Some effects of experimental acidification on phenoloxidase, trypsin and lysozyme activities in freshwater crayfish (Pontastacus leptodactylus)

Levels of phenoloxidase (Po), trypsin and lysozyme activities were determined following 48 hours exposing freshwater crayfish (Pontastacus leptodactylus) weighing 59.8±3.4g to different low pH values of 6.5, 5.5, 4 and 2.5 at 20-23˚C. Significant decrease were found (P<0.01) in levels of Po and trypsin activities in crayfish haemocyte lysate supernatant (HLS) at pHs 5.5 and 4 compared to the control group (pH 8). Also, plasma lysozyme activity showed a significant increase in water with pHs of 6.5, 5.5 and 4 (P<0.01). Furthermore, measurement of calcium and magnesium concentrations in sera samples showed a significant decrease for calcium ion at pHs 5.5 and 4, while magnesium concentration was significantly decreased only at pH 4 compared to control group (P<0.05). Crayfish exposed to pH 2.5 died within 24 hours post-exposure.