2019 Fiscal Year Research-status Report
Large brain evolution in cetaceans
| Project/Area Number |
18K14833
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| Research Institution | Hokkaido University |
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Principal Investigator |
PATZKE NINA 北海道大学, 高等教育推進機構, 助教 (20801690)
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| Project Period (FY) |
2018-04-01 – 2021-03-31
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| Keywords | whales / brain / neuronantomy / evolution / MRI / volumetric |
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| Outline of Annual Research Achievements |
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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| Current Status of Research Progress |
Current Status of Research Progress
3: Progress in research has been slightly delayed.
Reason
Whale brain samples are not always available and we have to rely on stranded animals or commercially hunted animals. This can lead to delays in the research progress. But to overcome this we used samples from the Museum.
The brains of whale are very big. The biggest brain in our samples was 5200g. In comparison a brain of a muse is only 1-2g. It takes much longer time to process the brains than we initially anticipated.
other than this the progress went rather smoothly.
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| Strategy for Future Research Activity |
At the moment we are analysis in a 3rd species the cell numbers. We are also conducting histological and immunohistochemical analysis on the brains.
In future we plan to extent the analysis to other marine mammals such as seals. in order to see how the marine environment can shape brain evolution
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| Causes of Carryover |
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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[Presentation] Baird's beaked whale brain in numbers2019
Author(s)
Fernandez Artiles IM, Watanabe A, Tha KK, Kobayashi M, Wada K, Matsushima T, Mota B, Patzke N.
Organizer
50th Annual Meeting of the Society-for-Neuroscience, Chicago, IL, USA
Int'l Joint Research
