Science News reports on chicks getting prepared to hatch into a hot world by hearing the “heat” songs of their parents:
As the heat punishes sun-crisped Australian woodlands, the adult birds make a rapid, peeping “heat call”. That signal kicks off genetic changes in unhatched baby zebra finches’ brains, researchers report June 11 in the Journal of Experimental Biology. The tune appears to give developing finches a physiology-bending forecast, giving them a leg up once they emerge into the broiling conditions on the other side of the eggshell.
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But it was unknown how hearing a simple song could trigger these kinds of physical and behavioral changes in the young. [Behavioral ecologist Mylene] Mariette, of Deakin University in Waurn Ponds, Australia and Julia George, a neuroscientist at Clemson University in South Carolina wanted to know if the songs might initiate changes in the hypothalamus, a small region of the brain heavily involved in regulating metabolism and responses to heat.
The researchers raised developing zebra finches (Taeniopygia guttata) at a consistent temperature, but exposed about half to playback of an adults’ heat call and the other half to a different control call for a few days. The team removed the embryos from the eggs and euthanized them. They cut out a small sample of the hypothalamus and extracted the RNA from the tissue. RNA is the messenger that DNA sends to carry genetic information to the protein-making components of the cell. So, by comparing levels of different RNAs, the researchers can see how certain genes are ramped up or down in their production of proteins.
The team thought there would be changes in hormonal genes within the hypothalamus in response to the heat calls, says George. But instead of hormonal genes, the heat calls dampened genes that regulate the contraction and dilation of blood vessels in the brain. The researchers think this helps the chicks dissipate heat in their brains.
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You can read more of the hypothalamus-transformation research here, in the Journal of Experimental Biology.