Sensilla coeloconica ringed by microtrichia in host-seeking biting midges

Area of Science:

• Entomology
• Sensory Biology
• Evolutionary Biology

Background:

• Ceratopogonidae, commonly known as biting midges, are diverse Diptera with significant roles as parasites and predators.
• Antennal sensilla are crucial sensory organs for insect olfaction, host-seeking, and prey detection.
• Sensilla coeloconica are a type of pit peg sensillum found on insect antennae, involved in chemoreception.

Purpose of the Study:

• To investigate the distribution and morphology of antennal sensilla coeloconica in various biting midge species.
• To understand the functional significance of microtrichia-ringed sensilla coeloconica in host- and prey-seeking behavior.
• To explore the evolutionary history of sensilla coeloconica with microtrichia within the Ceratopogonidae family.

Main Methods:

• Microscopic examination of antennal sensilla coeloconica in adult female biting midges from diverse genera (Forcipomyia, Atrichopogon, Austroconops, Culicoides, Brachypogon).
• Analysis of a fossil specimen of Archiculicoides from Lebanese amber to study evolutionary morphology.
• Comparative morphological analysis focusing on the structure of sensilla coeloconica, particularly the presence and arrangement of microtrichia.

Main Results:

• Sensilla coeloconica with microtrichia forming a 'picket fence' structure were identified in several Ceratopogonidae species.
• This 'picket fence' morphology appears to maintain humidity, facilitating odor molecule capture and transport.
• The 'picket fence' sensilla coeloconica were found to be effective chemoreceptors for host- and prey-seeking.
• Convergent evolution of microtrichia-ringed sensilla coeloconica occurred at least twice in vertebrate-feeding lineages and is described for the first time in Austroconops.

Conclusions:

• The specialized structure of microtrichia-ringed sensilla coeloconica represents an adaptation for efficient chemoreception in biting midges.
• This adaptation likely plays a critical role in the host- and prey-finding success of these parasitic and predaceous insects.
• The study highlights the evolutionary plasticity of sensory structures in response to ecological pressures within the Ceratopogonidae.