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Pinna nobilis Linnaeus, 1758

Noble Pen Shell

The noble pen shell (Pinna nobilis) is an endemic species of the Mediterranean that holds special significance for the marine ecosystem. Like other bivalves, the noble pen shell feeds by filtering (plankton and organic particles), thus improving water quality. It is known to filter up to 60 litres of water per hour. It is the largest bivalve in the Mediterranean, growing up to 120 cm in length. It provides shelter, feeding and spawning grounds for many species (up to 35) known collectively as epibionts. Even after death, the hard shells of this bivalve allow the colonisation of various sedentary and mobile organisms.

It can be found at depths of up to 60 metres, but it is most abundant in seagrass beds and in the intertidal zone, where it sometimes remains partially out of the water.

While is noble pen shell conservation necessary?

Mass mortality of the noble shell (Pinna nobilis) caused by the parasite Haplosporidium pinnae in the Mediterranean Sea is a serious ecological crisis that began in 2016. By 2020, these pathogens had spread uncontrollably throughout the Mediterranean, infecting almost all individuals in open waters and reducing populations by 99.99%.

Epidemic and pathogens

With financial support from the European Union of Aquarium Curators (EUAC), Aquarium Pula, in cooperation with the University of Dubrovnik, conducted fieldwork in the waters of Mljet in 2019, where they witnessed the mass mortality of the noble pen shell. This sight prompted Aquarium Pula to take conservation measures, approved by the Ministry, and it became a reception centre for infected noble pen shells, known as the "Noble Sanctuary".

Based on the experience of other aquariums (Oceanografic Valencia) and experts (Dr. José Tena and Dr. Jose Rafael Garcia-March from IMEDMAR), a suitable and scientifically based framework was developed for the conservation of noble shells in controlled conditions. Ideal temperature and salinity, optimal density of individuals and a variety of food are just some of the essential conditions for the conservation and survival of the species.

Since 2020, the national project "Conservation of the Noble Pen Shell (Pinna nobilis) in the Adriatic Sea" has been initiated, coordinated by the Institute for Environment and Nature Protection of the relevant Ministry, co-financed by the Environmental Protection and Energy Efficiency Fund, with Aquarium Pula as a partner.

Learn more about the work of the sanctuary

Experimental breeding under controlled conditions

In February 2024, with the approval of the Italian government, 10 adult noble pen shells from the Venetian Lagoon arrived at Aquarium Pula for a breeding attempt.

Not much is known about the life cycle of the noble pen shell because it is a protected and non-commercial species, and there have been no previous breeding attempts. The undertaking of breeding this species in controlled conditions has only commenced in response to its critical endangerment status. However, thus far, the completion of the life cycle has not been achieved. It is established that the noble pen shell, like certain other bivalves, is a hermaphrodite (specifically, a sequential hermaphrodite). To prevent self-fertilization, the male and female gametes are produced at different times (asynchronous gamete development). The noble pen shell reaches sexual maturity at approximately two years of age. Spawning in the natural environment commences with the increase in water temperature, typically occurring in late spring, with the peak spawning period occurring during the summer months. The life cycle of the noble pen shell is divided into three stages: larval, juvenile, and adult. Larvae (trochophore, veliger, pediveliger) develop in the plankton, while juvenile and adult individuals are attached to the substrate.

Education and raising public awareness

Aquarium Pula regularly informs the public about events related to noble pen shells, both within and outside the aquarium, through social media, television and radio broadcasts. It actively participates in conferences and scientific publications.

The 2020 short documentary film, "Noble sanctuary," produced by the Aquarium Pula staff, presents an account of the activities and dedication of the scientific community and Aquarium Pula personnel in the preservation of this significant marine species and its ecosystem.

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