Common name: Australian lungfish; Ceratodus; Queensland lungfish
Scientific name: Neoceratodus forsteri
Distribution: Australia
What are lungfish?
There are two known families of the amazing lungfish in the Dipnoi order. These incredible fish have numerous extinct species with only six species known today. The reason that the lungfish is such an interesting fish is because all six species are known to breathe air. Some do this even though they also use gills while others have developed a type of lungs that allows them to breath air which is gulped from the surface of the water. Of interest is the fact that these lung type organs are much like those of the ancient amphibians. The lungfish has a history that dates back to the Lower Devonian which is millions of years ago. Most of the species found today live in lakes or rivers in Australia, South America and Africa. Of the two families, which are Lepidosirenidae and Ceratodidae, the South American lungfish and African lungfish are in the Lepidosirenidae family. These fish have slender, long eel-like bodies that are equipped with two lungs. They sense their surroundings by using their fins and in the South American species tend to grow to lengths of over three feet. Of the African lung fish there are some species that reach sizes of over 6 feet long.
Besides their ability to breathe air, the lungfish has addition distinguishing characteristics that are fascinating. During the spawning season both species from the Lepidosirenidae family are known to very carefully construct nest for their young. After the eggs are deposited by the females the males watch over the nest, protecting them fiercely until the young have hatched. The young in this species have gills when they first appear but as they mature the gills tend to disappear. Adults take in air by swimming to the surface of the water and filling their lungs before moving back under water. Unlike the South American and African lungfish, the Australian lungfish do not build nest during the spawning period. Once mating has occurred the females will lay her eggs among the vegetation at the bottom of her habitat to hatch. This intriguing fish has only one lung but is considered to have a much older history than the African or South American species. Some studies suggest that the Australian lung fish genus Neoceratodus has gone through no changes in the last 100 million years. When taking in air the Australian lungfish reportedly swims to the waters surface displaying its nose above the surface to fill its lung. As it takes in air the mouth remains closed with the air passing through an opening from the nose to the mouth. During the majority of the season the Australian lungfish uses its gills to take oxygen from the water, only breathing air when the water levels lower.
Another of the very interesting characteristics of the lungfish in the Lepidosirenidae family is their ability to survive in little or no water. When the heat in South America dries up the water supply this species will dig into the mud at the bottom of their habitat and remain there with no activity until the waters rise. The African lungfishes also dig out holes in the mud but cover themselves completely with a secretion that is given off by their bodies. As the water level lowers the secretions on their bodies will dry to form a kind of leathery cocoon that encases them until sufficient water has returned. During this waterless type of hibernation, both species remain dormant until the rains come to release them from their shells. The Australian lungfish will first survive in whatever water is available as the dry season commences. As other fish die around it from lack of oxygen in the diminished water supply this fish begins to take its air from the atmosphere exclusively. These amazing fish have been found during a drought surviving in small puddles of water by surfacing for air when necessary. Studies have shown that during these dormant periods the metabolism of the lungfish is greatly diminished causing them to need very little to survive with the exception of oxygen. Even more incredible are the studies that have shown that some species of the lungfish can survive around two years under these conditions.
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