Contents lists available at ScienceDirect Journal of Thermal Biology journal homepage: www.elsevier.com/locate/jtherbio Dietary nano-silver: Does support or discourage thermal tolerance and biochemical status in air-breathing fish reared under multiple stressors? Neeraj Kumar a, ⁎ , K.K. Krishnani a , Paritosh Kumar a , Rupam Sharma b , Raju Baitha c , Dilip Kumar Singh d , Narendra Pratap Singh a a ICAR-National Institute of Abiotic Stress Management (NIASM), Baramati, Pune 413115, India b ICAR-Central Institute of Fisheries Education, Versova, Mumbai 400061, India c ICAR-Central Inland Fisheries Research Institute, Barrackpore, Kolkata 700120, India d ICAR-Central Institute of Fisheries Education, Salt Lake City, Kolkata Center, Kolkata 700091, India ARTICLE INFO Keywords: Silver nanoparticles Thermal tolerance Stress biomarkers Abiotic stress Channa striatus ABSTRACT Unexpected fluctuations in weather parameters due to global climate change have been observed in all eco- systems worldwide. The aquatic ecosystem shelters a great diversity of fishes in the upper region of the eco- system which adversely get affected due to their poikilothermic nature. The present study was designed to elucidate the impact of critical temperature minima (CTMin), lethal temperature minima (LTMin), critical temperature maxima (CTMax), and lethal temperature maxima (LTMax) on Channa striatus. Biologically syn- thesized silver nanoparticles (Ag-NPs) were evaluated for their potential to enhance thermal tolerance and improve the activities of biochemical enzymes of C. striatus reared under lead (Pb) and high temperature (34 °C) for 50 days. Three iso-caloric and iso-nitrogenous diets which included a basal diet and two supplemented diets with Ag-NPs @ 0.5 mg/kg, and 1 mg/kg were used in the study. Results suggested that CTMin and LTMin were significantly (p < 0.01) reduced and CTMax and LTMax were enhanced in the group fed with 0.5 mg/kg Ag-NPs supplemented feed. Pre-exposure to high temperature led to enhanced CTMax and LTMax in C. striatus. The biochemical enzymes involved in protein metabolism, carbohydrate metabolism, acetylcholine esterase and antioxidant activities were found to be normal in fish fed with 0.5 mg/kg Ag-NPs supplemented diet. Bioaccumulation of silver and Pb was determined in different fish tissues and experimental water. Overall, the incorporation of Ag-NPs at 0.5 mg/kg in diet can confer protection to fish against Pb and thermal stress and enhance thermal tolerance of C. striatus. 1. Introduction The world has witnessed enormous changes in low and high tem- peratures due to as a result of global climate change. The sudden change of climate observed throughout the year irrespective of the season in all the continents, is a serious concern with respect to aquatic animals. The global warming is a strong precursor of vulnerability to heavy metals, pesticide residue and household chemicals in fish, wild- life and, also humans (Lovett, 2009). The complex interactions between chemicals due to the climate change might be making chemicals more toxic and the environment more susceptible to damage (Lovett, 2009). The global climate change affects all the living organism including fish, which are more vulnerable due to their ectothermic nature. Fish growth development, ontogenesis and metabolism also depend on the thermal regime and change in the ambient temperature lead to a shift in the metabolic regulation system (Goncealves et al., 2010; Deutsch et al., 2015). Generally, temperature fluctuations go beyond optimal condi- tions in case of thermal stress condition (Axenov-Gribanov et al., 2016). The biochemical pathway attributes are major indicators of the ability of ectotherms to acclimate to a new stable state and are recognised as the key processes by which organisms will, or will not cope with cli- mate warming (Portner, 2002a; Calosi et al., 2008; Peck et al., 2010; Morley. et al., 2012). The thermal tolerance of animals including fish involve s the physiological and biochemical mechanisms responsible for thermal acclimation and any alterations in these may interfere with biochemical pathways in which can affect whole animal performance (Morley. et al., 2012). Under such condition, the limited capacity to provide oxygen to tissue and cover temperature-dependent oxygen demand initiates thermal limitation (Tripp-Valdeza et al., 2017). When temperature crosses the optimal range, the cardio-ventilatory capacity https://doi.org/10.1016/j.jtherbio.2018.08.011 Received 15 February 2018; Received in revised form 25 July 2018; Accepted 18 August 2018 ⁎ Corresponding author. E-mail address: neeraj_journal@live.in (N. Kumar). Journal of Thermal Biology 77 (2018) 111–121 Available online 20 August 2018 0306-4565/ © 2018 Elsevier Ltd. All rights reserved. T