Forcing host-pathogen interactions in C. gigas and M. galloprovincialis transplanted into the Goro lagoon (North Adriatic Sea, Italy)

Located south of the Po River Delta, the lagoon of Goro is one of the main clam farming areas in Italy and has been object of previous investigations. C. gigas is naturally present beyond the Scanno di Goro (off-shore) and has been reported inside the lagoon. In 2010, French oyster seed deployed locally resulted positive to OsHV-1 μVar, though no evidence of oyster mortality was recorded. For the monitoring purposes, juvenile native mussels and oysters obtained from French seed have been allowed to grow close, in sectors of baskets suspended in the lagoon water, hence more likely affected by potential pathogens and parasites. Bivalve mortality rates as well as biological and environmental parameters were monitored at each sampling. According to previous inter-laboratory calibration exercises, molecular and histological methods have been applied to the detection of OsHV-1 μVar and other typical pathogens. The presence of Vibrio splendidus and V. aestuarianus was analyzed in the bivalve flesh by culture-dependent and molecular assays. To better understand the effects of biotic and abiotic factors on the host defense mechanisms, selected paired sets of oyster and mussel tissues have been processed to purify the total RNA and perform comparative gene expression studies via advanced transcriptome sequencing (Illumina). The resulting output reads from both oysters and mussels have been re-assembled together with pre-existing sequence data in order to obtain a more comprehensive view of the species-specific transcriptomes.