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Polymelia: Animals With Extra Legs

Psyche Skinner is a psychologist with broad interests in the areas of literature, mythology, history, and technology.

All about polymelia in animals and humans

All about polymelia in animals and humans

What Is Polymelia?

There are many different conditions that can cause animals to be born with extra legs (a condition also called polymelia, pygomelia, or supernumerary limbs). Some examples are described below.

Causes of Polymelia

One cause of extra limbs is the partial development of a conjoined twin or a genetic mutation (spontaneous or inherited) that affects bodily development. It can also occur due to injuries, toxins, and/or infections during critical periods of fetal development. The most common causes suggested for polymelia seem to be:

  • Fragile chromosome resulting in chromosomal breaks, or
  • an incompleted conjoined twin, and
  • (in the case of amphibians) parasitic worm infection or high doses of vitamin A.

In domesticated cows, goats, and chickens, chromosome fragility has been found to be associated with polymelia and other defects. So while the condition is still considered to not have a known etiology, it seems that most cases can be traced to an acquired chromosomal vulnerability.

A cow with an extra limb growing from its neck

A cow with an extra limb growing from its neck

Polymelia in Cattle

There are quite a few examples of cattle that survive in good health with extra legs. The extra limbs often remain small and vestigial, allowing the bull or cow to function in a normal manner. They often seem to be attached to one side of the withers, where the animal can carry them fairly easily, and they remain relatively small in size.

However, extra limbs can also be large or larger in number–sometimes up to seven legs and other body parts. This condition can manifest more problematically, as it did for one particular calf in 1981; its extra limbs diverged at the knee rather than higher on the body, impeding locomotion and normal body postures.

Polymelia in cattle is sometimes found to be associated with chromosomes having multiple breaks. In other cases, it results from an incomplete conjoined twin.

For further examples, see these cases from Korea (2001) and Brazil (2008). These examples show polymelia happens around the world and to many different species and breeds of domestic cattle.

Deer

In 2008 a six-legged fawn was found. The fawn was separated from its mother and rescued when it was found under attack from dogs. As with many of the examples in cattle, the extra limbs belonged to a partially developed conjoined twin. In general, this condition seems to be especially rare in deer.

Dolphins

This dolphin, caught off the coast of Japan, was documented to have an extra set of fins. This abnormality was thought to reflect that dolphins evolved from species that have hind legs. These fins are not really an abnormality but may be caused by a mutation that activated a feature that was carried by the dolphin's evolutionary ancestors. Fins of this type are reported to occur occasionally and various species of dolphins and whales.

A frog with an extra leg

A frog with an extra leg

Frogs and Toads

Deformities, including extra limbs, are being seen more often in frogs around the world. Different explanations have been offered for these deformities including the effects of pollution, hormones, or climate change. The preferred explanation now is that deformities are produced when parasitic worms infect tadpoles. High doses of vitamin A are known to cause hind limb polymelia in toads.

Drawing of a cat with polymeila

Drawing of a cat with polymeila

Cats

A six-legged kitten born in Florida (2006) unfortunately died during surgery to remove the limbs. Victorian taxidermy also gives us this example of an eight-legged kitten. See more about other cases of polymelia in cats here.

Drawing of a dog with polymelia

Drawing of a dog with polymelia

Dogs

In 2009, a puppy with an extra leg was given surgery to remove the extra limb and avoid the animal being displayed in a modern freak show. The six-legged puppy shown above was discovered as a stray in 2005. In dogs, other body parts are often duplicated such as the lower colon or penis. For other examples see this specimen from Ukraine in 2009.

Stumpy, the duck with with an extra limb

Stumpy, the duck with with an extra limb

Poultry

Polymelia has been observed intermittently in chickens. A case was described in a slaughterhouse in 1985 and a four-legged chick was hatched in Australia in 2010.

In 2007 a four-legged duck was hatched in the United Kingdom. However, due to an accident "Stumpy" (shown above) ended up losing one extra leg. Another seemed to break off naturally. Thus Stumpy ultimately ended up living life as a conventional two-legged duck.

While still considered rare, duplication of wings is being increasingly reported such as in, this goose (2008) which has a third wing. The same condition has been observed in chickens and other fowl all around the world.

Sheep in Fragonard Museum, Paris

Sheep in Fragonard Museum, Paris

Sheep and Goats

Polymelia is not uncommon in sheep. With sheep, the extra limbs are often attached to the hindquarters. In 2002 a sheep was born in the Netherlands with a fifth leg. Other examples include New Zealand (2007), this unknown location (2009), and Iran (2012, 2013).

Swine

Duplicate limbs occur very rarely in pigs. One example known from 2008 had two extra hind legs and may have been the result of an extremely underdeveloped conjoined or parasitic twin.

Humans

Extra limbs on humans, when they occur, are generally not functional. In only a few cases, such as the human child Jie-Jie, was the limb sensitive to touch and able to move in a relatively normal manner.

Other human examples include: Josephene Myrtle Corbin, an American sideshow performer born in 1868, a four-legged girl named Maxine Mina (1896), and this male child (2014).

There is evidence that human cases can be traced to gene mutations in the parents.

Extra Fingers and Toes

Many species are sometimes born with extra fully or partially formed digits. Human polydactyly in the fingers is generally caused by a mutation that affects fetal development and may be associated with other abnormalities. However, these may be very mild. Anne Boleyn is one of the more famous examples, having six fingers on her right hand.

Polydactyly is also found in cats. Hemingway was known to own a cat with extra toes and its descendant still live in the Hemingway Museum. Hemingway acquired his cats from a sailor, many sailors believed these cats to be good luck. The mutation has also been found in horses and doves.

Snake with a leg

Snake with a leg

Other Animals With Extra Limbs

Extra limbs have also been known to occur in horses, the white stork, mice, newts, and pigeons.

And Finally...

A snake cannot really be said to have duplicate limbs, as it isn't supposed to have any in the first place. However, in 2009 this snake was found with a very uncharacteristic appendage—a leg! As with the dolphin, this probably reflects an accidental activation of ancient snake DNA, from a time when they still had legs.

Some modern species have small limb buds; ancient snakes had small hind legs, and even older ancestors would have had a full set of four. In 2008, a shark was caught that appeared to have two hind legs.

Sources and Further Reading

© 2010 Penny Skinner

Comments

peachy from Home Sweet Home on February 08, 2015:

wow, lots of animals have extra limbs too, were the pigs and ducks slaughtered or kept alive?

K Kiss from Newcastle upon Tyne, UK on January 24, 2013:

a very well written hub on an interesting, albeit sad, topic. Shared

Sarah on November 04, 2011:

That is sad but nasty at the same time..

TIC Publishing from Halifax, NS, Canada on July 04, 2011:

A snake with legs - Take that, creationists :-P

GetSmart on March 13, 2011:

This was a very interesting article. Thanks