Shorthead Lamprey, Mordacia mordax (Richardson 1846)

Other Names: Murray Lamprey, Short-headed Lamprey

Shorthead Lamprey, Mordacia mordax. Source: Rudie Kuiter / Aquatic Photographics. License: All rights reserved


Primitive jawless fishes with naked eel-like bodies, two low dorsal fins far back on the body and 7 pairs of enlarged pore-like gill openings. They have eyes on top of their and prominent hood-like sructure overhanging the mouth.

The oral sucking disc is armed with tooth plates arranged in a radial pattern. Their ammocoete larvae are worm-like and lack eyes and teeth.

Shorthead Lampreys have an anadramous life cycle, spending parts of their life cycle in freshwater and in the sea. The adults spawn in freshwater, and their ammocoete larvae spend several years living in freshwater streams.

Following metamorphosis, they migrate downstream and spend most of their adult lives at sea, before returning to freshwater streams to breed.

Cite this page as:
Martin F. Gomon & Dianne J. Bray, Mordacia mordax in Fishes of Australia, accessed 26 Sep 2023,

Shorthead Lamprey, Mordacia mordax (Richardson 1846)

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Endemic to temperate waters of southeastern Australia, including coastal rivers and streams, from the Hawkesbury River, NSW (33°30’S) to Kangaroo Island, SA (137°15’E). Shorthead Lampreys inhabit shallow coastal and inland waters that are connected to the sea.

They have an anadramous life cycle where the post-larvae and premature adults are marine, and the other stages live in freshwater.


Body eel-like, lacking scales; gill openings are 7 enlarged pores; mouth modified into an oral disc with sharp horny teeth in 2 large plates each with 3 large teeth and a series of smaller plates radiating outwards around mouth with smaller teeth; rim of sucking disc without fleshy papillae; single median nostril on top of head; eyes dorsolaterally on head; ammocoetes (<12cm) lack eyes and have a single undivided dorsal fin.

The two dorsal fins are set well back near the tail; first with short base, 2nd longer, (2 or more times length of 1st); anus below and behind midpoint of 2nd dorsal fin, usually below posterior 3rd of fin; lacking pectoral, ventral and anal fins.


To 56 cm TL, although usually between 35-40 cm. Most adults are 300-440 mm when they migrate back to freshwater.

Ammocoete larvae begin metamorphosis between 100 and 140 mm.


The early post-larvae are greyish-brown above and silvery below. Young adults are bright blue above, with silvery sides and ventral surface. Mature adults are blue-grey above, silvery below and have orange teeth when in freshwater.


The ammocoete larvae filter feed on plankton, detritus and microalgae. The adults are parasitic on other fishes and attach to their host with the suctorial disc.

They use their toothy tongue to rasp flesh and feed on the body fluids and muscle of the host. The adults cease to feed during their migration back to freshwater rivers to spawn, surviving on stored fats and body tissues.


Adults return to freshwater rivers where they usually spawn in small, shallow creeks and streams with gravelly substrates. The female prepares a small depression or nest in the substrate and attaches herself to a rock with the oral disc. The male attaches to the female with his oral disc and wraps around her to squeeze out eggs before releasing sperm. Adults die shortly after spawning.

Newly hatched larvae (ammocoetes) drift downstream into slow-flowing areas and burrow into muddy substrates. The larvae grow to a maxixum length of 17 cm and metamorphose after 3 to 4 years. The young migrate downstream during late winter and spring, and spend most of their adult lives in estuaries or at sea.


In the past, small numbers of Shorthead lampreys caught in the Yarra River were sold commercially.


Not evaluated.

Similar Species

Although the two species of Mordacia are very similar, Nonparasitic Lampreys (Mordacia praecox) lack radial tooth plates, are smaller in size and spend their entire lives in freshwater streams of southeastern Australia.

Species Citation

Petromyzon mordax Richardson 1846, Zool. Voy. Erebus and Terror 2: Tasmania.


Martin F. Gomon & Dianne J. Bray

Shorthead Lamprey, Mordacia mordax (Richardson 1846)


Allen, G.R. 1989 Freshwater fishes of Australia. T.F.H. Publications, Inc., Neptune City, New Jersey.

Allen, G.R, S.H. Midgley & M. Allen. 2002. Field Guide to the Freshwater Fishes of Australia. Western Australian Museum, Perth: 1-394.

Cadwallader, P.L. & G.N. Backhouse. 1983. A guide to the freshwater fish of Victoria. Victoria Government Printing Office. Melbourne: 1-249.

Chilcott, S.J. & P. Humphries. 1996. Freshwater fish of northeast Tasmania with notes on the dwarf galaxias. Records of the Queen Victoria Museum 103: 145-149.

Collin, S.P. 2009. Early evolution of vertebrate photoreception: lessons from lampreys and lungfishes. Integr. Zool. 4(1): 87-98.

Collin, S.P., N.S. Hart, K.M. Wallace, J. Shand & I.C. Potter. 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: 765-773.

Collin, S.P. & Potter, I.C. 2000. The ocular morphology of the southern hemisphere lamprey Mordacia mordax Richardson with special reference to a single class of photoreceptor and a retinal tapetum. Brain Behav. Evol. 55(3): 120-38.

Conlon, J.M., Wang, Y. & Potter, I.C. 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.

Gill, H.S., G.B. Renaud, F. Chapleau, R.L. Mayden & I.C. Potter. 2003. Phylogeny of living parasitic lampreys (Petromyzontiformes) based on morphological data. Copeia. 2003(4): 687-703.

