Resistant Capabilities of the Sterlet (Acipenser Ruthenus) In Modeling the Impact of Stress Factors in the form of Increasing the Temperature of the Aquatic Environment, Decreasing Oxygen in the Aquatic Environment and Crowding

Abstract

During the formation of resistance processes under the influence of such stress factors as a decrease in oxygen concentration and an increase in the temperature of the aquatic environment, as well as crowding in sterlet (Acipenser ruthenus), a significant change in humoral resistance and a slight change in cellular resistance (phagocytic activity of blood leukocytes) are observed.

A decrease in the amount of oxygen in the aquatic environment to 3.0 mg/l decreases the protein level in the blood serum of sterlet to 15.29±0.4 g/l, which is 37.7% (p<0.001) lower than in the control group, where the amount of oxygen in the aquatic environment was 8.3 mg/l. We noted an increase of lysozyme activity in the blood serum up to 28.87±0.58% which is 1.6 times (p <0.001) higher than in the control group, where the amount of oxygen in the aqueous was 8.3 mg/l. It was found that in the group where the amount of oxygen in the aquatic environment was 3.0 mg/l, the index of phagocytic activity of leukocytes was 21.24 ± 0.45% (p>0.05). The cortisol level was 223.33±2.18 nmol/l, which is 3.4 times (p <0.001) higher than in the control group, in which the amount of oxygen in the aqueous was 8.3 mg/l.

An increase in the temperature of the aquatic environment by more than 15 oC decreases the level of total serum protein after 3 hours to 17.5 ± 0.3 g/l, which is 30.5% (p <0.001) less than in the control group, in which this indicator is 25.31 ± 0.38 g/l. After 12 h, this indicator in the experimental group remains consistently lower and is 19.44 ± 0.29 g/l (in the control group 23.42 ± 0.36 g/l). An increase in the temperature of the aqueous medium leads after 3 hours to an increase in the activity level of serum lysozyme by 2.3 times (p <0.001) compared with the control group, in which this indicator is 16.65 ± 0.51%. After 12 hours, this indicator decreases, but remains 1.5 times higher than in the control group (17.31 ± 0.46%). An increase in the temperature of the aqueous medium does not have a significant effect on the level of phagocytic activity of blood leukocytes. An increase in the temperature of the aquatic environment by more than 15 oC increases the level of cortisol in the blood serum of sterlet. In the experimental group, this indicator after 3 hours was 223.67 ± 2.22 nmol/l, which is 3.9 times (p <0.001) higher than in the control group (58.33 ± 0.84 nmol/l). It remains at a high level after 12 hours and is 145.67 ± 2.16 nmol/l, in the control group 55.0 ± 0.77 nmol/l.

The study of crowding influence demonstrated that the level of total serum protein of sterlet in the group with a stoking density 25 fish/0,04 m3 by 39.6% (p <0.001) less than that in the control group (25.37 ± 0.35 g/l). Lysozyme activity of blood serum was 1.9 times higher (p <0.001) compared to the control group (15.32 ± 0.35). The results of experimental studies showed that the level of phagocytic activity of sterlet leukocytes in the group with a stocking density of 25 fish/0.04 m3 was 26.47 ± 0.5%, in the group with a stocking density of 5 fish/0.04 m3 - 24.27 ± 0.59% (p>0.05). The results of experimental studies showed that the serum cortisol index of sturgeon fish of the experimental group at a fish density of 25 fish/0,04 m3 was 213.8±2.06 (p<0.001) nmol/l, which is 3.1 times higher than in the control group. the group in which this indicator was 69.67 ± 1.13 nmol/l.