Abstract
Pinna nobilis is the largest bivalve of the Mediterranean Sea, where it represents a flagship species. As a possible consequence of several human disturbing activities, at the beginning of ‘80s, populations of fan mussel started a severe demographic decline. To reverse this trend, P. nobilis was included in a regime of full protection which led to a significant recovery of the species at the beginning of the millennium. Unfortunately, P. nobilis is presently facing a dramatic epidemic, which is bringing this species to the brink of extinction. This phenomenon started in early autumn 2016, from the Mediterranean coasts of Spain. Since then, the mass mortality spread quickly eastward reaching almost all Mediterranean areas. First epidemiological surveys ascribed the mass mortality of P. nobilis to the protozoan Haplosporidium pinnae, but recent studies indicated some species of bacteria belonging to the genera Mycobacterium and Vibrio as further or alternative etiological agents. Presently, a multifactorial disease mediated by the combined action of several pathogens seems to be the most probable responsible factor which is favouring the phenomenon. Despite the conservational prominence of P. nobilis, a low number of studies investigated the genetic structure of this species before its mass mortality and all were consistent in evidencing a very good health for populations throughout the whole Mediterranean, pointing out high levels of genetic variability and good genetic connectivity among areas. Now it would be useful to provide an extended molecular survey post-epidemic, for a deeper understanding of the causes of mass mortality of fan mussels.
Highlights
A white flag in the Mediterranean Sea? Biological traits of the threatened to extinction Pinna nobilisThe species Pinna nobilis (Linnaeus 1758), known as fan mussel or noble pen shell (Fig. 1) is a bivalve belonging to the order Ostreoida Fërussac 1822, and the family Pinnidae Leach 1819.Pinna nobilis represents the largest bivalve populating the Mediterranean Sea (Rabaoui et al, 2008), and one of the largest in the world since it can exceed one meter of total length (Zavodnik et al, 1991)
First epidemiological surveys ascribed this phenomenon to the infection of the protozoan Haplosporidium pinnae, but recent studies indicated some species of bacteria belonging to the genera Mycobacterium and Vibrio as further or alternative etiological agents
Scarpa & Sanna et al (2020) found H. pinnae in Mediterranean specimens of Ruditapes decussatus collected in 2014. This is suggestive of the fact that H. pinnae is not host specific for P. nobilis, as it was initially hypothesized (Catanese et al, 2018), and that this pathogen was already present in the Mediterranean basin years earlier the start of Mass Mortality Event (MME), at least since 2014 (Scarpa & Sanna et al, 2020)
Summary
A white flag in the Mediterranean Sea? Biological traits of the threatened to extinction Pinna nobilisThe species Pinna nobilis (Linnaeus 1758), known as fan mussel or noble pen shell (Fig. 1) is a bivalve belonging to the order Ostreoida Fërussac 1822, and the family Pinnidae Leach 1819.Pinna nobilis represents the largest bivalve populating the Mediterranean Sea (Rabaoui et al, 2008), and one of the largest in the world since it can exceed one meter of total length (Zavodnik et al, 1991). A low number of studies investigated the genetic structure of P. nobilis before its mass mortality and all were consistent in evidencing a very good health for populations throughout the whole Mediterranean, pointing out high levels of genetic variability and good genetic connectivity among areas.
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