Hearing differences of gregarious and solitary locusts (Schistocerca gregaria), an example of epigenetic effects
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1
University of Strathclyde, Department of Electronic and Electrical Engineering, United Kingdom
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2
University of Cambridge, Department of Zoology, United Kingdom
Environments vary creating different niches in which animals become suited. Commonly, animals are well matched to their specific habitat, based on their differing capabilities to receive signals from the environment. For example animals that see in dark conditions often have larger eyes or eyes with tapetum to reflect light. Animal ears too may be adapted or tuned to most efficiently receive predator or courtship signals. Such morphological traits are under constant evolution, driving the physical feature in one direction or another. However, some animals show different phenotypes based on environmental rearing conditions (epigenetic effects). For instance, genetically identical locusts exhibit two phases ‘solitary’ and ‘gregarious’ determined by their environment.
The gregarious and solitary locust phase animals differ not only in their physical appearance (e.g., color and size), but also in their behavioral and physiological traits. Recent studies demonstrate differences in visual abilities between the phases that match the needs of each phase (e.g., the ability to see looming objects). While an adult animal cannot change its physical form, the root of the epigenetic change can occur within a few days; for example, when exposing a solitary female to crowding conditions she will begin to lay gregarious eggs within a few days.
While much locust hearing research is aimed at understanding basic tympanal ear principles; phase has never been taken into consideration as an element that may differentiate hearing abilities. This study focuses on the hearing of locusts (Schistocerca gregaria) in the different phases. Specifically, we measure nanometer level movement of the traveling wave seen on locust tympana and neurobiological responses, over a range of frequencies (1-30 kHz) and amplitudes. In addition, we determine the general morphology of the tympanal membrane. Based on our results, we conclude that solitary locusts have more sensitive hearing, specifically in frequencies ranging from 3-6 kHz. Supporting their greater sensitivity, the shape of the solitary locust’s tympanal membrane is significantly wider in the region where the traveling wave occurs.
Understanding differences in the hearing capabilities of different phases of locusts has many implications. First of all, it is an example of how the environment can influence traits to be best suited for the animal’s needs. In this instance, solitary animals exhibit greater sensitivity perhaps to better perceive predators as they are not protected by living amongst others in a group. Alternatively, a greater hearing ability may be used for mate location over larger distances. These behavioral questions would be interesting as an avenue for further exploration. Additionally, understanding how minute physical differences in the tympana can create such a change in sensitivity also gives insight as to what elements are important for sound reception. Hearing has evolved at least seven times within insects so understanding the differences in the ears may also lead to evolutionary as well as mechanistic discoveries.
Keywords:
Communication,
environment,
epigenetic,
Hearing,
insect,
Locust,
morphology,
Neurophysiology
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: Audition
Citation:
Gordon
SD,
Rogers
S and
Windmill
J
(2012). Hearing differences of gregarious and solitary locusts (Schistocerca gregaria), an example of epigenetic effects.
Conference Abstract:
Tenth International Congress of Neuroethology.
doi: 10.3389/conf.fnbeh.2012.27.00122
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Received:
26 Apr 2012;
Published Online:
07 Jul 2012.
*
Correspondence:
Dr. Shira D Gordon, University of Strathclyde, Department of Electronic and Electrical Engineering, Glasgow, G1 1XW, United Kingdom, shira.gordon@ars.usda.gov