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Temperature is a key environmental factor, and understanding how its fluctuations affect physiological and metabolic processes is critical for fish. The present study characterizes the energy response and fatty acid metabolism in Onychostoma macrolepis exposed to low temperature (10 °C). The results demonstrated that cold stress remarkably disrupted the energy homeostasis of O. macrolepis, then the AMP-activated protein kinase (AMPK) could strategically mobilize carbohydrates and lipids. In particular, when the O. macrolepis were faced with cold stress, the lipolysis was stimulated along with the enhanced fatty acid β-oxidation for energy, while the fatty acid synthesis was supressed in the early stage. Additionally, the fatty acid composition analysis suggested that saturated fatty acid (SFA) might accumulate while monounsaturated fatty acid (MUFA) and polyunsaturated fatty acid (PUFA) in storage lipids (mainly containing non-polar lipid, NPL) could be utilized to supply energy during cold acclimation. Altogether, this study may provide some meritorious for understanding the cold-tolerant mechanism of fish in the viewpoint of energy balance combined with fatty acid metabolism, and thus to contribute to this species rearing in fish farms in the future., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

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., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Interleukin (IL)-23 is a heterodimeric IL-12 family cytokine composed of a p19 α-chain, linked to a p40 β-chain that is shared with IL-12. IL-23 is distinguished functionally from IL-12 by its ability to induce the production of IL-17, and differentiation of Th17 cells in mammals. Three isoforms of p40 (p40a, p40b and p40c) have been found in some 3R teleosts. Salmonids also possess three p40 isoforms (p40b1, p40b2 and p40c) although p40a is missing, and two copies (paralogues) of p40b are present that have presumably been retained following the 4R duplication in this fish lineage. Teleost p19 has been discovered recently in zebrafish, but to date there is limited information on expression and modulation of this molecule. In this report we have cloned two p19 paralogues (p19a and p19b) in salmonids, suggesting that a salmonid can possess six potential IL-23 isoforms. Whilst Atlantic salmon has two active p19 genes, the rainbow trout p19b gene may have been pseudogenized. The salmonid p19 translations share moderate identities (22.8-29.9%) to zebrafish and mammalian p19 molecules, but their identity was supported by structural features, a conserved 4 exon/3 intron gene organisation, and phylogenetic tree analysis. The active salmonid p19 genes are highly expressed in blood and gonad. Bacterial (Yersinia ruckeri) and viral infection in rainbow trout induces the expression of p19a, suggesting pathogen-specific induction of IL-23 isoforms. Trout p19a expression was also induced by PAMPs (poly IC and peptidoglycan) and the proinflammatory cytokine IL-1β in primary head kidney macrophages. These data may indicate diverse functional roles of trout IL-23 isoforms in regulating the immune response in fish., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Puffer fish saxitoxin and tetrodotoxin binding protein (PSTBP) is a glycoprotein (200 kDa as a dimer) that we previously isolated from the plasma of Fugu pardalis (Yotsu-Yamashita et al., 2001). For the study on functions of PSTBP, here we examined distribution of homologous proteins to PSTBP in the plasma of seven species of puffer fish, and among the tissues of F. pardalis by Western blot analysis probed with a polyclonal IgG against unglycosylated PSTBP1 expressed in Echelichia coli. One or two major positive broad bands were detected at 105-140 kDa molecular weight range in the plasma (0.5 microg protein) of all species of puffer fish tested, while no band was detected in the plasma (5 microg protein) of fish other than puffer fish. Glycopeptidase F treated plasma of all species of puffer fish tested commonly showed the bands at approximately 42 kDa that was consistent to the molecular weight of unglycosylated PSTBP. These data suggest that puffer fish commonly possess glycoproteins homologous to PSTBP, but the sizes of N-glycan are specific to the species. Among soluble protein extracts (5 microg protein) from the tissues of F. pardalis, PSTBP was detected in all tissues examined, most prominently in heart, skin, and gall., (Copyright 2009 Elsevier Ltd. All rights reserved.)