Non-parasitic Lamprey, Mordacia praecox Potter 1968


The Non-parasitic Lamprey is almost identical to its relative, the Shorthead Lamprey (Mordacia mordax). Adults are long and slender, with 7 gill openings behind the eyes, a single median nostril, two low dorsal fins far back on the body, and a prominent hood-like structure overhanging the well-developed oral sucking disc.

Lampreys lack scales and paired fins. The worm-like ammocoete larva lacks eyes and teeth. Non-parasitic lampreys spend their entire lives in freshwater.

Cite this page as:
Dianne J. Bray & M.F. Gomon, Mordacia praecox in Fishes of Australia, accessed 29 May 2024,

Non-parasitic Lamprey, Mordacia praecox Potter 1968

More Info


Endemic to a few temperate rivers Queensland and southern New South Wales and possibly Victoria, from the Deua and Moruya Rivers, to the Wallagaraugh River, which has its headwaters in New South Wales and flows into Mallacoota Inlet, Victoria.

There are unconfirmed reports of this species from the Latrobe River (Vic). In addition, specimens used by Gustafsson et al. (2008) were reportedly from the Yarra River.

Unlike the Shorthead Lamprey, Moradacia mordax, the Non-parasitic Lamprey completes its life-cycle entirely in freshwater rivers and streams.


Body eel-like, with gill openings as 7 enlarged pores and a single median nostril on top of the head. The jawless mouth is modified into an oral sucking disc with sharp separate teeth arranged in outer and inner rows, and a series of inconspicuous teeth around edge of mouth. The rim of the sucking disc lacks fleshy papillae.

The small primitive eyes are near the top of the head and have multifocal lenses, possibly capable of colour vision. The two dorsal fins are set well back near the tail. the first is short-based and the second is slioghtly longer (2 or more times length of the first dorsal fin). Scales, pectoral, pelvic and anal fins are absent.

The lateral line consists of a series of papillae forming a characteristic pattern under the eye and along the dorsal surface of the snout.

Ammocoete larvae (<12cm) lack eyes and have a single undivided dorsal fin.


Maximum size to 50cm TL, commonly 35-40cm TL. The ammocoete larvae rarely exceed 17 cm.


Adults are dark blue dorsally and greyish below. Females appear yelllowish below because the eggs are visible through to abdomen.


The ammocoetes (larvae) are filter feeders, consuming detritus, microscopic algae and plankton. Sub-adults are not parasitic on other fishes but little is known of the feeding habits of the older stages.


Adults spawn in the upper reaches of rivers during late winter or spring. Although little is known of the biology of this species, it is likely that spawning habits are similar to those of M. mordax.

It is thought that adults spawn after they metamorphose and die shortly after. Newly-hatched ammocoetes drift down-current and eventually burrow into soft sediments in slow-flowing areas.

Ammocoetes grow to about 17cm TL and metamorphose to young adult stage after 3 years.


Of no interest to fisheries.


IUCN: Listed as VULNERABLE on the 2011 IUCN Red List of Threatened Species.

Similar Species

Externally identical to Shorthead lampreys, M. mordax, in all stages. The teeth on the oral disc of Adult non-parasitic lampreys are separate and not arranged in radial plates.

Adult Non-parasitic lampreys are much smaller than those of M. mordax, rarley growing to more than 170 mm, vs more than 300 mm.

Species Citation

Potter, I.C. (1968). Mordacia praecox n. sp., a nonparasitic lamprey (Pectromyzontidae), from New South Wales, Australia. Proc. Linn. Soc. N.S.W. 92(3): 254-261.

Type locality: Moruya River, NSW.


Dianne J. Bray & M.F. Gomon

Non-parasitic Lamprey, Mordacia praecox Potter 1968


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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.

Gustafsson, O.S.E., Collin, S.P. & Kröger, R.H.H. 2008. Early evolution of multifocal optics for well-focused colour vision in vertebrates. J. Exp. Biol. 211: 1559-1564.

Hardisty, M.W. & Potter, I.C. 1971. The Biology of Lampreys. London, New York: Academic Press.

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.

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

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 p.

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Potter, I.C., Hilliard, R.W. & Neira, F.J. 1986. The biology of Australian Lamprey. In: DeDeckker, P. & Williams, W.D. (eds.) Limnology in Australia. CSIRO/Dr W. Junk Publishers, Dordrecht, Netherlands.

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.

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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:37003003

Conservation:IUCN Vulnerable

Habitat:Freshwater rivers, streams

Max Size:50 cm TL


Species Maps

CAAB distribution map