関連する実験動画
Updated: Aug 6, 2026

07:02
Extracellular Multi-Unit Recording from the Olfactory Nerve of Teleosts
Published on: October 6, 2020
鯨の水中聴覚の起源について
1Department of Biological Anthropology and Anatomy, Duke University Medical School, Durham, North Carolina 27710.
Nature
|February 4, 1993
まとめ
最も古いクジラであるパキセタスは,陸上の哺乳類と現代のクジラ類の間に中間的な耳の骨構造を持っていた. この発見は,Pakicetusが両生類であり,Artiodactylsが最も近いクジラ親戚であることを支持しています.
科学分野:
- パレオントロジー・パレオントロジー
- 比較解剖学 比較解剖学とは
- 進化生物学の進化生物学について
背景:
- 化石と近年の鯨類の耳骨 (malleus, incus, stapes) は,陸上の哺乳類と類似し,異なる.
- 鯨類の進化を理解するには,初期の化石の形態を調べる必要があります.
研究 の 目的:
- 最も古くから知られているクジラ,パキセタスの聴覚解剖を調査する.
- 鯨類の聴覚の進化段階を決定するために.
- 鯨類と陸上の哺乳類の関係を明確にするために.
主な方法:
- 化石の鯨類の耳骨 (インカス,マレウス,ステープス) と下の比較分析.
- パキセタスの聴覚構造における中間特性の検討.
- 耳への音波伝達経路の再構築.
主要な成果:
- パキセタスのインカスは,陸上の哺乳類や現代のクジラ類と比較して,膨張,比率,関節の位置付けにおいて中間的な特徴を示しています.
- パキセタスのと下は,陸上の哺乳類と同様に,耳に音の伝達を示唆しています.
- 化石の証拠は,パキセタスはおそらく両生類であったことを示しています.
結論:
- パキセタスは,クジラの進化における重要な移行形態であり,陸上の哺乳類と水生クジラの聴覚系を橋渡ししている.
- この発見は,アトリオダクティル類がクジラ類の最も近い親類であるという仮説を裏付けている.
関連する概念動画
Hair Cells
Hair cells are the sensory receptors of the auditory system—they transduce mechanical sound waves into electrical energy that the nervous system can understand. Hair cells are located in the organ of Corti within the cochlea of the inner ear, between the basilar and tectorial membranes. The actual sensory receptors are called inner hair cells. The outer hair cells serve other functions, such as sound amplification in the cochlea, and are not discussed in detail here.
The Cochlea
The cochlea is a coiled structure in the inner ear that contains hair cells—the sensory receptors of the auditory system. Sound waves are transmitted to the cochlea by small bones attached to the eardrum called the ossicles, which vibrate the oval window that leads to the inner ear. This causes fluid in the chambers of the cochlea to move, vibrating the basilar membrane.
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Scientists record evolutionary history by analyzing fossil, morphological, and genetic data. The fossil record documents the history of life on Earth and provides evidence for evolution. However, both fossil and living organisms offer evidence that outlines Earth’s evolutionary history.Phylogenetic trees illustrate the evolutionary relationships among these organisms. Scientists infer organisms’ common ancestry by evaluating shared morphological and genetic characteristics. Together, the fossil...
Anatomy of the Ear
Auditory sensation, commonly called hearing, involves the transformation of sonic waves into neural impulses facilitated by the structures of the auditory organ. The prominent, flesh-like structure on the side of the head, called the auricle, directs sound waves towards the auditory canal. The auricle is often mislabeled as the pinna, a term more aligned with mobile structures like a feline's external ear. The auditory canal penetrates the cranium via the external auditory meatus of the...
Auditory Pathway
Auditory pathways constitute the complex neural circuits responsible for transmitting and interpreting auditory information from the peripheral auditory system to the brain. Sound waves are initially captured by the outer ear, funneled through the ear canal, and reach the tympanic membrane (eardrum). These vibrations are transmitted via the middle ear's ossicles to the inner ear's cochlea.
When viewed cross-sectionally, the cochlea reveals the scala vestibuli and scala tympani flanking the...
When viewed cross-sectionally, the cochlea reveals the scala vestibuli and scala tympani flanking the...
Perceiving Loudness, Pitch, and Location
The human brain perceives pitch through two primary mechanisms reflected in place theory and frequency theory. Each mechanism describes how sound waves are interpreted as specific pitches by the brain, offering insights into the intricate processes of auditory perception.
Place theory, or place coding, suggests that different pitches are heard because various sound waves activate specific locations along the cochlea's basilar membrane. The brain determines the pitch of a sound by identifying...
Place theory, or place coding, suggests that different pitches are heard because various sound waves activate specific locations along the cochlea's basilar membrane. The brain determines the pitch of a sound by identifying...

