Digestive protease activity in juvenile Farfantepenaeus californiensis as a function of dissolved oxygen and temperature

Total protease, trypsin and chymotrypsin activities were examined in postlarval Farfantepenaeus californiensis (Holmes) after they had been reared for 50 days at two dissolved oxygen concentrations (5.8 and 2.6 mg L^-1) and three temperatures (19, 23 and 27°C). Three replicated experiments were performed with a 12-h light/dark photoperiod. Two-way analysis of variance indicated a significant effect of temperature and oxygen (P < 0.05) on total protease and chymotrypsin activities, but no effect of oxygen was found on trypsin activity. A tendency towards increased protease, trypsin and chymotrypsin activities with acclimation temperature was observed. Total protease activity (units per mg protein) varied from 0.26 in shrimp held at 19°C and low oxygen concentration to 1.41 in shrimp held at 23°C and high oxygen concentration. Trypsin activity (units per mg protein) varied from 0.16 in shrimp held at 19°C and low oxygen concentration to 0.86 in shrimp held at 27°C and high oxygen concentration. Chymotrypsin activity (units per mg protein) varied from 0.014 in shrimp held at 19°C and low oxygen concentration to 0.15 (units per mg protein) in shrimp held at 27°C and low oxygen concentration. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) zymograms of hepatopancreas from each of the treatment groups showed numerous bands. The results suggest that different digestive protease enzymes arise as an adaptation mechanism to temperature and dissolved oxygen variations at this particular stage of life.