African lungfishes are elongated, eel-like fishes, with thread-like pectoral and pelvic fins. They have soft scales, and the dorsal and tail fins are fused into a single structure. They can either swim like eels, or crawl along the bottom, using their pectoral and pelvic fins. The largest species reach about 200 cm (6.6 ft) long.
African lungfishes generally inhabit shallow waters, such as swamps and marshes; however, they are also found in larger lakes such as Lake Victoria. They can live out of water for many months in burrows of hardened mud beneath a dried-up stream bed. They are carnivorous, eating crustaceans, aquatic insect larvae, and molluscs.
The African lungfish is an example of how the evolutionary transition from breathing water to breathing air can happen. Lungfish are periodically exposed to water with low oxygen content or situations in which their aquatic environment dries up. Their adaptation for dealing with these conditions is an outpocketing of the gut, related to the swim bladder of other fishes, that serves as a lung. The lung contains many thin-walled blood vessels, so blood flowing through those vessels can pick up oxygen from air gulped into the lung.
The African lungfishes are obligate air breathers, with reduced gills in the adults. They have two anterior gill arches that retain gills, though they are too small to function as the sole respiratory apparatus. The lungfish heart has adaptations that partially separate the flow of blood into its pulmonary and systemic circuits. The atrium is partially divided, so that the left side receives oxygenated blood and the right side receives deoxygenated blood from the other tissues. These two blood streams remain mostly separate as they flow through the ventricle leading to the gill arches. As a result oxygenated blood mostly goes to the anterior gill arches and the deoxygenated blood mostly goes to the posterior arches.
African lungfishes breed at the beginning of the rainy season. They construct nests or burrows in the mud to hold their eggs, which they then guard against predators. When they hatch, the young resemble tadpoles, with external gills, and only later develop lungs and begin to breathe air.
Native Africans have been found to dig up lungfishes, burrow and all, and store them for later use when they want fresh fish to eat. These fish have also been carried in their mud burrows for exhibition in the United States. They have a strong taste. The taste is such that "it is locally either highly appreciated or strongly disliked". As technology advancements such as longlines and gillnets have been increasingly applied over the past 50 years, the lungfish populations there are believed to be decreasing. In Uganda, females do not eat the lungfish because they consider it a "sister fish", and therefore it is associated with men and manhood.
Species and subspecies
The family contains just four species:
- P. aethiopicus Heckel, 1851 - marbled lungfish
- P. amphibius (W. K. H. Peters, 1844) - gilled African lungfish or East African lungfish
- P. annectens (Owen, 1839) - West African lungfish
- P. a. annectens (Owen, 1839)
- P. a. brieni Poll, 1961 - southern lungfish
- P. dolloi Boulenger, 1900 - slender lungfish or spotted African lungfish
- Bruton, Michael N. (1998). Paxton, J.R. & Eschmeyer, W.N., ed. Encyclopedia of Fishes. San Diego: Academic Press. pp. 70–72. ISBN 0-12-547665-5.
- Froese, Rainer, and Daniel Pauly, eds. (2009). "Lepidosirenidae" in FishBase. January 2009 version.
- Kees (P. C.) Goudswaard, Frans Witte, Lauren J. Chapman, Decline of the African lungfish (Protopterus aethiopicus) in Lake Victoria (East Africa) East African Wild Life Society, African Journal of Ecology, 40, 42-52, 2002
- Purves, Sadava, Orians, Heller, "Life: THe Science of Biology" 7th ed. pg. 943. Courier Companies Inc: USA, 2004.