The ventilation mechanism of the Pacific hagfish Eptatretus stoutii |
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Authors: | Junho Eom Chris M Wood |
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Institution: | 1. Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada;2. Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
Bamfield Marine Sciences Centre, Bamfield, British Columbia, Canada |
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Abstract: | We made anatomical and physiological observations of the breathing mechanisms in Pacific hagfish Eptatretus stoutii, with measurements of nostril flow and pressure, mouth and pharyngo-cutaneous duct (PCD) pressure and velum and heart impedance and observations of dye flow patterns. Resting animals frequently exhibit spontaneous apnea. During normal breathing, water flow is continuous at a high rate (~125 ml kg?1 min?1 at 12°C) powered by a two-phase unidirectional pumping system with a fast suction pump (the velum, ~22 min?1) for inhalation through the single nostril and a much slower force pump (gill pouches and PCD ~4.4 min?1) for exhalation. The mouth joins the pharynx posterior to the velum and plays no role in ventilation at rest or during swimming. Increases in flow up to >400 ml kg?1 min?1 can be achieved by increases in both velum frequency and stroke volume and the ventilatory index (product of frequency x nostril pressure amplitude) provides a useful proxy for ventilatory flow rate. Two types of coughing (flow reversals) are described. During spontaneous swimming, ventilatory pressure and flow pulsatility becomes synchronised with rhythmic body undulations. |
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Keywords: | coughing pharyngo-cutaneous duct swimming two-phase ventilation velum ventilatory stroke volume |
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