Morphological Differences in the Cerebrum of Adult and Juvenile Thryonomys swinderianus (African Grasscutter)

The African grasscutter (AGC; Thryonomys swinderianus) has been observed to possess unique physiological and structural features enabling them to survive in challenging environments. This behavior displayed by AGCs across different age groups could be attributed to a well-developed CNS where M1 cerebrum plays a critical role. This study described the morphological (gross and microscopic) characteristics of the cerebrum of adult and juvenile AGCs. Eight AGCs were procured and euthanized, brain was excised for morphological characteristics (gyrifification, brain dimensions, and organosomatic index), light microscopic assessment of the cerebral M1 region using H&E stains for histological features, and Cresyl Violet stain for histometric analysis (pyramidal soma size). Results revealed similar gyrification patterns on the dorsal surface of cerebral hemispheres across the age groups. The assessed brain dimensions revealed higher values (p>0.05) for the adult, except in the cerebral dorsoventral length, compared to the juvenile AGCs. The organosomatic index was higher (p<0.05) in the juvenile compared to adult AGCs. Histologically, layers III and V of the cerebral M1 region presented with pyramidal neurons as the predominant cells across the age groups, and appeared denser in the juvenile AGCs. Histometrically, the juveniles revealed higher (p>0.05) pyramidal soma size values in cerebral M1 layers (III and V), compared to the adult AGCs. In conclusion, morphologic features of the AGC’s brain are relatively similar to those described in other rodents. Variations in the gross and microscopic features of the AGC cerebrum exist across age groups.

Key Words: gyrification, histology, histometry, laminae, pyramidal neurons