2025-10-30 カリフォルニア大学サンディエゴ校(UCSD)
Intricate dendrite sheets of specialized carbon dioxide-sensing neurons (foreground) aid the detection skills of a yellow fever mosquito, lurking in the background. Credit: Hassan Tahini @ ScienceBrush.
<関連情報>
- https://today.ucsd.edu/story/researchers-uncover-previously-unexplored-details-of-mosquitos-specialized-detection-mechanisms
- https://www.pnas.org/doi/10.1073/pnas.2514666122
蚊のCO₂感知嗅覚受容ニューロンの形態学的特殊化 Morphological specializations of mosquito CO2-sensing olfactory receptor neurons
Shadi Charara, Jonathan Choy, Kalyani Cauwenberghs, +7 , and Chih-Ying Su
Proceedings of the National Academy of Sciences Published:October 23, 2025
DOI:https://doi.org/10.1073/pnas.2514666122
Significance
Carbon dioxide (CO2) emitted by human hosts is a critical cue that mosquitoes use for host detection, yet the nanoscale three-dimensional (3D) structure of their CO2-sensing neurons and associated cells remains unclear. Elucidating the anatomy of these cells will yield structural insight into the sensory biology which drives mosquito-host interactions. Using volume electron microscopy, we reveal that Aedes aegypti CO2-sensing neurons exhibit striking structural specializations—including enlarged CO2-sensing surface areas, unique axonal architecture enriched with mitochondria, and unusual somatic ensheathing by support and glial cells—that likely enhance CO2 detection and support signal transmission. Our detailed anatomical characterization provides a structural basis for the mosquito’s exceptional host-seeking capabilities.
Abstract
Hematophagous mosquitoes use CO2 as a key arousal signal that gates behavioral responses to host-derived cues. In Aedes aegypti, CO2 is detected by olfactory receptor neurons (ORNs) housed in the sensory hairs (sensilla) on the maxillary palp. While the molecular mechanism and behavioral significance of CO2 sensing have been well studied in mosquitoes, the nanoscale three-dimensional structures of their CO2-sensing ORNs and associated cells have remained unclear. Using serial block-face scanning electron microscopy, we characterize the CO2-sensing cpA neuron and its odor-sensitive neighbors, cpB and cpC, within the capitate sensilla of A. aegypti. Notably, cpA neurons are significantly larger, with an outer dendritic surface area 8 to 12 times greater than that of cpB and cpC neurons. This expanded CO2-sensing surface arises from its unique architecture, consisting of numerous flattened dendritic sheets folded into intricate lamellae. In contrast, cpB and cpC dendrites exhibit sparse, narrow cylindrical branches. Moreover, the cpA axon displays a prominent pearls-on-a-string morphology, with numerous mitochondria-rich, nonsynaptic varicosities connected by thin cables. Remarkably, a glial cell and an auxiliary cell together ensheathe the cpA soma but not cpB or cpC, suggesting a specialized role in supporting cpA function. Compared to Drosophila CO2-sensitive ORNs, a larger portion of the cpA outer dendrite is embedded within the sensillum cuticle, potentially improving access to environmental CO2. These findings reveal key morphological specializations of cpA neurons, thereby advancing our understanding of mosquito sensory biology and laying the groundwork for future studies on the molecular basis and functional ramifications of these anatomical adaptations.
