Students can come into my lab and say they are interested in behavior, physiology or molecular biology, and we've been able to craft projects for them, no matter what level of biology they are interested in.
A mother's experiences while she is pregnant - or in the case of birds, preparing to lay an egg - has a big effect on the children, or chicks. "Maternal effects" occur when changes in a mother's body get transmitted to developing offspring. For example, in some avian species, mothers that experience a shortage of food when they are preparing to lay eggs might, in turn, endow their eggs with lower levels of androgens, a group of steroid hormones that includes testosterone. If this is the case, and considering that androgens cause chicks to grow faster and stronger, it would seem that receiving less would be disadvantageous for the chick.
Assistant Professor of Biology Morgan Benowitz-Fredericks is questioning this hypothesis. Are such maternal effects merely a constraint of physiology, where stress changes the mother's own hormone levels and therefore what she passes on to her eggs? Or, is there actually an advantage to the chicks that receive yolk hormone levels that have been modified in response to the mother's environment? If the chick hatches into a world where food is still in short supply, it might actually fare better if its body isn't trying to grow too fast. "Maybe these maternal effects are a way to better match the offspring to their environment," Benowitz-Fredericks says.
Similar hypotheses have been raised for humans. Diabetes and heart disease could be the result of what was once an advantageous system for making the most of precious calories gone terribly awry in the modern, calorie-laden world.
Egg-laying makes birds an especially advantageous system for studying such questions. "Everything mom puts in there when she is making the egg - that's it," Benowitz-Fredericks says. "That's what is in that egg and that is what that embryo is forced to be bathed in, is forced to work with." That means that she can inject eggs with hormones and know that any changes in the developing chick were caused directly by those hormones, not by an indirect cascade of effects back and forth between mother and offspring, as happens in mammals.
With student research interests spanning the spectrum from molecular to ecological questions, Benowitz-Fredericks has enjoyed working with a variety of students in her lab during her three years as a visiting professor at Bucknell.
"Students can come into my lab and say they are interested in behavior, physiology or molecular biology, and we've been able to craft projects for them, no matter what level they are interested in," she says.
Posted Sept. 27, 2010
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