Echidna

Echidnas[1]
Fossil range: Miocene–Recent
Western Long-beaked Echidna
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Monotremata
Family: Tachyglossidae
Gill, 1872
Species

Genus Tachyglossus
   T. aculeatus
Genus Zaglossus
   Z. attenboroughi
   Z. bruijnii
   Z. bartoni
   †Z. hacketti
   †Z. robustus
Genus †Megalibgwilia
   †M. ramsayi
   †M. robusta
A Short-beaked Echidna curled into a ball; the snout is visible on the right.
In Australia the Short-beaked Echidna may be found in many environments, including urban parkland such as the shores of Lake Burley Griffin in Canberra, as depicted here.
Short-beaked Echidna Skeleton, Articulated by Skulls Unlimited International.
Short-beaked Echidna

Echidnas (pronounced /ɨˈkɪdnə/), also known as spiny anteaters,[2] belong to the family Tachyglossidae in the monotreme order of egg-laying mammals. There are four extant species, which, together with the Platypus, are the only surviving members of that order and are the only extant mammals that lay eggs.[3] Although their diet consists largely of ants and termites, they are only distantly related to the true anteaters of the Americas. They live in New Guinea and Australia. The echidnas are named after a monster in ancient Greek mythology.

Contents

Description

Echidnas are small mammals that are covered with coarse hair and spines. Superficially they resemble the anteaters of South America and other spiny mammals like hedgehogs and porcupines; this is due to convergent evolution. They have snouts which have the functions of both mouth and nose. Their snouts are elongated and slender. They have very short, strong limbs with large claws and are powerful diggers. Echidnas have a tiny mouth and a toothless jaw. They feed by tearing open soft logs, anthills and the like, and use their long, sticky tongue, which protrudes from their snout, to collect their prey. The Short-beaked Echidna's diet consists largely of ants and termites, while the Zaglossus species typically eat worms and insect larvae.[4]

The long-beaked echidnas have tiny spines on their tongues that help capture their prey.[4]

Echidnas and the Platypus are the only egg-laying mammals, known as monotremes. The female lays a single soft-shelled, leathery egg twenty-two days after mating and deposits it directly into her pouch. Hatching takes place after ten days; the young echidna, called a puggle, then sucks milk from the pores of the two milk patches (monotremes have no nipples) and remains in the pouch for forty-five to fifty-five days,[5] at which time it starts to develop spines. The mother digs a nursery burrow and deposits the puggle, returning every five days to suckle it until it is weaned at seven months.

Male echidnas have a four-headed penis. During mating, the heads on one side "shut down" and do not grow in size; the other two are used to release semen into the female's two-branched reproductive tract. The heads used are swapped each time the mammal copulates.[6]

Contrary to previous research, the echidna does enter REM sleep, albeit only when the ambient temperature is around 25°C. At temperatures of 15°C and 28°C, REM sleep is suppressed.[7]

Evolution

Molecular clock and fossil dating suggest echidnas split from platypuses 19–48 million years ago. Echidnas evolved from water-foraging ancestors which returned to living completely on the land, even though this put them in competition with marsupials.[8] Because of this, it has been suggested that "oviparous reproduction in monotremes confers advantages over marsupials, a view consistent with present ecological partitioning between monotremes and marsupials."[8]

Taxonomy

Echidnas are classified into three genera. The genus Zaglossus includes three extant species and two species known only from fossils, while only one, extant species from the genus Tachyglossus is known. The third genus, Megalibgwilia, is known only from fossils.

Zaglossus

The three living Zaglossus species are endemic to New Guinea. They are rare and are hunted for food. They forage in leaf litter on the forest floor, eating earthworms and insects. The species are:

The two fossil species are:

Tachyglossus

The Short-beaked Echidna (Tachyglossus aculeatus) is found in southeast New Guinea and also occurs in almost all Australian environments, from the snow-clad Australian Alps to the deep deserts of the Outback, essentially anywhere that ants and termites are available. It is smaller than the Zaglossus species, and it has longer hair.

Megalibgwilia

The genus Megalibgwilia is known only from fossils:

References

  1. ↑ Groves, C. (2005). Wilson, D. E., & Reeder, D. M, eds. ed. Mammal Species of the World (3rd ed.). Baltimore: Johns Hopkins University Press. pp. 1–2. ISBN 0-801-88221-4. OCLC 62265494. http://www.bucknell.edu/msw3/browse.asp?id=10300002. 
  2. ↑ http://www.enchantedlearning.com/subjects/mammals/echidna/Echidnaprintout.shtml Retrieved on 21 October 2007
  3. ↑ "The Enigma of the Echidna" by Doug Stewart, National Wildlife, April/May 2003.
  4. ↑ 4.0 4.1 Zaglossus bruijni
  5. ↑ Short-beaked echidna Arkive.org
  6. ↑ Shultz, N. (26 October 2007). "Exhibitionist spiny anteater reveals bizarre penis". New Scientist website. http://environment.newscientist.com/article.ns?id=dn12838. Retrieved 27 October 2006. 
  7. ↑ SC Nicol, NA Andersen, NH Phillips, RJ Berger (11 February 2000), "The echidna manifests typical characteristics of rapid eye movement sleep", Neuroscience letters 
  8. ↑ 8.0 8.1 Phillips MJ, Bennett TH, Lee MS. (2009). Molecules, morphology, and ecology indicate a recent, amphibious ancestry for echidnas. PNAS. 106:17089–17094. doi:10.1073/pnas.0904649106

External links