Gomon, M.F., D.J. Bray & R.H. Kuiter (eds). 2008. Fishes of Australia’s Southern Coast. Reed New Holland Press, Chatswood, Australia. 928 pp.

Hammer, M.P. & K.F. Walker. 2004. A catalogue of South Australian freshwater fishes, including new records, range extensions and translocations. Transactions Royal Society of South Australia 128(2): 85-97.

Hardisty, M.W. & I.C. Potter (eds). 1971. The Biology of Lampreys. Academic Press, London, 2 vols.

Hoese, D.F., D.J. Bray, J.R. Paxton & G.R. Allen. 2006. Fishes. In Beesley, P.L. & A. Wells. (eds) Zoological Catalogue of Australia. Volume 35. ABRS & CSIRO Publishing: Australia. parts 1-3, pages 1-2178.

Hombrados, I., Vidal ,Y., Rodewald, K., Braunitzer, G. & Neuzil, E. 1991. The primary structure of the hemoglobins of a southern hemisphere lamprey (Mordacia mordax, Cyclostomata). Biol. Chem. Hoppe Seyler 372(1): 49-56.

Hughes, R.L. & Potter, I.C. 1969. Studies on gametogenesis and fecundity in the lampreys Mordacia praecox and M. mordax (Petromyzonidae). Aust. J. Zool. 17: 447-464.

McDowall, R.M. 1988 Diadromy in fishes: migrations between freshwater and marine environments. Croom Helm, London.

Neira, F.J., J.S. Bradley, I.C. Potter F.L.S. & R.W. Hilliard. 1988. Morphological variation among widely dispersed larval populations of anadromous southern hemisphere lampreys (Geotriidae and Mordaciidae). Zoological Journal of the Linnean Society 92(4): 383-408.

Paxton, J.R., J.E. Gates & D.F. Hoese. 2006. Petromyzontidae, pp. 42-44. In : Beesley, P.L. & A. Wells. Zoological Catalogue of Australia. Volume 35. ABRS and CSIRO Publishing, 3 vols.

Potter, I.C. 1970. The life cycles and ecology of Australian lampreys of the genus Mordacia. Journal of Zoology, London 161: 487-511.

Potter, I.C. 1980. The Petromyzontiformes, with particular reference to paired species. Canadian Journal of Fisheries and Aquatic Sciences 37(11): 1595-1615.

Potter, I.C. 1980. Ecology of larval and metamorphosing lampreys. Canadian Journal of Fisheries and Aquatic Sciences 37: 1641-1657.

Potter, I.C. 1986. The distinctive characters of Southern Hemisphere lampreys (Geotriidae and Mordaciidae). pp. 9–29 In T. Uyeno, R. Arai, T. Tanuchi & K. Matsuura (Eds.) Proceedings of the Second International Conference on Indo-Pacific Fishes. Tokyo : Fishes. The Ichthyological Society of Japan, 985 pp.

Potter, I.C. 1996. Shortheaded lampreys, pp. 32-35, In : McDowall, R.M. Freshwater fishes of south-eastern Australia. Reed Books, Chatswood, Australia. 247 p.

Potter, I.C. 1996. Pouched lampreys, pp. 36-38, In : McDowall, R.M. Freshwater fishes of south-eastern Australia. Reed Books, Chatswood, Australia. 247 p.

Potter, I.C., Lanzing, W.J.R. & Strahan, R. 1968. Morphometric and meristic studies on populations of Australian lampreys of the genus Mordacia. Journal of the Linnean Society of London 47: 533-546.

Potter, I.C., Macey, D.J., Roberts, A.R. & Withers, P.C. 1998. Oxygen Consumption, Carbon Dioxide Excretion and Respiratory Quotient of Larval Lampreys (Mordacia mordax) in Air. Comparative Biochemistry and Physiology - Part A: Molecular & Integrative Physiology 119(2): 607-611.

Potter, E.C., E.S. Robinson & S.M. Walton 1968 The mitotic chromosomes of lamprey, Mordacia mordax (Agnatha: Petromyxonidae). Experientia 24: 966-967.

Potter, I.C. & Strahan, R. 1968. The taxonomy of the lampreys Geotria and Mordacia and their distribution in Australia. Proceedings of the Linnean Society 179: 229–240.

Raadik, T.A. 1992. Distribution of freshwater fishes in east Gippsland, Victoria, 1967–1991. Proceedings of the Royal Society of Victoria 104: 1-22.

Strahan, R. 1960. A comparison of the ammocoete and macrophthalmia stages of Mordacia mordax and Geotria australis (Petromyzonidae). Pacific Science 14: 416-420.

Strahan, R. 1964. Lampreys in Australia. Australian Natural History 14: 334-336.

Strahan, R. 1980. Family Mordaciidae: short-headed lampreys; Family Geotriidae: pouched lamprey, pp. 38–43, 6 figs In McDowall, R.M. (ed.) Freshwater Fishes of South-eastern Australia. Sydney : A.H. & A.W. Reed 208 pp. figs.

Yamazaki, Y. & A. Goto. 2000. Present status and perspectives on the phylogenetic systematics and speciation of lampreys. Japanese Journal of Ichthyology 47(1): 1-28.

Quick Facts

CAAB Code:37003002


Feeding:Parasitic carnivores

Habitat:Freshwater, marine

Max Size:56cm TL


Species Image Gallery

Species Maps

CAAB distribution map