Effects of salinity on metabolic rate and branchial expression of genes involved in ion transport and metabolism in Mozambique tilapia (Oreochromis mossambicus)

• Published in: Comparative biochemistry and physiology. Part A, Molecular & integrative physiology Vol. 178; pp. 121 - 131
• Main Authors: Zikos, Aris, Seale, Andre P., Lerner, Darren T., Grau, E. Gordon, Korsmeyer, Keith E.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.12.2014
• Subjects: Animals; Aquaculture; Branchial Region - enzymology; Branchial Region - growth & development; Branchial Region - physiology; COX; Electron Transport Complex IV - genetics; Electron Transport Complex IV - metabolism; Energy Metabolism; Fish Proteins - genetics; Fish Proteins - metabolism; Fresh Water; Gene Expression Regulation, Developmental; Gills - enzymology; Gills - growth & development; Gills - physiology; Glycogen Phosphorylase - genetics; Glycogen Phosphorylase - metabolism; Male; Mitochondria-rich cells; Mitochondrial biogenesis; NCC; NKCC; NRF-1; Osmolality; Osmoregulation; PGC-1α; Principal Component Analysis; Respirometry; Salinity; Seawater; Solute Carrier Family 12, Member 1 - genetics; Solute Carrier Family 12, Member 1 - metabolism; Solute Carrier Family 12, Member 3 - genetics; Solute Carrier Family 12, Member 3 - metabolism; Stress, Physiological; Tilapia - growth & development; Tilapia - physiology; Transcription Factors - genetics; Transcription Factors - metabolism; Mitochondrial biogenesis; Respirometry; NRF-1; Osmoregulation; NKCC; PGC-1α; Osmolality; COX; Mitochondria-rich cells; NCC
• ISSN: 1095-6433; 1531-4332
• DOI: 10.1016/j.cbpa.2014.08.016

This study investigated the effects of two rearing salinities, and acute salinity transfer, on the energetic costs of osmoregulation and the expression of metabolic and osmoregulatory genes in the gill of Mozambique tilapia. Using automated, intermittent-flow respirometry, measured standard metabolic rates (SMRs) of tilapia reared in seawater (SW, 130mgO2kg−1h−1) were greater than those reared in fresh water (FW, 103mgO2kg−1h−1), when normalized to a common mass of 0.05kg and at 25±1°C. Transfer from FW to 75% SW increased SMR within 18h, to levels similar to SW-reared fish, while transfer from SW to FW decreased SMR to levels similar to FW-reared fish. Branchial gene expression of Na+–K+–2Cl− cotransporter (NKCC), an indicator of SW-type mitochondria-rich (MR) cells, was positively correlated with SMR, while Na+–Cl− cotransporter (NCC), an indicator of FW-type MR cells, was negatively correlated. Principal Components Analysis also revealed that branchial expression of cytochrome c oxidase subunit IV (COX-IV), glycogen phosphorylase (GP), and a putative mitochondrial biogenesis regulator in fish, peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α), were correlated with a higher SMR, plasma osmolality, and environmental salinity, while expression of glycogen synthase (GS), PGC-1β, and nuclear respiratory factor 1 (NRF-1) had negative correlations. These results suggest that the energetic costs of osmoregulation are higher in SW than in FW, which may be related to the salinity-dependent differences in osmoregulatory mechanisms found in the gills of Mozambique tilapia.