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Embryonic development of the emu, Dromaius novaehollandiae
Author(s) -
Nagai Hiroki,
Mak SiuShan,
Weng Wei,
Nakaya Yukiko,
Ladher Raj,
Sheng Guojun
Publication year - 2011
Publication title -
developmental dynamics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.634
H-Index - 141
eISSN - 1097-0177
pISSN - 1058-8388
DOI - 10.1002/dvdy.22520
Subject(s) - biology , embryo , embryogenesis , heterochrony , hatching , andrology , primitive streak , anatomy , blastoderm , in ovo , microbiology and biotechnology , ontogeny , genetics , ecology , gastrulation , medicine
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. Developmental Dynamics, 2011. © 2010 Wiley‐Liss, Inc.