Geometric morphometric investigation of ossicula auditus in two breed sheep

The ossicular chain consists of three joined ossicles: the first and largest bone is the auditory bone, the malleus, consisting of a stalk, head, and neck (collum mallei) in direct contact with the tympanic membrane; the second bone, the incus, is divided into a body, long crus, lenticular extension (processus lenticulare), and short crus. Geometric morphometry is used in a number of fields (e.g. paleontology, anthropology, biology, zooarchaeology, medicine, engineering, etc.) where the measurement of morphological variation is important. The aim of this study was to reveal the differences and similarities in shape by geometric morphometric analysis of the ossicula auditus of akkaraman and morkaraman sheep. For this purpose, ossicula of male and female Akkaraman and Morkaraman breeds were removed, imaged under steromicroscope and geometric morphometric analyses were performed. In the study, 16, 12 and 8 principal components were calculated for sheep malleus, incus and stapes. The separation of individuals according to the breed factor was more pronounced than the sex factor. Accordingly, shape differences became evident in the medial surface of the corpus mallei and the processus muscularis in the malleus, in the peripheral corners in the incus, and in the caput and crus rostrale in the stapes. In terms of breed, shape variation between groups was only partially seen in LM9 in malleus, LM6 and 7 in incus. As a result of the discriminant function analysis, the weakest and strongest grouping was seen in the stapes in terms of gender factor.