An insight into milt antioxidant, fatty acid, amino acid composition and testis histology of an anadromous euryhaline fish Tenualosa ilisha, Ham. 1822 for its conservation and aquaculture perspectives

Abstract

Hilsa, Tenualosa ilisha, Ham. 1822, is the prime table fish and important commercial fish in the Indo-Pacific region. However, the species has recently declined drastically due to various factors. Our earlier studies recorded a significant association between the breeding season and its migration. Studies on milt and its biochemical properties are essential to ensure its successful conservation and artificial breeding. Here, milt samples of the hilsa of varied sizes were evaluated for their antioxidant property, fatty acid and amino acid content, and the histology of the testis. Analysis of milt antioxidants was done using free radicals DPPH, FRAPS & ABTS methods and compared with the free-radical quenching properties of the synthetic antioxidants. High performance liquid chromatography (HPLC) and gas chromatography and mass spectrometry (GC/MS) determined the composition of amino acids and fatty acids, respectively. The highest and lowest antioxidant activity was exhibited by hilsa milt samples M3 (b.wt 358.6 ± 0.75 g) i.e. 84.59 ± 0.48% and M12 (b.wt 168.35 ± 0.12 g) i.e. 27.53 ± 3.59%. Most notably, the antioxidant activity was found to follow a body weight gradient. Omega (ꙍ)-3 polyunsaturated fatty acids (PUFAs), docosahexaenoic acid (C22:6, DHA) and eicosapentaenoic acid (C20:5, EPA) were the predominant PUFAs and among the amino acids, arginine (0.70 g/100 g) was present in the highest quantity followed by glutamic acid (0.14 g/100 g) and proline (0.14 g/100 g). The histology study of the testis reveals the changes in the cells during the process of spermatogenesis. Histological images demonstrated the different stages of testis maturation of males sampled at the spawning sites. This baseline information generated is of its first kind in hilsa, a transboundary migratory fish in South Asian countries supporting conservation and artificial breeding for commercial production.