Zebra Finch Embryos Show Gene Changes in Brain After Heat-Call Exposure

Adult zebra finches produce a rapid, high-pitched peeping heat call when temperatures rise; exposure to these calls altered expression of about 2 percent of hypothalamic genes in unhatched embryos, Science News reported. Researchers published the findings June 11 in the Journal of Experimental Biology.

The study examined how the calls affect the hypothalamus, a brain region that regulates metabolism and responses to heat.

Behavioral ecologist Mylene Mariette of Deakin University in Waurn Ponds, Australia, and neuroscientist Julia George of Clemson University in South Carolina led the work. A decade earlier, Mariette and colleagues found that heat-call exposure altered chick growth rate, nest-site preference, and heat tolerance. In the new experiments, researchers raised zebra finch embryos at constant temperature.

They played either heat calls or control calls to two groups for several days. Embryos were then removed from eggs, euthanized, and hypothalamic tissue was sampled for RNA extraction. Heat-call exposure altered expression of genes regulating contraction and dilation of brain blood vessels.

Hormonal genes remained unaffected. Approximately 2 percent of hypothalamic RNA showed altered levels due to the exposure. Julia George stated that some consequences of the call are permanent. The birds will choose warmer nest sites as adults if they are exposed to heat calls as embryos, and they will produce more offspring in those warmer environments.

George added that it is important that the temperature of the brain is kept cool, even in hot temperatures. She described the calls as a little weather forecast that allows the finches to fine-tune their physiology to be better suited to the environment right after they hatch. The scientific name of the zebra finch is Taeniopygia guttata.