AGE-RELATED CHANGES IN THE MORPHOPHYSIOLOGY OF THE TESTIS AND EPIDIDYMIS OF THE AFRICAN GREATER CANE RAT (Thryonomys swinderianus TEMMINCK, 1827)

Abstract

African Greater Cane Rat (AGCR) is a wild rodent currently being domesticated as an alternative source of animal protein in West African countries. Available research reports on the reproductive biology of the male AGCR have focused mainly on the adult without any information on age-related changes in the reproductive organs of the animal. This study was therefore designed to investigate age-related changes in the morphophysiology of the testis and epididymis of the AGCR. Fifty-two AGCR of known ages obtained from a commercial farm were used for the study. The rats were randomly assigned into 4 groups (n=13). Group I [prepubertal: ≤4 months]; group II [pubertal: >4≤12 months]; group III [adult: >12≤30 months] and group IV [aged: >30 months]. All rats were acclimatised for 7 days. On day 8, blood samples were collected for serum hormonal assay [testosterone, Follicle Stimulating Hormone (FSH), Luteinising Hormone (LH) and oestrogen, and testis and epididymis were harvested. Semen characteristics (sperm motility, livability, sperm concentration) were studied from epididymal tissue. Light microscopy and transmission electron microscopy were used to study age-related morphological changes in testis and epididymis. Testicular and epididymal immunoreactivities to vimentin, S-100, neurofilament and Glial Fibrillary Acid Protein (GFAP) were also estimated using standard methods. Data were analysed using descriptive statistics and one-way ANOVA at α0.05. There were significant increases in the concentration of testosterone (2.02±0.19, 3.85±0.29,4.12±0.15 ng/mL) and oestrogen (0.94±0.00, 1.48±0.4, 4.33±0.82 pg/mL) for prepubertal, pubertal and adult, respectively as age increases, while there were no significant differences in these hormones between adult and aged AGCR. The concentrations of FSH (12.33±0.83, 10.58±0.95, 9.250±0.6 mIU/mL)and LH (15.50±0.88, 12.83±1.20, 10.17±0.83 mIU/mL) decreased significantly for prepubertal, pubertal and adult, respectively, while the adult and aged were similar. No spermatozoa was observed for the prepubertal rats. Sperm motility and concentration (80.00±4.08%; 135.3±6.42 x 106 sperm/mL, respectively) significantly increased in adult rats compared to pubertal (62.50±4.79%; 101.50±7.96 x 106 sperm/mL) and aged rats (55.00±5.00%; 91.25±2.56 x 106 sperm/mL). However, sperm livability showed no significant difference across pubertal, adult and aged rats. The canalisation of the seminiferous tubules was absent in prepubertal rats, while it showed significant increases from pubertal to aged. Spermatogonia and spermatocytes in prepubertal had more mitochondria compared to others. Sertoli cell nuclei were uniquely roundish in prepubertal compared to their triangular shape in pubertal, adult and aged. Also, epididymal epithelium changed from simple cuboidal in prepubertal to pseudostratified columnar in other groups. Vimentin, S-100, neurofilament and GFAP were markedly expressed in the testis and epididymis of adult AGCR compared to other groups. Age-related morphophysiological changes in the testis and epididymis of African greater cane rats were established. Hence, the adult cane rat is recommended for breeding programme.