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Pinna nobilis Linnaeus, 1758

Noble Pen Shell

The noble pen shell (Pinna nobilis) is an endemic species with rich history and of particular significance for the marine ecosystem. It is the largest bivalve in the Mediterranean and cannot be found anywhere else than in this unique, enclosed sea. Noble pen shell individuals can grow more than a metre in length, weigh more than three kilograms, and live as long as 50 years. They live in shallow areas under the influence of tides, which can leave the noble pen shells partly outside of the water. The noble pen shell is present even at depths of 60 metres, but it is most numerous on seagrass meadows, where it uses its byssus threads to attach itself to the substrate and become a part of one of the most productive marine habitats.

The noble pen shell offers a hiding place, feeding ground and nursery for a large number of organisms that we know by a single name: epibionts. Colonising the solid structure of this bivalve has proven to be a successful strategy for the survival of both immobile and mobile organisms. An individual noble pen shell can harbour more than 35 species of animals and algae.

While is noble pen shell conservation necessary?

Autumn 2016 marked the beginning of one of the hardest and most disastrous periods in the history of the noble pen shell’s existence. A newly discovered parasite, Haplosporidium pinnae, in synergy with the bacterium Mycobacterium sherrisii, killed noble pen shell populations in the Spanish Balearic. By 2020, these pathogens dispersed uncontrollably throughout the Mediterranean and infected almost all individuals in the wild. While thousands of individuals still thrive in the lagoons of France,
Spain, and Italy, only ten individuals per country can be found in the
open waters of the Mediterranean.

Find out more about the epidemic and pathogens by clicking on the link.

During the field evaluation of Mljet National Park in 2019, together with associates from the University of Dubrovnik, the Aquarium Pula team witnessed a noble pen shell mass mortality event. That disastrous sight was an incentive to carry out conservation activities to protect any last viable individuals in the northern Adriatic, which the Ministry approved.

Due to the alarming situation for noble pen shells in the Mediterranean, Aquarium Pula, with financial assistance from the European Union of Aquarium Curators (EUAC), took appropriate preventive action and became the first reception centre known as a “Noble Sanctuary”.

We developed an expert base to keep live noble pen shells in controlled conditions based on the experience of other aquariums (Oceanografic Valencia) and their experts (Sergio Trigos). Ideal temperature and salinity, the optimal density of individuals, diversity of food and exposure to the sun are just some of the many conditions needed to keep them in good health.

A series of quarantine tanks with recirculated purified seawater was established in record time, including a whole live food culture plant. Life support systems were divided into groups of noble pen shells taken from different locations. We isolated and took care of more than three hundred wild noble pen shells and filled the “Noble Sanctuary” to capacity.

NEW HOPE – Young noble pen shells

Tatjana Bakran-Petricioli, PhD and Silvija Kipson, PhD successfully transplanted noble pen shells from the Pula harbour into Brijuni National Park in 2017 through the project MERCES (Marine Ecosystem Restoration in Changing European Seas). They realised that it is possible to collect noble pen shell larvae from locations affected by a mass mortality event and bring them to safety. They launched the initiative of placing larvae collectors through a new project called “PinnAdriaNet”, which was joined by many partners from academic, research and public institutions, and NGOs throughout Croatia. This project resulted in the signing of an agreement with the Ministry of Economy and Sustainable Development in 2020, when Aquarium Pula became the leading institution in Croatia responsible for keeping young and adult individuals in controlled (ex-situ) conditions. Funding also co-finances individual activities that are carried out by our partners: monitoring of locations with surviving individuals, placing larvae collectors, keeping adult and young individuals in controlled conditions (ex-situ) and raising public awareness through different educational activities.

As part of the project, collectors for young individuals were placed in 15 different locations across the Adriatic in June 2020. They were extracted at the end of the year. A total of fifteen larvae were found in three locations, and those individuals are kept in quarantine at Aquarium Pula. Specially treated, purified, UV sterilised, and micron filtered seawater is used for keeping young individuals. Young noble pen shells are held in tanks with an enclosed system and separated into groups by the location in which they were found. All parameters of the system: temperature, salinity, pH, oxygen concentration and metabolic excretions (ammonia, nitrites, nitrates), are controlled daily. They must be fed multiple times a day. Food comprises unicellular algae – phytoplankton (Tysochrisis sp., Tetraselmis sp., Nanocloropsis sp. and diatoms) with a little zooplankton.

The first feathers arrived

Omišanka, Rovinjke & Brionke

The first young noble pen shell named “Omišanka” arrived at the aquarium on 19 November. Jelena Kurtović Mrčetić, a biologist from the Public Institution “More i Krš”, found a young noble pen shell, 1.5 cm in length, in the Omiš harbour at a depth of 6 metres after a thorough collector inspection. A few days later, “Rovinjke” arrived, individuals found after a collector inspection in the bay of Leso, headed by Andrej Jaklin, PhD. At the end of December, “Brionke” also arrived at Aquarium Pula. They were found during a careful inspection of larvae collectors in Brijuni National Park and delivered by the team headed by Tatjana Bakran-Petricioli, PhD. Young individuals are fed multiple times a day: by hand (at least four times) and with the help of an automatic feeder (every hour).

Education and raising public awareness

Public education about problems affecting marine ecosystems has always been a vital part of the conservation of nature and its resources. With that in mind, Aquarium Pula accomplished a series of achievements in raising public awareness about possible noble pen shell extinction. The main goal was to present our activities to the public, sensitise people and give them an incentive to become involved in the conservation of this noble species. Numerous reports from the field provided by citizens are often crucial to getting the bigger picture about the status of the population in need of our protection.

“Noble Sanctuary” – A documentary

A short documentary, “Noble Sanctuary”, shows the noble pen shell as the biggest Mediterranean bivalve whose absence would adversely affect the balance of the marine ecosystem that we know today. It introduces the audience to the mass mortality event; the unexpected pathogen spread that brought the noble pen shell to the brink of extinction. Watch “Noble Sanctuary” and follow the activities of the scientific community and Aquarium Pula staff that dedicate their time and resources to conserving this noble species vital for the marine ecosystem.

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