Olfactory sensitivity in tsetse flies: a daily rhythm

Area of Science:

• Entomology
• Neuroethology
• Chronobiology

Background:

• Tsetse flies (Glossina morsitans morsitans) exhibit distinct diurnal biting patterns, with activity peaks in early morning and late afternoon.
• Locomotor activity in laboratory settings mirrors these diurnal patterns, suggesting underlying daily rhythms in sensory systems.
• Previous research has documented daily fluctuations in motor and sensory-motor systems, but the patterning of sensory response levels remained unstudied.

Purpose of the Study:

• To investigate the daily modulation of the olfactory sense in tsetse flies.
• To determine if olfactory cell sensitivity parallels other daily activity rhythms in Glossina species.
• To explore the potential economic benefits of tuning olfactory receptor sensitivity.

Main Methods:

• Stimulating tsetse fly antennae with host-derived odors at varying concentrations.
• Measuring the spiking rate of olfactory cells across different times of the photophase.
• Utilizing electroantennography (EAG) to assess olfactory responses in Glossina morsitans and Glossina fuscipes.

Main Results:

• Demonstrated a daily modulation in the sense of smell for Glossina morsitans, with sensitivity fluctuating in parallel with other daily rhythms.
• Observed similar olfactory response patterns in Glossina fuscipes, correlating with their distinct locomotor activity profiles.
• Concentration-response curves indicated that antennal olfactory cell sensitivity follows daily rhythms.

Conclusions:

• The sensitivity of tsetse fly olfactory receptors is subject to daily rhythmicity.
• This olfactory modulation appears to be conserved across different Glossina species with varying activity patterns.
• Reduced olfactory receptor sensitivity during anticipated inactivity likely serves an energy-saving function for the organism.