| Budget Amount *help |
¥2,300,000 (Direct Cost: ¥2,300,000)
Fiscal Year 1998: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 1997: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 1996: ¥900,000 (Direct Cost: ¥900,000)
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| Research Abstract |
The aims at obtaining good understanding of dolphin shoulder musculature in the light of phylogenetical investigations and considerations, During the course of research I found the astounding fact that most of the former works contain several erroneous descriptions. Therefore, I made more detailed descriptions on the Delphinidae shoulder musculature including data on the nerves of innervation. The result were compared with terrestrial mammalian shoulder muscles and I reached interesting results.
Materials : 2 common dolphins (Delphinus delphis), 3 bottlenose dolphins (Tursiops truncatus), 1 Pacific white sided dolphin (Lagenorhynchus obliquidens) and 1 melon headed dolphin (Peponocephala electra).
Findings : Dolphin species examined have the trapezius muscle (two portions) although Strickler (1976) stated that the odontocetes have no trapezius. Their plexus contain nerve bundles from 7 spinal segments (04 through Th1) and a little contribution from 03. Nerves recognized as ventral member
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s were : supra scapular (03-6), phrenic(03-6), cranial pectoral (03-6), musculo cutaneous (05-Th1), intermedial pectoral (05-Th1), median (05-Th1) ulnar (05-Th1), caudal pectoral (05-Th1), while in the dorsal group were subscapular (05-Th1), axillary (05-Th1), radial (05-Th1), thoracodorsal (05-Th1).
Discussion : Comparing these findings with data on the terrestrial mammals it is striking that the basic structure is more resembled with human' condition. The dorso-ventral gradients among those nerves are fundamentally identical to those of terrestrial mammals. Remarkably, number of muscles is more similar to humans rather than the other terrestrial quadruped mammals. This can be so because forelimbs of the terrestrial mammals are for supporting the weight of cranial portion of the body whereas in humans and dolphins anterior extremities are free from weight bearing and more freedom in the forelimb movement is more important for these animals. In conclusion, dolphins and humans are both more like groups of mammals with structure of shoulder more suitable for much more free movement. We should consider these animals with more exact understanding on their body structure. Less
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