title: Effects of salinity on metabolic rate and branchial expression of genes involved in ion transport and metabolism in Mozambique tilapia (Oreochromis mossambicus).
abstract: 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, 130 mg O₂ kg⁻¹ h⁻¹) were greater than those reared in fresh water (FW, 103 mg O₂ kg⁻¹ h⁻¹), when normalized to a common mass of 0.05 kg 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.
authors.affiliation: Department of Natural Sciences, Hawai'i Pacific University, Kāne'ohe, HI 96744, USA.
authors.forename: Aris
authors.initials: A
authors.lastname: Zikos
authors.affiliation: Hawai'i Institute of Marine Biology, University of Hawai'i, Kāne'ohe, HI 96744, USA.
authors.forename: Andre P
authors.initials: AP
authors.lastname: Seale
authors.affiliation: Hawai'i Institute of Marine Biology, University of Hawai'i, Kāne'ohe, HI 96744, USA; University of Hawai'i Sea Grant College Program, University of Hawai'i, Honolulu, HI 96822, USA.
authors.forename: Darren T
authors.initials: DT
authors.lastname: Lerner
authors.affiliation: Hawai'i Institute of Marine Biology, University of Hawai'i, Kāne'ohe, HI 96744, USA.
authors.forename: E Gordon
authors.initials: EG
authors.lastname: Grau
authors.affiliation: Department of Natural Sciences, Hawai'i Pacific University, Kāne'ohe, HI 96744, USA. Electronic address: kkorsmeyer@hpu.edu.
authors.forename: Keith E
authors.initials: KE
authors.lastname: Korsmeyer
mesh_terms: D000818:Animals; D017756:Aquaculture; D001934:Branchial Region / Q000201:enzymology / Q000254:growth & development / Q000502:physiology*; D003576:Electron Transport Complex IV / Q000235:genetics / Q000378:metabolism; D004734:Energy Metabolism; D029941:Fish Proteins / Q000235:genetics / Q000378:metabolism; D005618:Fresh Water; D018507:Gene Expression Regulation, Developmental; D005880:Gills / Q000201:enzymology / Q000254:growth & development / Q000502:physiology; D024981:Glycogen Phosphorylase / Q000235:genetics / Q000378:metabolism; D008297:Male; D064587:Osmoregulation; D025341:Principal Component Analysis; D054712:Salinity; D012623:Seawater; D064466:Solute Carrier Family 12, Member 1 / Q000235:genetics / Q000378:metabolism; D064486:Solute Carrier Family 12, Member 3 / Q000235:genetics / Q000378:metabolism; D013312:Stress, Physiological; D017210:Tilapia / Q000254:growth & development / Q000502:physiology*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D029941:Fish Proteins; D064466:Solute Carrier Family 12, Member 1; D064486:Solute Carrier Family 12, Member 3; D014157:Transcription Factors; C111264:peroxisome-proliferator-activated receptor-gamma coactivator-1; D003576:Electron Transport Complex IV; D024981:Glycogen Phosphorylase
keywords: COX; Mitochondria-rich cells; Mitochondrial biogenesis; NCC; NKCC; NRF-1; Osmolality; Osmoregulation; PGC-1α; Respirometry