Data from: Morphological specializations of mosquito CO2-sensing olfactory receptor neurons
Data files
Jun 15, 2026 version files 63.14 GB
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Mosquito_Palp.mrc
63.14 GB
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README.md
3.73 KB
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.
Dataset DOI: 10.5061/dryad.x0k6djj1d
Description of the data and file structure
For SBEM experiments, the mosquitoes were anesthetized on ice, and their maxillary palps were removed by pinching the first or second palp segment with fine forceps. The SBEM volume of the A. aegypti maxillary palp was generated following the CryoChem protocol. Briefly, dissected olfactory tissues were immediately subjected to high-pressure freezing, followed by freeze-substitution, rehydration, en bloc heavy metal staining, dehydration, and resin infiltration. Microcomputed X-ray tomography was used to determine the position and proper orientation of the resin-embedded specimens. Samples were mounted on aluminum pins with conductive silver epoxy and sputter coated with gold-palladium for SBEM imaging with a Gemini SEM 300 (Zeiss) equipped with a Gatan 3View 2XP microtome system and the OnPoint backscatter detector.
The antennal SBEM volume was acquired at 2.5 kV using a 30-μm aperture, with the electron gun set to analytic mode and the beam operating in high-current mode. Nitrogen gas was used for focal charge compensation to reduce charging artifacts. Imaging was performed with a dwell time of 1 μs, a pixel size of 5 nm, and a Z-step of 40 nm. The X and Y pixel numbers were 1,733 and 1,549, respectively, and there were a total of 2,942 Z slices. After data collection, the images were converted to MRC format, and rigid alignment of the image slices was performed using cross-correlation in the IMOD image processing package.
Files and variables
File: Mosquito_Palp.mrc
Description: Mosquito maxillary palp serial block-face electron microscopy volume. The X and Y pixel numbers were 1,733 and 1,549, respectively, and there were a total of 2,942 Z slices.
Code/Software
Option 1. IMOD
We used the IMOD image processing package (https://bio3d.colorado.edu/imod/) to view these volumes. Download the appropriate version that is compatible with your operating system.
- Open the 3dmod application (the main viewing component of IMOD).
- In the startup window, click on "Select..." next to "Image file(s)" and browse to select the downloaded file.
- In case of low system memory: Before clicking "Open", look for the "Cache" option in that same startup window. Set the cache to 5 sections. This reduces the memory used so the file can load smoothly.
- Click Open.
Option 2: Fiji / ImageJ
If you do not have specialized electron microscopy software, you can open the file in Fiji using the Bio-Formats plugin to bypass memory limits. However, this option results in poorer image quality.
- Open Fiji/ImageJ.
- Go to File > Import > Bio-Formats.
- Select the .mrc file.
- In the Bio-Formats Import Options window that pops up, look under the "Dataset Organization" section.
- Check the box for "Use virtual stack".
- Click OK. The file will stream directly from your storage without overloading your computer's RAM.
System Requirements
Because these volumes are large, the primary bottleneck is system memory (RAM).
- Minimum RAM: 8 GB (but the file must be opened with cache turned on, as described above).
- Recommended RAM: 16 GB or higher to load the volume at full resolution.
- Operating System: Windows, macOS, or Linux.
Access information
Other publicly accessible locations of the data:
- Cell Image Library (https://www.cellimagelibrary.org/) with the accession number CIL:57520.