Mature Non-parasitic Lamprey adults have been caught in the Moruya and Tuross rivers in southern New South Wales. Although Non-parasitic Lamprey is almost certainly present in other rivers in south-eastern Australia (they were also recently recorded from the nearby Bega and Wallagaraugh rivers), and possibly also Tasmania, difficulties in distinguishing between all but the mature adult stage of this species and those of Shorthead Lamprey (Mordacia mordax) has made it difficult to elucidate the precise distribution of Non-parasitic Lamprey. However, the available data suggest this species is never abundant and is certainly less numerous than Shorthead Lamprey (Mordacia mordax). (NSW).
The life cycle of the Non-parasitic Lamprey comprises distinct larval (ammocete) and adult phases. Mature males and females both have a dark dorsal surface. In contrast, the ventral surface of the trunk, i.e. the region between the last gill aperture and the cloaca, is a mottled grey in mature males and, through the partial visibility of eggs in the body cavity, yellowish in mature females. Also the suctorial disc is larger in males than females. The total length of mature adults ranges from 115 to 160 mm. In contrast to mature adults, the ammocoetes of Non-parasitic Lamprey do not possess either eyes or a suctorial disc and their dorsal fins are not as well developed. All stages except the mature adults remain burrowed in the substrata of rivers.
Ecology/Way of Life:
The ammocetes of Non-parasitic Lamprey live in the soft substrata found in the slow-flowing regions of rivers. They feed on the diatoms and detritus that they extract from the surrounding water. Length-frequency data indicate that larval life typically lasts for at least four years. In the Moruya River, metamorphosis commences in mid-spring and eventually leads into the development of a mature adult by the following late winter or early spring. During this period of nearly a year, Non-parasitic Lamprey does not feed. However, as with the morphologically very similar Shorthead Lamprey (Mordacia mordax), a tooth-bearing tongue-like piston, suctorial disc, eyes and prominent dorsal fins are developed by Non-parasitic Lamprey (Mordacia praecox) during metamorphosis. Since these structures are used by Shorthead Lamprey (Mordacia mordax) to locate and attach to fish and then to extract blood from that host, it is assumed that the Non-parasitic Lamprey (Mordacia praecox) evolved from the parasitic Shorthead Lamprey (Mordacia mordax). While Non-parasitic Lamprey spends the whole of its life cycle in fresh water, the completion of metamorphosis by Shorthead Lamprey (Mordacia mordax) is accompanied by a downstream migration to the sea and the start of parasitic feeding. As a consequence of this adult trophic phase, the adults of Shorthead Lamprey (Mordacia mordax) have attained, by the time they return to the rivers to breed, lengths of 300–450 mm, which are thus far greater than the maximum length of ca 160 mm reached by Non-parasitic Lamprey (Mordacia praecox)
Interaction with Humans/Threats:
There can be little doubt that certain anthropogenic changes to river systems have had a deleterious effect on the abundance of lamprey species, including Non-parasitic Lamprey (Mordacia praecox). This non-parasitic species is listed as endangered.
Mordacia praecox was named by Potter in 1968. The name is based on Greek, praecox meaning early development.
Allen, G. R., Midgley, S. H. & Allen, M. (2002). Field Guide to the Freshwater Fishes of Australia. Western Australian Museum. Perth. 394pp.
Merrick, J. R. & Schmida, G. E. (1984). Australian Freshwater Fishes: Biology and Management. Griffith Press Ltd. 409pp.
Potter, I.C. (1968). Mordacia praecox, n.sp., a nonparasitic lamprey (Petromyzonidae), from New South Wales, Australia. Proceedings of the Linnean Society of New South Wales. 92: 254–261.
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., 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 (Zoology). 47 : 533–546.
Text: Ian C. Potter. Distribution map: Peter J. Unmack. Photographer: Ian C. Potter.
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|Distribution of Mordacia praecox|
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