Craniofacial development of hagfishes and the evolution of vertebrates


Cyclostomes, the living jawless vertebrates including hagfishes and lampreys, represent the most basal lineage of vertebrates. Although the monophyly of cyclostomes has been supported by recent molecular analyses, the phenotypic traits of hagfishes, especially the lack of some vertebrate-defining features and the reported endodermal origin of the adenohypophysis, have been interpreted as hagfishes exhibiting a more ancestral state than those of all other vertebrates. Furthermore, the adult anatomy of hagfishes cannot be compared easily with that of lampreys. Here we describe the craniofacial development of a series of staged hagfish embryos, which shows that their adenohypophysis arises ectodermally, consistent with the molecular phylogenetic data. This finding also allowed us to identify a pan-cyclostome pattern, one not shared by jawed vertebrates. Comparative analyses indicated that many of the hagfish-specific traits can be explained by changes secondarily introduced into the hagfish lineage. We also propose a possibility that the pan-cyclostome pattern may reflect the ancestral programme for the craniofacial development of all living vertebrates.

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Figure 1: Cyclostomes and gnathostomes.
Figure 2: Craniofacial development of E. burgeri.
Figure 3: Embryonic gene expression in Eptatretus burgeri.
Figure 4: Comparison of vertebrate heads.
Figure 5: Evolution of the vertebrate head.

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Primary accessions


Data deposits

Sequences for EbPitxA, EbSix3/6A, EbFgf8/17, EbHh1, EbTbx1/10A, EbSoxB1, EbLhx3/4A and EbNkx2.1 from E. burgeri are deposited in DDBJ/GenBank/EMBL under accession numbers AB703678AB703682, AB729075AB729076, and AB747372.


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We thank O. Kakitani of Shimane Fishermen’s Union and K. Kayano of Sekikatsu Inc. for hagfish sample collection; T. Kawamoto for technical advice on paraffin sectioning; I. Kamimura for advice on the Avizo technique; T. Imai and Y. Ashida for advice on the technique for section in situ hybridization; and M. Takechi, T. Hirasawa, N. Adachi, Y. Murakami, S. Yonemura, K. Misaki, K. Yasui, S.-i. Aota, M. Nozaki and H. Koyama for their technical support and advice. We also thank M. Tanaka and K. Onimaru for providing the LjTbx1/10A plasmid, and H. Nagashima, R. Ladher, F. Sugahara and J. Pascual Anaya for critical reading of the manuscript.

Author information




Y.O. performed sample collection, maintenance of aquarium tanks, histological preparation and three-dimensional reconstructions. Y.O. and S.F. performed the molecular cloning of EbPitxA, EbSix3/6A, EbFgf8/17A, EbHh1, EbTbx1/10A, EbSoxB1, EbLhx3/4A and EbNkx2.1 genes and in situ hybridization. S. Kuraku performed the molecular evolutionary analysis. Y.O. and S. Kuratani wrote the first draft of the manuscript. K.G.O., S. Kuraku and S. Kuratani wrote the final version of the manuscript. All of the authors discussed the results and commented on the manuscript.

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Correspondence to Shigeru Kuratani.

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The authors declare no competing financial interests.

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This file contains Supplementary Figures 1-12, which show embryonic morphological data, Supplementary Table 1 and additional references. (PDF 12829 kb)

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Oisi, Y., Ota, K., Kuraku, S. et al. Craniofacial development of hagfishes and the evolution of vertebrates. Nature 493, 175–180 (2013).

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