Seasonality in Synergism with Multi-Pathogen Presence Leads to Mass Mortalities of the Highly Endangered Pinna nobilis in Greek Coastlines: A Pathophysiological Approach

Abstract

Mortalities of Pinna nobilis populations set at risk the survival of the species from many Mediterranean coastline habitats. In many cases, both Haplosporidium pinnae and Mycobacterium spp. are implicated in mass mortalities of P. nobilis populations, leading the species into extinction. In the context of the importance of these pathogens’ role in P. nobilis mortalities, the present study investigated two Greek populations of the species hosting different microbial loads (one only H. pinnae and the second both pathogens) by the means of pathophysiological markers. More specifically, the populations from Kalloni Gulf (Lesvos Island) and from Maliakos Gulf (Fthiotis), seasonally sampled, were chosen based on the host pathogens in order to investigate physiological and immunological biomarkers to assess those pathogens’ roles. In order to determine if the haplosporidian parasite possesses a major role in the mortalities or if both pathogens are involved in these phenomena, a variety of biomarkers, including apoptosis, autophagy, inflammation and heat shock response were applied. The results indicated a decreased physiological performance of individuals hosting both pathogens in comparison with those hosting only H. pinnae. Our findings provide evidence for the synergistic role of those pathogens in the mortality events, which is also enhanced by the influence of seasonality.

Histopathology and Phylogeny of the Dinoflagellate Hematodinium perezi and the Epibiotic Peritrich Ciliate Epistylis sp. Infecting the Blue Crab Callinectes sapidus in the Eastern Mediterranean

“…Global climate changes, in combination with direct impacts on marine ecosystems (temperature rise, salinity changes, ocean acidification), are key drivers in shifting the flora and fauna in ecosystems [ 6 , 34 ]. Hence, the impacts of global climate change tend to also affect the physiology of the hosts and the susceptibility of marine species in infectious diseases [ 35 , 36 , 37 , 38 , 39 ]. Elevated temperatures not only impact the host, but also promote the proliferation of pathogenic microorganisms and their seasonality pattern by prolonging their favored temperature [ 40 ].…”

“…The invasion in the inner part of the Mediterranean Sea was documented in 1949 and was attributed to ballast waters [ 14 ]. Since then, the crab has been reported to invade marine ecosystems in the Iberian Peninsula, in the Italian Peninsula, in Greece, in Turkey, and in Morocco [ 11 , 12 , 37 , 38 , 39 , 40 ]. Despite the invasive nature and the general ecological traits of the species, including early maturity, rapid growth rates, opportunist diets, and a high reproduction rate, there is a lack of knowledge of this invading species regarding its interactions with the endemic benthic communities and the negative impact of its presence in local ecosystems [ 14 , 41 ].…”