Differential Effects of Temperature on Oxygen Consumption and Branchial Fluxes of Urea, Ammonia, and Water in the Dogfish Shark (Squalus acanthias suckleyi)

• Autor: Giacomin, Marina ; Schulte, Patricia M. ; Wood, Chris M.
• Assuntos: Ammonia - metabolism ; Animals ; Gills - physiology ; Nitrogen - metabolism ; Oxygen Consumption - physiology ; Permeability ; Sharks - physiology ; Temperature ; Urea - metabolism ; Water - metabolism
• É parte de: Physiological and biochemical zoology, 2017-11, Vol.90 (6), p.627-637
• Notas: ObjectType-Article-1
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• Descrição: Environmental temperature can greatly influence the homeostasis of ectotherms through its effects on biochemical reactions and whole-animal physiology. Elasmobranchs tend to be N limited and are osmoconformers, retaining ammonia and urea-N at the gills and using the latter as a key osmolyte to maintain high blood osmolality. However, the effects of temperature on these key processes remain largely unknown. We evaluated the effects of acute exposure to different temperatures (7°, 12°, 15°, 18°, 22°C) on oxygen consumption, ammonia, urea-N, and diffusive water fluxes at the gills of Squalus acanthias suckleyi. We hypothesized that as metabolic demand for oxygen increased with temperature, the fluxes of ammonia, urea-N, and ³H2O at the gills would increase in parallel with those of oxygen. Oxygen consumption (overall Q10 = 1.76 from 7.5° to 22°C) and water fluxes (overall Q10 = 1.96) responded to increases in temperature in a similar, almost linear, manner. Ammonia-N efflux rates varied the most, increasing almost 15-fold from 7.5° to 22°C (Q10 = 5.15). Urea-N efflux was tightly conserved over the 7.5°–15°C range (Q10 ∼ 1.0) but increased greatly at higher temperatures, yielding an overall Q10 = 1.45. These differences likely reflect differences in the transport pathways for the four moieties. They also suggest the failure of urea-N- and ammonia-N-conserving mechanisms at the gill above 15°C. Hyperoxia did not alleviate the effects of high temperature. Indeed, urea-N and ammonia-N effluxes were dramatically increased when animals were exposed to high temperatures in the presence of hyperoxia, suggesting that high partial pressure of oxygen may have caused oxidative damage to gill epithelial membranes.
  
• Editor: United States: The University of Chicago Press
  
• Idioma: Inglês