Pouched lamprey

Pouched lamprey
Drawing by W. Wing
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Cephalaspidomorphi
Order: Petromyzontiformes
Family: Geotriidae
D. S. Jordan, 1923
Genus: Geotria
J. E. Gray, 1851
Species: G. australis
Binomial name
Geotria australis
J. E. Gray, 1851
Synonyms
  • Dionisia Lahille 1915 non Landau Chabaud, Miltgen & Baccam 1980
  • Exomegas [Burmeister 1868] Gill 1883
  • Macrophthalmia Plate 1897
  • Neomordacia Castelnau 1872
  • Thysanochilus Troschel 1857 non Butler 1878
  • Velasia Gray 1853
  • Yarra Castelnau 1872 non Krapp-Schickel 2000

The pouched lamprey (Geotria australis) also known as wide-mouthed lamprey, is the only species in genus Geotria, which is in turn the only genus in the family Geotriidae. It is native to the southern hemisphere. It spends the early part of its life in fresh water, migrating to the sea as adult, and returning to fresh water to spawn and die.

Description

Geotria australis, Northland, New Zealand

G. australis, like other lampreys, has a thin eel-like body, and grows up to 60 cm (24 in) long.[1] It has two low dorsal fins 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.

Life cycle

The freshwater ammocoete or larval 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,[2] changing to silver with blue-green stripes. The central nervous system of the pouched lamprey develops notably during metamorphosis to the large-eyed macropthalmia stagee, with particularly large increases in the volume of visual areas of the brain.[3] At this point they migrate downstream to the sea.

Adult eyes are relatively small, and located on the side of the head. When fully mature, males develop a baggy pouch under their eyes, the function of which is unknown. However, there have been suggestions that the pouch in Northern hemisphere species has been used by males during breeding times for gathering stones to make a nest.[4] Adults spend some of their life in the open sea, living as a parasite on other fish. They attach themselves to the gills or side of the fish and rasp at the tissues below. Adults returns to fresh water to breed, spending up to eighteen months sexually maturing before spawning and dying shortly afterwards.

Distribution and habitat

The pouched lamprey is widespread in the Southern Hemisphere, occurring in New Zealand, Chile, Argentina, and the southwest and southeast corners of Australia.

References

  1. Dianne J. Bray & Martin F. Gomon, 2011, Pouch Lamprey, Geotria australis, in Fishes of Australia, accessed 07 Oct 2014, http://www.fishesofaustralia.net.au/home/species/3415
  2. "Geotria australis: Pouched lamprey". Fishbase. Retrieved 2013-12-15.
  3. Salas; et al. (2015). "Ontogenetic shifts in brain scaling reflect behavioral changes in the life cycle of the pouched lamprey Geotria australis". Frontiers in Neuroscience 9. doi:10.3389/fnins.2015.00251.
  4. Pouch use

External links

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