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First published online March 2, 2006
Journal of Experimental Biology 209, 1074-1084 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02104
Seismic signal production in a wolf spider: parallel versus serial multi-component signals
1 Division of Life Sciences, Integrative Behaviour and Neuroscience,
University of Toronto at Scarborough, Ontario, M1C 1A4, Canada
2 Departments of Zoology and Botany, University of British Columbia,
Vancouver, V6T 1Z4, Canada
3 School of Biological Sciences, University of Nebraska, Lincoln, NE 68588,
USA
* Author for correspondence (e-mail: elias{at}utsc.utoronto.ca)
Accepted 17 January 2006
Animal signals can consist of multiple parts within or across sensory modalities (multi-component signals or multimodal signals). While recent work has focused on multimodal signals, the production, processing and evolution of multi-component signals has received considerably less attention. Here, using synchronous high-speed video and laser vibrometer recordings followed by experimental manipulations of putative sound-producing structures, we explored the mechanisms of seismic signal production in the courtship display of Schizocosa stridulans Stratton. Two types of seismic courtship signals were observed: `rev' and `idle' signals. Revs consist of a high-frequency component produced by flexions of the male pedipalp (stridulation) simultaneous with a low-frequency component produced by movements of the abdomen (tremulation). This multi-component signal is produced by independent structures and represents a parallel multi-component display. By contrast, idle displays consist of a high-intensity component produced by drumming of the forelegs on the substrate (percussion) followed by a high-frequency component produced by flexions of the male pedipalp (stridulation). While the components of the idle display are also produced by independent structures, the leg drumming and palp flexions occur serially and do not overlap in time. We discuss the selective pressures that may drive the evolution of multiple sound-producing structures as well as the selective pressures that drive the evolution of parallel versus serial multi-component signals.
Key words: seismic signal, courtship display, Schizocosa stridulans, signal evolution, multiple signal, vibratory display