Electrotaxis Induced Neuromuscular Response of the Tardigrade Species Hypsibius exemplaris in a Microfluidic Environment

Research related to medicine has been centered around testing and finding a cure for diseases. Model organisms such as mice and monkeys have been key to the drug discovery process but the use of these organisms is becoming difficult due to ethical concerns. Tardigrades are a species of invertebrate organisms that could be widely used in drug discovery as they have a complex nervous system for their size, possess a transparent exoskeleton which makes observing neural activity accessible, and there are currently no ethical constraints regarding their use. Analyzing the movement of model organisms in response to stimuli is a very common method in drug discovery, previously used with another invertebrate organism C. elegans. This paper aims to analyze the movement response of tardigrades to electric stimuli to map the neuromuscular response, which can be used as a standard to measure the neurological effect of drug testing. This study shows that tardigrades respond to low-voltage electric fields in a microfluidic environment without long-lasting side effects. The tardigrades were shown to have a neuromuscular response to electric fields, which can be used to test the effects of drug candidates on the organism. The tardigrades were attracted toward the negative electrode in electric field intensities of 3-8 V/cm with average speeds ranging from 154.90-259.00 µm/s. The neuromuscular response seen in tardigrades towards the electric field can be used in drug discovery by tracking its response before and after the drug has been administered. The use of tardigrades in medical research can provide an alternative solution to the ethical dilemma faced with the use of vertebrate organisms.