Abstract
The European flat Ostrea edulis is highly susceptible to intracellular parasitic infections, particularly bonamiosis and marteiliosis. The defensive response of oyster to both bonamiosis and marteiliosis is typically mediated by hemocytes, which play a pivotal role in immune system homeostasis. In the present study, we first used a DNA-based tool in order to rapidly and specifically detect the presence of parasites in oysters from natural banks in the middle Adriatic Sea. In a second step, we used qRT-PCR to analyze the mRNA levels of a set of genes (i.e., superoxide dismutase (SOD), glutathione S-transferase (GST), metallothionein (MT), heat shock protein (HSP) 70 and 90, inhibitor of apoptosis (IAP), fas ligand (FAS), galectin (GAL) and extracellular superoxide dismutase (Ec-SOD)) expressed by hemocytes of flat oysters infected by the parasites, present singularly or in combination, compared to hemocytes from non-infected specimens. The results indicate that the presence of parasite DNA may be associated to a general upregulation of host genes related to apoptosis, detoxification and oxidative stress protection, with the exception of Ec-SOD, whose trend to a downregulation might reflect a mechanism for parasite escape before internalization.
Highlights
Ostrea edulis is the native European oyster species, with a natural range that typically includes all the Mediterranean basin
Wild populations of O. edulis have shown a decline throughout European waters most likely due to multiple factors, including combined habitat loss and degradation [3] and pathogenic diseases [4,5,6]
Most of these infectious diseases have been found to be the result of intracellular infections by protozoan parasites such as, among others, Bonamia ostreae and Marteilia refringens
Summary
Ostrea edulis is the native European oyster species, with a natural range that typically includes all the Mediterranean basin. Wild populations of O. edulis have shown a decline throughout European waters most likely due to multiple factors, including combined habitat loss and degradation [3] and pathogenic diseases [4,5,6]. Most of these infectious diseases have been found to be the result of intracellular infections by protozoan parasites such as, among others, Bonamia ostreae and Marteilia refringens. Bonamia ostreae is the causative agent of bonamiosis, a disease of oyster hemocytes, which has caused extensive mortalities among O. edulis leading to a decline in distribution range for this species [7]
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