The Implication of Vibrio Bacteria in the Winter Mortalities of the Critically Endangered Pinna nobilis

Abstract

Pinna nobilis populations, constituting the largest bivalve mollusk endemic to the Mediterranean, is characterized as critically endangered, threatened by extinction. Among the various factors proposed as etiological agents are the Haplosporidium pinnae and Mycobacterium sp. parasites. Nevertheless, devastation of the fan mussel populations is still far from clear. The current work is undertaken under a broader study aiming to evaluate the health status of Pinna nobilis population in Aegean Sea, after the mass mortalities that occurred in 2019. A significant objective was also (a) the investigation of the etiological agents of small-scale winter mortalities in the remaining populations after the devastating results of Haplosporidium pinnae and Mycobacterium sp. infections, as well as (b) the examination of the susceptibility of the identified bacterial strains in antibiotics for future laboratory experiments. Microbiological assays were used in order to detect the presence of potential bacterial pathogens in moribund animals in combination with molecular tools for their identification. Our results provide evidence that Vibrio bacterial species are directly implicated in the winter mortalities, particularly in cases where the haplosporidian parasite was absent. Additionally, this is the first report of Vibrio mediterranei and V. splendidus hosted by any bivalve on the Greek coastline.

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

“…Despite its endangered status, P. nobilis populations are highly threatened by human activities, such as illegal fishing for commercial and consumption purposes [ 6 , 7 ]. However, significant mortalities, even extinction in some cases, of P. nobilis within its natural habitats are mostly due to various pathogen infections [ 8 ]. While records of this phenomenon began in 2016, it continues to devastate the populations of fan mussels to the present day [ 9 ].…”

“…belonging to the Splendidus and Mediterranei clades were detected during mortality events in P. nobilis populations. Experimental laboratory conditions detecting the infection of P. nobilis by Vibrio spp have transformed the phenomenon of mortalities into a complicated matter [ 8 , 19 , 20 , 21 , 22 ]. Investigation of P. nobilis mortalities continued and more potential threats were implicated in the devastation of its natural populations [ 23 , 24 ].…”

A Review of the Environmental Trigger and Transmission Components for Prediction of Cholera

“…In Northern Europe and the Atlantic coast of the United States, heatwaves and warming sea temperatures (up to~1.5 • C over the past half-century) have been associated with long-term increases in abundance of certain pathogenic Vibrio spp., namely V. cholerae, V. parahaemolyticus, and V. vulnificus [21]. While it is worth noting that other Vibrio spp., such as Vibrio splendidus, express virulence factors at low temperatures [63], observed increases in Vibrio spp. abundance in Northern Europe and the US were associated with an unprecedented occurrence of environmentally acquired Vibrio infections in the human population [21].…”

Nitrogen Isotope Sclerochronology—Insights Into Coastal Environmental Conditions and Pinna nobilis Ecology

“…as the likely cause (Darriba, 2017;Catanese et al, 2018). However, further research has indicated that other pathogens, such as bacteria from the genus Mycobacterium and Vibrio, were also involved (Carella et al, 2019;Šarić et al, 2020;Scarpa et al, 2020;Lattos et al, 2021). Moreover, according to these reports, the mass mortality events were presumably caused by polymicrobial disease associated with various abiotic factors, and the pathogenesis has not yet been fully elucidated.…”