Brown snakes

from Wikipedia, the free encyclopedia
Brown snakes
Brown snake (Pseudonaja sp.)

Brown snake ( Pseudonaja sp.)

Systematics
without rank: Toxicofera
Subordination : Snakes (serpentes)
Superfamily : Adder-like and viper-like (Colubroidea)
Family : Poison Snakes (Elapidae)
Subfamily : Hydrophiinae
Genre : Brown snakes
Scientific name
Pseudo yes
Günther , 1858

The pseudonaja ( pseudo Well ), also known as Australian aspidelaps referred are, one in Australia and New Guinea widespread species of snakes from the family of poisonous snakes (Elapidae). The scientific name Pseudonaja means "False Naja", where Naja stands for the real cobras . The unusual way of hunting is characteristic of brown snakes: Most species kill their prey by taking a poison bite and entangling them at the same time. The common brown snake ( Pseudonaja textilis ) is one of the most venomous snakes in the world.

features

anatomy

Brown snakes are small to very large poisonous snakes; the animals reach total lengths of up to 2.2 m. They are slender, the head is relatively small and only in the strongest individuals is wider than the neck. The canthus is sharp-edged.

Scaling

Like all venomous snakes, brown snakes have nine large, symmetrical shields on their heads. The front has straight sides and is significantly longer than it is wide. The nasal is undivided. The animals have one primary and two secondary temporalia . They have six supralabials and six to seven infralabials . The back scales are smooth. The animals have 17 to 21 dorsal rows of scales in the middle of the body. The anal shield is divided, the subcaudalia are all divided.

coloring

The German name "Braunschlangen", like the English name "Brown Snakes", is only partially applicable. Some species (e.g. P. ingrami and P. textilis ) are monochrome light brown to dark brown on top, but other species are more or less spotted on a brown background ( P. affinis , P. inframacula ) and some morphs of P. . guttata , P. modesta and P. nuchalis are finally clearly light-dark banded or the head area is clearly set off in color from the rest of the upper side. In addition, in most species there are clear differences in color between young and adult animals.

distribution and habitat

Pseudonaja textilis

The genus occurs in Australia and New Guinea. Six of the seven species are endemic to Australia, the common brown snake ( Pseudonaja textilis ) also occurs in eastern New Guinea. Four of the seven species have relatively small ranges; three species ( P. modesta , P. nuchalis and P. textilis ) each inhabit large parts of Australia.

Brown snakes use a wide range of habitats from tropical rainforests in the north and east to arid areas in the west of the continent. The three species P. affinis , P. nuchalis and P. textilis are cultural followers and are also common on agriculturally used land and in the vicinity of towns and villages.

Systematics

Seven species are currently recognized:

Six of these species have also been confirmed by recent molecular genetic and morphometric studies. For Pseudonaja nuchalis , however, three well differentiable clades could be distinguished in these investigations , which apparently represent three different species. According to this, P. nuchalis can be divided into three types; the names P. aspidorhyncha and P. mengdeni have been proposed for the two new species . The closest relatives of the brown snakes are the taipans .

Lifestyle, Diet and Reproduction

Brown snakes are predominantly diurnal and apparently exclusively ground-dwelling. The animals move very quickly and have comparatively large spaces for action . When threatened, like the real cobras, they spread a hood behind their heads.

The diet consists mainly of lizards and frogs. However, three species ( P. affinis , P. nuchalis and P. textilis ) have found the house mouse introduced in Australia as a new source of food; in P. textilis the species accounts for approx. 25% of the prey. The way of hunting is unusual because, with the exception of P. modesta , brown snakes kill their prey with a venomous bite and entanglement at the same time. All species lay eggs ( oviparous ).

Poison

The species of the genus are described as very agile and some species bite very quickly when disturbed; this applies in particular to P. textilis . The brown snakes are therefore one of the species of venomous snakes that bite people most frequently in Australia. The poison of the brown snake mainly contains anticoagulant and nerve-damaging (neurotoxic) components. It is extremely effective - the LD 50 value of the poison of P. textilis in mice is 0.41 mg per kg, of P. nuchalis 0.34 mg per kg and P. affinis 0.66 mg per kg. After the inland taipan, which also occurs in Australia, P. textilis has the most effective poison known to affect land snakes.

However, the fangs are very short and the average amount of venom per bite is comparatively low. For the three species P. textilis , P. nuchalis and P. affinis it is given as 4 to 6.5 mg dry weight. Most of the bites therefore remain without serious consequences for humans. The smallest species, P. modesta , is even considered harmless despite its toxicity. In bites of the larger species, especially P. textilis and P. nuchalis , severe poisoning and even death occur; Children in particular are at risk.

Individual evidence

  1. ^ A. Skinner: A multivariate morphometric analysis and systematic review of Pseudonaja (Serpentes, Elapidae, Hydrophiinae). Zoological Journal of the Linnean Society 155, Issue 1, 2009, pp. 171-197. doi : 10.1111 / j.1096-3642.2008.00436.x
  2. ↑ Doughty, P., B. Maryan, SC Donnellan and MN Hutchinson: A new species of taipan (Elapidae: Oxyuranus) from central Australia. Zootaxa 1422, 2007, pp. 45-58.
  3. ↑ Shine, R. and J. Covacevich: Ecology of Highly Venomous Snakes: the Australian Genus Oxyuranus (Elapidae). Journal of Herpetology 17, No. 1, 1983, pp. 60-69.
  4. ↑ a b Mirtschin, PJ, GR Crowe and R. Davis: Dangerous Snakes Of Australia. In: P. Gopalakrishnakone, LM Chou: Snakes of Medical Importance. Venom and Toxin Research Group, National University of Singapore, 1990, pp. 49-77.
  5. ↑ Mirtschin, PJ, GR Crowe and R. Davis: Dangerous Snakes Of Australia. In: P. Gopalakrishnakone, LM Chou: Snakes of Medical Importance. Venom and Toxin Research Group, National University of Singapore, 1990, pp. 49-77, here p. 49

literature

  • Mirtschin, PJ, GR Crowe, and R. Davis: Dangerous Snakes of Australia. In: P. Gopalakrishnakone, LM Chou: Snakes of Medical Importance. Venom and Toxin Research Group, National University of Singapore, 1990, ISBN 9971-62-217-3 , pp. 1-174.
  • Storr, GM, LA Smith and RE Johnstone: Snakes of Western Australia . Perth 1986, ISBN 0-7309-0399-0 , pp. 90-96.

Web links

Commons : Braunschlange  - Album with pictures, videos and audio files