Breeding for QX disease resistance negatively selects one form of the defensive enzyme, phenoloxidase, in Sydney rock oysters

Reduced salinity, but not estuarine acidification, is a cause of immune-suppression in the Sydney rock oyster Saccostrea glomerata

“…This is consistent with previous studies linking hyposalinity with reduced immune function. Extensive research has implicated the involvement of the phenoloxidase enzyme in the survival of S. glomerata during M. sydneyi infection (Newton et al 2004, Bezemer et al 2006, Butt & Raftos 2008, and inhibition of the phenoloxidase enzyme has been observed in S. glomerata during the QX-disease risk period (Peters & Raftos 2003, Butt & Raftos 2007. A drop in salinity from 34 to 13.5 ppt for 12 d or longer has been linked with inhibition of the phenoloxidase enzyme .…”

Elucidating the life cycle of Marteilia sydneyi, the aetiological agent of QX disease in the Sydney rock oyster (Saccostrea glomerata)

“…Studies on the mechanism of resistance developed through the SRO selective breeding program conducted by the NSW DPI (see Nell and Perkins (2006)) implicates one form of the defensive enzyme, phenyloxidase, as being negatively selected in resistant lines (Bezemer et al, 2006). Furthermore, resistant lines have now been shown to have higher phagocytic and phenyloxidase activity, a greater number of circulating haemocytes, and a higher percentage of granulocytes than wild-type oysters (Butt and Raftos, 2008;Kuchel et al, 2010;Dang et al, 2011).…”

“…As a consequence of the significant impact the disease may have during outbreaks (i.e. ≥ 95% mortality; (Bezemer et al, 2006)), control measures typically require quarantining entire estuaries in order to restrict the movement of infected stock. In the absence of data on transmission and the causative elements that promote these outbreaks, this has been the most conservative course of action and, until recently, the only management tool available to protect the SRO industry.…”

“…In the absence of data on transmission and the causative elements that promote these outbreaks, this has been the most conservative course of action and, until recently, the only management tool available to protect the SRO industry. However, with reports indicating that M. sydneyi is present in most estuaries in which major SRO culture is undertaken (Adlard and Wesche, 2005), even though many have never suffered significant disease events, research has turned to investigating the contribution of oyster immuno-competence to disease inhibition (Bezemer et al, 2006;Butt and Raftos, 2008;Green et al, 2009;Dang et al, 2011), the production of QX disease-resistant oysters (Nell et al, 2000;Nell, 2001;Green et al, 2008) and disease resistance biomarkers (Simonian et al, 2009). …”

Disease Prevention Strategies for QX Disease (Marteilia sydneyi) of Sydney Rock Oysters (Saccostrea glomerata)

“…Attempts to minimize these risks to the S. glomerata selective breeding program have included the use of large numbers of contributing parents per line (a minimum of 216 parent per generation and, when possible, equal number of each sex) (O'Connor & Dove 2009), periodic microsatellite diversity assessment, assessment of single-paired matings to determine the genetic contribution of individual parents, and investigation of allozyme and DNA markers for QX resistance (Newton et al 2004, Bezemer et al 2006) so that marker-assisted selection can occur independently of exposing broodstock to field infections of QX disease.…”