Evidence and characterization of lysozyme in six species of freshwater crayfishes from astacidae and cambaridae families

1. 1. A lysozyme activity was found in four Astacidae and two Cambaridae species. 2. 2. Tested on Micrococcus luteus cell wall, the reaction was stable when heated in acidic buffer but heat labile in an alkaline one. 3. 3. The activity is present in serum, hemocyte lysate and plasma. 4. 4. In serum, the lysis occurred within the first 15 min; the less active was the plasma. 5. 5. In the six species, the kinetics followed the same pattern. 6. 6. Different animals of the same species exhibited a great variability in lysozyme activity: 32–53.8% of lysis after 1 hr in serum, 7–31.7% in plasma, and 20–50.3% in hemocyte lysate. 7. 7. Different stresses weakening the animals lowered the response to less than 25% of lysis after 1 hr instead of 60–86% in serum or 38–72% in hemocyte lysate. 8. 8. The lysozyme molecules seemed to be located in hemocytes and released during experimental cell lysate or in vitro coagulation. 9. 9. Plasma reaction could represent the background of the hemolymph activity occurring in natural conditions.