As a sequel to the current advancement in ethology, this study was designed to provide information on the brain size of the African grasscutter at specific postnatal periods and to extrapolate these findings to the behaviour of the rodent in its natural habitat. Brain samples were extracted from African grasscutter neonates on postnatal day 6, juveniles on postnatal day 72 and adults on postnatal day 450 by basic neuro-anatomical techniques. The weight, volume and dimensions of the brain samples were determined in absolute and relative terms. Their encephalisation quotient was also computed. There was a very strong positive correlation between nose-rump length and brain length in the neonates. The relative brain weight of neonates, juveniles and adults were 3.84 ± 0.12 %, 2.49 ± 0.07 % and 0.44 ± 0.03 %, respectively. The differences were significant (P < 0.05). The encephalisation quotient of juveniles was 1.62 ± 0.03 while that of the adult was 0.49 ± 0.02. The difference was significant (P < 0.05). The results were extrapolated to the animal’s cognitive ability, and compared with other rodents. It was concluded that the juvenile African grasscutter may have higher cognitive ability than the adult rodent, thus, juveniles should be preferred in physiological studies of memory and cognition.
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1. Adu, E. K., Yeboah, S., 2000: The efficacy of the vaginal plug formation after mating for pregnancy diagnosis and embryonic resorption in utero in the greater cane rat (Thryonomys swinderianus, Temminck). J. Trop. Anim. Health Prod., 32, 1-10.
2. Amori, G., Gippoliti, S., 2002: Rodents and the bushmeat harvest in Central Africa. In Mainka, S., Trivedi, M.: Links between Biodiversity Conservation, Livelihoods and Food Security. The Sustainable Use of Wild Species for Meat. IUCN Species Survival Commission, 24, 95-100.
3. Asibey, E. O. A., Addo, P. G., 2000: The grasscutter, a promising animal for meat production. In Turnham, D.: African Perspectives. Practices and Policies Supporting Sustainable Development. Scandinavian Seminar College, Denmark, in association with Weaver Press, Harare, Zimbabwe, 120 pp.
4. Bronner, G. N., Hoffmann, M., Taylor, P. J., Chimimba, C. T., Best, P., Matthee, C. A., Robinson, T. J., 2003: A revised systematic checklist of the extant mammals of the southern African subregion. Durban Mus. Novit., 28, 56-95.
5. Byanet, O., Dzenda, T., 2014: Quantitative biometry of body and brain in the Grasscutter (Thryonomys swinderianus) and African giant rat (Cricetomys gambianus): encephalization quotient implication. Res. Neurosci., 3, 1-6.
6. Deary, I. J., 2000: Looking Down on Human Intelligence: from Psychometrics to the Human brain. Oxford: Oxford University Press, DOI:10.1093/acprof:oso/9780198524175.001.0001.
7. Gage, G. J., Kipke, D. R., Shan, W., 2012: Whole animal perfusion fixation for rodents. JVE, 65, e3564.
8. Gläscher, J., Rudrauf, D., Colom, R., Paul, L. K., Tranel, D., Damasio, H., Adolphs, R., 2010: Distributed neural system for general intelligence revealed by regional mapping. In Proceedings of the National Academy of Sciences of the United States of America, doi:
8. Gläscher, J., Rudrauf, D., Colom, R., Paul, L. K., Tranel, D., Damasio, H., Adolphs, R., 2010: Distributed neural system for general intelligence revealed by regional mapping. In Proceedings of the National Academy of Sciences of the United States of America, doi: 10.1073/pnas/ /0910397107.)| false
9. Herculano-Houzel, S., 2007: Encephalization, neuronal excess and neuronal index in rodents. Anat. Rec., 290, 128-1287.
10. Ibe, C. S., Onyeanusi, B. I., Hambolu, J. O., 2014: Functional morphology of the brain of the African giant pouched rat (Cricetomys gambianus, Waterhouse, 1840). Onderstepoort J. Vet. Res., 81, 7. http://dx.doi.org/10.4102/ojvr.v81i1.644.
11. Ibe, C. S., Onyeanusi, B. I., Hambolu, J. O., Ayo, J. O., 2010: Sexual dimorphism in the whole brain and brainstem morphometry in the African giant pouched rat (Cricetomys gambianus, Waterhouse 1840). Folia Morphol., 69, 69-74.
