An investigation on the effects of selenium added to the diet of crayfish on the pleopodal egg and stage 1 juvenile numbers, oxidative stress and some antioxidant enzymes.

In this study, the effects of selenium added to the diets of Astacus leptodactylus at different ratios on the number of pleopodal egg and stage I juvenile, lipid peroxidation (MDA) and reduce glutathione (GSH) level, glutathione peroxidase (GSH-Px), glutathione reductase (GR), glutathione S transferase (GST), paraoxonase (PON) and arylesterase (ARE) enzyme activities in the muscle, hepatopancreas, gill and gonad tissues were investigated. In addition, selenium accumulation in muscle tissue of crayfish was examined.For this purpose, control (K), trial 1 (D1), trial 2 (D2) and trial 3 (D3) were prepared at the selenium levels of 0.3, 0.6, 0.9 and 1.2 mg/kg, respectively. The crude protein and total energy levels of experimental diets were equalized. 12 pools in 2x2x1 dimensions were used. 75 female and 25 males crayfish were stocked in each pool (totally 1200). This study was carried out in triplicate. The crayfish were fed twice in a day during 9 months.At the end of the trial, the results showed a statistically important difference in the produced number of pleopodal egg and stage I juvenile between the crayfish fed D1, D2, D3 and control diet. The best results for the number of pleopodal egg and stage I juvenile number were obtained from the crayfish fed trial 3 (D3) diet. It was followed by the crayfish fed trial 2 (D2), trial 1 (D1) and control diets, respectively.Significant differences were observed in the MDA and GSH levels, GSH-Px, GR, GST, PON and ARE enzyme activities in the muscle, hepatopancreas, gill and gonad tissues taken monthly from the crayfish. The level of MDA, a oxidative stress indicator, and the GST enzyme activity increased significantly (P < 0.05), whereas the GSH-Px, GR, PON and ARE enzyme activities and the GSH level decreased significantly (P < 0.05) in the crayfish tissues during the breeding season and incubation period. It was also found that the selenium administration decreased the MDA level and GST activity, while the GSH-Px, GR, PON and ARE enzyme activities and the GSH level increased. On the other hand, no statistically significant difference was found in the muscle selenium level of groups at the beginning between the trial (P>0.05). At the end of the trial, it was determined that the levels of selenium in the muscle of crayfish fed D1, D2 and D3 showed a statistically significant difference compared to the crayfish fed control diet (P<0.05).In conclusion, the inclusion of selenium to the diet of A.leptodactylus gives rise to a significant increase in the number of produced pleopodal egg and stage one juvenile number. In addition, it causes a significant decrease in the stress of crayfish during mating, pleopodal egg laying and pleopodal egg carrying. This situation shows that the oxidative stress in A.leptodactylus can be reduced, therefore, the reproductive efficiency of this species can be improved by adding 0.9 ? 1.2 mg selenium/kg diet to the diet.