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The accessory role of the diaphragmaticus muscle in lung ventilation in the estuarine crocodile Crocodylus porosus


Munns, SL and Owerkowicz, T and Andrewartha, SJ and Frappell, PB, The accessory role of the diaphragmaticus muscle in lung ventilation in the estuarine crocodile Crocodylus porosus, Journal of Experimental Biology, 215, (5) pp. 845-852. ISSN 0022-0949 (2012) [Refereed Article]

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Copyright 2012 The Company of Biologists Ltd.

DOI: doi:10.1242/jeb.061952


Crocodilians use a combination of three muscular mechanisms to effect lung ventilation: the intercostal muscles producing thoracic movement, the abdominal muscles producing pelvic rotation and gastralial translation, and the diaphragmaticus muscle producing visceral displacement. Earlier studies suggested that the diaphragmaticus is a primary muscle of inspiration in crocodilians, but direct measurements of the diaphragmatic contribution to lung ventilation and gas exchange have not been made to date. In this study, ventilation, metabolic rate and arterial blood gases were measured from juvenile estuarine crocodiles under three conditions: (i) while resting at 30C and 20C; (ii) while breathing hypercapnic gases; and (iii) during immediate recovery from treadmill exercise. The relative contribution of the diaphragmaticus was then determined by obtaining measurements before and after transection of the muscle. The diaphragmaticus was found to make only a limited contribution to lung ventilation while crocodiles were resting at 30C and 20C, and during increased respiratory drive induced by hypercapnic gas. However, the diaphragmaticus muscle was found to play a significant role in facilitating a higher rate of inspiratory airflow in response to exercise. Transection of the diaphragmaticus decreased the exercise-induced increase in the rate of inspiration (with no compensatory increases in the duration of inspiration), thus compromising the exercise-induced increases in tidal volume and minute ventilation. These results suggest that, in C. porosus, costal ventilation alone is able to support metabolic demands at rest, and the diaphragmaticus is largely an accessory muscle used at times of elevated metabolic demand.

Item Details

Item Type:Refereed Article
Keywords:ventilation, breathing pattern, oxygen consumption, blood gases, exercise, hypercapnia, crocodilian
Research Division:Biological Sciences
Research Group:Evolutionary biology
Research Field:Animal systematics and taxonomy
Objective Division:Environmental Management
Objective Group:Coastal and estuarine systems and management
Objective Field:Coastal or estuarine biodiversity
UTAS Author:Andrewartha, SJ (Dr Sarah Andrewartha)
UTAS Author:Frappell, PB (Professor Peter Frappell)
ID Code:76253
Year Published:2012
Web of Science® Times Cited:20
Deposited By:Zoology
Deposited On:2012-03-02
Last Modified:2019-03-28

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