12. Jerison, H. J., 1977: The theory of encephalisation. Ann. N. Y. Acad. Sci., 299, 146-160.
13. Kinser, P. A., 2000: Chart of Approximate Brain and Body Sizes of Various Animals. In http://serendip.brynmawr.edu/bb/kinser/ Sizechart.html. Accessed: 07/09/2015. 17:44:23 GMT.
14. 14. Krubitzer, L., Campi, K. L., Cooke, D. F., 2011: All rodents are not the same: a modern synthesis of cortical organization. Brain Behav. Evol., 78, 51-93.
15. Lefebvre, L., Reader, S. M., Sol, D., 2004: Brains, innovations and evolution in birds and primates. Brain Behav. Evol., 63, 233-246.
16. Marino, L., 2002: Convergence of complex cognitive abilities in cetaceans and primates. Brain Behav. Evol., 59, 21-32.
17. Martin, R. D., 1984: Body size, brain size and feeding strategies. In Chivers, D., Wood, B., Bilsborough, A.: Food Acquisition and Processing in Primates. Plenum Press, New York, 73-103.
18. McDaniel, M. A., 2005: Big-brained people are smarter: A meta-analysis of the relationship between in vivo brain volume and intelligence. Intelligence, 33, 337-346.
19. Mensah, G. A., Okeyo, A. M., 2005: Continued harvest of the diverse African animal genetic resources from the wild through domestication as a strategy for sustainable use: A case of the larger grasscutter: Thryonomys swinderianus. In http://agtr.ilri.cgiar.org/index.php?option=com_content&task=view&id=177&Itemid=199. Accessed: 27/10/2012, 23: 12: 34 GMT.
20. Moore, J., 1999: Allometry. University of California, San Diego. In http://pages.ucsd.edu/~jmoore/courses/allometry/allometry.html. Accessed: 02/10/2017, 01: 45: 23 GMT.
21. Narr, K. L., Woods, R. P., Thompson, P. M., Szeszko, P., Robinson, D., Dimtcheva, T. et al., 2007: Relationships between IQ and regional cortical gray matter thickness in healthy adults. Cereb. Cortex, 17, 2163-2171.
22. Olude, A. M., Olopade, J. O., Ihunwo, A. O., 2014: Adult neurogenesis in the African giant rat (Cricetomys gambianus, Waterhouse). Metabol. Brain Dis., 29, 857-866.
23. Onebunne, A., 2010: Grasscutter Farming - the Pathway to Wealth. In http://grasscutterfarmingbest.blogspot.com. Accessed: 16:08:2014. 16:07:27 GMT.
24. Onwuama, K. T., Ojo, S. A., Hambolu, J. O., Salami, O. S., Dzenda, T., 2014: Gross-anatomical and morphometric studies of the grasscutter (Thryonomys swinderianus), axial skeleton. Stand. Sci. Res. Ess., 2, 406-417.
25. Papini, M. R., 2008: Evolution of the vertebrate brain and behaviour. In Comparative Psychology: Evolution and Development of Behaviour. 2nd edn., Psychology press, 270 Madison Avenue, New York, 273-277.
26. Peters, R., 2006: Ageing and the brain. Postgrad. Med. J., 2006, 82, 84-88.
27. Rieke, G., 2011: Lecture notes: Emergence of intelligence. Natural Sciences, 102, University of Arizona.
28. Roth, G., Dicke, U., 2005: Evolution of the brain and intelligence. Trends in Cognitive Sciences, 9, 250-257.
29. Sahin, B., Aslan, H., Unal, B., Canan, S., Bilgig, S., Kaplan, S., Tumkaya, L., 2001: Brain volumes of the lamb, rat and birds do not show hemispheric asymmetry: A stereological study. Image Anal. Stereol., 20, 9-13.
30. Simonton, D. K., 2003: An interview with Dr. Simonton. In Plucker, J. A.: Human Intelligence: Historical Influences, Current Controversies, Teaching Resources. Accessed online from http://indiana.edu/_intell. Accessed: 21/04/2014; 04:23:31 GMT.
31. Van der Merwe, M., 2007: Discriminating between Thryonomys swinderianus and Thryonomys gregorianus. African Zoology, 42, 165-171.
32. Zilles, K., Palomero-Gallagher, N., Amunts, K., 2013: Development of cortical folding during evolution and ontogeny. Trends Neurosci., 36, 75-284.