Page 28 - AT

A28 SCIENCE
Thursday 6 december 2018

New parasite decimates giant clam species in Mediterranean

By ELENA BECATOROS Otero said. "There's almost
Associated Press no question."
ANAVYSSOS, Greece (AP) One thing's clear: the para-
— With rapid efficiency, a site is very particular in its
mysterious parasite is seek- choice of victim. A smaller,
ing out and killing a giant related species, the Pinna
species of clam found only rudis, which also exists out-
in the Mediterranean Sea. side the Mediterranean, is
Unless scientists can find unaffected.
a way of stopping it soon, "We don't know how it has
they say the mollusk could appeared in the Mediterra-
go extinct. nean... We only know that it
For thousands of years, the causes mortality only in the
emblematic noble pen Pinna nobilis," Issaris said.
shell has been intrinsically In the clear, shallow waters
connected to human civi- south of the Greek capital,
lization. The largest bivalve dozens of dead pen shells
in the Mediterranean can lie scattered in a seagrass
grow to more than a meter meadow, testament to the
(three feet) long and has devastation.
provided food and one of Peering through a micro-
the world's rarest materials: scope at the tissue of an
sea silk spun from fibers it infected individual in his
uses to secure itself to the office in Crete, Kathari-
seabed. The mollusk also os points out the culprit:
contributes to clear water small, oval-shaped para-
by filtering out organic par- In this Sunday, Sept. 14, 2008 underwater photo, pen shells stand on the seabed in the Aegean sites spread throughout the
ticulates. Sea. Associated Press sample.
The pen shell, Pinna nobilis, Scientists are puzzling over
has been on the European infected animal is also un- the bivalve's food source, testing proved him right. why an organism would be
Union's protected species able to close its shell, in- but nobody knows for cer- Now the question is how to so lethal to the very species
list for decades because capacitating its defense tain. tackle the outbreak. it depends on for its own
of overfishing, pollution against predators. Once "We cannot be sure of any- "This is very fresh for the sci- survival.
and the destruction of its infected, death is almost thing at this point," said entific community," Issaris "Normally parasites in na-
natural habitat, mean- certain. Pantelis Katharios, senior said. "We're still at the stage ture do not have any ben-
ing any fishing is banned. "In less than a year it wiped researcher at the Institute of recording where it has efit from harming the host,
But the ban is often poorly out (the pen shell popula- of Marine Biology, Biotech- spread to." because they depend
enforced, with the animal tion of) the Spanish coast," nology and Aquaculture of Some parts of Greece still on the host," Katharios ex-
harvested for food or for its said Maria del Mar Otero of the Hellenic Center for Ma- have healthy populations plained. "But once in a
shell, which is used for dec- the International Union for rine Research , or HCMR. of the mollusks, he noted, while we may come across
orative purposes. Conservation of Nature. "What we know now is whereas in other areas they incidents like this, where we
The pen shells, which have Soon parts of France, Mal- that the Pinnas are dying, have been wiped out. have massive mortalities."
a life span of several de- ta, Tunisia and Italy were that the cause is this para- Protecting the pen shell in This could just be a natural
cades and take years to affected. In recent weeks, site, and we know that it's its natural habitat — sandy phenomenon in which the
reach reproductive age, tests confirmed the same spreading very, very rapid- seabeds or seagrass mead- parasite will eventually be
were already dying faster parasite, Haplosporidium ly," he said. "And that is go- ows — appears "difficult to wiped out along with its
than they could be re- pinnae, is responsible for ing to be a huge problem impossible," Issaris said, par- host, he said. Another pos-
placed. So the spread of pen shell die-offs in parts of (for) the ecology and the ticularly without knowing sibility is that it originated in
the microscopic parasite, Greece, and researchers balance of the ecosystem how the parasite spreads. a different species and for
which first appeared in the have reported mass mor- in the Mediterranean." In Spain, some healthy in- some reason jumped to the
western Mediterranean in tality as far east as Turkey Yiannis Issaris, marine ecol- dividuals were moved to pen shell. A third is that the
late 2016 and was identi- and Cyprus. ogist at the HCMR's Institute aquariums. pen shell's immune system
fied just this year as a new Scientists are now racing of Oceanography, initially Although tests are pend- has been compromised by
species, has alarmed ex- to understand how the noticed widespread pen ing in some Mediterranean factors such as pollution,
perts. parasite spreads and its life shell death off the coast countries witnessing mass climate change or water
Exactly how the parasite cycle — essential informa- of Anavyssos, southeast of die-offs, experts have little temperature fluctuations.
kills isn't completely clear, tion for a successful rescue Athens, in mid-summer. He doubt what the results will "It's extremely, extremely
although scientists have program. One theory is suspected the culprit could show. difficult to find the truth at
found it attacks the pen that it could be spreading be the same one causing "It's very, very, very likely" this stage," Katharios said.q
shell's digestive system. The through phytoplankton, mortality in Spain — and to be the same parasite,

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