Morphological Assessments and Sexual Dimorphism of the Visual Pathway Structures of Cricetomys gambianus (African Giant Rats Waterhouse-1840)

Abstract

BACKGROUND AND AIM: Cricetomys gambianus (African Giant Rat (AGR) a nocturnal rodent has recently been a choice model for several areas of neuroscience research. This study assessed sexual differences in the morphometric parameters of visual pathway structures of the AGR.

MATERIALS AND METHODS: Ten healthy adult AGRs (n=5; Male (M) and Female (F)) were captured from the wild and used for this study. The ARGs were sedated and body weight obtained before perfusion and decapitation. The weight and dimensions of the brain, eyeballs, optic nerve, optic chiasma and optic tract were obtained using digital weighing balance and Vernier caliper, respectively. Data obtained were analyzed using Statistical Package for the Social Sciences (SPPS) version 23. Results were expressed as mean ± SEM.

RESULTS:  Average body weight of AGRs was 787±208.6 g for males and 926±133.0 g for females; Brain weight was 6.7±0.6 g for males and 6.9±0.6 g females; while eyeball weight was 0.23±0.02 g for males and 0.22±0.02 g for females. Significant (p<0.05) sexual differences were observed in the dimensions of eyeball antero-posterior diameter (M=7.19±0.24 mm; F= 6.56±0.17 mm); Eyeball right-left diameter (M=6.12±0.11 mm; F= 5.27±0.19 mm); Optic nerve length (M=2.18±0.18 mm; F=1.42±0.13 mm); Optic tract length (M=1.21±0.16 mm; F=1.02±0.08 mm); Optic chiasma antero-posterior length (M=1.02±0.24 mm; F=0.66±0.05 mm) and Optic chiasma right-left length (M=0.80±0.07 mm; F=0.73±0.05 mm).

CONCLUSION: There exists sexual dimorphism in the morphometric parameters of visual pathway structures in the AGR. These differences are suggestive of evolutionary advantage in males compared to females as they go out in search for food and easy escape from predators within their natural habitat.