Use este identificador para citar ou linkar para este item: https://repositorio.inpa.gov.br/handle/1/17208
Título: Nitrogen metabolism in tambaqui (Colossoma macropomum), a neotropical model teleost: hypoxia, temperature, exercise, feeding, fasting, and high environmental ammonia
Autor: Wood, Chris M.
Souza Netto, José Gadelha de
Wilson, Jonathan
Duarte, Rafael Mendonça
Val, Adalberto Luis
Palavras-chave: Ammonia
Nitrogen
Urea
Animals
Animals Experiment
Characiformes
Environment
Feeding Behavior
Gill
Hypoxia
Kidney
Metabolism
Oxygen Consumption
Temperature
Ammonia
Animal
Characiformes
Environment
Feeding Behavior
Gills
Hypoxia
Kidney
Nitrogen
Oxygen Consumption
Physical Conditioning, Animals
Temperature
Urea
Data do documento: 2017
Revista: Journal of Comparative Physiology B: Biochemical, Systemic, and Environmental Physiology
É parte de: Volume 187, Número 1, Pags. 135-151
Abstract: The total rate of N-waste excretion (MN) in juvenile tambaqui living in ion-poor Amazonian water comprised 85 % ammonia-N (MAmm-N) and 15 % urea-N (MUrea-N). Both occurred mainly across the gills with only ~5 % of MAmm-N and ~39 % of MUrea-N via the urine. Tambaqui were not especially tolerant to high environmental ammonia (HEA), despite their great resistance to other environmental factors. Nevertheless, they were able to maintain a continued elevation of MAmm-N during and after 48-h exposure to 2.5 mmol L−1 HEA. The normally negative transepithelial potential (−18 mV) increased to −9 mV during the HEA period, which would help to reduce branchial NH4 + entry. During 3 h of acute environmental hypoxia (30 % saturation), MAmm-N declined, and recovered thereafter, similar to the response seen in other hypoxia-tolerant teleosts; MUrea-N did not change. However, during gradual hypoxia, MAmm-N remained constant, but MUrea-N eventually fell. The acute temperature sensitivities of MAmm-N and MN were low from 28 °C (acclimation) to 33 °C (Q10 ~1.5), but high (~3.8) from 33 to 38 °C, relative to MO2 (~1.9 throughout). In contrast, MUrea-N exhibited a different pattern over these temperature ranges (Q10 2.6 and 2.1, respectively). The nitrogen quotient (NQ = 0.16–0.23) was high at all temperatures, indicating a 60–85 % reliance on protein to fuel aerobic metabolism in these fasting animals. During steady-state aerobic exercise, MO2 and MUrea-N increased in parallel with velocity (up to 3.45 body lengths s−1), but MAmm (and thus MN) remained approximately constant. Therefore, the NQ fell progressively, indicating a decreasing reliance on protein-based fuels, as work load increased. In group feeding trials using 45 % protein commercial pellets, tambaqui excreted 82 % (range 39–170 %) of the dietary N within 24 h; N-retention efficiency was inversely related to the ration voluntarily consumed. MAmm-N peaked at 4–6 h, and MUrea-N at 6–9-h post-feeding, with an additional peak in MAmm-N only at 21 h. During subsequent fasting, MN stabilized at a high endogenous rate from 2 through 8 days post-feeding. Possible reasons for the high wasting of protein-N during both fasting and feeding are discussed. © 2016, Springer-Verlag Berlin Heidelberg.
DOI: 10.1007/s00360-016-1027-8
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