Development Genes and Evolution

, Volume 220, Issue 3–4, pp 117–122 | Cite as

Head patterning and Hox gene expression in an onychophoran and its implications for the arthropod head problem

  • Bo Joakim Eriksson
  • Noel N. Tait
  • Graham E. Budd
  • Ralf Janssen
  • Michael Akam
Short Communication


The arthropod head problem has puzzled zoologists for more than a century. The head of adult arthropods is a complex structure resulting from the modification, fusion and migration of an uncertain number of segments. In contrast, onychophorans, which are the probable sister group to the arthropods, have a rather simple head comprising three segments that are well defined during development, and give rise to the adult head with three pairs of appendages specialised for sensory and food capture/manipulative purposes. Based on the expression pattern of the anterior Hox genes labial, proboscipedia, Hox3 and Deformed, we show that the third of these onychophoran segments, bearing the slime papillae, can be correlated to the tritocerebrum, the most anterior Hox-expressing arthropod segment. This implies that both the onychophoran antennae and jaws are derived from a more anterior, Hox-free region corresponding to the proto and deutocerebrum of arthropods. Our data provide molecular support for the proposal that the onychophoran head possesses a well-developed appendage that corresponds to the anterior, apparently appendage-less region of the arthropod head.


Onychophora Hox genes Head segmentation Arthropoda 



This work was funded by the Marie Curie Training Network ZOONET and BBSRC grant BBS/B/07519 to MEA. We thank Leyli Samadi (University of Vienna) for carrying out the phylogenetic analysis.

Supplementary material

427_2010_329_MOESM1_ESM.pdf (351 kb)
ESM 1 (PDF 351 kb)


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Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  • Bo Joakim Eriksson
    • 1
    • 4
  • Noel N. Tait
    • 2
  • Graham E. Budd
    • 3
  • Ralf Janssen
    • 3
  • Michael Akam
    • 1
  1. 1.University Museum of Zoology and Department of ZoologyCambridgeUK
  2. 2.Department of Biological SciencesMacquarie UniversitySydneyAustralia
  3. 3.Dept Earth Sciences, PaleobiologyUppsala UniversityUppsalaSweden
  4. 4.School of Biological and Chemical SciencesQueen Mary University of LondonLondonUK

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