Effect of acclimatization on hemocyte functional characteristics of the Pacific oyster ( Crassostrea gigas) and carpet shell clam ( Ruditapes decussatus)

• Published in: Fish & shellfish immunology 2011-12, Vol.31 (6), p.978-984
• Main Authors: Hurtado, Miguel Ángel, Mirella da Silva, Patricia, Le Goïc, Nelly, Palacios, Elena, Soudant, Philippe
• Format: Article
• Language: English
• Subjects: Acclimatization - physiology; Animals; Bivalve; Bivalvia - cytology; Bivalvia - physiology; Blood Cell Count - veterinary; Cellular immunity; Crassostrea - cytology; Crassostrea - physiology; Crassostrea gigas; Environmental Sciences; Flow Cytometry; Hemocytes - chemistry; Hemocytes - physiology; Marine; Mollusca; Phagocytosis; Phagocytosis - physiology; Reactive Oxygen Species - metabolism; ROS production; Ruditapes decussatus; Species Specificity
• ISSN: 1050-4648; 1095-9947
• DOI: 10.1016/j.fsi.2011.08.016

Most experimental procedures on molluscs are done after acclimatization of wild animals to lab conditions. Similarly, short-term acclimation is often unavoidable in a field survey when biological analysis cannot be done within the day of sample collection. However, acclimatization can affect the general physiological condition and particularly the immune cell responses of molluscs. Our aim was to study the changes in the hemocyte characteristics of the Pacific oyster Crassostrea gigas and the carpet shell clam Ruditapes decussatus acclimated 1 or 2 days under emersed conditions at 14 ± 1 °C and for 1, 2, 7, or 10 days to flowing seawater conditions (submerged) at 9 ± 1 °C, when compared to hemolymph withdrawn from organisms sampled in the field and immediately analyzed in the laboratory (unacclimated). The hemocyte characteristics assessed by flow cytometry were the total (THC) and differential hemocyte count, percentage of dead cells, phagocytosis, and reactive oxygen species (ROS) production. Dead hemocytes were lower in oysters acclimated both in emersed and submerged conditions (1%–5%) compared to those sampled in the field (7%). Compared to oysters, the percentage of dead hemocytes was lower in clams (0.4% vs. 1.1%) and showed a tendency to decrease during acclimatization in both emersed and submerged conditions. In comparison to organisms not acclimated, the phagocytosis of hemocytes decreased in both oysters and clams acclimated under submerged conditions, but was similar in those acclimated in emersed conditions. The ROS production remained stable in both oysters and clams acclimated in emersed conditions, whereas in submerged conditions ROS production did not change in both the hyalinocytes and granulocytes of oysters, but increased in clams. In oysters, the THC decreased when they were acclimated 1 and 2 days in submerged conditions and was mainly caused by a decrease in granulocytes, but the decrease in THC in oysters acclimated 2 days in emersed conditions was caused by a decrease in hyalinocytes and small agranular cells. In clams, the THC was significantly lower in comparison to those not acclimated, regardless of the conditions of the acclimatization. These findings demonstrate that hemocyte characteristics were differentially affected in both species by the tested conditions of acclimatization. The phagocytosis and ROS production in clams and phagocytosis in oysters were not different in those acclimated for 1 day under both conditions, i.e