I am an active researcher into the material properties of the exoskeleton (called cuticle) of the Ixodidae family of ticks (known as the hard ticks, although relative to insects their exoskeleton is anything but hard). The females engorge on large amounts of blood, and grow to a grotesque size, after which they detach, lay eggs, and die. The female tick only wants to retain her host’s red blood cells to be used in egg production, so the serum is passed through the gut and injected back into the host. It is this reinjection of fluid that transports bacteria and/or viruses that are harmful to the host; Lyme disease is one of many tick borne diseases.
The key research question for myself and Reuben Kaufman of the Biological Sciences Department is how does the exoskeleton accommodate this weight increase of 70 to 140 fold: how is structural integrity maintained? As when one investigates any “pixel” of science, one discovers complexity. We have found that the stiffness and viscosity of the cuticle varies during the feeding cycle, to make it easier for the cuticle to stretch. We have also found that the female generates a very high internal pressure, higher than a giraffe’s blood pressure, to stretch the cuticle. The pressure is not continuous but rather occurs as high frequency pulses, about 50 times per second. We think that this pattern enables the tick to keep “breathing” through its spiracles, multiple holes in the body that connect to tubes in which oxygen exchange takes place.
In our five publications we have compared the cuticle of one of the largest with that of the smallest species in the Ixodidae family. We hope to compare these results to a different family of ticks, the Argasidae, the so called soft bodied ticks, whose lifestyle is quite different, including multiple feeding and egg laying stages with a ten-fold rather than 100 fold increase in weight.
My participation grew out of my long-term fascination with insects and spiders. The work is curiosity driven; it has the merit of keeping the mind young.
I also continue to teach a one day short course in understanding financial statements; this is offered through the Executive Education arm of the U of A School of Business.