3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item A study of the subcortical anatomy of the brain of the African elephant (Loxodonta africana)(2013-08-06) Maseko, Busisiwe ConstanceAfrican elephants are one of the iconic mammalian species of the continent, and are the largest terrestrial mammals on the planet. While being a well-known species, with intensive behavioural studies having been undertaken, studies of the elephant brain are limited. Given that elephants do show a unique and interesting set of behaviours, including infrasonic communication, unique control of the trunk, and that they eat around 500 kg of low quality plant matter each day, the current study aimed to investigate the neural underpinnings of these and many other behaviours exhibited by elephants. While not all aspects of elephant neuroanatomy are covered in the current set of studies, the results have provided a great deal of data for regions of the brain that have not been examined for almost 50 years, and applied modern neuroanatomical methods to this task. This thesis outlines how to obtain elephant brains amenable to modern neuroanatomical study, demonstrates that the ventricles are of a size predictable for a mammal with a 5 kg brain, and that the cerebellum is relatively the largest mammalian cerebellum studied to date. A microscopic examination of the cerebellar cortex revealed that the elephants have a greater amount of a potentially more complexly organized cerebellar cortex. In addition, an architectonic study of the diencephalon and brainstem revealed that elephants, while having a mostly standard mammalian diencephalon and brainstem, do show unique features that correlate to control of specialized behaviours. In summary, the current study shows that the system for motor timing, infrasound production and reception, and the systems for satiety and wakefulness are specialized in the elephant, all of which correlate to the overt behaviours previously studied. In addition, the current studies indicate potential paths to follow for the study of behaviour in these species that will hopefully lead to a better understanding of these animals. There is still much to explore and learn about the elephant brain and it is hoped this thesis creates a platform that provides the impetus for many future studiesItem An assessment of phylogenetic origin in Chiroptera using the neuromodulatory system(2008-03-11T06:48:32Z) Maseko, Busisiwe ConstanceABSTRACT The current study documents the findings from immunohistochemical examination of the brains of microbats and megabats (Chiroptera) using antibodies for cholineacetyltransferase (cholinergic neurons), tyrosine hydroxylase (dopaminergic, adrenergic and noradrenergic neurons), and serotonin (serotonergic neurons). The objective of the study was firstly to describe the anatomical organization and morphology of the neuromodulatory systems (nuclear complement) in both microbats and megabats, as there is no literature on these systems in the brains of chiropterans. Secondly, we aimed to investigate whether or not there are differences in these systems between the two suborders of chiroptera in hopes to shed some light on the phylogeny of the two, which is a controversial subject. The two groups were found to possess clear differences in their respective neuromodulatory nuclear complements. The differences observed between the two groups include a dorsal division of the locus coeruleus (A6d), which was absent in microbats but present in megabats, also the absence of an A4 in microbats but clear presence in megabats, and the parabigeminal (PBg) nucleus that was absent in microbats but clearly visible in megabats. The microbats were found to possess a complement that appeared similar to that of insectivores; whereas megabats had a complement resembling that of primates, carnivores and rodents. The differences found between the two groups suggest a diphyletic origin for the two groups.