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The presence of an embryonic opercular flap in amniotes

journal contribution
posted on 2023-06-09, 02:17 authored by Jo Richardson, Takanori Shono, Masataka Okabe, Anthony Graham
The operculum is a large flap consisting of several flat bones found on the side of the head of bony fish. During development, the opercular bones form within the second pharyngeal arch, which expands posteriorly and comes to cover the gill-bearing arches. With the evolution of the tetrapods and the assumption of a terrestrial lifestyle, it was believed that the operculum was lost. Here, we demonstrate that an embryonic operculum persists in amniotes and that its early development is homologous with that of teleosts. As in zebrafish, the second pharyngeal arch of the chick embryo grows disproportionately and comes to cover the posterior arches. We show that the developing second pharyngeal arch in both chick and zebrafish embryos express orthologous genes and require shh signalling for caudal expansion. In amniotes, however, the caudal edge of the expanded second arch fuses to the surface of the neck. We have detailed how this process occurs and also demonstrated a requirement for thyroid signalling here. Our results thus demonstrate the persistence of an embryonic opercular flap in amniotes, that its fusion mirrors aspects of amphibian metamorphosis and gives insights into the origin of branchial cleft anomalies in humans.

History

Publication status

  • Published

File Version

  • Published version

Journal

Proceedings of the Royal Society B: Biological Sciences

ISSN

0962-8452

Publisher

The Royal Society

Issue

1727

Volume

279

Department affiliated with

  • Biochemistry Publications

Full text available

  • No

Peer reviewed?

  • Yes

Legacy Posted Date

2016-07-27

First Compliant Deposit (FCD) Date

2016-07-27

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