The cranial neural crest (CNC) arises within the developing central nervous system, but then migrates away from the neural tube in three consecutive streams termed mandibular, hyoid and branchial, respectively, according to the order along the anteroposterior axis. While the process of neural crest emigration generally follows a conserved anterior to posterior sequence across vertebrates, we find that ray-finned fishes (bichir, sterlet, gar, and pike) exhibit several heterochronies in the timing and order of CNC emergence that influences their subsequent migratory patterns. First, emigration of the cranial neural crest in these fishes occurs prematurely compared to other vertebrates, already initiating during early neurulation and well before neural tube closure. Second, delamination of the hyoid stream occurs prior to the more anterior mandibular stream; this is associated with early morphogenesis of key hyoid structures like external gills (bichir), a large opercular flap (gar) or first forming cartilage (pike). In sterlet, the hyoid and branchial CNC cells form a single hyobranchial sheet, which later segregates in concert with second pharyngeal pouch morphogenesis. Taken together, the results show that despite generally conserved migratory patterns, heterochronic alterations in the timing of emigration and pattern of migration of CNC cells accompanies morphological diversity of ray-finned fishes.

颅神经嵴 (CNC) 出现在发育中的中枢神经系统内，然后根据沿前后轴的顺序，以三个连续的流分别称为下颌、舌骨和鳃，从神经管迁移离开。虽然神经嵴迁移的过程在脊椎动物中通常遵循一个保守的前后顺序，但我们发现射线鳍鱼（比奇尔、斯特雷特、雀鲷和梭鱼）在 CNC 出现的时间和顺序上表现出几种异时性，这影响了它们随后的迁移。迁移模式。首先，与其他脊椎动物相比，这些鱼的颅神经嵴的迁移发生得过早，在神经管形成早期和神经管闭合之前就已经开始。第二，舌骨流的分层发生在更前的下颌流之前；这与关键舌骨结构的早期形态发生有关，如外鳃 (bichir)、大鳃盖瓣 (gar) 或最初形成的软骨 (pike)。在 sterlet 中，舌骨和鳃 CNC 细胞形成单个舌鳃片，随后与第二个咽囊形态发生一起分离。综上所述，结果表明，尽管迁徙模式普遍保守，但 CNC 细胞迁徙时间和迁徙模式的异时性变化伴随着射线鳍鱼的形态多样性。舌骨和鳃 CNC 细胞形成单个舌鳃片，随后与第二个咽囊形态发生分离。综上所述，结果表明，尽管迁徙模式普遍保守，但 CNC 细胞迁徙时间和迁徙模式的异时性变化伴随着射线鳍鱼的形态多样性。舌骨和鳃 CNC 细胞形成单个舌鳃片，随后与第二个咽囊形态发生分离。综上所述，结果表明，尽管迁徙模式普遍保守，但 CNC 细胞迁徙时间和迁徙模式的异时性变化伴随着射线鳍鱼的形态多样性。