An engorged female tick, nearly 100 times her normal size, carries an unfed counterpart on her back.
Professor Emeritus, Dr. Peter Flynn has taken the opportunity of retirement to pursue research into his lifelong passion - bugs.
"I've had a lifelong curiosity about insects. There's a beauty about them," he muses.
After ten years as the Ernst and Gertrude Poole Chair in Management for Engineers in the U of A's Department of Mechanical Engineering, Flynn decided retirement was the perfect time to "get serious" about insects. To gear up for his serious retirement project, Flynn registered to audit a course in biology taught by Professor Reuben Kauffman.
"Of course I was 63," recalls Flynn. "And everyone else in the class was 22. So I stuck out a bit."
Flynn introduced himself to Kauffman as a fellow professor and Kauffman soon asked to buy Flynn a coffee in exchange for his thoughts on a research problem. Kauffman had been studying the life cycles of ticks. Ticks are obligate hematophages; they only consume blood. In preparation for laying eggs, one family of female ticks, the ixodid ticks, attach themselves to a host and, during what is called the 'rapid engorgement phase,' grow to 100 times their original size. The question of how it is physically possible for the insect to undergo such rapid growth, had stymied biologists for decades.
"But, thinking as an engineer," says Flynn, "I was able to suggest different ways to characterize the data. We needed to normalize the stress and the strain."
And so began the Flynn-Kauffman collaboration.
Flynn and Kaufman began to consider the material properties of the tick's exoskeleton by putting stress on the materials. Knowing how much stress was needed to stretch the exoskeleton, Flynn could calculate the pressure the tick needed to generate internally to produce the stretch. What he found was that, in order to grow so much, so rapidly, the tick must generate pressure more than 5 times higher than human blood pressure; a pressure even higher than a giraffe's blood pressure.
"Reuben was a little surprised by the prediction," laughs Flynn. "I don't think you can print what he called them, but he thought they might work well as fertilizer."
Of course, skepticism drives science and Kauffman set out to measure the ticks to confirm Flynn's calculations. He managed to glue tubes to live ticks and hook them up to a pressure transducer. Although the experiment only worked on 2 of 16 ticks, the results he got from the 2 corroborated Flynn's mathematical analysis.
Flynn and Kauffman then learned that the tick does not exert this pressure continually. Instead, they pulse up to 50 times per second. Flynn speculates that the pressure is exerted in pulses because ticks breathe through holes, or spiracles, on their bodies; a continual pressure would close the spiracles for too long and the insect would suffocate. The pulse of pressure is rapid enough that the exoskeleton does not have time to recoil while still allowing air exchange through the spiracles.
Flynn and Kauffman have also found evidence that suggests that ticks secrete a neurotransmitter that lowers the pH of their exoskeleton, softening it during the phase of rapid engorgement.
The Flynn-Kauffman collaboration is now in its tenth year. Flynn works from Arizona and Edmonton, and Kauffman from Salt Spring Island. Their fifth paper, comparing the properties and life cycles of the smallest species of ixodid ticks to those of the largest species, was just accepted for publication. They are awaiting samples of the other family of ticks, the argasids, a type of tick they have yet to investigate. Argasid ticks do not feed the same way as the ixodid ticks and Flynn and Kauffman will investigate if this difference is associated with different exoskeleton properties.
"It's a wonderful way to spend your time," says Flynn. "It keeps the mind young."