Directional and fluctuating asymmetries in domestic sheep skulls

Parés-Casanova P. M., Bravi R.


Morphological symmetry and asymmetry of three different sheep geographical populations (n=39), managed under semi-extensive conditions, were decomposed using geometric morphometric methods, on dorsal aspect of skulls. Fluctuating asymmetry (FA) was used as an indicator of environmental stress, and directional asymmetry (DA) as biomechanical constraints. The two-dimensional coordinates of 21 landmarks were digitized and analyzed using geometric morphometrics. Multivariate analyses showed the presence of subtle but significant directional asymmetry and fluctuating asymmetry in the entire sample, but no distinctive differences were detected between populations. These results are on the whole indicative that environmental stress, if present was not sufficient to infer on symmetry of the skull, and no alterations could be noted on functional loadings. On the whole morphometric studies should open up promising areas of research in this almost unexplored field, in domestic ungulates.


Key words: geometric morphometric, morphological variation, Ovis, symmetry

Full Text:



JH Graham; DC Freeman; JM Emlen. Antisymmetry, directional asymmetry, and dynamic morphogenesis. Genetica 1993, 89, 121-187.

AR Palmer. Fluctuating asymmetry analyses: A primer. In T. A. Markows (Ed.), Developmental instability: Its origin and evolutionary implications. Kluwer Academic Press, Norwell, 1994; 335-364.

AR Palmer. Symmetry Breaking and the Evolution of Development. Science 2004, 306, 5697, 828-833.

L Van Valen. A study of fluctuating asymmetry. Evolution 1962, 16, 125-142.

AR Palmer, C Strobeck. Fluctuating asymmetry: measurement, analysis, patterns. Annual Review of Ecology and Systematics 1986, 17, 391-421.

FJ Rohlf. TPS Dig version 2.10. Department of Ecology and Evolution, State University of New York at Stony Brook, Stony Brook. 2006.

CP Klingenberg MORPHOJ: an integrated software package for geometric morphometrics. Molecular Ecology Resources 2011, 11, 353-357.

FJ Rohlf; D Slice. Extensions of the Procrustes method for the optimal superimposition of landmarks. Systematic Zoology 1990, 39, 40e59.

IL Dryden; KV Mardia. Statistical Shape Analysis. Wiley, Chichester 1998.

CP Klingenberg; M Barluenga; A Meyer. Shape analysis of

symmetric structures: quantifying variation among individuals and asymmetry. Evolution 2002, 56, 1909-1920.

CP Klingenberg; GS McIntyre GS. Geometric morphometrics of developmental instability: analyzing patterns of fluctuating asymmetry with Procrustes methods. Evolution 1998, 52, 5, 1363-1375.

CP Klingenberg; LRMonteiro LR. 2005. Distances and directions in multidimensional shape spaces: implications for morphometric applications. Systematic Biology 2005, 54, 678-688.

SW Herring; S Teng. Strain in the braincase and its sutures

during function. American Journal of Physical Anthropology 2000, 112, 575-593.

KL Rafferty; SW Herring; F Artese. Three-dimensional loading and growth of the zygomatic arch. The Journal of Experimental Biology 2000, 203, 2093-3004.

SW Herring; DJ Decker; ZL Liu; T Ma. Temporomandibular joint in miniature pigs: anatomy, cell replication, and relation to loading. The Anatomical Record 2002, 266, 152-166.

KM Dyce; WO Sack; CJG Wensing. Anatomía veterinaria. MacGraw-Hill, Mexico, 2006.

SJ Turkawski; TM Van Eijden; WA Weijs WA. Force vectors of single motor units in a multipennate muscle. Journal of Dental Research 1998, 77, 10, 1823-1831.

C Vishalakshi; BN Singh BN. Effect of developmental temperature stress on fluctuating asymmetry in certain morphological traits in Drosophila ananassae. Journal of Thermal Biology 2008, 33, 201-208.

AK Knecht; M Bronner-Fraser. Induction of the neural crest: a multigene process. Nature Review Genetics 2002, 3, 6, 453-461.

V Erjavec; D Crossley. Initial observations of cheek tooth abnormalities in sheep in Slovenia. Veterinary Record 2010, 167, 134-137.


  • There are currently no refbacks.

<Journal of Zoological and Bioscience Research>