Use este identificador para citar ou linkar para este item: https://repositorio.inpa.gov.br/handle/1/16929
Título: The physiology of the Tambaqui (Colossoma macropomum) at pH 8.0
Autor: Wood, Chris M.
Gonzalez, Richard J.
Ferreira, Márcio Soares
Braz-Mota, Susana
Val, Adalberto Luis
Palavras-chave: Ammonia
Hydrocortisone
Urea
Animals
Blood
Characiformes
Gill
Glucose Blood Level
Metabolism
Oxygen Consumption
Ph
Ammonia
Animal
Blood Glucose
Characiformes
Gills
Hydrocortisone
Hydrogen-ion Concentration
Oxygen Consumption
Urea
Data do documento: 2018
Revista: Journal of Comparative Physiology B: Biochemical, Systemic, and Environmental Physiology
É parte de: Volume 188, Número 3, Pags. 393-408
Abstract: The Tambaqui is a model neotropical teleost which is of great economic and cultural importance in artisanal fisheries and commercial aquaculture. It thrives in ion-poor, often acidic Amazonian waters and exhibits excellent regulation of physiology down to water pH 4.0. Curiously, however, it is reported to perform poorly in aquaculture at pH 8.0, an only slightly alkaline pH which would be benign for most freshwater fish. In initial experiments with Tambaqui of intermediate size (30–50 g), we found that ammonia excretion rate was unchanged at pH 4, 5, 6, and 7, but elevated after 20–24 h at pH 8, exactly opposite the pattern seen in most teleosts. Subsequent experiments with large Tambaqui (150–300 g) demonstrated that only ammonia, and not urea excretion was increased at pH 8.0, and that the elevation was proportional to a general increase in MO2. There was an accompanying elevation in net acidic equivalent excretion and/or basic equivalent uptake which occurred mainly at the gills. Net Na+ balance was little affected while Cl− balance became negative, implicating a disturbance of Cl− versus base exchange rather than Na+ versus acid exchange. Arterial blood pH increased by 0.2 units at pH 8.0, reflecting combined metabolic and respiratory alkaloses. Most parameters recovered to control levels by 18–24 h after return to pH 6.0. With respect to large Tambaqui, we conclude that a physiology adapted to acidic pH performs inappropriately at moderately alkaline pH. In small Tambaqui (4–15 g), the responses were very different, with an initial inhibition of ammonia excretion rate at pH 8.0 followed by a subsequent restoration of control levels. Elevated ammonia excretion rate occurred only after return to pH 6.0. Furthermore, MO2, plasma cortisol, and branchial vH+ATPase activities all declined during pH 8.0 exposure in small Tambaqui, in contrast to the responses in larger fish. Overall, small Tambaqui appear to cope better at pH 8.0, a difference that may correlate with their natural history in the wild. © 2017, Springer-Verlag GmbH Germany, part of Springer Nature.
DOI: 10.1007/s00360-017-1137-y
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