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Comparative Respiration of an Air-Breathing and a Non-Air-Breathing Characoid Fish and the Evolution of Aerial Respiration in Characins

1978; University of Chicago Press; Volume: 51; Issue: 3 Linguagem: Inglês

10.1086/physzool.51.3.30155745

1937-4267

Jeffrey B. Graham, Donald L. Kramer, Elpidio Pineda,

Water Quality Monitoring Technologies

The respiration physiology of Piabucina festae, an air-breathing characin fish in the family Lebiasinidae, has been compared with that of P. panamensis, a closely related non-air-breathing species. The gas bladder of P. festae is highly modified for rapid O₂ absorption through the presence of a specialized region in the posterior chamber. In P. panamensis this organ has no respiratory specializations, but low rates of O₂ absorption do occur. Piabucina festae has a higher metabolic rate than P. panamensis and can maintain its routine V̇O2 without air breathing in normoxic water. The capacity for aquatic respiration of P. festae is reduced compared with that of P. panamensis. Piabucina festae has a lower resistance to aquatic hypoxia. It cannot greatly increase its rate of gill ventilation and has a critical oxygen tension (PCO₂) of 70 torr. By contrast, P. panamensis can increase gill ventilation by five times and has a critical PCO₂ of 25 torr. Air-breathing characins occur only in the Neotropical families Lebiasinidae and Erythrinidae which are very similar but not closely related. It is reasoned that air breathing, although highly similar, evolved independently in both families. The transition to air breathing in characins may have involved selection for the motions involved in controlling the volume of the physostomous gas bladder.