Embryonic development of the emu, Dromaius novaehollandiae

Dev Dyn. 2011 Jan;240(1):162-75. doi: 10.1002/dvdy.22520.


The chick, Gallus gallus, is the traditional model in avian developmental studies. Data on other bird species are scarce. Here, we present a comparative study of the embryonic development of the chick and the emu Dromaius novaehollandiae, a member of Paleognathae, which also includes the ostrich, rhea, tinamou, kiwi, and cassowary. Emu embryos ranging from Hamburger and Hamilton (HH) equivalent stages 1 to 43 were collected and their gross morphology analyzed. Its early development was studied in detail with time-lapse imaging and molecular techniques. Emu embryos in general take 2-3 times longer incubation time to reach equivalent chicken stages, requiring 1 day for HH2, 2.5 days for HH4, 7 days for limb bud initiation, 23 days for feather germ appearance, and approximately 50-56 days for hatching. Chordin gene expression is similar in emu and chick embryos, and emu Brachyury is not expressed until HH3. Circulation is established at approximately the 27- to 30-somite stage. Forelimb buds are formed and patterned initially, but their growth is severely retarded. The size difference between an emu and a chick embryo only becomes apparent after limb bud formation. Overall, emu and chick embryogenesis proceeds through similar stages, but developmental heterochrony between these two species is widely observed.

Publication types

  • Comparative Study

MeSH terms

  • Animals
  • Cell Size
  • Chick Embryo
  • Cloning, Molecular
  • Dromaiidae / embryology*
  • Dromaiidae / genetics
  • Embryo, Nonmammalian
  • Embryonic Development / genetics
  • Embryonic Development / physiology*
  • Fetal Proteins / genetics
  • Gene Expression Regulation, Developmental
  • Genes, Developmental
  • Glycoproteins / genetics
  • Hedgehog Proteins / genetics
  • Intercellular Signaling Peptides and Proteins / genetics
  • Somites / embryology
  • Somites / growth & development
  • T-Box Domain Proteins / genetics
  • Time-Lapse Imaging
  • Zygote / cytology
  • Zygote / growth & development


  • Fetal Proteins
  • Glycoproteins
  • Hedgehog Proteins
  • Intercellular Signaling Peptides and Proteins
  • T-Box Domain Proteins
  • chordin
  • Brachyury protein