Pathophysiological Responses of Pinna nobilis Individuals Enlightens the Etiology of Mass Mortality Situation in the Mediterranean Populations

Abstract

Due to the rapid decrease of Pinna nobilis populations during the previous decades, this bivalve species, endemic in the Mediterranean Sea, is characterized as ‘critically endangered’. In addition to human pressures, various pathogen infections have resulted in extended reduction, even population extinction. While Haplosporidium pinnae is characterized as one of the major causative agents, mass mortalities have also been attributed to Mycobacterium sp. and Vibrio spp. Due to limited knowledge concerning the physiological response of infected P. nobilis specimens against various pathogens, this study’s aim was to investigate to pathophysiological response of P. nobilis individuals, originating from mortality events in the Thermaikos Gulf and Lesvos and Limnos islands (Greece), and their correlation to different potential pathogens detected in the diseased animals. In isolated tissues, several cellular stress indicators of the heat shock and immune response, apoptosis and autophagy, were examined. Despite the complexity and limitations in the study of P. nobilis mortality events, the present investigation demonstrates the cumulative negative effect of co-infection additionally with H. pinnae in comparison to the non-presence of haplosporidian parasite. In addition, impacts of global climate change affecting physiological performance and immune responses result in more vulnerable populations in infectious diseases, a phenomenon which may intensify in the future.

Are Marine Heatwaves Responsible for Mortalities of Farmed Mytilus galloprovincialis? A Pathophysiological Analysis of Marteilia Infected Mussels from Thermaikos Gulf, Greece

“…Marteliosis or ‘’Aber disease’’ has been correlated with mortalities in Greek shellfish populations in the past in M. galloprovincialis and O. edulis [ 46 , 58 ]. However, disease etiology is considered complex in the concomitant presence of microorganisms and the ongoing rapid climate changes [ 59 , 60 ]. M. refringens dynamics in Mediterranean marine bivalve species are correlated with temperature rise [ 61 ].…”

“…Although the multiplication and transmission of the parasite are triggered at temperatures above 17 °C, many studies have indicated that the parasite seems to be abundant at mature stages also when exposed to winter temperatures [ 61 , 62 , 63 ]. The presence of protozoan parasites and specifically M. refringens has been associated many times with down-regulation in the physiology and immune responses of marine bivalves [ 60 , 64 , 65 ]. Apart from the presence of pathogenic microorganisms that affect the physiology of the marine bivalves, abiotic factors also possess a key role in the physiology of the marine organisms [ 4 ].…”

Worldwide overview of reproduction, juvenile collection, spat production and cultivation of pen shells

“…13,21,22 In particular, Pinna nobilis is now a critically endangered species with severe population declines resulting from mass mortalities associated with pathogens and the effect of climate change. 23,24 Aquaculture is an alternative to reduce adverse impacts on natural pen shell populations as it contributes to conservation and sustainable production while fostering social development by producing high-quality protein for rural areas. 25 Pen shells are suitable candidates for aquaculture given the large number of Atrina and Pinna species, their global distribution, high demand and fast growth rate (the fastest among bivalves).…”

“…The above has led to a drastic decline of wild populations of various Atrina and Pinna species over the past decades 13,21,22 . In particular, Pinna nobilis is now a critically endangered species with severe population declines resulting from mass mortalities associated with pathogens and the effect of climate change 23,24 …”

How Safe to Eat Are Raw Bivalves? Host Pathogenic and Public Health Concern Microbes within Mussels, Oysters, and Clams in Greek Markets

“…For instance, recently in Greece, Vibrio spp. decimated Pinna nobilis populations, with a synergistic effect on other microorganisms as well [14][15][16][17]. In this context, protozoan or protistan parasites, such as Marteilia refringens and Bonamia ostreae, respectively, have been detected during summer temperatures, causing heavy mortalities in flat oyster O. edulis populations, limitations due to lowering physiological functions, and also mortalities in cultured mussels, M. galloprovincialis, in Thermaikos gulf, Thessaloniki [18][19][20].…”