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.
The main causes of extra limbs is the partial development of a conjoined twin, or a genetic mutation (spontaneous or inherited) that affects fetal development. It can also occur due to injuries, toxins, and/or infections during critical periods of fetal development.
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. The 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 they can also be large or comprise of up to seven legs and other body parts. Or cases like this one from 1981 which are more disabling to the calf, as the extra limbs diverge at the "knee" rather than higher in the body, and so impede locomotion and normal body postures.
Polymelia in cattle is sometimes found to be associated with chromosomes having multiple breaks. In other cases is results from an incomplete conjoined twin. For further examples see: Japan (1985), Korea (2001), Korea (2007), Brazil (2008), United States/Nebraska (2007), India (2010), (2014). These examples show polymelia happens around the world and to many different species and breeds of domestic cattle.
- Muirhead, T. L., Pack, L., & Radtke, C. L. (2014). Unilateral notomelia in a newborn Holstein calf. The Canadian Veterinary Journal, 55(7), 659.
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.
This dolphin, caught off the coast of Japan, was documented to have an extra set of fins (2006). This abnormality was though to reflect that dolphins evolved from species that has hind legs. These fins are not really an abnormality, but may be cause by a mutation that activated a feature that was carried by the dolphins evolutionary ancestors, but is not normally expressed in modern dolphin. Fins of ths type are reported to occur occasionally and various species of dolphin and whale.
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 hing limb polymelia in toads.
- Bruschelli, G. M., & Rosi, G. (1971). Polymelia induced by vitamin A in larvae of Bufo vulgaris. Rivista di biologia, 64(3/4), 271-283.
- Mahapatra, P. K., Mohanty-Hejmadi, P., & Dutta, S. K. (2001). Polymelia in the tadpoles of Bufo melanostictus (Anura: Bufonidae). Current Science, 1447-1451.
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 to the right was discovered as a stray in 2005. In dogs ather body parts are often duplicated such as the lower colon or penis. For other examples see: Ukraine(preserved specimen, 2009), poodle with an extra hind limb (2018).
- Daneze, E. R., & Brasil, F. B. (2018). Polymelia and duplication of the descending colon in a Poodle dog. VeterINarSkI arhIV, 88(1), 149-157.
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. Other cases include a leghorn (2015).
In 2007 a four legged duck was hatched in the United Kingdom. However due to an accident "Stumpy" (right) 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 observed in Fayoumi chickn (2013). Nigerian Nera black chicken (2013) Shakani chicken (2014) and Iranian indigenous fowl (2017) -- amongst others.
- Abu-Seida, A. M. (2013). Amputation of polymelia in a layer chicken. Avian diseases, 58(2), 330-332.
- Amatya, B. (2014). First Report of Polymelia in Shakini Breed Chicken from Nepal. Journal of Natural History Museum, 28, 175-177.
- Azeez, O. I., & Oyagbemi, A. A. (2013). First report of polymelia and a rudimentary wing in a Nigerian Nera black chicken. Journal of the South African Veterinary Association, 84(1), 1-3.
- Barua, P. M., Kalita, D., Goswami, S., Ahmed, K., & Sarma, D. K. (2015). Pygomelia (Polymelia) in a fowl-a case report. North-East Veterinarian, 15(1), 25-26.
- Hassanzadeh, B., & Rahemi, A. (2017). Polymelia with unhealed navel in an Iranian indigenous young fowl. In Veterinary Research Forum (Vol. 8, No. 1, p. 85). Faculty of Veterinary Medicine, Urmia University, Urmia, Iran.
- Hinchliffe JR (1967). Limb development in the polydactylous talpid3 mutant of the fowl[pdf]
Sheep and Goats
In 2002 the shown to the right sheep was born in the Netherlands with a fifth leg. Polymelia is a defect considered not uncommon in sheep. Unlike the example pictures, with sheep the extra limbs are often attached to the hindquarters. Other examples include: New Zealand (2007), Nigeria (2008), Unknown location (2009), Iran (2012, 2013), Skeleton: Fragonard Museum, Paris (year unknown).
- Eftekhari, Z., Nourmohammadzadeh, F., Jeloudari, M., Alighazi, N., & Mohsenzadeghan, A. (2012). Supernumerary ectopic limb in lamb: a case report. Comparative Clinical Pathology, 21(6), 1207-1209.
Duplicate limbs occur very rarely in pigs. One example known from 2008 had two extra hing legs and may be the result of an extremely underdeveloped conjoined or parasitic twin. Other examples include: China (year unknown) and Nigeria (2018).
- Ajadi, T. A., & Olaniyi, M. O. (2018). Pygomelia and True Hermaphroditism in a Nine Week Old Large White Piglet Case Report. Folia Veterinaria, 62(3), 62-67.
- Bodemer, C. W. (1958). The development of nerve‐induced supernumerary limbs in the adult newt, Triturus viridescens. Journal of Morphology, 102(3), 555-581.
- Chase HB (1951). Inheritance of polydactyly in the mouse. Genetics Soc America
- Corbera, J. A., Morales, I., Arencibia, A., Morales, M., & Gutiérrez, C. (2012). Caudal duplication (dipygus) in a Rock Pigeon (Columba livia). Eur J Anat, 16(3), 221-223.
Extra limbs, when they occur, are general not functional or useful. In only a few cases, such as the human child Jie-Jie, is the limb sensitive to touch and able to move in a relatively normal manner.
Other human examples include: Josephene Myrtle Corbin (1868) and Maxine Mina (1896), female child (2013--), male child (2014)
There is evidence that human cases can be trace to gene mutations in the parents.
- Luo, T., Chen, Z., Li, Z., Chen, Q., Liu, S. M., Bao, J., ... & Xu, J. (2018). Polymelia Treatment, Whole-Exome Sequencing and Disease Network Analysis. Whole-Exome Sequencing and Disease Network Analysis (July 12, 2018).
- Verma, S., Khanna, M., Tripathi, V. N., & Yadav, N. C. (2013). Occurrence of polymelia in a female child. Journal of clinical imaging science, 3.
- Montalvo, N., Redrobán, L., & Espín, V. H. (2014). Incomplete duplication of a lower extremity (polymelia): a case report. Journal of medical case reports, 8(1), 184.
Extra Fingers and Toes
Many species are sometimes born with extra fully or partially formed digits. Human polydachtyly in the fingers is generally caused by a mutation that effects 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. Polydachtyly is also found on 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.
The two 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.
- Wójcik, E., Andraszek, K., Ciszewska, M., & Smalec, E. (2013). Sister chromatid exchange as an index of chromosome instability in chondrodystrophic chickens (Gallus domesticus). Poultry science, 92(1), 84-89.
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.
- REINER, G., HECHT, W., BURKHARDT, S., KÖHLER, K., HAUSHAHN, P., REINACHER, M. ERHARDT, G. (2008). A complex malformation in a pig: case report and review of the literature [pdf]
- Ducos A, Revay T, Kovacs A, Hidas A, Pinton A, Bonnet-Garnier A, Molteni L, Slota E, Switonski M, Arruga MV, van Haeringen WA, Nicolae I, Chaves R, Guedes-Pinto H, Andersson M, Iannuzzi L: Cytogenetic screening of livestock populations in Europe: an overview. Cytogenet Genome Res 2008;120:26-41 . [pdf]
© 2010 Penny Skinner
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