Infrared (FTIR) spectral features of honey bee (Apis mellifera L.) hemolymph

Hemolymph is a colorless or slightly yellowish liquid of the open circulatory system of the honey bee (Apis mellifera L.) which represents a functional equivalent of vertebrate blood and lymph. It has a complex chemical composition and contains water, numerous proteins, amino acids, carbohydrates (glucose, fructose, trehalose) and lipid-based components. Understanding the biochemical features of the hemolymph is of great importance as it reflects the physiological state of honey bee organism. The aim of this study was to determine the overall biochemical composition of honey bee hemolymph based on chemical characterization using Fourier transform infrared (FTIR) spectroscopy. Individual hemolymph samples (~4-5 μL/bee) of two age groups of workers (newly emerged bees-1 day old, n=31 ; foragers-42 days old, n=18) were collected by extraction from the thorax after removing the legs (to avoid contamination with nectar and/or gut content that often occurs when applying other extraction methods) using 10 μL glass microcapillary tubes. The IR spectra of individual hemolymph samples were analysed by FTIR-ATR (Attentuated Total Reflectance) recording technique. The results have revealed a unique IR chemical fingerprint of honey bee hemolymph. Characteristic age-related spectral features indicating compositional variations between newly emerged bees and foragers were observed. The major differences were reflected in the higher proportion of proteins, amino acids and lipid-based components in the hemolymph of newly emerged bees compared to foragers hemolymph. Contrary, it was observed that foragers hemolymph contains higher amount of water and carbohydrates which can be associated with age/task relating metabolic changes - foraging activity (nectar collection).