Abstract

The objective of this study was to determine what effect the neonicotinoid imidacloprid has on crayfish neuronal action potentials. Different amounts of imidacloprid were added to an exposed crayfish nervous system. The action potentials before and after the treatment were recorded using a home-made suction electrode and PowerLab software. After data analysis, we found out that exposure to imidacloprid causes an inhibitory effect on the neuronal action potentials of crayfish, being the extent of inhibition related to the concentration of imidacloprid to which the crayfish nervous system was exposed.

Introduction

Imidacloprid is a neurotoxin exogenous to the invertebrate nervous system that is selectively
more toxic to insects than to warm-blooded animals. Imidacloprid interferes with the
transmission of stimuli in the nervous system by causing a blockage in the nicotinergic neuronal
pathway, which is a neuronal pathway that is more abundant in insects than in warm-blooded
animals. This blockage leads to the accumulation of acetylcholine, resulting in the animal’s
paralysis, and eventually death in some cases. Because of its mode of action, imidacloprid affects
mainly the motor cells of animals.
    Previous research on clothianidin, a neonicotinoid similar to the neonicotinoid used in this
experiment (imidacloprid) shows that crayfish exhibited reduced responsiveness to stimulus with
increasing clothianidin concentration (Miles et al, 2017). That being considered, we expect the
imidacloprid treatment to reduce the responsiveness to stimulus in crayfish, which should be
seen as a decrease in the firing rate of neurons. Additionally, this experiment also attempts to
explore any other effects that imidacloprid may have on neuronal firing rates in crayfish.
For this experiment, crayfish were used because their nervous system has relatively few neurons
and their firing rates can be recorded easily. Additionally, there is previous research on
neonicotinoids done on crayfish, so using this animal as a model for this experiment allows for a
comparison of the results obtained here with those available in the existing literature.