OMIA 000302-9940 : Dwarfism, Ancon in Ovis aries

Mendelian trait/disorder: yes

Mode of inheritance: Autosomal Recessive

Considered a defect: yes

Key variant known: no

Species-specific name: Otter

Species-specific description: The main distinguishing feature of this type of dwarfism was the short and crooked limbs and loose articulation. When the animals walked, their crooked forelimbs looked like elbows, which led a Dr Shattuck, who dissected a specimen in Boston, to suggest the name Ancon, from the Greek word for elbow (Humphreys, 1813). Ancons proved to be quite popular with New England farmers, because they were unable to jump over the low stone fences. Despite this perceived advantage, the breed appears to have become extinct by the end of the nineteenth century. A similar mutation occurred in 1919 in a Cheviot flock in Norway (Wriedt, 1925). Descendants of this mutant were exported to the Storrs Agricultural Experiment Station at the University of Connecticut, where they were studied by Landauer and Chang (1949) and Landauer (1950). Yet another similar mutation occurred in a Merino flock at the Livestock and Forage Research Center at McGregor, Texas, in 1962 (Shelton, 1968). Unfortunately, both of these mutants also became extinct.

History: The first recorded case of this type of dwarfism was a ram lamb born on a farm in Massachusetts in 1791 (Humphreys, 1813). An entertaining history of the mutation (on which the following account is largely based) has been presented by Schwartz and Vogel (1994). The farmer, Seth Wight (or Wright or Wite) kept the ram and, by mating him to related ewes, produced several more dwarfs, eventually giving rise to a new breed of short-legged sheep. The results of the initial matings and the true-breeding nature of the breed suggested that this form of dwarfism was an autosomal recessive trait. Humphreys (1813) suggested the name Otter for the breed, because of the "real or imaginary resemblance to that animal . . . by some supposed to have been caused by an unnatural intercourse" (i.e., by a mating between an otter and a sheep!) Darwin (1859, p. 30; 1868, p. 100) was impressed with the way in which offspring of Ancons mated to non-dwarf breeds "perfectly resemble either parent" rather than "being intermediate in character". He cited this as evidence against blending inheritance.

Gidney (2006) reported that "The excavation of a 16th century archaeological site in Leicester, UK, produced sheep bones exhibiting the characteristic deformation of the Ancon dwarf but predating the earliest historical record of this mutation by some 200 years."

References


Note: the references are listed in reverse chronological order (from the most recent year to the earliest year), and alphabetically by first author within a year.
2008 Thompson, K.G., Piripi, S.A., Dittmer, K.E. :
Inherited abnormalities of skeletal development in sheep. Vet J 177:324-33, 2008. Pubmed reference: 17910925. DOI: 10.1016/j.tvjl.2007.08.015.
2006 Gidney, L. :
Earliest archaeological evidence of the Ancon mutation in sheep from Leicester, UK International Journal of Osteoarchaeology 17:318–321, 2006. DOI: 10.1002/oa.872.
Theissen, G. :
The proper place of hopeful monsters in evolutionary biology. Theory in Biosciences 124:349-69, 2006. Pubmed reference: 17046365. DOI: 10.1016/j.thbio.2005.11.002.
2005 Bergman, G. :
Ancon sheep: a now disproven example of macroevolution. Rivista de Biologica 98:435-48, 2005. Pubmed reference: 16440280.
1994 Schwartz, K.V., Vogel, J.G. :
Unraveling the yarn of the Ancon sheep Bioscience 44:764-768, 1994. Pubmed reference: 11539596.
1981 Sjokvist-Hyden, K. :
Medfodda defekter hos far [Congenital defects in sheep] Farskotsel 61:24-25, 1981.
1968 Shelton, M. :
A recurrence of the Ancon dwarf in Merino sheep Journal of Heredity 59:267-268, 1968. Pubmed reference: 5753237.
1950 Landauer, W. :
The Massachusetts Ancon sheep Journal of Heredity 41:144 only, 1950.
1949 Chang, T.K. :
Crippling in chondrodystrophic (Ancon) sheep Growth 13:299-307, 1949. Pubmed reference: 18142372.
Chang, T.K. :
Morphological study on the skeleton of Ancon sheep Growth 13:269-297, 1949. Pubmed reference: 18142371.
Chang, TK. :
Skeletal growth in Ancon sheep. Growth 13:221-67, 1949. Pubmed reference: 18142370.
Chang, TK. :
Calcification in the fetuses of normal and Ancon sheep. Anat Rec 105:723-35, 1949. Pubmed reference: 15403871.
Landauer, W., Chang, T.K. :
The Ancon or otter sheep Journal of Heredity 40:105-112, 1949.
1937 Davenport, C.B. :
Home of the Ancon sheep Science 86:422 only, 1937. Pubmed reference: 17835782. DOI: 10.1126/science.86.2236.422.
1925 Wriedt, C. :
Das Anconschaf [The Ancon sheep] Zeitschrift fur Induktive Abstammungs Vererbungslehre 39:281-286, 1925.
1873 Caverno, C. :
Ancon or otter sheep American Naturalist 7:742-743, 1873.
1868 Darwin, C.R. :
The variation of animals and plants under domestication, vol. I. London: John Murray. :page 100, 1868.
1859 Darwin, C.R. :
On the Origin of Species by Means of Natural Selection John Murray, London :, 1859.
1818 Humboldt, A. von :
Personal narrative of travels to the equinoctial regions of the New Continent, during the years 1799-1804. By Alexander de Humboldt, and Aimé Bonpland; with maps, plans, &c. written in French by Alexander de Humboldt, and trans. into English by Helen Maria Williams. 7 vols. London: Longman, Hurst, Rees, Orme and Brown. Vol. 3 :page 297, 1818.
1813 Humphreys, D. :
On a new variety in breeds of sheep Philosophical Transactions of the Royal Society, London 1:88-95, 1813.

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  • Created by Frank Nicholas on 06 Sep 2005
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