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Speers-Roesch B.,Memorial University of Newfoundland | Robinson J.L.,Memorial University of Newfoundland | Val A.L.,Brazilian National Institute for Research of the Amazon | Almeida-Val V.M.F.,Brazilian National Institute for Research of the Amazon | Driedzic W.R.,Memorial University of Newfoundland

The Serrasalmidae is a speciose family of Neotropical freshwater fishes with diverse interspecies dietary preferences, from the herbivorous or frugivorous pacus to the omnivorous or carnivorous piranhas. The Serrasalmidae is an ideal comparative model to explore the biochemical correlates of dietary preference. For example, debate exists about whether variation in dietary preference among fishes influences the capacities for de novo glucose synthesis (gluconeogenesis) or glucose use as metabolic fuel (glycolysis). We predicted that carnivory in piranhas would be associated with an enhanced gluconeogenic capacity compared with the herbivorous pacus, because carnivores consume less carbohydrate. As a corollary, we expected similar glycolytic capacities at a major site of glucose use (heart) in fishes with different diets. We measured activities of key enzymes of gluconeogenesis and the opposing reactions of glycolysis in liver (the primary gluconeogenic site) and heart of five serrasalmid species showing an interspecies dietary gradient from herbivory to omnivory to carnivory. The interspecific variation in enzyme activities was, in general, unrelated to dietary preference. Glycolytic capacity in heart was lower in herbivores but this may be related to non-diet factors. Among serrasalmid fishes, the enzymatic capacities of glucose metabolism are not overtly influenced by interspecific divergence of dietary preference. © 2015 Springer International Publishing Switzerland Source

Prado-Lima M.,Brazilian National Institute for Research of the Amazon | Prado-Lima M.,Federal University of Para | Val A.L.,Brazilian National Institute for Research of the Amazon

Climate change substantially affects biodiversity around the world, especially in the Amazon region, which is home to a significant portion of the world's biodiversity. Freshwater fishes are susceptible to increases in water temperature and variations in the concentrations of dissolved gases, especially oxygen and carbon dioxide. It is important to understand the mechanisms underlying the physiological and biochemical abilities of fishes to survive such environmental changes. In the present study, we applied RNA-Seq and de novo transcriptome sequencing to evaluate transcriptome alterations in tambaqui when exposed to five or fifteen days of the B1, A1B and A2 climate scenarios foreseen by the IPCC. The generated ESTs were assembled into 54,206 contigs. Gene ontology analysis and the STRING tool were then used to identify candidate protein domains, genes and gene families potentially responsible for the adaptation of tambaqui to climate changes. After sequencing eight RNA-Seq libraries, 32,512 genes were identified and mapped using the Danio rerio genome as a reference. In total, 236 and 209 genes were differentially expressed at five and fifteen days, respectively, including chaperones, energetic metabolism-related genes, translation initiation factors and ribosomal genes. Gene ontology enrichment analysis revealed that mitochondrion, protein binding, protein metabolic process, metabolic processes, gene expression, structural constituent of ribosome and translation were the most represented terms. In addition, 1,202 simple sequence repeats were detected, 88 of which qualified for primer design. These results show that cellular response to climate change in tambaqui is complex, involving many genes, and it may be controlled by different cues and transcription/translation regulation mechanisms. The data generated from this study provide a valuable resource for further studies on the molecular mechanisms involved in the adaptation of tambaqui and other closely related teleost species to climate change. © 2016 Prado-Lima, Val. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Source

Duarte R.M.,Brazilian National Institute for Research of the Amazon | Ferreira M.S.,Brazilian National Institute for Research of the Amazon | Wood C.M.,Brazilian National Institute for Research of the Amazon | Wood C.M.,McMaster University | Val A.L.,Brazilian National Institute for Research of the Amazon
Comparative Biochemistry and Physiology - A Molecular and Integrative Physiology

