Field Performance and QPX Disease Progress in Cultured and Wild-Type Strains ofMercenaria mercenariain New York Waters

Differential immune response in the hard clam (mercenaria mercenaria) against bacteria and the protistan pathogen QPX (quahog parasite unknown)

“…Similarly, phagocytosis activity, protein concentration in plasma and anti-QPX activity were lower in FL-c clams compared to NY-c clams. Similar observations of lower immune performances in FL clams, particularly with regard to anti-QPX activity, were also made in previous studies [26,34] and could be related to the susceptibility of this broodstock compared to NY clams [23,30]. La Peyre et al [56] compared defense parameters in the closelyrelated oysters C. virginica and C. gigas and found lower proportions of granulocytes and associated phagocytosis in C. virginica.…”

“…Ragone Calvo [24] suggested that both host genotype and environmental parameters were important determinants in clam susceptibility to QPX disease and the impact of genetic variation on overall performance of geographically different hard clam populations was previously demonstrated [55]. Therefore, two different clam broodstocks that were previously shown to display different susceptibility toward QPX disease [23,30] were used in this study with one batch of QPX-susceptible clams from Florida and another of resistant clams from New York.…”

“…We have been successfully using these aquacultured clam lines for comparative studies because of their confirmed differential susceptibility to QPX infections in laboratory settings [23,26] and in the field [30]. A sub-sample (30 clams/stock) was checked for pre-established QPX infections before the initiation of the experiment using standard histopathology techniques [25] and all tested clams were negative.…”

“…These tissues were chosen because they are involved in QPX pathology [25,30] and because they were shown to consistently express targeted genes (metallothionein and ferritin). For instance, our preliminary studies compared transcription levels of these genes in hemocytes, gills, mantle, foot and visceral tissues individually processed from 4 unchallenged NY clams (see result Section 3.3).…”

Effects of temperature on hard clam (Mercenaria mercenaria) immunity and QPX (Quahog Parasite Unknown) disease development: II. Defense parameters

“…Three groups composed of 18 tanks each (six controls FL [FL-c], six QPX-challenged FL [FL-q] and 6 MA [MA]) were exposed to 13, 21 or 27°C. These temperatures represent the range observed in New York clamming waters between spring and fall (Dahl et al, 2010) and have been shown to differentially affect the in vitro performance of QPX (Perrigault et al, 2010). Temperature adjustments (13 and 27°C) were performed within 8 days in water baths equipped with electronically-controlled heaters and chillers by increasing or decreasing the temperature by 1°C per day according to each treatment.…”