Research article

Gross–anatomical and morphometric studies of the Grasscutter (thryonomysswinderianus), axial skeleton

*Onwuama Kenechukwu Tobechukwu, Ojo Samuel Adeniyi, Hambolu Joseph Olajide, Salami Oluwoye Sulaiman and Dzenda Tavershima

Department of Veterinary Anatomy, Faculty of Veterinary Medicine, Ahmadu Bello University, Zaria, Nigeria

*Corresponding Author E-mail: kenexcares@yahoo.com, profsaojo@yahoo.com, hambolujoseph@yahoo.com, salamiwoye@yahoo.com, drdzenda@yahoo.com;   Tel: 08036425961, 08037037316, 08034509759, 08030681730, 07037484188

Accepted 15 September 2014

Abstract

The Axial skeleton of the Grasscutter (Thryonomysswinderianus) was studied using twelve (12) adult rats of both sexes with mean weights of 1.4167±0.2023kg and 0.8167±0.1276kg for bucks and does respectively. Characteristics of the bones were studied by gross observation after preparation. Three methods of bone preparation; Maceration, Chemical (Sodium hydroxide) and Burial were employed. The rats were housed and prepared in the Department of Anatomy laboratory, Faculty of Veterinary Medicine, Ahmadu Bello University, Zaria, Nigeria. Measurements of different segments of the Axial skeleton were also taken giving a total length of 57.9cm out of which the tail took 15.0cm (26%).Correlation coefficient between length of each bone segment and weight of each animal revealed statistical significance (P < 0.05) in all bone segments when both sexes (n = 12) were considered signifying a positive relationship between weight of the animal and its bone size. The skull presented an elongated structure of flat bones separated by sutures with the long nasal bones positioned dorsal to the premaxilla only. The vertebral formula of the Grasscutter was C7 T13 L6 S4 C18-23 with no transverse foramen on the 7th cervical vertebra and a prominent mammillary and accessory processes on the lumbar vertebrae. The Thorax presented thirteen (13) pairs of ribs, drumstick clavicle and six (6) sternebrae. The average total number of bones in the Axial skeleton of the rat was eighty eight (88) bones. Sexual dimorphism was not noticed except in the number of coccygeal vertebra which was twenty (20) in the Does and eighteen (18) in the Bucks.

Keywords: Grasscutter, Axial skeleton, vertebral formula