The pouched lamprey (''Geotria australis''), also known as the piharau in

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

North Island The North Island ( , 'the fish of Māui', historically New Ulster) is one of the two main islands of New Zealand, islands of New Zealand, separated from the larger but less populous South Island by Cook Strait. With an area of , it is the List ...

, korokoro, kanakana in the

South Island The South Island ( , 'the waters of Pounamu, Greenstone') is the largest of the three major islands of New Zealand by surface area, the others being the smaller but more populous North Island and Stewart Island. It is bordered to the north by ...

, or wide-mouthed lamprey, is a species in the genus ''Geotria'', which is the only genus in the family Geotriidae. The second species in the genus is the Argentinian lamprey (''Geotria macrostoma''), which was revalidated as a separate species in 2020. The pouched lamprey is native to the southern hemisphere. It spends the early part of its life in fresh water, migrating to the sea as an adult, and returning to fresh water to spawn and die.

Description

''G. australis'', like other

lamprey Lampreys (sometimes inaccurately called lamprey eels) are a group of Agnatha, jawless fish comprising the order (biology), order Petromyzontiformes , sole order in the Class (biology), class Petromyzontida. The adult lamprey is characterize ...

s, has a thin

eel Eels are ray-finned fish belonging to the order Anguilliformes (), which consists of eight suborders, 20 families, 164 genera, and about 1000 species. Eels undergo considerable development from the early larval stage to the eventual adult stage ...

-like body, and grows up to long. It has two low

dorsal fin A dorsal fin is a fin on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...

s on the back half. Like other lampreys, it has no jaws, only a sucker. The skin is a striking silver in adult lampreys caught fresh from the sea but soon changes to brown after they have been in fresh water for some time, due to deposition of

biliverdin Biliverdin (from the Latin for green bile) is a green tetrapyrrolic bile pigment, and is a product of heme catabolism.Boron W, Boulpaep E. Medical Physiology: a cellular and molecular approach, 2005. 984–986. Elsevier Saunders, United States. ...

. Adult's eyes are relatively small and located on the side of the head. When fully mature, males develop a baggy pouch under their eyes, which may be used to massage and oxygenate their eggs. There have also been suggestions that the pouch in northern hemisphere species has been used by males during breeding times for gathering stones to make a nest.

Life cycle

The freshwater ammocoete or

larva A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect development such as insects, some arachnids, amphibians, or cnidarians typically have a larval phase ...

l stage of the life cycle are a dull brown in colour for most of their lives. Ammocoetes remain in fresh water for about four years until undergoing a six-month

metamorphosis Metamorphosis is a biological process by which an animal physically develops including birth transformation or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and different ...

, changing to silver with blue-green stripes. The central nervous system of the pouched lamprey develops notably during metamorphosis to the large-eyed macropthalmia stage, with particularly large increases in the volume of visual areas of the brain. At this point they migrate downstream to the sea. Adults spend some of their lives in the open sea, living as parasites on other fish. They attach themselves to the gills or side of the fish and rasp at the tissues below. Adults return to fresh water to breed, spending up to eighteen months sexually maturing before spawning. Adults have been recorded living up to 105 days after spawning and wrapping themselves around egg masses to provide parental care.

Distribution and habitat

The pouched lamprey is widespread in the Southern Hemisphere, occurring in

Chile Chile, officially the Republic of Chile, is a country in western South America. It is the southernmost country in the world and the closest to Antarctica, stretching along a narrow strip of land between the Andes, Andes Mountains and the Paci ...

Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...

, the

Falkland Islands The Falkland Islands (; ), commonly referred to as The Falklands, is an archipelago in the South Atlantic Ocean on the Patagonian Shelf. The principal islands are about east of South America's southern Patagonian coast and from Cape Dub ...

South Georgia South Georgia is an island in the Atlantic Ocean, South Atlantic Ocean that is part of the British Overseas Territories, British Overseas Territory of South Georgia and the South Sandwich Islands. It lies around east of the Falkland Islands. ...

and the southwest and southeast corners of

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

. It is the only lamprey species found in New Zealand.

Threats

Lampreys are preyed on by albatrosses, shags, large fish and marine mammals. It has been hypothesised that the apparent decline in lamprey numbers could be caused by the degradation of water quality in lowland waterways.

History

Pouched lampreys are a traditional

Māori Māori or Maori can refer to: Relating to the Māori people * Māori people of New Zealand, or members of that group * Māori language, the language of the Māori people of New Zealand * Māori culture * Cook Islanders, the Māori people of the Co ...

delicacy in New Zealand. Traditional methods for catching lampreys included disturbing the lampreys as they ascended waterfalls and capturing them, or by using , which involved placing a

weir A weir or low-head dam is a barrier across the width of a river that alters the flow characteristics of water and usually results in a change in the height of the water level. Weirs are also used to control the flow of water for outlets of l ...

across larger rivers which led to a hīnaki (woven trap). Some across the

Whanganui River The Whanganui River is a major river in the North Island of New Zealand. It is the country's third-longest river, and has special status owing to its importance to the region's Māori people. In March 2017 it became the world's second natur ...

were more than across. Pouched lampreys were widely seen in New Zealand in the mid-19th century, and were adopted as a food by European settlers, due to the history of lampreys as delicacies in Europe.

References

External links

* New Zealand lamprey discussed on RadioNZ ''Critter of the Week''
12 February 2016
{{DEFAULTSORT:Pouched Lamprey Lampreys Fish of New Zealand Fish of the Pacific Ocean Fish described in 1851 Taxa named by John Edward Gray Freshwater fish of New Zealand