Developmental cardiorespiratory physiology of the air-breathing tropical gar, Atractosteus tropicus
The physiological transition to aerial breathing in larval air-breathing fishes is poorly understood. We investigated gill ventilation frequency (f ), heart rate (f ), and air breathing frequency (f ) as a function of development, activity, hypoxia, and temperature in embryos/larvae from day (D) 2.5...
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Published in | American journal of physiology. Regulatory, integrative and comparative physiology Vol. 311; no. 4; pp. R689 - R701 |
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Main Authors | , , , , , , |
Format | Journal Article |
Language | English |
Published |
United States
American Physiological Society
01.10.2016
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Subjects | |
Online Access | Get full text |
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Summary: | The physiological transition to aerial breathing in larval air-breathing fishes is poorly understood. We investigated gill ventilation frequency (f
), heart rate (f
), and air breathing frequency (f
) as a function of development, activity, hypoxia, and temperature in embryos/larvae from day (D) 2.5 to D30 posthatch of the tropical gar, Atractosteus tropicus, an obligate air breather. Gill ventilation at 28°C began at approximately D2, peaking at ∼75 beats/min on D5, before declining to ∼55 beats/min at D30. Heart beat began ∼36-48 h postfertilization and ∼1 day before hatching. f
peaked between D3 and D10 at ∼140 beats/min, remaining at this level through D30. Air breathing started very early at D2.5 to D3.5 at 1-2 breaths/h, increasing to ∼30 breaths/h at D15 and D30. Forced activity at all stages resulted in a rapid but brief increase in both f
and f
, (but not f
), indicating that even in these early larval stages, reflex control existed over both ventilation and circulation prior to its increasing importance in older fishes. Acute progressive hypoxia increased f
in D2.5-D10 larvae, but decreased f
in older larvae (≥D15), possibly to prevent branchial O
loss into surrounding water. Temperature sensitivity of f
and f
measured at 20°C, 25°C, 28°C and 38°C was largely independent of development, with a Q
between 20°C and 38°C of ∼2.4 and ∼1.5 for f
and f
, respectively. The rapid onset of air breathing, coupled with both respiratory and cardiovascular reflexes as early as D2.5, indicates that larval A. tropicus develops "in the fast lane." |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0363-6119 1522-1490 |
DOI: | 10.1152/ajpregu.00022.2016 |