Department of Zoology, University of Oklahoma, Norman, Oklahoma 73019, USA.
Dev Dyn. 2009 Dec;238(12):3126-38. doi: 10.1002/dvdy.22164.
Evolution of the skeleton was a key transition in early vertebrates. Lampreys lack a mineralized skeleton but possess cartilaginous neurocranial and viscerocranial elements. In lampreys, the visceral skeleton develops as a fused branchial basket supporting the pharynx. Here, we have adapted Alcian blue staining of lamprey cartilage and show this method results in cartilage fluorescence that we used to describe development of the branchial skeleton in Petromyzon marinus between 17 and 63 days of development. We show that skeletal rods develop from condensations of flattened discoidal chondrocytes and may involve cellular intercalation. Lamprey trabecular, parachordal, and subchordal cartilages consist of aggregations of polygonal chondrocytes positioned on the ventral and lateral surfaces of the notochord. We speculate that morphological differences relate to functional differences in the cartilage. We show that differentiated skeletal rods are derived from neural crest. Finally, we show how branchial muscles intercalate with skeletal rods of the branchial basket.
骨骼的进化是早期脊椎动物的一个关键转变。七鳃鳗没有矿化的骨骼，但具有软骨性的颅神经和内脏颅元素。在七鳃鳗中，内脏骨骼作为一个融合的鳃篮发育，支撑着咽部。在这里，我们已经适应了七鳃鳗软骨的阿尔辛蓝染色，并表明这种方法会导致软骨荧光，我们用它来描述在 Petromyzon marinus 中从 17 到 63 天发育过程中的鳃骨骼的发育。我们表明，骨骼棒是从扁平盘状软骨细胞的凝聚物发育而来的，可能涉及细胞插入。七鳃鳗的小梁、副脊索和下脊索软骨由聚集在脊索腹侧和侧面的多边形软骨细胞组成。我们推测形态差异与软骨的功能差异有关。我们表明，分化的骨骼棒是由神经嵴衍生而来的。最后，我们展示了鳃肌是如何与鳃篮的骨骼棒交错的。
