Enhance energy supply of largemouth bass (Micropterus salmoides) in gills during acute hypoxia exposure

Abstract

Gills are the location of gas exchange and also the rst target organ of sh response for environmental stress. As a multifunctional organ, its energy supply, when faced with insu cient dissolved oxygen in the water, remain unclear. In this study, largemouth bass were subjected to hypoxia stress (1.2 mg/L) for 24 h and 12 h reoxygenation (R12) to evaluate energy supply strategy of gills. Under hypoxia, gills respond rstly and rapidly by increasing respiratory rate and changing gene expression. Transcriptome data showed that 2026 differential expressed genes (DGEs) were detected in the early stage of hypoxia exposure, including genes related to oxygen sensor and transport. KEGG functional analysis of DEGs revealed that the glycolysis/gluconeogenesis pathway was enriched across all the sampling points (0, 4, 8, 12, 24h, R12). The gene expression and enzyme activity of three rate-limiting enzymes (hexokinase, phosphofructokinase-6, pyruvate kinase) in glycolysis pathway were signi cantly increased. The increase of glycolysis products pyruvate and lactic acid, as well as the number of mitochondria, suggest the enhancement of aerobic and anaerobic metabolism of glucose. These results suggest that gill of largemouth bass enhanced energy supply during acute exposure to hypoxia stress.

Mechanisms of acclimation to chronic intermittent hypoxia in the gills of Largemouth bass (Micropterus salmoides)

“…This strategy has been documented in more than a dozen sh species from several different orders, but some sh species do not have this ability (Gilmour and Perry, 2018). In this study, we found that hypoxia was able to induce gill remodeling in largemouth bass, which is consistent with our previous study (Liu et al, 2022). Moreover, the longer daily exposure of sh to hypoxia, the more dramatic the gill remodeling was.…”

“…The signi cantly up-regulation mRNA expression levels of numerous genes (fba, pgam1, pepck, atp-pfk, pfk-2, g6pi, gapd-1 and pk) involved in glycolysis signaling indicates that glycolysis was enhanced. Enhanced glycolysis in gills of largemouth bass was also observed under acute hypoxia exposure (Liu et al, 2022). Glycolysis not only produces ATP but also generates pyruvate, which can enter the mitochondria and produce more ATP (Knox et al, 1980).…”

Are the effects of catch-and-release angling evident in changes to mRNA abundances related to metabolism, acid–base regulation and stress in lake trout (Salvelinus namaycush) gills?

“…A brief, 180 s, air exposure also yielded mostly insignificant impacts on the mRNA abundances of metabolic genes in the livers of rainbow trout ( Oncorhynchus mykiss ) and brook trout ( Salvelinus fontinalis ) ( Ikert et al, 2021 ). Conversely, studies that have found significant changes in glycolytic genes and TCA cycle associated genes in the gills of largemouth bass ( Micropterus salmoides ) ( Liu et al, 2022 ) and yellow croaker ( Larimichthys crocea ) ( Mu et al, 2020 ) exposed to hypoxia for at least 10 min. Exhaustive exercise should also impact metabolism, where increases in anaerobic metabolism have been observed in strenuously exercised rainbow trout ( Wiseman et al, 2007 ; Lopez-Patino et al, 2014 ).…”

“…We chose these targets based on their rapid induction in response to stressors similar to C&R angling (e.g. Liu et al, 2022 ; Beemelmanns et al, 2021 ; Sun et al, 2021 ; Zarantoniello et al, 2021 ; Esbaugh et al, 2012 ; Georgalis et al, 2006 ). We developed primer sets ( Table 1 ) for each target and three reference genes using data available from GenBank (National Center for Biotechnology Information; NCBI) via Primer 3 Plus version 3.2.6 ( Untergasser et al, 2012 ), Primer Express 3.0.1 (Applied Biosystems, ThermoFisher Scientific) and Geneious Prime (Dotmatics, Boston, MA, USA).…”

“…As an intermediate between DNA and protein, quantifying mRNA abundance serves as a proxy for changes in gene expression. Although a transcript-level approach has not yet been used to study the effects of C&R angling in fish, this approach has successfully been used to evaluate the effects of a wide variety of other stressors on fishes, including exercise to exhaustion ( Wiseman et al, 2007 ), hypoxia ( Khansari et al, 2018 ; Mu et al, 2020 ; Ikert et al, 2021 ; Liu et al, 2022 ), hypercapnia ( Edwards et al, 2005 ; Georgalis et al, 2006 ), heat exposure ( Quinn et al, 2011 ; Sun et al, 2021 ) and a combined exhaustive exercise and air exposure stressor which simulated angling ( Donaldson et al, 2014 ). It is possible that C&R angling will produce similar cellular responses as the stressors listed above.…”