The influence of external electric fields on the olfactory function of the bumblebee Bombus terrestris

Abstract

In nature, bees are positively charged, flowers are negatively charged, and resultant electric fields (e-fields) between flowers and bees can reach magnitudes of over 5kVm-1 as the bee approaches the flower for pollination. Placodes (pore-plate sensilla) exist along bee antennae, which are innervated by a particularly high number of olfactory receptor neurons (ORNs), bathed in an extracellular lymph filled with charged ions, whose current enables excitation of ORNs. This thesis asks whether floral e-fields are integrated into the bumblebee’s olfactory sensing by influencing the excitation of these ORNs, therefore possibly increasing excitation and sharpening the temporal component of the antenna’s neural olfactory response, for greater olfactory sensitivity and localization ability; olfactory coding presents as highly challenging, particularly since the distribution of odours in space does not provide reliable directional information to its source. Electroantennogram recordings from bumblebee antennae were used to test these hypotheses. Olfactory stimuli were delivered, with and without e-field treatment. Measurements of deflection intensity (V) and time from olfactory stimulus onset to neural response peak (s) were analysed from these recordings. E-fields were tested across a range of ecologically-relevant magnitudes, with negative, positive, or zero DC offsets. E-field treatment was found to be a significant fixed effect predictor for deflection intensity (V) according to e-fields of all DC offsets, as well as for time (s) according to positive and zero DC offsets. Pairwise analyses showed some significant effects for each e-field magnitude (V) category; it is possible that statistical power was lost in pairwise comparisons. This project highlights the importance of conducting lab experiments which simulate the various modalities of information which are present in natural ecological interactions, as well as the possibility of multiple modalities interacting at the level of the sensory neuron.

Date of Award	4 Feb 2025
Original language	English
Awarding Institution	University of Bristol
Supervisor	Daniel Robert (Supervisor)