Wednesday, August 15, 2007
Tuesday, August 14, 2007
The liger is a hybrid cross between a male Panthera leo (lion), and a female Panthera tigris (tiger) and is denoted scientifically as Panthera tigris × Panthera leo. A liger resembles a lion with diffused stripes. They are the largest cats in the world although the Siberian Tiger is the largest pure sub-species. Like tigers, but unlike lions, ligers enjoy swimming. A similar hybrid, the offspring of a male tiger and a female lion is called a tigon. According to The Tiger, Symbol of Freedom rare reports have been made of tigresses mating with lions in the wild. Under exceptional circumstances it has been known for a tiger to be forced into ranges inhabited by the Asiatic Lion, Panthera leo persica; however, this combination of species in the wild is considered highly unlikely.The present day range of wild lions and tigers no longer overlap.
Imprinted genes may be a factor contributing to liger size. These are genes that may or may not be expressed depending on the parent they are inherited from, and that occasionally play a role in issues of hybrid growth. For example, in some mice species crosses, genes that are expressed only when maternally-inherited cause the young to grow larger than is typical for either parent species. This growth is not seen in the paternal species, as such genes are normally "counteracted" by genes inherited from the female of the appropriate species.
The tiger produces a hormone that sets the fetal liger on a pattern of growth that does not end throughout its life. The hormonal hypothesis is that the cause of the male liger's growth is its sterility — essentially, the male liger remains in the pre-pubertal growth phase. This is not upheld by behavioural evidence - despite being sterile, many male ligers become sexually mature and mate with females. Male ligers also have the same levels of testosterone ng/dl on average as an adult male lion. In addition, female ligers also attain great size, weighing approximately 700 lb (320 kg) and reaching 10 feet (3.05 m) long on average, but are often fertile.
Shasta, a ligress (female liger) was born at the Hogle Zoo in Salt Lake City on May 14th, 1948 and died in 1972 at age 24. The 1973 Guinness world records reported an 18-year-old, 798-kg (1756 lb) male liger living at Bloemfontein zoological gardens, South Africa in 1888. Valley of the Kings animal sanctuary in Wisconsin has a 21-year-old male liger named Nook who weighs 550 kg (1210 lb), and is still living as of January 2007. http://www.votk.org/pictures/index.php
While male ligers are sterile, female ligers are fertile, and they can reproduce. Because only female ligers and tigons are fertile, a liger cannot reproduce with a tigon.
If a liger were to reproduce with a tiger, it would be called a ti-liger, and if it were to reproduce with a lion, it would be called a li-liger. The fertility of hybrid big cat females is well-documented across a number of different hybrids. This is in accordance with Haldane's rule: in hybrids of animals whose gender is determined by sex chromosomes, if one gender is absent, rare or sterile, it is the heterogametic sex (the one with two different sex chromosomes e.g. X and Y).
According to Wild Cats of the World (1975) by C. A. W. Guggisberg, ligers and tigons were long thought to be sterile: In 1943, however, a fifteen-year-old hybrid between a lion and an 'Island' tiger was successfully mated with a lion at the Munich Hellabrunn Zoo. The female cub, although of delicate health, was raised to adulthood.
Ligers have a tiger-like striping pattern on a lion-like tawny background. In addition they may inherit rosettes from the lion parent (lion cubs are rosetted and some adults retain faint markings). These markings may be black, dark brown or sandy. The background color may be correspondingly tawny, sandy or golden. In common with tigers, their underparts are pale. The actual pattern and color depends on which subspecies the parents were and on the way in which the genes interact in the offspring.
White tigers have been crossed with lions to produce "white" (actually pale golden) ligers. In theory white tigers could be crossed with white lions to produce white, very pale or even stripeless ligers. A black liger would require both a melanistic tiger and a melanistic lion as parents. Very few melanistic tigers have ever been recorded, most being due to excessive markings (pseudo-melanism or abundism) rather than true melanism. No reports of black lions have ever been substantiated. A hypothetical procedure to breed black ligers is explained here. The blue or Maltese Tiger is now unlikely to exist, making grey or blue ligers an impossibility. It is not impossible for a liger to be white, but it is very rare.
In caz ca inca nu credeti, cateva linkuri video should do it:
Exista chiar si o organziatie dedicata acestor hibrizi: http://www.liger.org/
Asta nu e tot. Dintre cele patru specii de feline mari actuale (panthera leo-leul, p. onca-jaguarul, p. pardus-leopardul si p. tigris), sunt posibile inca cateva combinatii genomice.
Hibrizii acestor specii se numesc:
Liguar - mascul leu, femela jaguar
Liard - mascul leu, femela leopard
Tiguar - mascul tigru, femela jaguar
Tigard - mascul tigru, femela leopard
Jagupard - mascul jaguar, femela leopard
Leopon - mascul leopard, femela leu
Leotig - mascul leopard, femela tigru
Leguar - mascul leopard, femela jaguar
Jaglion - mascul jaguar, femela leu
Jaguatiger - mascul jaguar, femela tigru
Tigon - mascul tigru, femela leu
Si iata un jaguapard:
Mai multe despre acesti hibrizi aici http://en.wikipedia.org/wiki/Panthera_hybrid