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The effects of photoperiodism on the histomorphometry of the thyroid gland of African giant rats (AGR)­waa investigated. A total of 30 captive AGR of both sexes were randomly divided into 3 different photoperiodic groups of 10 rats each (5 males and 5 females). Group 1 rats had 12 hours darkness and 12 hours lighting for 8 weeks, Group 2 rats had total darkness (24 hours) for 8 weeks while, Group 3 rats had total lighting (24 hours) for 8 weeks. Each rat was euthanized using sodium pentobarbital at 86mg/kg BW intraperitoneally. There was no significant increase (P>0.05) in the body weight of the rats in exposed to total darkness (Group 2). However, there was a significant decrease in the body weight of rats exposed to light for 8 weeks (P<0.05) when compared to rats in control group. Continuous lighting decreases the adipose tissue of thyroid glands with increase number of follicular cells, while, continuous darkness decreases follicular cells with increased adipose tissue. The thyroid weights increased significantly (P<0.05) in Group 3 and Group 2 rats when compared to Group 1. Exposure of AGR to continuous light significantly decreased the body weight and increased the weight and width of the thyroid gland. It is therefore recommended to house AGR under controlled conditions with at least 12 hours each of light and darkness


African giant rat; Darkness; Light; Photoperiodism; Thyroid gland.‎

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Zubairu, M., Ali, M. N., Umosen, A. D., Muazu, T. A., Baso, A., Atabo, S. M., & Usman, M. D. (2021). Effects of Photoperiodism on the Histomorphometry of the Thyroid Gland of ‎the African Giant Rat (Cricetomys gambianus)‎). Sahel Journal of Veterinary Sciences, 18(4), 7-13.


