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Article

Synaptic Interactions in Scorpion Peg Sensilla Appear to Maintain Chemosensory Neurons within Dynamic Firing Range

Department of Biology, University of Oklahoma, Norman, OK 73019, USA
*
Author to whom correspondence should be addressed.
These authors contributed equally to this work.
Academic Editors: Brian H. Smith and Matthieu Dacher
Insects 2021, 12(10), 904; https://doi.org/10.3390/insects12100904
Received: 17 August 2021 / Revised: 24 September 2021 / Accepted: 28 September 2021 / Published: 3 October 2021
(This article belongs to the Collection Insect Senses: From Perception to Cognition)
Scorpions have unusual taste organs called pectines that they drag over the ground as they walk. Minute, peg-shaped sensilla adorn the ground-facing surfaces of the pectines, and each of these “pegs” contains several chemosensitive neurons and at least one mechanosensitive neuron. Of particular interest is that some of these neurons interact synaptically at the level of the peg sensillum prior to relay to the scorpion brain. Here we use a technique called “conditional cross-interval correlation analysis” to show that heightened activity of two of the neurons appears to induce a third neuron, which in turn inhibits the previous two. We suggest that the dynamics of this simple feedback circuit might serve to maintain the sensory neurons in a sensitive range so that substrate information can be accurately detected and processed, such as during tracking sexual pheromone trails and/or recapitulating home-directed training paths.
Scorpions have elaborate chemo-tactile organs called pectines on their ventral mesosoma. The teeth of the comb-like pectines support thousands of minute projections called peg sensilla (a.k.a. “pegs”), each containing approximately 10 chemosensory neurons. Males use pectines to detect pheromones released by females, and both sexes apparently use pectines to find prey and navigate to home retreats. Electrophysiological recordings from pegs of Paruroctonus utahensis reveal three spontaneously active cells (A1, A2, and B), which appear to interact synaptically. We made long-term extracellular recordings from the bases of peg sensilla and used a combination of conditional cross-interval and conditional interspike-interval analyses to assess the temporal dynamics of the A and B spike trains. Like previous studies, we found that A cells are inhibited by B cells for tens of milliseconds. However, after normalizing our records, we also found clear evidence that the A cells excite the B cells. This simple local circuit appears to maintain the A cells in a dynamic firing range and may have important implications for tracking pheromonal trails and sensing substrate chemistry for navigation. View Full-Text
Keywords: pectines; navigation; electrophysiology pectines; navigation; electrophysiology
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MDPI and ACS Style

Gaffin, D.D.; Shakir, S.F. Synaptic Interactions in Scorpion Peg Sensilla Appear to Maintain Chemosensory Neurons within Dynamic Firing Range. Insects 2021, 12, 904. https://doi.org/10.3390/insects12100904

AMA Style

Gaffin DD, Shakir SF. Synaptic Interactions in Scorpion Peg Sensilla Appear to Maintain Chemosensory Neurons within Dynamic Firing Range. Insects. 2021; 12(10):904. https://doi.org/10.3390/insects12100904

Chicago/Turabian Style

Gaffin, Douglas D., and Safra F. Shakir. 2021. "Synaptic Interactions in Scorpion Peg Sensilla Appear to Maintain Chemosensory Neurons within Dynamic Firing Range" Insects 12, no. 10: 904. https://doi.org/10.3390/insects12100904

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