One fine day, two firm friends happened to meet up in a lush green field. Storm clouds began to gather when neither could agree on the name of a fish that one of them had seen during a dive and this incident would give birth to an argument that would plague them all the days of their life. Watch below to see what happened!
Do you think they came to the right conclusion? Or do you think you know better? Guess this fish! Banded morwong, magpie morwong or crested morwong?
The Australian lungfish, or Neoceratodus forsteri as it is also known, is by no means just another fish. It is the sole remaining member of its family alive today, and has a history extending back to the time of the dinosaurs. Interestingly, fossils of the Australian lungfish were described years before the living animal became known to modern science (although the indigenous Australians had known of its existence for thousands of years). Lungfish tooth plates of Cretaceous age (more than 65 million years old) have been discovered in New South Wales, and are indistinguishable from those of living lungfish. It is for this reason Neoceratodus is often described as a ‘living fossil’ as it is the most enduring vertebrate species on Earth! Unbelievable – imagine if T-Rex or Muttaburrasaurus (an Australian dinosaur)were still roaming around!
The Australian lungfish at Museum Victoria (photo: A. Clement)
As its name suggests, lungfish have both gills and lungs with which to breathe oxygen. This was one of the reasons scientists had such trouble deciding what sort of animal Neoceratodus and its kin were. Some claimed it was ‘undoubtedly a reptile’, others considered it an amphibian, and others still thought it was a perfect intermediate between fish and amphibians. It is now widely accepted that lungfish are indeed fish, in fact they are one of only two groups of ‘lobe-fins,’ or sarcopterygian fish still alive today- other than the coelacanth. This makes them the closest living sister taxa to the tetrapods, the group that includes land animals (such as us!) In other words they are sort of like our ‘fishy cousins.’
Neoceratodus – the most enduring vertebrate species on Earth! (photo: A. Clement)
There are three extant genera of lungfishes; the Australian lungfish, Lepidosiren from South America and four species of Protopterus from Africa. Neoceratodus is considered the most primitive of all six living species. The Australian lungfish comes to the water surface to gulp air during times of high activity (such as when feeding or during mating season) or when swimming in stagnant pools low in oxygen. The African lungfish however, can actually survive breathing air cocooned in dry mud for up to six months waiting for the rains to return! Lungfish burrows with remains fossilised inside them are known since Permian times (roughly 250-300 million years ago), but the history of the group extends back much further to the Devonian Period, over 400 million years ago.
Neoceratodus looks very different from its earliest ancestors; the fins have merged to form a continuous body fin, the skeleton is now almost completely cartilaginous and the dentition is made of distinctive seven-bladed crushing tooth plates. Adult lungfish can grow to more than 1.5 metres and weigh up to 40 kilograms, with some research suggesting that the fish may live up to 100 years. Neoceratodus is currently listed as a vulnerable species under the Environmental Protection and Biodiversity Conservation Act 1999, and with a history like that you can see why they warrant protection! Their biggest threat to survival is the destruction of suitable habitat for spawning, or from competition with introduced species. You can come and see one of these great Australian icons for yourself in the Evolution Exhibition in the Science and Life Gallery at Melbourne Museum, Victoria (pictured below). What a lovely, lovely fish!
Neoceratodus, a lobe-finned fish(photo: A. Clement)
Dr. Alice Clement recently completed her doctorate at Museum Victoria (in conjunction with Australian National Univeristy, Canberra) on lungfishes. Her Ph.D focussed on both the living and extinct members, but particularly the Australian lungfish, Neoceratodus, and fossils from the Devonian Period, the ‘Age of Fishes’ (359-416 million years ago.) Her research touched on diverse themes such as anatomy, taxonomy, speciation, phylogeny, ecology, and biomechanics.
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Janvier, P. 1996. Early Vertebrates. Oxford University Press, New York.
Kemp, A. and Molnar, R. E. 1981. Neoceratodus forsteri from the Lower Cretaceous of New South Wales, Australia. Journal of Palaeontology, 55, 211-217.
Krefft, G. 1870. Description of a gigantic amphibian allied to the genus Lepidosiren, from the Wide-Bay district, Queensland. Proceedings of the Zoological Society of London, 1870, 221-224.
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no commentsPublished onJuly 2, 2012bydbray Head of a Serpent Black Dragonfish, Idiacanthus fasciola (Robin McPhee / NORFAN Founding Parties)
Dragonfishes of the deep-sea family Stomiidae are scary-looking fishes with rows of light organs and fearsome teeth. The family contains more than 290 species found in the oceanic’ twilight’ or mesopelagic zone – at depths between 200 and 1000 metres, or in even deeper waters where no light from the sun ever penetrates. Dragonfishes are voracious predators and most species have a bioluminescent “fishing lure” on their chin, thought to attract prey.
Like the larvae of all bony fishes, baby dragonfishes have a spinal support structure called a notochord – a flexible, rod-like structure that ossifies to become the backbone of vertebrates during larval development. As the larvae grow, the notochord is normally replaced by bone to become the vertebral column or backbone.
Head of a Sloane’s Viperfish, Chauliodus sloani, showing the enormous fangs (Robin McPhee / NORFANZ Founding Parties)
In most bony fishes, the backbone or vertebral column begins at the base of the skull. However, all dragonfishes have a puzzling boneless space between the back of the skull (the occiput) and the first vertebra – called the occipito-vertebral gap.
Scientists have long thought that this gap, or lack of rigid vertebrae, allows dragonfishes to bend their heads far back to swallow very large prey. Food is relatively scarce in the deep-sea, so these voracious predators take advantage of any meal that comes their way – sometimes even eating fishes larger than themselves.
In 2010, an international team of scientists solved the puzzle of these missing neckbones or vertebra. By studying larval and adult dragonfishes, Drs Nalani Schnell, Ralf Britz and Dave Johnson discovered that in 26 genera of stomiid fishes they studied, this gap is due to a remarkable extension of the notochord.
Head of a cleared and stained Black Loosejaw, Malacosteus niger, showing the cartilage in blue, and the bone in red (Credit: Nalani Schnell)
The team used a technique called ‘clearing and staining’ to examine specimens of 270 dragonfish species. First, an enzyme called trypsin was used to ‘clear’ the flesh of the specimens, making them almost invisible. The specimens were then stained with two dyes – alcian blue which stains cartilage, and alizarin red which stains bone.
The gap between the back of the skull and the first vertebra can be clearly seen in this image of a cleared and stained Black Loosejaw (Malacosteus niger). The notochord extension shows up as a bluish rod between the back of the skull and the first vertebra which are both stained red. This flexible extension of the notochord allows Black Loosejaws to bend their head far back while at the same time ‘throwing’ their jaws far forward to capture prey with their praying mantis-like jaws.
The team also discovered that the dragonfish notochord begins ossifying into bony vertebrae tail-first. This is completely in the opposite direction to the vertebral ossification in most other bony fishes where the backbone develops from the skull towards the tail.
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Schnell, N.K., Bernstein, P. & Maier, W. 2008. The pseudo-craniovertebral articulation of Stomias boa(Stomiidae, Teleostei). Journal of Morphology269(5): 513-521.
Schnell, N.K., Britz, R. & Johnson, G.D. 2010. New insights into the complex structure and ontogeny of the occipito-vertebral gap in barbeled dragonfishes (Stomiidae, Teleostei). Journal of Morphology 271(8): 1006-1022.
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