Cardiorespiratory reflexes and aquatic surface respiration in the neotropical fish tambaqui (Colossoma macropomum): acute responses to hypercarbia |
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Authors: | Luiz?H.?Florindo,Stephen?G.?Reid,Ana?L.?Kalinin,William?K.?Milsom,Francisco?T.?Rantin author-information" > author-information__contact u-icon-before" > mailto:ftrantin@power.ufscar.br" title=" ftrantin@power.ufscar.br" itemprop=" email" data-track=" click" data-track-action=" Email author" data-track-label=" " >Email author |
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Affiliation: | (1) Department of Physiological Sciences, Federal University of São Carlos, Via Washington Luiz, km 235, 13565-905 São Carlos, SP, Brazil;(2) Division of Life Sciences, University of Toronto at Scarborough, Scarborough, Ontario, Canada;(3) Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada |
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Abstract: | We examined the cardiorespiratory responses to 6 h of acute hypercarbia (1, 2.5, and 5% CO2) in intact and gill-denervated (bilateral denervation of branchial branches of cranial nerves IX and X) tambaqui, Colossoma macropomum. Intact fish exposed to 1 and 2.5% CO2 increased respiratory frequency (fR) and ventilation amplitude (VAMP) slowly over a 1- to 3-h period. Denervated fish did not show this response, suggesting that tambaqui possess receptors in the gills that will produce excitatory responses to low levels of hypercarbia (1 and 2.5% CO2) if the exposure is prolonged. The cardiac response to stimulation of these receptors with this level of CO2 was a tachycardia and not a bradycardia. During exposure to 5% CO2, intact fish increased fR and VAMP, and showed a pronounced bradycardia after 1 h. After 2 h, the heart rate (fH) started to increase, but returned to control values after 6 h. In denervated fish, the increase in fR was abolished. The slow increase in VAMP and the bradycardia were not abolished, suggesting that these changes arose from extra-branchial receptors. Neither intact nor denervated fish developed the swelling of the lower lip or performed aquatic surface respiration, even after 6 h, suggesting that these are unique responses to hypoxia and not hypercarbia.Abbreviations ASR aquatic surface respiration - fH heart frequency - fR respiratory frequency - VAMP ventilation amplitude - TOT total ventilation |
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Keywords: | Cardiorespiratory reflexes Hypercarbia CO2/pH chemoresponses Respiratory frequency Heart frequency |
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