| Short-headed lamprey | |
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| Species: | M. mordax
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| Binomial name | |
| Mordacia mordax (J. Richardson, 1846)
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Mordacia mordax, known as the short-headed lamprey, Australian lamprey or Murray lamprey, is a species of Mordacia that lives in south-eastern Australia and Tasmania. Mordaciidae is made up of three species M. praedox, M. mordax, and M. lapicida.[1] M. mordax is a relatively rare, parasitic vertebrate and, along with the hagfishes, is part of the only surviving group of jawless organisms throughout vertebrate evolution.[2] It has a thin eel-like body up to 50 cm long, with two low dorsal fins on the back half. The skin is blue-gray or brown. Its eyes are small, and located on the top of its head.
Evolution edit
Members of Agnatha have been found in the fossil record for approximately five hundred million years and it has been identified as an important group in tracking vertebrate evolution.[3] Despite being spatially close to the other southern hemisphere family Geotriidae (which is made up of Geotria australis only), M. mordax has been shown to have key proteins with vastly different amino acid compositions.[4] [5] One such study of insulin extracted from organisms of both species indicated that 18 amino acids are different between G. australis and M. mordax when with northern hemisphere lampreys (P. marinus and L. fluviatilis) there is only a 4 amino acid different. This data indicates that the southern hemisphere lampreys likely diverged evolutionarily a long time before.[6] It has also been determined that Geotriidae and Petromyzontidae (the family of northern hemisphere lampreys) likely share a more recent common ancestor than either does with any Mordacia species.[7]
Behavior and Ecology edit
Adult M. mordax are parasites on other fish. They are anadromous, breed in fresh water, however, migrating up streams in southeastern Australia from Shoalhaven River, New South Wales to Gulf St Vincent, South Australia. The ammocoetes (lamprey larvae) remain in fresh water until undergoing extreme physiological changes that allow them to move from eating plankton to larger fish.[8] This leads to them migrating to the South Pacific and Southern Oceans around three to four years after hatching.[9] Adults have been found to travel hundreds of miles to spawn.[10] Feeding occurs in the open ocean until full sexual maturation occurs when M. mordax returns to freshwater rivers, spawns, and dies.[11]
Physiology edit
Larval M. mordax are between 20 and 150 mm in length depending on their stage of development and when fully developed typically measure 300 to 420 mm.[12] As it develops, M. mordax undergoes a number of extreme dental changes. It starts with a series of radial plates, and as it grows they separate and break into separate teeth.[13] These teeth are pointed, unlike the other southern hemisphere lamprey Geotria australis which has spatulate (broad and rounded) teeth.[14] The eyes of Mordacia are dorsolaterally located, which is unlike the other known lamprey species, and they contain a photoreceptor that has both rod and cone characteristics.[15] This photoreceptor is also unique to M. mordax and enhances vision in darkness by optimizing photon reception. It is not unlike deep sea fish eye anatomy, in that sense as M. mordax only comes out of the sediment of rivers at night to travel.[16] The posterior and anterior dorsal fins of Mordacia are continuous to the caudal fin, unlike G. australis. When M. mordax is fully developed those anterior and posterior dorsal fins are well separated, which distinguishes them from northern hemisphere lampreys.[17] Lampreys have been established as worthy models in understanding the development of higher vertebrate anatomy and physiology, with one such experiment determining that major classes of lipoproteins are similar in Mordacia to what you would find in humans.[18] Also, M. mordax and the lamprey group have been shown to be the lowest vertebrate to have clear roles for neurohormones in the hypothalamic-pituitary-gonadal axis.[19]
mordax
Category:Freshwater fish of Australia
short-headed lamprey
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- ^ Collin, S; Hart, N; Wallace, K; Shand, J; Potter, I (2004). "Vision in the southern hemisphere lamprey Mordacia mordax: Spatial distribution, spectral absorption characteristics, and optical sensitivity of a single class of retinal photoreceptor". Visual Neuroscience. 21 (5): 765–773. doi:doi:10.1017/S0952523804215103.
{{cite journal}}: Check|doi=value (help) - ^ Conlon; Wang; Potter (2001). "The structure of Mordacia mordax insulin supports the monophyly of the Petromyzontiformes and an ancient divergence of Mordaciidae and Geotriidae". Comparative Biochemistry and Physiology, Part B. 129 (1): 65–71.
