle, which is essential information for a successful rescue programme.