The ability to recognize changes in temperature is vitally important to survival in most species. The thermosensory system can keep an animal (or human) from exposure to extreme temperatures (such as the jerk reflex when touching a hot stove). It can help an animal find an appropriate environment in which to live. Some animals can even use it to find prey. A snake, for example, has infrared sensors in its facial pit; these sensors can detect a 0.003°C change in temperature, allowing the snake to catch prey even in the dark. A human can sense temperature changes as small as 0.1°C. Thermosensory behavior is even seen in the common fruit fly, Drosophila melangastor. But the genetic and molecular mechanisms behind this behavior are not yet fully understood.
Dr. Garrity’s lab uses both the adult and larval fruit fly to study these mechanisms. D. melangastor larvae are quite sensitive to temperature changes, and, when placed on a dish that is cool on one side and warm on the other, they will move toward the cooler side. The Garrity lab has identified a gene, dTRP1a, which is essential for thermotaxis, the recognition of temperature. When this gene is knocked out in larvae, they can no longer make the choice between cool and hot. Dr. Garrity’s team found that dTRP1a is needed for thermotaxis in both larvae and adults, but not for high-temperature recoil, a behavior in flies similar to jerking away from a hot stove. Flies lacking in dTRP1a are still able to exhibit recoil behavior, meaning there is a separate neural circuit involved.
Dr. Garrity ended his talk with a discussion of a new comparative study the lab is involved in, comparing D. melangastor with another type of fruit fly, Drosophila mojanvensis, which lives in the Sonoran desert. These flies live in cacti and can survive temperatures up to 110°F. They are comparing the two dTRP1a genes to see what differences between them can account for the different heat thresholds seen in these two related species.
