SPLTRAK Abstract Submission
DASPEI Imaging: In Search of Earthworm Chemoreceptors Using a Live Cell Dye
Eui Y Kim, Eileen M Reed, Glen S Marrs, Cecil J Saunders, Wayne L Silver
Wake Forest University, Winston-Salem, NC, United States

Earthworms play an important role in soil ecology and agriculture. The number of earthworms in an area is commonly used to assay a soil ecosystem’s health. A standard means of sampling earthworm  populations is the application of allyl isothiocyanate (AITC) to expel earthworms from an area. Despite AITC being a common earthworm expellant, how these animals detect AITC and other chemicals is poorly understood. We report here the use of DASPEI, a dye that fluorescently labels electrically active cells, to measure activity in epidermal cells of Eisenia hortensis after stimulation by AITC and other compounds. The epithelium of the second segment of three earthworms per concentration was imaged using a confocal microscope. In each worm, three regions of interest were selected to avoid setae and thresholded at 3 times the maximum background. Worms treated with AITC yielded significantly higher fluorescence compared to worms treated with DASPEI and vehicle alone (p<0.01, ANOVA) and in a dosage-dependent manner (1mM vs. 10mM, p<0.01, ANOVA) while no significance was noted between the PBS and 10% mineral oil. In addition to AITC, a significant difference was noted for 500mM potassium chloride (p<0.001, ANOVA) but not for 16mM capsaicin (p=0.0857, ANOVA). Two fungal compounds, ethyl hexanoate and ethyl pentanoate, previously reported as being appetitive were tested with only 25mM ethyl pentanoate (p<0.001, ANOVA) showing significance. From various neurotransmitters, only 100µM octopamine showed significance(p<0.01, ANOVA). Our results provide support for a novel method of imaging chemoreceptor cell activity. We demonstrated that earthworm epidermal cells respond to a variety of chemical stimuli. This is an early step in our efforts to identify how earthworms detect chemicals in their environment.