The fan mussel or noble pen shell is the largest bivalve mollusc of the Mediterranean. (Photo: Oceanogràfic València)

Valencian scientists discover treatment against lethal disease affecting fan mussels

SPAIN
Monday, December 18, 2017, 22:20 (GMT + 9)

A work team of the Oceanogràfic de València has for the first time in the world managed to stop a disease that has begun to devastate the fan mussel (Pinna nobilis) stock of the Mediterranean Sea.

It is a parasitic disease hitherto unknown to this bivalve, and whose ravages in the population have made their situation declared as "catastrophic".

The fan mussel or noble pen shell is the largest bivalve mollusc in the Mediterranean, endemic to this sea. It lives mainly in the meadows of Posidonia oceanica and can reach more than one metre in length and exceed 20 years of age. Spanish populations have experienced a significant increase in mortality in different areas of the coast since mid-September 2016, extending alarmingly along the coasts of Andalusia, Murcia, Valencia and the Balearic Islands during 2017. There has been a decline in more than 80 per cent, in most cases, and has reached 100 per cent in many points.

At this time, only the populations of fan mussel from the north coast of Cataluña are considered free from the disease, but it is feared that they may soon be affected.

This emblematic species has been affected by the Haplosporidium protozoon, which is suspected to be the cause of the massive mortality observed recently in the Spanish coasts and that could affect the survival of the species.

Faced with this dramatic reality, technicians, biologists and veterinarians of the Oceanogràfic of Valencia have successfully managed, and for the first time, to treat several specimens of this species that is protected by the EU Habitats Directive and included in the Spanish Catalog of Endangered Species. This advance represents a transcendent finding for the survival of this bivalve, which has great relevance in the marine ecosystem, given that, among other reasons, these noble pen shells, which favour marine biodiversity, produce an ecosystem around their shells in which other species of micro invertebrates live and breed.

The specimens successfully treated by introducing changes in salinity, water temperature and feeding are part of a project aimed at achieving gonadal maturation of the species, with a view to its reproduction for subsequent reintroduction into the natural environment.

The specimens are being cared for by the Quarantine team at the Oceanogràfic facilities prepared for this project jointly developed by the Oceanogràfic Foundation and the IMEDMAR Institute (Catholic University of Valencia).

The survival of these four specimens, originally infected but now fully recovered, could represent a historic milestone for the conservation of the fan mussel, since it opens a path of hope for the recovery of the species, currently considered as "catastrophic", according to the Ministry of Agriculture and Fisheries, Food and Environment (MAPAMA).

So far, no other infected specimens have survived and it is unknown, for the time being, if these specimens, once the disease has been overcome, could have developed some type of immunity that makes them more resistant to reinfection.

The Directorate General for Sustainability of the Coast and the Sea of ​​MAPAMA issued a resolution on October 17, 2017, approved by the Council of Ministers, reason for which the rescue of 215 specimens of fan mussels and their maintenance in specialized centres was deemed as an emergency. This extraordinary operation is coordinated by the Institute of Research in Environment and Marine Science (IMEDMAR) and it has been joined by the Institute of Research and Training in Agriculture and Fisheries (IFAPA) of Huelva, the Spanish Institute of Oceanography (IEO) of Murcia, the Institut de Recerca i Tecnologia Agroalimentàries (IRTA), in Tarragona, and the Oceanogràfic de València.

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