Effect of starvation on biological factors related to immunological defence in the Sydney rock oyster (Saccostrea glomerata)

The effects of starvation on various factors related to immunological defence in Sydney rock oysters (Saccostrea glomerata) were tested in controlled laboratory experiments. A range of parameters was assessed, including total haemocyte counts, and phenoloxidase (PO), superoxide, acid phosphatase and peroxidase activities. Condition indices were also monitored as an indicator of oyster fitness. We found that the frequency of haemocytes and phenoloxidase activity decreased by 25% and 14% respectively when oysters were fed half-satiation rations for three weeks. These decreases became statistically significant when oysters were starved for three weeks. Superoxide and peroxidase activities also decreased significantly when oysters were starved for two to four weeks, while phenoloxidase and acid phosphatase activities were significantly inhibited after oysters had been starved for at least three weeks. All of the immunological parameters returned to at least their original levels after starved oysters were fed to satiation for six days. Phenoloxidase activities over-compensated during the recovery response, so that levels post-recovery were substantially higher than those evident before starvation. There were no significant changes in condition indices during any of the starvation treatments. These data indicate that starvation compromises immunological activity, and that the duration and intensity of starvation differentially affect immune responses.