Del Pino Eugenia M
Escuela de Ciencias Biológicas, Pontificia Universidad Católica del Ecuador, Quito, Ecuador.
Results Probl Cell Differ. 2019;68:379-418. doi: 10.1007/978-3-030-23459-1_16.
The developmental adaptations of the marsupial frogs Gastrotheca riobambae and Flectonotus pygmaeus (Hemiphractidae) are described and compared with frogs belonging to seven additional families. Incubation of embryos by the mother in marsupial frogs is associated with changes in the anatomy and physiology of the female, modifications of oogenesis, and extraordinary changes in embryonic development. The comparison of early development reveals that gene expression is highly conserved. However, the timing of gene expression varies between frog species. There are two modes of gastrulation according to the onset of convergent extension. In gastrulation mode 1, convergent extension is an intrinsic mechanism of gastrulation. This gastrulation mode occurs in frogs with aquatic reproduction, such as Xenopus laevis. In gastrulation mode 2, convergent extension occurs after the completion of gastrulation movements. Gastrulation mode 2 occurs in frogs with terrestrial reproduction, such as the marsupial frog, G. riobambae. The two modes of frog gastrulation resemble the two transitions toward meroblastic cleavage of ray-finned fishes (Actinopterygii). The comparison indicates that a major event in the evolution of frog terrestrial development is the separation of convergent extension from gastrulation.
描述了袋蛙（Gastrotheca riobambae和Flectonotus pygmaeus，雨蛙科）的发育适应性，并与另外七个科的蛙类进行了比较。袋蛙中由母体孵化胚胎与雌性的解剖学和生理学变化、卵子发生的改变以及胚胎发育的异常变化有关。早期发育的比较表明基因表达高度保守。然而，基因表达的时间在不同蛙类物种之间有所不同。根据汇聚延伸的起始情况，有两种原肠胚形成模式。在原肠胚形成模式1中，汇聚延伸是原肠胚形成的内在机制。这种原肠胚形成模式发生在进行水生繁殖的蛙类中，如非洲爪蟾（Xenopus laevis）。在原肠胚形成模式2中，汇聚延伸发生在原肠胚形成运动完成之后。原肠胚形成模式2发生在进行陆生繁殖的蛙类中，如袋蛙G. riobambae。蛙类的两种原肠胚形成模式类似于硬骨鱼（辐鳍鱼纲）向不完全卵裂的两次转变。比较表明，蛙类陆生发育进化中的一个主要事件是汇聚延伸与原肠胚形成的分离。
