Due to the alarming situation for noble pen shells in the Mediterranean, Aquarium Pula, with the financial help from the European Union of Aquarium Curators (EUAC), took adequate preventive actions and became a first reception center known by the name “Noble Sanctuary“.
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The Ministry of Nature Conservation and Energy gave us a permission to gather and keep 33 healthy individuals from coastal areas in Pula in June 2019. Except for everyday monitoring of parameters, construction of live food culturing establishment for large filtrates was needed. Seeing as the end of 2019 was marked by the mass mortality event of pen shells in the Bay of Trieste, and not long after that in Piran's aquatorium, persuaded us to ask for the Ministry's permission to isolate individuals from other locations.
Pathogen analysis for Haplosporidium pinnae and Mycobacterium spp. was conducted in the Croatian veterinary institute (HVI) for every individual on three tissue samples (mantle, adductor muscle and digestive gland). Analysis was conducted exclusively on dead or sacrificed individuals. To check the condition of noble pen shells in the northern Adriatic, we tested three individuals from three locations (Pula-Stoja, Ližnjan and Peroj). After receiving negative results on H. pinnae and M. sherrisii., we isolated 34 individuals from the location “Valovine“ in Pula on October 4, 2019, and placed them in separated tanks. Unfortunately, after some time, we detected changes in the speed of shell opening and closing, and also the look of the mantle. That was the time when first individuals in the Sanctuary started to die off. Analysis conducted on dead individuals showed that those individuals were infected with M. Sherrisii (19th February 2020 and 27th May 2020). From 34 viable pen shells until today (25th January 2021), there is only one individual left alive.
Other three groups came from three different locations: Vinkuran, Štinjan and Rovinj, in February 2020. From each group, at their arrival, one sacrificed individual was tested. Results of the analysis of H. pinnae and of M. sherrisii were negative. Unfortunately, with the increase of sea temperature (in May 2020), a significant mortality occurred. We tested three dead individuals. Results showed that all three were already infected with H. Pinnae, and two of them also had M. sherrisii present in their tissues. Our’s and the opinion of the Veterinary Institute, was that all of these individuals that arrived at the Sanctuary in February 2020 were already infected, but because of lower temperatures, we weren't able to detect the presence of the parasite.
First online IUCN (International Union for Nature Conservation) congress, at which we presented our results, showed us new knowledge gathered about the situation with wild pen shells across the Mediterranean; a small number of individuals are alive in France, Spain and Turkey, while a few scientific institutions and aquariums are keeping around a hundred live pen shells, of which the most is kept in Spain.