Trent Researcher Studies "Sneaky" Little Fish
There may be advantages for little fish in big ponds - contrary to popular belief.
According to a recent study by Trent University's Dr. Gary Burness, the race goes to the swiftest, at least if you're a sperm. The study, which measured sperm swimming speeds in bluegill sunfish, has been pre-published on-line in the journal Behavioral Ecology and Sociobiology.
Prof. Burness chose to study the bluegill because of its bizarre lifestyle. Smaller male bluegill - called "sneakers" - steal fertilizations by cuckolding their larger male counterparts. How the sneakers actually managed to fertilize more eggs was unknown. But by applying techniques developed by hospitals to measure human sperm quality, Prof. Burness and a team of researchers from Queen's University, showed that sneakers compensate for their diminutive size by producing faster swimming sperm. However, these sperm don't swim for as long - they live fast and die young, he says.
"When I was young, and catching these things on my fishing line, I never realized that these tiny fish were actually adults," says Prof. Burness, whose research is at the interface of physiology, ecology and evolutionary biology.
The study's results signify the first time within a species that two different morphs have been identified as producing sperm with different swimming speeds. But there's no reason to think this isn't the case in other externally fertilizing fish species.
In terms of evolutionary biology, Prof. Burness's specialty, he says it's about survival. The optimal strategy for the sneaker is to stay small, and put energy into sperm production rather than into growth. Prof. Burness started on the project two years ago as an NSERC post-doctoral fellow at Queen's, and having joined Trent's Department of Biology in July 2004, hopes to continue these studies in collaboration with the Ministry of Natural Resources.
Aside from this study, Prof. Burness's primary research is on energy expenditure in animals, particularly birds. This summer, Prof. Burness and his student will study whether tree swallows nesting in areas where there are low amounts of food show higher levels of stress, and overall poorer health, than those birds nesting in food-rich areas. He hopes their findings will be of use to other researchers trying to predict the impact of human disturbance on a bird's health.
In addition to his work on tree swallows, Prof. Burness is interested in understanding why different animal species have evolved to spend energy at very different rates. He points out that while some species appear frugal in their use of energy, other species live lifestyles that appear energetically extravagant.
To understand how such differences between species may have evolved, Prof. Burness plans to study zebra finches, a small bird available in pet stores. By following the lead of farmers, who have selectively bred chickens for egg laying ability, Prof. Burness plans to selectively breed finches for differences in metabolism and energy use. Over a few years of selective breeding, he hopes to generate a strain of fast-metabolism zebra finches. Such a strain of birds will allow his students to begin to unravel why species differ in energy use.
He acknowledges that selective breeding will not create hummingbirds from finches, but it will provide clues as to how a fast-metabolism species could have evolved from a slower- metabolism ancestor. "That," Prof. Burness says, "would be very exciting."
Posted April 16, 2004
