最も初期のテトラポッドの前肢の発達軌道を比較する
Viviane Callier1, Jennifer A Clack, Per E Ahlberg
1University Museum of Zoology Cambridge, Downing Street, Cambridge CB2 3EJ, UK.
Science (New York, N.Y.)
|April 18, 2009
まとめ
初期の四足類イチソステガ (Ichthyostega) とアカントソステガ (Acanthostega) は,手足の発達がはっきりしている. イチソステガ (イチソステガ) とは
科学分野:
- パレオントロジー・パレオントロジー
- 進化生物学の進化生物学について
- 比較解剖学 比較解剖学とは
背景:
- イチオステガ (Ichthyostega) と アカントステガ (Acanthostega) は,初期のテトラポッドの重要な種である.
- アカントホステガは通常,より原始的なものと見なされます.
- その四肢の発達を理解することは,四足類の進化の洞察を与えてくれます.
研究 の 目的:
- イチホステガとアカントホステガにおける前肢発達のオントジェネティック経路を調査する.
- これらの初期の四足類と幹四足類の筋肉の結合パターンを比較するために.
- 陸上の移動と系統遺伝関係の違いを推論する.
主な方法:
- イチソステガとアカントソステガの新しい骨格物質の分析.
- 異なるオントジェネティック段階におけるヒトゲの筋肉結合部位の比較試験.
- 新しく特定された原始的な特徴を組み込んだ系統遺伝学的分析.
主要な成果:
- Ichthyostega humeriは,魚のような筋肉の付着パターンから四足類のような筋肉の付着パターンへの発達的なシフトを示しています.
- Acanthostega humeriは,発達を通して,テトラポッドのような筋肉の結合パターンを一貫して示しています.
- 新たに発見された原始的な特徴は,イクチオステガが,アカントステガよりも原始的かもしれないことを示唆している.
結論:
- イチオステガは,その発達過程で,より大きな運動器の地球化を示した可能性が高い.
- Ichthyostegaの系統的位置は,以前考えられていたよりも潜在的に基礎的であり,再評価を必要とするかもしれません.
- オントジェネティックデータは,初期の四足類の進化と陸上の適応を理解するための重要な証拠を提供します.
関連する概念動画
01:09Changes in the Appendicular Skeleton with Age
The upper and lower limb initially develops as a small bulge called a limb bud, which appears on the lateral side of the early embryo. The upper limb bud appears near the end of the fourth week of development, with the lower limb bud appearing shortly after.
Initially, the limb buds consist of a core of mesenchyme covered by a layer of ectoderm. The ectoderm at the end of the limb bud thickens to form a narrow crest called the apical ectodermal ridge. This ridge stimulates the underlying...
Initially, the limb buds consist of a core of mesenchyme covered by a layer of ectoderm. The ectoderm at the end of the limb bud thickens to form a narrow crest called the apical ectodermal ridge. This ridge stimulates the underlying...
01:07Development of the Limb Synovial Joints
Joints form during embryonic development in conjunction with the formation and growth of the associated bones. The embryonic tissue that gives rise to all bones, cartilage, and connective tissues of the body is called mesenchyme.
The mesenchymal stem cells differentiate into chondrocytes that form the hyaline cartilage, and later the cartilaginous model of the bone. This model further transforms into a bone. This process is known as endochondral ossification.
During development, the limbs...
The mesenchymal stem cells differentiate into chondrocytes that form the hyaline cartilage, and later the cartilaginous model of the bone. This model further transforms into a bone. This process is known as endochondral ossification.
During development, the limbs...
01:19Bones of the Upper Limb: Humerus
The upper limb consists of the arm, forearm, wrist, and hand bones. The humerus is the single bone of the upper arm region. Proximally, it has a large, spherical, smooth head that articulates with the glenoid cavity of the scapula to form the glenohumeral or shoulder joint. The margin of the head is the anatomical neck, a residual epiphyseal plate. Laterally it extends to form bony projections called the greater tubercle and the lesser tubercle. Next to the tubercles is the surgical neck, a...
01:15Bones of the Upper Limb: Ulna
The ulna and radius are parallel bones of the antebrachium or the forearm. The ulna lies medially and consists of a bony tip called the olecranon process at its proximal end. This hook-like projection articulates with the olecranon fossa of the humerus and forms the "hinged" ulnohumeral part of the elbow joint. This joint facilitates forearm extension and flexion while preventing its hyperextension. Similarly, the coronoid process, another bony projection on the proximal/anterior side of the...
01:54Convergent Evolution
Evolution shapes the features of organisms over time, ensuring that they are suited for the environments in which they live. Sometimes, selection pressure leads to the rise of similar but unrelated adaptations in organisms with no recent common ancestors, a process known as convergent evolution.The structures that arise from convergent evolution are called analogous structures. They are similar in function even if they are dissimilar in structure. Further, structures can be analogous while also...
01:10Bones of the Lower Limb: Tibia and Fibula
The tibia is the main weight-bearing bone of the lower leg. It is larger than the fibula with which it is paired. The tibia is also the second longest bone in the body and is located right below the skin. The proximal end of the tibia forms the medial and the lateral condyle, which articulates with the condyles of the femur to form the knee joint. Between the articulating surfaces is the irregular elevated area known as the intercondylar eminence that serves as the inferior attachment point for...