科研之友
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摘要
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 degrees, 12 degrees, 15 degrees, 18 degrees, 22 degrees 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 (H2O)-H-3 at the gills would increase in parallel with those of oxygen. Oxygen consumption (overall Q(10) = 1.76 from 7.5 degrees to 22 degrees C) and water fluxes (overall Q(10) = 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 degrees to 22 degrees C (Q(10) = 5.15). Urea-N efflux was tightly conserved over the 7.5 degrees-15 degrees Crange (Q(10) similar to 1.0) but increased greatly at higher temperatures, yielding an overall Q(10) = 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 degrees 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.
- 出版日期2017-12