- ^ Collin, S; Hart, N; Wallace, K; Shand, J; Potter, I (2004). "Vision in the southern hemisphere lamprey Mordacia mordax: Spatial distribution, spectral absorption characteristics, and optical sensitivity of a single class of retinal photoreceptor". Visual Neuroscience. 21 (5): 765–773. doi:doi:10.1017/S0952523804215103.
{{cite journal}}: Check|doi=value (help) - ^ Baldwin, Mortimer (1988). "Evolutionary relationships among lamprey families: Amino acid composition analysis of lactate dehydrogenase". Biochemical Systematics and Ecology. 16 (3): 351–353.
- ^ Conlon; Wang; Potter (2001). "The structure of Mordacia mordax insulin supports the monophyly of the Petromyzontiformes and an ancient divergence of Mordaciidae and Geotriidae". Comparative Biochemistry and Physiology, Part B. 129 (1): 65–71.
- ^ Conlon; Wang; Potter (2001). "The structure of Mordacia mordax insulin supports the monophyly of the Petromyzontiformes and an ancient divergence of Mordaciidae and Geotriidae". Comparative Biochemistry and Physiology, Part B. 129 (1): 65–71.
- ^ Baldwin, Mortimer (1988). "Evolutionary relationships among lamprey families: Amino acid composition analysis of lactate dehydrogenase". Biochemical Systematics and Ecology. 16 (3): 351–353.
- ^ Collin, S; Hart, N; Wallace, K; Shand, J; Potter, I (2004). "Vision in the southern hemisphere lamprey Mordacia mordax: Spatial distribution, spectral absorption characteristics, and optical sensitivity of a single class of retinal photoreceptor". Visual Neuroscience. 21 (5): 765–773. doi:doi:10.1017/S0952523804215103.
{{cite journal}}: Check|doi=value (help) - ^ Conlon; Wang; Potter (2001). "The structure of Mordacia mordax insulin supports the monophyly of the Petromyzontiformes and an ancient divergence of Mordaciidae and Geotriidae". Comparative Biochemistry and Physiology, Part B. 129 (1): 65–71.
- ^ Potter, I; Strahan, F (1968). "The taxonomy of the lampreys Geotria and Mordacia and their distribution in Australia". Proceedings of the Linnean Society of London. 179 (2): 229–240.
- ^ Potter, I; Hilliard, R; Neira, F (1986). "The Biology of Australian Lampreys".
{{cite journal}}: Cite journal requires|journal=(help) - ^ Potter, I; Hilliard, R; Neira, F (1986). "The Biology of Australian Lampreys".
{{cite journal}}: Cite journal requires|journal=(help) - ^ Potter, I; Strahan, F (1968). "The taxonomy of the lampreys Geotria and Mordacia and their distribution in Australia". Proceedings of the Linnean Society of London. 179 (2): 229–240.
- ^ Potter, I; Strahan, F (1968). "The taxonomy of the lampreys Geotria and Mordacia and their distribution in Australia". Proceedings of the Linnean Society of London. 179 (2): 229–240.
- ^ Collin, S; Hart, N; Wallace, K; Shand, J; Potter, I (2004). "Vision in the southern hemisphere lamprey Mordacia mordax: Spatial distribution, spectral absorption characteristics, and optical sensitivity of a single class of retinal photoreceptor". Visual Neuroscience. 21 (5): 765–773. doi:doi:10.1017/S0952523804215103.
{{cite journal}}: Check|doi=value (help) - ^ Potter, I; Hilliard, R; Neira, F (1986). "The Biology of Australian Lampreys".
{{cite journal}}: Cite journal requires|journal=(help) - ^ Potter, I; Strahan, F (1968). "The taxonomy of the lampreys Geotria and Mordacia and their distribution in Australia". Proceedings of the Linnean Society of London. 179 (2): 229–240.
- ^ Fellows, Florence; Mclean, Robyn (1982). "A study of the plasma lipoproteins and the tissue lipids of the migrating lamprey, Mordacia mordax". Lipids. 17 (10): 741–747.
- ^ Sower; Mcgregor; Materne; Chase; Potter; Joss (2000). "Evidence for Lamprey GnRH-I and -III-like Molecules in the Brains of the Southern Hemisphere Lampreys Geotria australis and Mordacia mordax". General and Comparative Endocrinology. 120 (2): 168-175.