Encoding of stimulus velocity by insect cercal system wind-sensitive interneurons: A comparative study.
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1
College of Charleston, Department of Biology, United States
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2
College of Charleston, Program in Neuroscience, United States
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3
College of Charleston, Department of Psychology, United States
The wind-sensitive cercal sensory system is an ancestral structure of insects. Previous work suggests that this system has been modified within each species based on its evolutionary and life history. Variations in the cercal system include the: 1) number/location of the cercal filiform hairs; 2) number/size of wind-sensitive primary interneurons (WSIs) that transmit wind information to the thoracic motor areas that generate behavior; and 3) wind-evoked behaviors exhibited by different insect species (i.e. terrestrial escape responses and/or flight maintenance). These differences make the cercal sensory system well-suited for studying how nervous systems evolve since it is an ancient system found in the oldest insect species and accessible for conducting experiments at the physiological, anatomical, and behavioral levels. Though there has been extensive previous research on the cercal sensory system in various species, different methodologies make direct comparisons to assess the change in the cercal sensory system across species difficult.
The present study begins an extensive investigation of how nervous systems evolve using the cercal sensory system as a model. Using extracellular recordings, we measured neural responses from the wind-sensitive interneuron (WSI) population to 250 ms wind puffs with velocities between 0-300 cm/s. From these data, we generated stimulus-response (S-R) curves for the first 100 ms and second 150 ms of the response (corresponding to the periods dominated by the acceleration and velocity components of wind, respectively). The study included four related cockroach species (Periplaneta americana, Blaberus craniifer, Gromphadorhina portentosa, and Blattella germanica) and two more distant species (the house cricket Acheta domesticus and the Chinese mantis Tenodera aridifolia). The role wind may have in these species varies, including species that: 1) exhibit a strong wind-mediated terrestrial escape response and possess wings (P. americana, B. germanica, A. domesticus); 2) exhibit weak escape responses (B. craniifer); 3) possess wings but exhibits no wind-mediated terrestrial escape response (T. aridifolia); 4) neither possess wings nor exhibits a wind-mediated terrestrial escape response (G. portentosa). Comparing S-R curves across species can provide insight into how WSI responses relate to both phylogenetic relationships and function of the wind-sensitive cercal system. Since the WSIs provide the ‘driving force’ for activating thoracic premotor and motor neurons to generate behavior, differences in WSI responses could contribute to the differences in wind-evoked behaviors across species.
During the first 100 ms of the stimulus, wind elicited stronger responses (i.e. more neural spikes) in species that exhibit wind-mediated terrestrial escape responses (P. americana, B. germanica, A. domesticus) than those that do not (G. portentosa, T. aridifolia). However, wind elicited the strongest responses B. craniifer, which only exhibits a weak wind-mediated terrestrial escape response. Compared to the first 100 ms of the stimulus, wind-evoked responses during the second 150 ms were similar in B.craniifer but were greatly reduced in P. americana, B. germanica, and A. domesticus. These results suggest that decreased responses in the WSI population could contribute to the lack of a wind-elicited terrestrial response in those species but the synaptic interactions between the WSIs and thoracic neurons are also important.
Acknowledgements
NIH National Center for Research Resources Grant P20 RR-016461 (SC-INBRE), Howard Hughes Medical Institute (HHMI), and College of Charleston Department of Biology.
Keywords:
Cercal system,
Comparative,
Escape,
Insects,
Invertebrates,
Mechanosensation,
sensory,
Wind
Conference:
Tenth International Congress of Neuroethology, College Park. Maryland USA, United States, 5 Aug - 10 Aug, 2012.
Presentation Type:
Poster (but consider for Participant Symposium)
Topic:
Sensory: Mechanosensation
Citation:
Triblehorn
JD,
Newman
CN and
McGorry
CA
(2012). Encoding of stimulus velocity by insect cercal system wind-sensitive interneurons: A comparative study..
Conference Abstract:
Tenth International Congress of Neuroethology.
doi: 10.3389/conf.fnbeh.2012.27.00269
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Received:
30 Apr 2012;
Published Online:
07 Jul 2012.
*
Correspondence:
Dr. Jeffrey D Triblehorn, College of Charleston, Department of Biology, Charleston, SC, United States, triblehornj@cofc.edu