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 and a mouth in the shape of an oral disc fringed with skin flaps and armed with many small, horny teeth.

Pouch Lampreys have cartilaginous skeletons, primitive eyes, a single median nostril. They 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:

Dianne J. Bray & Martin F. Gomon, 2011, Pouch Lamprey, Geotria australis, in Fishes of Australia, accessed 26 Jul 2014, http://www.fishesofaustralia.net.au/home/species/3415

Pouch Lamprey, Geotria australis Gray 1851

More Info


Distribution

Widespread throughout cold temperate waters of the Southern Hemisphere, from South America, Australia and New Zealand. In Australian waters, Pouched Lampreys live in marine, estuarine and coastal rivers and streams on the south coast, from about Lakes Entrance, Victoria, to Perth, Western Australis.

They have an anadromous life cycle. Adults spawn in freshwater, and the worm-like ammocoete larvae live in muddy burrows in the upper reaches of coastal streams for about 4 years. As young adults, the lampreys migrate downstream and spend about two years in the Southern Ocean, before returning to breed in freshwater.

Features

Body eel-like with 7 pore-like gill openings and a single median nostril on top of the 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. The ammocoetes (<12cm) 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.

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 around oover round to make their way upstream.

Species Citation

Geotria australis Gray 1851, List fish Brit. Mus. Part I: 142, Pl. 1 (fig. 3), Pl. 2. Type locality: Hobson’s Bay or Onkaparinga, SA.

Author

Dianne J. Bray & Martin F. Gomon

Pouch Lamprey, Geotria australis Gray 1851

References


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Quick Facts


CAAB Code:37003001

Behaviour:Migratory

Biology:Primitive jawless fishes

Feeding:Parasitic carnivore

Habitat:Freshwater, marine

Max Size:60 cm TL

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