Protopterus

About: Protopterus is a research topic. Over the lifetime, 292 publications have been published within this topic receiving 5572 citations. The topic is also known as: african lungfish.

Respiration in the African lungfish Protopterus aethiopicus. I. Respiratory properties of blood and normal patterns of breathing and gas exchange.

Abstract: 1. Respiratory properties of blood and pattern of aerial and aquatic breathing and gas exchange have been studied in the African lungfish, Protopterus aethiopicus . 2. The mean value for haematocrit was 25%. Haemoglobin concentration was 6.2 g% and O2 capacity 6.8 vol. %. 3. The affinity of haemoglobin for O2 was high. P 50 was 10 mm. Hg at P COCO2, 6 mm. Hg and 25 °C. The Bohr effect was smaller than for the Australian lungfish, Neoceratodus , but exceeded that for the South American lungfish, Lepidosiren . The O2 affinity showed a larger temperature shift in Protopterus than Neoceratodus . 4. The CO2 combining power and the over-all buffering capacity of the blood exceeded values for the other lungfishes. 5. Both aerial and aquatic breathing showed a labile frequency. Air exposure elicited a marked increase in the rate of air breathing. 6. When resting in aerated water, air breathing accounted for about 90% of the O2 absorption. Aquatic gas exchange with gills and skin was 2.5 times more effective than pulmonary gas exchange in removing CO2. The low gas-exchange ratio for the lung diminished further in the interval between breaths. 7. Protopterus showed respiratory independence and a maintained O2 uptake until the ambient O2 and CO2 tensions were 85 and 35 mm. Hg respectively. A further reduction in O2 tension caused an abrupt fall in the oxygen uptake. 8. Gas analysis of blood samples drawn from unanaesthetized, free-swimming fishes attested to the important role of the lung in gas exchange and the high degree of functional separation in the circulation of oxygenated and deoxygenated blood. This work was supported by grant GB 4038 from the National Science Foundation and grant HE-08405 from the National Institute of Health. Established Investigator, American Heart Association. Work supported by Northeastern Chapter, Washington State Heart Association.

The natural history of African lungfishes

Abstract: Remarkably little is known about the biology of the four Protopterus species, apart from certain detailed studies on their nesting behavior and estivating habits. What information we do have indicates that the species are essentially omnivorous carnivores (especially as predators on molluscs) and that they occupy a wide variety of habitats both lentic and lotic. As obligatory air-breathers able to survive temporary and sometimes extended desiccation of a habitat, lungfishes are often permanent residents in areas from which most actinopterygian fishes are excluded. All four species are able to survive prolonged dry periods. The methods they employ in so doing are varied, and include the secretion of subterranean cocoons, lying-up in water-filled subsurface burrows, or simply burrowing into moist regions of the substrate. Some populations of at least two species live in permanent water and so do not estivate, although they apparently retain the ability to do so. Three of the four species spawn in some form of seemingly constructed or prepared nest. The architecture of these nests shows marked inter- and intraspecific variability and is likely to be determined largely by various environmental factors. All three species show some type of parental care. The breeding biology of the fourth species, P. amphibius, is still unknown. Other aspects of the breeding biology and behavior of Protopterus require a great deal more investigation, as does the biology of the young.

Circulation and respiration in lungfishes (Dipnoi)

Abstract: This paper reviews the cardiorespiratory morphology and physiology of the living lungfishes, in the special context of their highly effective use of both air and water for gas exchange. Particular emphasis is placed on describing those features of the circulatory and respiratory systems that distinguish Neoceratodus from the Lepidosirenidae (Protopterus, Lepidosiren), and which, in turn, distinguish lungfishes from other aquatic vertebrates. Morphological and physiological characters that represent the plesiomorphic condition for the living Dipnoi are indicated (e.g., separate atrial chambers, vertical septum in ventricle, pulmonary veins, conal valves, twisting of bulbus cordis), as are those characters that may be shared derived features of the Lepidosirenidae (e.g., paired lungs, reduced anterior gill arches, well-developed spiral valve in conus). Morphological and physiological comparisons and contrasts with tetrapods are made to elucidate systematic relationships of the Dipnoi with other vertebrates.

A functional analysis of the aquatic and aerial respiratory movements of an African lungfish, Protopterus aethiopicus, with reference to the evolution of the lung-ventilation mechanism in vertebrates.

Abstract: 1. The anatomy of the head and branchial region of Protopterus has been studied by dissection and section techniques to show the relation between skeletal and muscular elements. X-ray cinematographic, pressure and electromyographic techniques have been used to show how the muscular and skeletal systems interact to produce the respiratory movements. The mechanisms involved in aquatic and aerial respiration in Protopterus have thus been elucidated. 2. The mechanisms of branchial irrigation has been shown to be basically similar to that seen in teleost and elasmobranch fishes, and also similar to that seen in larval amphibia. 3. The aerial cycle is composed of a series of aquatic-type cycles, each of which is modified slightly to serve a specific function in the aerial cycle. Inspiration occurs by a buccal force-pump mechanism. Expiration occurs by the release of compressed pulmonary gas, aided by the elasticity of the lung wall. 4. In this animal the air-breathing mechanism is derived from the aquatic mechanism. The modifications are relatively simple and produce an efficient ventilation mechanism. 5. No movements of the ribs can be seen associated with the respiratory cycles. It is suggested that the aspiratory ventilation mechanisms were not present in the prototetrapods and were not evolved until a later, more fully terrestrial stage was reached. 6. The evidence suggests that the air-breathing mechanism of the tetrapods was powered by a buccal force-pump mechanism which evolved directly from the aquatic system. The evolution of a new mechanism for lung ventilation in the prototetrapods is considered unnecessary.