Experimental Biology Online - EBO 

ISSN 1430-3418 

The Society for Experimental Biology
Annual Meeting

The University of York
22-27 March 1998

A6 GENERAL RESPIRATION

Organised by K.C. Lowe for the Animal Respiration Group 

A6.1 - Aspects of the respiratory physiology of the South American lungfish, Lepidosiren paradoxa - a field study.

V. Harder¹, V. Pinto-Silva², and C.R. Bridges¹

The extant lungfishes (Dipnoi) represent a link in the vertebrate transition from water- to airbreathing, show physiological characters similar to those of the tetrapod ancestors (rhipidistians) and possess a true paired lung, which evolved from the air-bladder. Airbreathing events in the recent lungfishes are known to be associated with cardiovascular alterations, which improve the efficiency of intermittent lung ventilation. These periodical alterations are mainly characterized by an increase in the pulmonary blood flow in the obligate airbreathing African, Protopterus (Burggren & Johansen, 1986, J. Morphol. Suppl., 1:217-236), and South American lungfish, Lepidosiren (Axelsson et al., 1989, Comp.Biochem.Physiol., 93A: 561-565), and the facultative airbreathing Australian lungfish, Neoceratodus (Fritsche et al., 1993, Resp.Physiol., 94:173-187) during aerial gas exchange.

In the present study heart rate, airbreathing rate and gill ventilation rate of active, aquatic and of inactive, burrowed South American lungfish have been measured in situ on a diurnal basis. Since obvious physiological differences between Lepidosiren and its African counterpart Protopterus (Lepidosirenidae) have been induced by ecological differences between their habitats (Liem, 1986, J.Morphol. Suppl., 1:299-303), in addition physico-chemical parameters have been determined to elucidate the role of environmental stressors. Our results offer a quantification of the short term cardiovascular alterations, that were observed in Lepidosiren in its natural habitat during exposure to severe aquatic hypoxia and in response to the partial drying up of the habitat.

Last change: April 1, 1998
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