Development and evolution of the vertebrate primary mouth

摘要: The vertebrate oral region represents a key interface between outer and inner environments, its structural functional design is among the limiting factors for survival of owners. Both formation respective opening (primary mouth) establishment food-processing apparatus (secondary require interplay several embryonic tissues complex rearrangements. Although many aspects secondary mouth formation, including development jaws, teeth or taste buds, are known in considerable detail, general knowledge about primary regrettably low. In this paper, reviewed from comparative point view order to reveal underestimated morphogenetic diversity among, also within, particular clades. general, three main developmental modes were identified. most common characterized by via deeply invaginated ectodermal stomodeum subsequent rupture bilaminar membrane. However, salamander, lungfish some frog species, develops alternatively stomodeal collar contributed both ecto- endoderm. ray-finned fishes, on other hand, forms an ectoderm wedge later horizontal detachment initially compressed epithelia with probably mixed germ-layer derivation. A very intriguing situation can be seen agnathan fishes: whereas lampreys develop their manner similar gnathostome pattern, hagfishes seem undergo unique oropharyngeal morphogenesis when compared vertebrates. discussing early formative correlates likely responsible evolutionary–developmental modifications area, we stress essential role four factors: first, positioning amount yolk tissue; closely related to, second, endoderm during gastrulation, which initiates process constrains possible evolutionary changes within area; third, incipient structure primordium at anterior neural plate border, where component prospective formed; fourth, prime Pitx genes vertebrates non-vertebrate chordates.