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Embryonic Development and Skeletogenesis of the Pharyngeal Jaw Apparatus in the Cichlid Nile Tilapia ( Oreochromis niloticus )
Author(s) -
le Pabic Pierre,
Stellwag Edmund J.,
Scemama JeanLuc
Publication year - 2009
Publication title -
the anatomical record: advances in integrative anatomy and evolutionary biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.678
H-Index - 62
eISSN - 1932-8494
pISSN - 1932-8486
DOI - 10.1002/ar.20960
Subject(s) - hox gene , biology , cichlid , body plan , neurocranium , nile tilapia , oreochromis , vertebrate , anatomy , evolutionary biology , zoology , skull , embryo , fish <actinopterygii> , gene , genetics , fishery , transcription factor
The evolution of a specialized pharyngeal jaw apparatus (PJA) has been argued to be the key evolutionary innovation that allowed the explosive adaptive radiation of cichlid fishes in East African lakes. Subsequent studies together with recent molecular phylogenies have shown that similar innovations evolved independently several times within the teleosts, which poses the questions: (1) how similar are the developmental mechanisms responsible for these changes in divergent taxa and (2) how did such complex features arise independently in evolution? A detailed knowledge of PJA development in cichlids and other teleosts is needed to address these questions. Here, we provide a detailed account of the development of the PJA in one species of cichlid, the Nile tilapia ( Oreochromis niloticus ), from the early segmentation and patterning of its embryonic precursors – pharyngeal arches 3 to 7 – to its ossification. We find that pharyngeal segmentation occurs sequentially from anterior to posterior during early segmentation stages through the mid‐pharyngula period. We show a clear combinatorial code of Hox gene expression such that each posterior arch is defined by a distinctive Hox signature. Posterior arch chondrogenesis in tilapia is essentially complete by the end of the hatching period, and most elements become ossified over the next two days. Our results reveal that both the fusion of lower jaw bones and articulation between the neurocranium and upper jaws occur during post‐embryonic development. Abstract end data should be: Anat Rec, 2009. © 2009 Wiley‐Liss, Inc.