Mouth development in the Senegal bichir Polypterus senegalus does not involve the oropharyngeal membrane: possible implications for the ecto-endoderm boundary and tooth initiation.
Abstract
Polypterid fishes are considered the basal-most group of extant actinopterygians and thus may serve as a direct link to understand the evolution of the first bony fishes. Embryonic and larval specimens, however, are extremely scarce, making it difficult to study their developmental patterns and processes.
During the past few years we collected many embryos and larvae of the Senegal bichir Polypterus senegalus and in this paper we describe some novel observations concerning the supposed ecto-endoderm border in the mouth and consecutive initiation of dental development. The mouth of the Senegal bichir does not develop via a classical oropharyngeal membrane but instead, opening the mouth occurs via a separation of the upper and lower jaws that are connected by epithelial bridges.
These structures are bilaterally symmetrical and are found invariantly at places of the earliest tooth bud development.