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First scientific record of two cases of partial twinning in the chick embryo, Gallus gallus domesticus


Bicephalia is one of the scarcest malformations reported in birds and needs to be fully investigated in chick embryos. Among 1500 fertilised eggs used to examine the primordial germ cells in 2-day and 5.5-day chick embryos Gallus gallus domesticus, bicephalia was found and the condition of the heads, the heart and other parts of the body was fully described. Each twin had its own head; hearts were not completely separated from each other and the rest of the bodies were externally unique. This investigation urges others including poultry farms to share their data on a bigger scale. It may also encourage the monitoring of abnormalities randomly seen during early chick embryogenesis and consideration of environmental factors when poultry farms are faced with high percentages of unsuccessful hatching. The report can shed some light on developmental processes and may also help to clarify why bicephalia is not more common.

  • malformation
  • fertilized egg
  • Poultry
  • dicephalic
  • chick development

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