Oxidative Stress in the Symbiotic Sea Anemone Aiptasia pulchella (Carlgren, 1943): Contribution of the Animal to Superoxide Ion Production at Elevated Temperature.

Production of superoxide ions within tissues of the symbiotic sea anemone Aiptasia pulchella was detected using SOD-inhibitable cytochrome c reduction and quantified by SOD-inhibitable reduction of nitro blue tetrazolium (NBT). Intact aposymbiotic and symbiotic specimens of A. pulchella produced superoxide in response to acute, sublethal thermal stress. Neither light nor inhibition of symbiont photosynthesis by (3,4-di-chlorophenyl) -1, 1-dimethylurea (DCMU) affected superoxide production. The time course of superoxide ion production strongly resembled the time course of increased dark respiration by intact anemones, suggesting that the effect of elevated temperature on host mitochondria may account for increased superoxide production. Interestingly, freshly isolated algae (FIZ) did not release superoxide ions in response to elevated temperature, and net oxygen production decreased greatly in both intact symbiotic anemones and in FIZ within 20 minutes after temperature elevation. These results show that oxidative stress in A. pulchella is primarily an animal response, and suggest that the presence of symbiotic algae, although sufficient to cause hyperoxia, is not necessary for the appearance of oxidative stress in these anemones at elevated temperature.