Changes in hemolymph glutathione status after variation in photoperiod and light-irradiance in crayfish Procambarus...

This work studied the effect of light-stressors, irradiance and photoperiod length on the status of hemolymph glutathione in two species of crayfish, Procambarus clarkii and Procambarus digueti. Adult animals of each species were submitted to two experimental approaches: (1) two batches of each species were placed under low or high light irradiant conditions of light-dark (LD) 24 h cycles of two different photoperiod lengths, one normal LD 12: 12 and one extreme LD 20:4 low and high irradiance for 10 weeks. Time-dependent light changes on hemolymph glutathione concentration were determined throughout the entire experimental period; and (2) three batches of the two species were submitted to independent treatments consisting of the same LD 12:12 cycles of high and low irradiance and 20:4 high-irradiance LD cycles. Reduced and oxidized glutathione hemolymph concentrations were determined and total glutathione was calculated. In addition midgut glutathione reductase activity in both species was determined. The two species showed different hemolymph glutathione reactivity and glutathione status for the two light parameters. Dissimilar responses of both species, as well as the rate of mortality of P. digueti represent specific differences in the metabolic responses, as well as tolerance to photo-oxidative stress produced by light. The role of glutathione in the tolerance of crayfish to photo-oxidative stress is discussed.