| 研究実績の概要 |
In the funding period we successfully collected 3 Baird’s beaked whale (ca. 5000g) and 2 harbor porpoise brains, one Pacific whitesided dolphin brain, one Zika deer brain and 2 cow brains. The external and internal anatomical organization revealed typical characteristics, which were previously observed in other Odontoceti. All specimes were subjected to MRI analysis. From this we could demonstrate the cortical volume and exposed surface reveal the same scaling relationship as that of a multi-species data set previous reported. This finding indicates that overall external shape of the odontocete cortex is typical mammalian, despite its unusual detailed shape, large size and high gyrification level.
In the next step we counted the neuronal and non-neuronal cells in the cortex and other brain areas using the isotropic fractionator techniques. We demonstrated that that toothed whales have more neurons in the cortex than expected for its brains size. Our findings demonstrated for the first time that besides primates also toothed whales have deviated from this rule and have more neurons than expected for its brain size. Contrarily, toothed whales confirm to the glial scaling rule that applies to all mammals including primates. These results are in favor for the cognitive hypothesis, rather than the thermogenesis hypothesis in the Odontocete, the toothed whales. this analysis has been conducted for 2 whales, a 3rd is being analyzed at the moment.
Histological and immunohistochemical analysis on the cortex including amygdala and hippocampus are now being conducted.
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| 次年度使用額が生じた理由 |
The reason for the extension is, that we managed to collect an additional Pacific white sided dolphin brain specimen at the end of July 2019. This specimen is very import as it adds a whale group that was not present in our analysis yet. However, to process the brain it requires longer than 8 months, including MRI and DTI analysis, histology, immunohistochemistry and cell counting.
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