Comparative study on the encoding of communication signals in two species of weakly electric fish
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1
Ludwig-Maximilians Universität München, Biologie II, Germany
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2
Eberhard Karls Universität Tübingen, Institut für Neurobiologie, Germany
Communication signals play an important role in separating sympatric species. In particular, mating signals of closely related species often differ dramatically and thus ensure a reproductive barrier. The question arises how sensory systems provide the necessary flexibility to appropriately encode these quickly evolving signals. We here investigate this topic on the example of chirping behavior and its encoding in two closely related species of Gymnotiform weakly-electric fish – a well established model system for studying sensory processing on the cellular level.
Weakly electric fish generate an electric field around their body by producing weak electric discharges with a specialized organ in their tail. Electroreceptors distributed over their body they are able to sense this field and distortions of it. The quasi-sinusoidal electric organ discharges (EOD) are used by the fish for navigation, electrolocation and communication purposes. Here we focus on the communication behavior. When two fish meet, there individual EODs interfere and lead to an amplitude modulation (AM) of the EOD, the beat. Since EOD frequencies are sexually dimorphic (male and female fish have higher or lower EOD frequencies, or vice versa depending on the species) the beat frequency carries information about the nature of the encounter. During such interactions the fish produce stereotyped communication signals, so called chirps. These consist of transient increases of the EOD frequency affecting the AMs of the EOD in distinct ways.
In behavioral experiments we studied the chirping behavior of two different wave-type species of weakly-electric fish, Apteronotus albifrons and Apteronotus leptorhynchus. In so called chirp chamber experiments fish were stimulated with sinusoidal, EOD like stimuli mimicking the presence of a conspecific to induce chirping behavior. We observed several differences between the chirps of both species. A. albifrons generally emits chirps of longer duration and sometimes larger complexity than A. leptorhynchus.
In a second step electrophysiological playback experiments were performed in which the recorded chirps were used as stimuli. We analyzed how these are encoded in the responses of one population of electroreceptors, the P-units, that in particular encode AMs of the EOD. Chirps of both species are encoded in the same way by the P-units of either species. The differences in the chirps, however, evoke quite different responses, so that they can be potentially well distinguished by the animals. Species specific adapations thus must occur on high levels of information processing.
Keywords:
amplitude modulations,
Communication signals,
Sensory coding,
wekly electric fish
Conference:
Bernstein Conference 2012, Munich, Germany, 12 Sep - 14 Sep, 2012.
Presentation Type:
Poster
Topic:
Sensory processing and perception
Citation:
Kümpfbeck
F,
Grewe
J,
Walz
H and
Benda
J
(2012). Comparative study on the encoding of communication signals in two species of weakly electric fish.
Front. Comput. Neurosci.
Conference Abstract:
Bernstein Conference 2012.
doi: 10.3389/conf.fncom.2012.55.00023
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Received:
29 May 2012;
Published Online:
12 Sep 2012.
*
Correspondence:
Miss. Franziska Kümpfbeck, Ludwig-Maximilians Universität München, Biologie II, Planegg-Martinsried, Germany, kuempfbeck@googlemail.com