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  • Author: S. O. Salami x
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Abstract

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.

Abstract

The Lagos Lagoon is under increased pressure from growth in human population, growing demands for natural resources, human activities, and socioeconomic factors. The degree of these activities and the impacts are directly proportional to urban expansion and growth. In the light of this situation, the objectives of this study were: (i) to estimate through satellite imagery analysis the extent of changes in the Lagos Lagoon environment for the periods 1984, 2002, 2013 and 2019 using Landsat-derived data on land cover, Land Surface Temperature (LST), Normalised Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI); and (ii) to evaluate the relationship between the derived data and determine their relative influence on the lagoon environment. The derived data were subjected to descriptive statistics, and relationships were explored using Pearson's correlation and regression analysis. The effect of land cover on LST was measured using the Contribution Index and a trend analysis was carried out. From the results, the mean LSTs for the four years were 22.68°C (1984), 24.34°C (2002), 26.46°C (2013) and 28.40°C (2019). Generally, the mean LSTs is in opposite trend with the mean NDVIs and EVIs as associated with their dominant land cover type. The strongest positive correlations were observed between NDVI and EVI while NDVI had the closest fit with LST in the regression. Built-up areas have the highest contributions to LST while vegetation had a cooling influence. The depletion in vegetative cover has compromised the biodiversity of this environment and efforts are required to reverse this trend.