• Question: How does a chick know when to break out of their egg?

    Asked by lottiemccormac to Charlie, Eoin, Jemma, Julian, Steve on 17 Mar 2011.
    • Photo: Charlie Ryan

      Charlie Ryan answered on 16 Mar 2011:

      Hi lottie, i have no idea!! you could try asking one, although they might be a little unresponsive!!
      We used to have chickens when i was younger, and i remember watching them hatch under a heat lamp. Very cool to watch – and cute! I do remember them having an eggtooth – a special tooth that allows them to break through the shell!

    • Photo: Julian Rayner

      Julian Rayner answered on 17 Mar 2011:

      A very timely question, given the season! My children’s school has some eggs in an incubator which have just hatched, so they want to know the answer too!

      I don’t honestly know, but I presume that it is partly due to growth – once the chick development has reached a certain point, it triggers a signal that leads to a mechanical reflex that leads them to break the egg shell and get out.

      Malaria parasites do the same thing – they get inside your red blood cell and eat your hemoglobin (the protein that carries oxygen around your body) to give them food to grow and divide. Then 48 hours after one parasite went in, 8-32 parasites are ready to come out, so they break open the red blood cell, and set off to find new red blood cells to invade. What triggers them to break open the red blood cell? Again, a developmental thing – once they are fully developed, it triggers a signal that releases and enzyme that breaks down the red blood cell membrane. One of the drugs we are trying to develop would block that process – the parasites would get in, but never be able to break out, so would stop their growth.

    • Photo: Jemma Ransom

      Jemma Ransom answered on 17 Mar 2011:

      A very good question.

      All animals when they are developing follow a developmental programme which is largely determined by genes. These are activated sequentially so once one developmental stage is complete, a new set of genes is activated and so on until the animal is fully developed. It is after the developmental programme has run its course completely that a successfully developed chick will be able to punch its way out of the egg.

    • Photo: Eoin Lettice

      Eoin Lettice answered on 17 Mar 2011:

      Hi Lottie,
      Eventually the chick uses up all the food reserves in the egg and is triggered to go looking for more food. It is then strong enough to break out of the shell and find some!
      Eoin

    • Photo: Stephen Moss

      Stephen Moss answered on 17 Mar 2011:

      Hi Lottie
      By the time a chick has reached its maximum size it has used up all the food that was in the egg (the yolk), and in order to survive and get to more food it instinctively breaks through the shell. It’s interesting that chicks apparently never seem to try this before it’s time – perhaps also when they’re smaller they just don’t quite have the strength.

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