We evaluated the effects of acute exposure to low pH on Na+ regulation in two Amazon cichlids collected from natural ion-poor "blackwaters", angelfish (Pterophyllum scalare) and discus (Symphysodon discus). Na+ uptake kinetic parameters, unidirectional Na+ fluxes, and net Cl- fluxes were determined at pH6.0 and 3.6. At pH6.0, both species presented low unidirectional Na+ flux rates, with kinetics showing a relatively low affinity for Na+ (angelfish Km=79, discus Km=268μmolL-1), with similar maximum transport capacities (Jmax~535nmolg-1h-1). Overall, there appeared to be high sensitivity to inhibition by low pH, yet low intrinsic branchial permeability limiting diffusive ion effluxes, resulting in relatively low net loss rates of Na+, the same strategy as seen previously in other blackwater cichlids, and very different from the strategy of blackwater characids. At low pH, Na+ uptake in angelfish was inhibited competitively (increased Km=166μmolL-1) and non-competitively (decreased Jmax=106nmolg-1h-1), whereas in discus, only a decrease in Jmax (112nmolg-1h-1) was statistically significant. An acute reduction in H+-ATPase activity, but not in Na+/K+-ATPase activity, in the gills of angelfish suggests a possible mechanism for this non-competitive inhibition at low pH. Discus fish were more tolerant to low pH than angelfish, as seen by lesser effects of exposure to pH3.6 on unidirectional Na+ uptake and efflux rates and net Na+ and Cl- loss rates. Overall, discus are better than angelfish in maintaining ionic balance under acidic, ion-poor conditions. © 2013 . Source

Val A.L.,Brazilian National Institute for Research of the Amazon | Paula-Silva M.D.N.,Brazilian National Institute for Research of the Amazon | Almeida-Val V.M.F.,Brazilian National Institute for Research of the Amazon | Wood C.M.,Brazilian National Institute for Research of the Amazon | Wood C.M.,University of British Columbia
Journal of Fish Biology

Blood-O2 affinities (P50) were measured over a physiologically relevant pH range at 31 (highest temperature average of Rio Negro over the last 8 years), 33 and 35° C for 10 species of the Rio Negro, aiming to test the acute effects of temperature foreseen by the IPCC (Intergovernmental Panel on Climate Change) for coming years. The animals were collected during an expedition to the Anavilhanas Islands of the Rio Negro, 110 km upstream from Manaus (2° 23′ 41″ S; 60° 55′ 14″ W). Hoplias malabaricus showed higher blood-O2 sensitivity to pH changes (Bohr effect, Φ = Δlog10 P50 ΔpH−1) at both 31° C (Φ = −0·44) and 35° C (Φ = −0·26) compared to Osteoglossum bicirrhosum (Φ = −0·54 at 31° C and Φ = −0·58 at 35° C), but lower P50 under most conditions, and a greater sensitivity of P50 to temperature. Two out of the 10 analysed species had significant increases of P50 (lower blood-O2 affinity) at the highest temperature throughout the pH range tested. For all other species, a minor increase of P50 over the assay-tested temperatures was observed, although all presented a normal Bohr effect. Overall, a diversity of intensities of pH and temperature effects on blood-O2 affinities was observed, which seems to be connected to the biological characteristics of the analysed species. Thermal disturbances in their habitats, likely to occur due to the global warming, would impair blood-O2 binding and unloading in some of the analysed fish species. Copyright © 2016 John Wiley & Sons, Ltd. © 2016 The Fisheries Society of the British Isles Source

Val A.L.,Brazilian National Institute for Research of the Amazon | Gomes K.R.M.,Brazilian National Institute for Research of the Amazon | de Almeida-Val V.M.F.,Brazilian National Institute for Research of the Amazon
Comparative Biochemistry and Physiology -Part A : Molecular and Integrative Physiology

Prochilodus nigricans, locally known as curimatã, is an Amazonian commercial fish that endures adverse environmental conditions, in particular low dissolved oxygen, during its migration. Poorer environmental conditions are expected in the near future. Prochilodus nigricans overcomes current seasonal and diurnal changes in dissolved oxygen by adjusting erythrocytic levels of ATP and GTP, modulators of Hb-O2 affinity. Will this fish species be endangered under more extreme environmental conditions as hypoxia and acidification tend to occur in a shorter period of time? As P. nigricans does not exhibit any apparent morphological alterations to exploit the air-water interface, it must rely on fast adjustments of blood properties. To investigate this aspect, basic hematology indices, pHe, pHi, plasma lactate, erythrocytic levels of ATP and GTP and functional properties of the hemolysate of P. nigricans were analyzed over a period of 6h in hypoxia and subsequent recovery in normoxia. The levels of erythrocytic GTP were four times higher than ATP and were reduced to 1/4 of the original level after 3h under hypoxia. Erythrocytic levels of ATP were unaffected over the experimental period. All other analyzed blood parameters exhibited a time-course change in animals under hypoxia and returned to normoxic levels. Considering the hemolysate functional properties and the ability to regulate the above mentioned blood characteristics, P. nigricans is able to endure short-term changes in dissolved oxygen. © 2015 Elsevier Inc. Source

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