Stabilimenta shape on catching speed

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doi: 10.1098/rspb.2000.1038 , 565-569 267 2000 Proc. R. Soc. Lond. B Takeshi Watanabe regulates prey-catching behaviour , Octonoba sybotides Web tuning of an orb-web spider, References http://rspb.royalsocietypublishing.org/content/267/1443/565#related-urls Article cited in: Email alerting service here right-hand corner of the article or click Receive free email alerts when new articles cite this article - sign up in the box at the top http://rspb.royalsocietypublishing.org/subscriptions go to: Proc. R. Soc. Lond. B To subscribe to This journal is © 2000 The Royal Society on November 8, 2010 rspb.royalsocietypublishing.org Downloaded from
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Web tuning of an orb-web spider, Octonoba sybotides , regulates prey-catching behaviour Takeshi Watanabe Department of Zoology, Faculty of Science, Kyoto University, Kyoto 606^8502, Japan ( [email protected] ) An uloborid spider ( Octonoba sybotides ) constructs two types of web which are distinguished by linear or spiral stabilimenta. Food-deprived spiders tend to construct webs with spiral stabilimenta and food- satiated spiders tend to construct webs with linear stabilimenta. I experimentally examined the in£uence of web type on the speed of a spider's response to small and large £ies. The results indicated that web type rather than the spiders' energetic condition in£uences the response speed to small or large Drosophila £ies. I also examined whether thread tension a¡ects the response speed of spiders by increasing the tension of the radial threads. The results showed that spiders on an expanded web responded to small prey as quickly as spiders on webs with spiral stabilimenta. The tension of the radial threads may be regulated by the degree of distortion of the radial threads at the hub. O. sybotides seems to construct orb webs which induce di¡erent responses for smaller, less-pro¢table prey according to its energetic state. The spider appears to increase the tension of the radial threads so that it can sense smaller prey better when hungry. Keywords: vibration; information; tension; Octonoba ; response speed 1. INTRODUCTION The interaction between organisms and their environ- ment, including other organisms, is a fundamental facet of animal ecology. One important interaction between organisms and their environment is the transmission of information (Dusenbery 1992). Web-spinning spiders acquire much of the information about their prey on their webs from vibrations transmitted through the web threads (KlÌrner & Barth 1982). Their response to prey seems to be physiologically tuned to transmitted vibrations of a speci¢c frequency and amplitude range and spiders need to be stimulated above a threshold level to induce prey-catching behaviour (KlÌrner & Barth 1982; Masters 1984 b ; Landolfa & Barth 1996). In general, small prey items of relatively little nutritional value are rarely attacked (Riechert & Luczak 1984; Uetz & Hartsock 1987) and foraging models which include diet width predict the advantage of such tactics (Charnov 1976). Prey discrimination (size or prey species) may use frequency or amplitude information (Landolfa & Barth 1996). Physiological studies on web
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