EFFECT OF VARIATION IN PHOTOPERIOD AND LIGHT-INTENSITY ON OXYGEN-CONSUMPTION, LACTATE CONCENTRATION AND BEHAVIOR IN CRAYFISH PROCAMBARUS-CLARKII AND PROCAMBARUS-DIGUETI

The effects of light intensity and duration on metabolic and behaviora l parameters of two species of crayfish, Procambarus clarkii and Proca mbarus digueti, were studied. Sixty animals of each species were submi tted to high irradiance conditions of two different photoperiod length s, one normal light/dark (LD) 12:12 and one extreme LD 20:4 for 2 week s. Hemolymph, lactate and oxygen consumption were determined throughou t the experimental period. Simultaneously in 18 additional animals of each species, motor activity was individually recorded under the same control and experimental conditions. Both species showed a decrease in oxygen uptake and an increase in hemolymph lactate concentration. The statistical significance of this finding was higher for LD 20:4. This extreme condition evoked a significant decrease of motor activity in P. clarkii and a high mortality rate in P, digueti. P. digueti did not survive after the experiment, whereas P. clarkii survived and adapted to the laboratory conditions. Changes in metabolic and behavioral par ameters could indicate different adaptation abilities in these species . (C) 1998 Elsevier Science Inc.