Aims: Arachidonic acid is an essential fatty acid that plays an important role in the fish reproduction process by regulating the function of the intravenous system, including the synthesis of steroid hormones. The aim of this study was to evaluate the effect of different levels of dietary arachidonic acid on calcium, thyroid hormone, and cortisol levels in vitellogenesis and maturation stages of female blue gourami (Trichopodus trichopterus).
Materials and Methods: In this applied research, 150 one-month blue gourami were distributed among 15 aquariums (3 replicates for each treatment) and fed with 5 different dietary ARA levels (0.02, 0.53, 1.05, 1.6 and 2.12% of diet) until the completion of maturation over 5 months. After they reached sexual maturity, 12 females from each treatment were selected; calcium level in plasma, cortisol concentrations in serum, and thyroid hormones, triiodothyronine (T₃) and thyroxine (T₄), were measured in ovary in both vitellogenesis and maturation stages by photometry and ELISA methods, respectively. The data were analyzed by one-way ANOVA after Kolmogorov-Smirnov test. Duncan’s multiple range test was used at 5% level for a meaningful comparison between the means. Pearson correlation coefficient was used to calculate the relationship between arachidonic levels of diet and the measured parameters. All analyses were performed by SPSS 22 software.
Findings: In the vitellogenesis stage, in the treatments with high arachidonic levels, calcium ion had the highest and cortisol hormone had the lowest levels (p<0.05). The level of cortisol in the maturation stage was higher than that of the vitellogenesis and also increased with increasing arachidonic levels. The level of T₃ in the ovaries of fish in both stages of vitellogenesis and maturation increased significantly with increasing ARA levels (p<0.05). The level of T₄ in the ovaries of the fish did not have a significant relationship with the increase in ARA levels in the vitellogenesis stage, while in the maturation stage, with increasing ARA, the amount of storage of this hormone significantly increased (p<0.05).
Conclusion: Using high levels of arachidonic in the reproduction stage can increase the level of calcium and thyroid hormones and, as a result, improve the vitellogenesis. In the maturation stage, increasing arachidonic levels up to 1.6% increases the levels of cortisol.