Pouch Lamprey, Geotria australis Gray 1851


Other Names: Narrow-mouthed Lamprey, Piharau, Pouched Lamprey, Velasia, Wide-mouthed Lamprey

A Pouch Lamprey, Geotria australis. Source: Rudie H. Kuiter / Aquatic Photographics. License: All rights reserved

Summary:

Primitive eel-like fishes with two dorsal fins near the tail, 7 pairs of pore-like gill openings, a mouth in the shape of an oral disc fringed with skin flaps and armed with many small, horny teeth, including spatulate lateral teeth, and eyes positioned on the side of the head.

Pouch Lampreys have a cartilaginous skeleton, primitive eyes, a single median nostril, and lack true jaws, paired fins and scales. Breeding males have a large baggy pouch on the underside of the head.

These jawless fishes are anadromous - adults spawn in the headwaters of freshwater rivers and streams, and when the larvae or ammocoetes hatch, they drift downstream and burrow into soft muddy sediments. They spend the next few years filter-feeding on micro-organisms from the water above.

After metamorphosis, young adults migrate downstream to estuaries and coastal waters, where they feed parasitically by rasping flesh from other fishes with their toothy tongues. They eventually cease feeding and migrate back to freshwater to breed.

Video of Pouched Lamprey in south Western Australia


Cite this page as:
Bray, D.J. & Gomon, M.F. 2020, Geotria australis in Fishes of Australia, accessed 29 Mar 2024, https://fishesofaustralia.net.au/home/species/3415

Pouch Lamprey, Geotria australis Gray 1851

More Info


Distribution

Marine, estuarine and coastal rivers and streams on the south coast, from the Gippsland Lakes, Victoria, to the Moore River north of Perth, Western Australia, including coastal rivers and streams in Tasmania. Elsewhere the species is widespread in cold temperate waters of the Southern Hemisphere: southern Australia, New Zealand, South America, Falkland Islands, and South Georgia.

Pouched Lampreys are anadromous, with adults spawning in freshwater. The worm-like ammocoete larvae live in muddy burrows in the upper reaches of coastal streams for about 4 years, before migrating downstream as young adults to spend about two years in the Southern Ocean, before returning to freshwaters to breed.

Features

Body eel-like with 7 pore-like gill openings, a single median nostril on top of the head, and eyes positioned laterally on side of head. The mouth lacks jaws, and is modified into an oral disc with many blunt, overlapping, flat, horny teeth in curved rows and several larger central teeth. The oral disc is fringed by short, fleshy papillae. Mature males have an enlarged oral disc and sometimes a baggy pouch beneath the head. Two dorsal fins are set well back near the tail, the first short-based and the second slightly longer, ending near the origin of caudal fin. Scales, pectoral, ventral and anal fins are absent. Ammocoete larvae lack eyes and have a single undivided dorsal fin.

Size

Ammocoete larvae to ~10cm; adults to 60cm TL.

Colour

Adults are dark brown to grey, and the ammocoetes are brown. Young adults at sea are silver or silvery cobalt blue, with two greenish or blue-green dorsal stripes.

Feeding

The larvae or ammocoetes begin their life as filter feeders, living mostly on detritus and microscopic algae. After metamorphosis, southern lampreys become parasitic. They use their sucker-like mouth and horny rasping teeth to attach to other fishes and tear into the flesh of their prey. Adults stop feeding when they return to freshwater rivers to spawn, surviving on stored fats and body tissues during their migration.

Biology

Newly hatched ammocoete larvae drift downstream and eventually burrowing into muddy substrates. After 4-5 years, the ammocoetes metamorphose into young adult lampreys over a period of about six months. During this time their eyes become larger and develop the visual pigments essential for life at sea. They migrate downstream, leaving behind their life as filter-feeders to become parasites on other fishes.

They spend the next two years or so in the Southern Ocean before undertaking a long migration of up to 18 months back to the headwaters of freshwater streams to breed. Remarkably, the lampreys do not feed during this time. Once in freshwater, they lose their brilliant colour, becoming a drab brown. Males may also develop the large characteristic pouch on the underside of the head behind the mouth.

Adults usually spawn in small, shallow, gravel-bottomed streams. The female prepares a small depression or nest in the substrate and attaches herself to a rock with her oral disc. The male attaches to the female with his oral disc and wraps around her to squeeze out her eggs before releasing his sperm. Adults die shortly after spawning.

Conservation

Lamprey populations are affected by the regulation of rivers including the construction of barriers such as dams and weirs. regulation and construction of barriers (barrages, weirs and dams).Climate change and predation by invasive species such as trout also deleteriously affect lamprey populations.

Remarks

When lampreys migrate upstream to spawn they must often negotiate obstacles such as rapids, waterfalls and even dams. Pouched lampreys are able to climb structures by gripping onto rocks and other surfaces with their sucking mouths, gradually inching their way upstream. They can even move over land to make their way upstream.

Etymology

The specific name australis (= southern) in reference to the type locality in Australia.

Species Citation

Geotria australis Gray 1851, List fish Brit. Mus. Part I: 142, Pl. 1 (fig. 3), Pl. 2. Type locality: Hobsons Bay, Victoria, or Onkaparinga, South Australia.

Author

Bray, D.J. & Gomon, M.F. 2020

Resources

Atlas of Living Australia

Pouch Lamprey, Geotria australis Gray 1851

References


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Quick Facts


CAAB Code:37003001

Behaviour:Migratory

Conservation:IUCN Data Deficient

Feeding:Parasitic carnivore

Habitat:Freshwater, marine

Max Size:60 cm TL

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CAAB distribution map