A Comparison of Thermal Responses Across the Phylum Nematoda
Open AccessEscape responses are important for survival, as they help organisms avoid harmful stimuli. In this project, we analyzed how escape responses to thermal stimuli differ across the developmental stages (L1, L2, L3, and L4) and first five days of adulthood in Caenorhabditis elegans. We also compared thermal escape responses across four different species of nematodes: Ancylostoma caninum, Ancylostoma ceylanicum, Heterorhabditis bacteriophora, and C. elegans. Our experimental apparatus consists of an open-frame microscope with a 1480 nm infrared laser adapted to provide thermal stimulation. This wavelength optimized the amount of heat that was absorbed by the worm, which increased the efficiency and rate of heating or ramp rate. Previous studies have shown that the strength and speed of C. elegans’ escape response increases with ramp rate, making this wavelength of light important. We have conducted trials at three laser pulses: 2ms, 9ms, and 12ms, providing a comparison of how each nematode responds to different temperatures. Videos of the worms were captured and digitized on a laptop computer. Worms were stimulated while a video was captured. The stimulation was repeated until the worm did not respond. The worm’s velocity and acceleration following each stimulation was computed. Additionally, habituation to the stimuli was compared across the life stages of C. elegans, as well as across species by comparing the number of stimuli required until each nematode stopped responding to heat. Results show differences between life stages in C. elegans. Response velocities and accelerations are lowest in L1 and L2 nematodes, and increase throughout the larval stages, peaking in L4 and D1 worms. In adult nematodes, response velocities and accelerations decrease as C. elegans age, and are lowest in D4 and D5 nematodes. Results also show differences between each of the species of nematode, which are likely due to differences in their lifecycles. C. elegans, a free-living nematode, shows an escape response at all three temperatures that were tested, and require fewer stimuli to habituate at higher temperatures. However, A. caninum and A. ceylanicum, two types of parasitic hookworm, only begin showing an escape response at the 9ms laser pulse, moving towards the heat at the lower temperature. In H. bacteriophora, velocity, acceleration, and number of stimuli required to habituate increase remain consistent with each increase in heat delivered. Taken together these data reveal how unique species of nematodes are tuned to specific thermal preferences that may reflect lifestyle adaptations.
- All rights reserved
Notice to Authors
If you are the author of this work and you have any questions about the information on this page, please use the Contact form to get in touch with us.