Vol. 10, Special Issue 11 (2021)

Author(s):
NM Rajashailesha, RV Prasad, Arun A Sha, KV Jamuna, ML Satyanarayana and S Ganga Naik

Abstract:
The extra-ocular muscles of are accessory organs of the eye (Organa oculi accessoria) which are involved in ocular movement and are located between the sclera and the wall of the orbit. These muscles are classically classified as four rectus, two oblique and one retractor bulbi. Though, their details and potential associations with sloth bear behaviour are limited. The aim of this study is to characterise extraocular muscles in sloth bear from its habitat with behaviour. The right and left eyeball with intact extraocular muscles of six adult sloth bears were collected during post mortem examination of bears that had died due to natural causes and extraocular muscles were dissected and utilized for gross and histomorphological studies. Extraocular muscles of sloth bear comprised of dorsal (M. rectus dorsalis), ventral (M. rectus ventralis), lateral (M. rectus lateralis), medial rectus muscles (m. rectus medialis), the dorsal oblique (M. obliquus dorsalis) ventral oblique muscles (M. obliquus ventralis) and the retractor bulbi muscle (M. retractor bulbi) as like in domestic animals. Among extraocular muscles, m. dorsal oblique was the longest, m. lateral rectus was broadest and thinnest muscle and m. retractor bulbi was composed of four fascicles. The extraocular muscles were skeletal in nature, each muscle fascicle presented few homogenous slow twitch muscle fibers and more granular fast twitch muscle fibers. Nerve fiber bundles were more in number around the muscle fascicles in this study.