Molecular characterization of four innate immune genes in Tor putitora and their comparative transcriptional abundance during wild- and captive-bred ontogenetic developmental stages.

The current study was designed to characterize immune genes and compare their expression during ontogenetic developmental stages in progenies of wild-collected and captive-matured T. putitora. The full-length cDNA sequences of Tptlr2, Tpmyd88, Tpcd36, and Tpil8 were 2814, 1545, 1807, and 653 bp in length, with ORFs of 2379 bp, 855 bp, 1410 bp, and 297 bp, encoding for putative peptides of 793, 284, 469 and 98 amino acids, respectively. The predicted peptide sequences of the genes had high sequence homology and structural conservation with other teleost fishes, especially cyprinids. The expression of Tptlr2 was relatively low in both wild- and captive-bred offsprings during the early embryonic stages, but significantly increased later in development. The mRNA abundance of the Tpmyd88 gene was significantly low until the blastula stage, then increased notably from the gastrula stage to the advanced fry stage. The Tpcd36 expression elevated during later developmental stages, peaking at advanced fry stage in both. On the other hand, expression of Tpil8 was relatively low until the blastula stage and showed a moderate increase from the organogenesis stage onwards in wild-bred offsprings, whereas a significant upregulation was seen in the captive-bred offsprings from the organogenesis stage until the advanced fry stage, with its maximum expression at the pre-metamorphosis stage. Overall, the findings suggest the crucial role of Tpmyd88, Tptlr2, Tpcd36, and Tpil8 in inducing innate immunity in embryonic and larval stages of T. putitora. Further, the considerably higher expression of the immune genes in the embryonic and larval stages of captive-bred offsprings may indicate a stronger immune system.

Effect of photoperiod and temperature on indicators of immunity and wellbeing of endangered golden mahseer (Tor putitora) broodstock.

Recently, we reported the possibility of successfully inducing captive maturation and spawning in golden mahseer through photothermal manipulation. Subsequently, we felt that it was imperative to understand the impact of these environmental manipulations on immunity, stress response, antioxidant potential, and general well-being of adult mahseer to develop a healthy broodstock. For this purpose, two experiments were carried out with changes in photoperiod (experiment I) and temperature (experiment II). In experiment I, random groups of adult female and male Tor putitora were subjected to three photoperiods (8L:16D, 12L:12D and 16L:8D) for 100 days. Decreasing levels of plasma melatonin with increasing photoperiod confirmed the physiological significance of different light-dark conditions in mahseer brooders. In terms of stress, plasma cortisol levels showed a linear increase with decreasing light duration in both males and females. Similarly, the level of thiobarbituric acid reactive substances was also significantly higher in males kept at 8L:16D. Plasma concentration of total immunoglobulins was found reduced in female brooders at 8L:16D, but this was not evident in males. In females, total antioxidants were found significantly elevated at 12L:12D. On the contrary, superoxide dismutase activity was lower at 12L:12D in females. The photoperiod has substantially influenced the plasma total protein and albumin levels in males. In experiment II, random groups of adult T. putitora were reared at ambient (21.2 ± 1.4 °C) or elevated temperature (23.7 ± 1.3 °C) groups for 121 days. The higher temperature was found to significantly decrease lysozyme, myeloperoxidase, and anti-protease activities in female mahseer brooders. However, total immunoglobulin levels were reduced significantly at elevated temperature both in males and females. No other temperature-related significant changes were observed in antioxidant potential, anti-oxidative enzymes or well-being related indices.

Reproductive dysfunction in females of endangered golden mahseer (Tor putitora) in captivity.

The present study was undertaken to gain insight on the physiological basis underlying the constraints in attaining maturity of endangered golden mahseer (Tor putitora) in captivity. Selected hormone levels and stress biomarkers were analysed in wild and captive reared brooders to address the above objectives. As compared to their captive counterparts, plasma 17ß-estradiol was significantly (p<0.05) higher in wild caught females. A concurrent trend was observed for plasma vitellogenin, aromatase, 17α, 20ß-dihydroxy progesterone (17α, 20ß DHP), luteinizing hormone (LH) and11-ketotestosterone (11-KT) indicating a weak hormone response in captive females that potentially hindered maturity. To the contrary, the plasma11-KT levels were not significantly different between wild and captive males. Plasma 17α, 20ß DHP level was found significantly (p<0.05) higher in wild caught females compared to females reared in captivity. However, both males of wild and captivity registered significantly higher 17α, 20ß DHP than captive females. Plasma 11-KT level was significantly higher in males compared to females. However, the captive females had higher level of 11-KT than captive males. Stress biomarkers viz., cortisol, superoxide dismutase (SOD) and glutathione peroxidase (GPx) were also estimated both in wild and captive brooders. There was no significant difference in plasma cortisol levels of wild and captive reared brooders. However, plasma GPx and SOD activity were significantly higher in captive reared T. putitora as compared to wild brooders counterpart manifesting prevailing oxidative stress in captivity. Overall results showed endocrine and stress differences between wild and captive reared brood fishes during early spawning period which highlighted the endocrine failure of female reproductive maturity in captivity.