  1. Ali, M. N., Rashid, S., Nafees, S., Hasan, S.K., Shahid, A., ‎Majed, F. and Sultana, S. (2017). Protective effect ‎of Chlorogenic acid against methotrexate induced ‎oxidative stress, inflammation and apoptosis in rat ‎liver: An experimental approach. Chemico-‎Biological Interactions, 272: 80-91. ‎‎
  2. Ayo, J. O., Oladele, S. B., Ngam, S., Fayomi, A. and ‎Afolayan, S. B. (1999). Diurnal fluctuations in ‎rectal temperature of the Red Sokoto Goat during ‎the harmattan season. Research in Veterinary ‎Science, 66 (1): 7-9. ‎‎
  3. Boron, W.F. and Boulapep, E.L. (2012). Medical Physiology ‎‎(2nd ed.). Philadelphia: Saunders. Pp. 1052. ISBN ‎‎978-1-4377-1753-2.‎
  4. Casal, J. J. (2014). Light perception and signaling by ‎phytochrome A. Journal of Experimental Biology, ‎‎65 (11): 2835-2845. Doi:10.1093/jxb/ert379‎
  5. Dalley, A.F. and Moore, K. L. (2006). Embryological and ‎Surgical Anatomy of the Intrahepatic and ‎Extrahepatic Biliary Tree. In Liver and Biliary ‎Tract Surgery, Springer, Pp. 3-16. ‎‎
  6. Dzenda, T., Ayo, J. O., Lakpini, C. A. M. and Adelaiye, A. B. ‎‎(2011). Diurnal, seasonal and sex variations in ‎rectal temperature of African Giant rats ‎‎(Cricetomysgambianus, Waterhouse). Journal of ‎Thermal Biology, 36: 255-263. ‎‎
  7. Eleiwe, S. E., Nibras, H. K. and Shilan, H. K. (2014). ‎Continuous darkness induces structural changes in ‎thyroid gland of adult male rats. Journal of ‎Science and Medicine in Sports, 4 (1): 1 - 9. ‎‎
  8. El-Rouby, N. M. (2010). A Histological Study on the Effect ‎of Diclofenac Sodium (Declophen) Administration ‎on Thyroid Follicular Cells of Albino Rats. ‎Egyptian Journal of Histology, 33: 213 - 223.‎
  9. Enemali, F.U., Hambolu, J.O., Alawa, J.N. and Anosike, I.V. ‎‎(2016). Gross Anatomical, Histological and Histo-‎chemical Studies of Thyroid Glands of African ‎Giant Rat (CricetomysgambianusWaterhouse, ‎‎1840). Journal of Pharmacy and Biological. ‎Sciences, 11(4): 40-43.‎‎1104024043.‎
  10. Getty, R., Sission, S. and Grossman, J. D. (1986). The ‎Anatomy of Domestic Animals. 5th Ed., W.B. ‎Saunders Company. Philadelphia, USA.‎
  11. Igbokwe, C.O. (2010). Gross and microscopic anatomy of ‎thyroid gland of the wild African grasscutter ‎‎(Thryonomys swinderianus, Temminck) in ‎Southeast Nigeria. European Journal of Anatomy, ‎‎14: 5-10.‎
  12. Kenfack, A., Fonou, L.T. and Fopa, C.F. (2020). Effects of ‎photoperiod on growth performances in female ‎African Giant Rat (Cricetomysgambianus). ‎International Journal Agronomy and Agricultural ‎Research, 17(4): 11-16. ‎
  13. Kiernan, J.A. (2007). Histochemistry of staining methods ‎for normal and degenerating myelin in the central ‎and peripheral nervous systems. Journal of ‎Histotechnology; 30(2): 87-91. ‎‎
  14. Kowal, J. M. and Knabe, D. T. (1972). An Agro-Climatic ‎Atlas of the northern states of Nigeria. Ahmadu ‎Bello University Press, Zaria, Nigeria.‎
  15. Mauseth, J. D. (2003). Botany: An Introduction to Plant ‎Biology (3rd ed.). Sudbury, MA: Jones and Bartlett ‎Learning. Pp. 422–27. ISBN 978 – 0 – 7637 – ‎‎2134-3. ‎
  16. Mistlberger, R. E., Refinetti R. and Kriegsfeld, L. J. ‎‎(2013). Circadian Rhythms and Physiological ‎Processes. Encyclopedia of Sleep, Elsevier ‎Incorporated, Pp.418-425.‎‎0-12-378610-4.00093-0.‎
  17. Nelson R. J. (2005). An Introduction to Behavioral ‎Endocrinology (p.189). Sunderland, MA: Sinauer ‎Associates. ‎
  18. Oke, O.A. (2008). Evaluation of the Effectiveness of Three ‎Insecticides to control Diamond Back moth ‎‎(Plutellaxylostella) in cabbage (Brassica oleracea ‎Var. Capital L). European Journal of Scientific ‎Research, 22(3): 391-395.‎
  19. Olatunji-Bello, I. and Sofola, O. A. (2001). Effect of ‎Continuous Light and Darkness Exposure on the ‎Pituitary-Gonadal Axis and thyroid activity in ‎male rats. African Journal of Biomedical ‎Research, 4: 119 - 122. ‎v4i3.53888.‎
  20. Pyter, L. M., Adelson, J. D. and Nelson, R. J. (2007). Short ‎days increase hypothalamic pituitary adrenal axis ‎responsiveness. Endocrinology, 148: 3402-3409. ‎‎
  21. Radhiah, N. A. and Azhar, L. J. (2020). Effect of Evisect on ‎Organo-Somatic Index and Pathohistological ‎changes of some vital organs in white Mice. ‎Systematic Reviews in Pharmacy, 11 (11): 1910-‎‎1914.‎
  22. Schwartz, H.J. and Dioli, M. (1992). The one-humped camel ‎in Eastern Africa. A pictorial guide to diseases, ‎health care and management. Schonwald Druck, ‎Berlin. F.R. Germany, Pp. 228-229.‎
  23. Tavolaro, F.M., Thomson, L.M., Ross, A.W., Morgan, P.J. ‎and Helfer, G. (2015). Photoperiodic Effects on ‎Seasonal Physiology, Reproductive Status and ‎Hypothalamic Gene Expression in Young Male F ‎‎344 Rats. Journal of Neuroendocrinology, 27(2): ‎‎79-87.‎