''Mordacia praecox'', the Australian brook lamprey or nonparasitic lamprey, is a

freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does include ...

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of southern topeyed lamprey that occurs in south-eastern

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

. It has a thin

eel Eels are ray-finned fish belonging to the order Anguilliformes (), which consists of eight suborders, 19 families, 111 genera, and about 800 species. Eels undergo considerable development from the early larval stage to the eventual adult stage ...

-like body around 12 to 15 cm long, with two low

dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...

s on the back half. The skin is dark blue above and gray below. Its eyes are small, and located on the top of its head. Unlike '' M. mordax'', ''M. praecox's'' eyes appear to have the potential for dichromatic vision (despite being similarly adapted for low-light environments). ''M. praecox'' is known only from the

Moruya Moruya is a town located on the far south coast of New South Wales, Australia, situated on the Moruya River. The Princes Highway runs through the town that is about south of Sydney and from Canberra. At the , Moruya had a population of 4 ...

and

Tuross River The Tuross River, an open semi-mature wave dominated barrier estuary or perennial stream, is located in the South Coast region of New South Wales, Australia. Course and features Tuross River rises of the eastern slopes of the Kybeyan Range, p ...

s in southern

New South Wales ) , nickname = , image_map = New South Wales in Australia.svg , map_caption = Location of New South Wales in AustraliaCoordinates: , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , es ...

. Unlike most other species of lampreys, it spends its entire life in fresh water. The

ammocoetes Lampreys (sometimes inaccurately called lamprey eels) are an ancient extant lineage of jawless fish of the order Petromyzontiformes , placed in the superclass Cyclostomata. The adult lamprey may be characterized by a toothed, funnel-like s ...

(lamprey

larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. The ...

e) take around three years to reach maturity. Ammocoetes and juvenile adults are indistinguishable from those of '' M. mordax'', which also occurs within its distribution, but the adults are easily distinguished by their size and colouration.

References

* * * Warrington, Rachael (2016). ''Retinal photoreception in southern hemisphere lampreys (PhD)''. University of Western Australia. * praecox Freshwater fish of Australia Vulnerable fauna of Australia {{jawless-fish-stub