Hairy kisses: tactile cheliceral courtship affects female mating decisions in Leucauge mariana (Araneae, Tetragnathidae)

Abstract

Sexual selection is thought to be an important force driving the evolution of sexually dimorphic morphology and behavior, but direct experimental tests of the functions of species-specific details of morphology are rare and usually incomplete. The males of most species of the large spider family Tetragnathidae possess large sexually dimorphic chelicerae that are used when the sexes lock together before and during mating. In Leucauge mariana, the female's chelicerae clasp those of the male; mating does not begin until the female's chelicerae seize the male and does not end until they release him. In addition, females contribute material to form genital plugs in the female's genitalia. Male chelicerae have sexually dimorphic and species-specific setae and ledges in areas that contact the female during cheliceral clasps. We tested the hypothesis that stimuli from these structures trigger mating processes that are controlled by the female which could increase male reproductive success. We reduced or eliminated possible stimulation of the female in two ways: removing male cheliceral setae that contact the female, and removing setae on the female's chelicerae and endites that are contacted by and could thus be stimulated by the male's chelicerae and their setae. Both male and female modifications had similar effects that likely reduced the male's chances of paternity: female receptivity to re-mating increased, copulatory plug formation decreased, and interruptions during copulation became more frequent. As expected under the stimulation hypothesis, blocking female sensory abilities generally had greater effects on these responses than modifying male stimulatory structures.

Post-copulatory Sexual Selection in Two Tropical Orb-weaving Leucauge Spiders

“…Male chelicerae are narrower in the region (just short of the tip) that the female clasps with her chelicerae (Fig. 4.2a;Eberhard and Huber 1998a;Aisenberg et al 2015).…”

“…The anterior edge of the sternum of the female (b) has longer setae than those of the male, and these are deflected by movements of the male fangs during a clasp (c, d). The female's fang clamps the distal portion of the basal segment of the male's chelicera (c) (a from Eberhard and Huber 1998a; b-d from Aisenberg et al 2015) functions to induce these female acceptance responses. In addition, there is no way that a male can force a female to copulate in either species.…”

“…The morphological details of the cheliceral clasps observed in L. mariana were as follows (Eberhard and Huber 1998a;Aisenberg et al 2015). The female always opened her chelicerae wide as the male approached (usually with his own The endites and labium of female, before (e) and after (f) setae, were shaved off.…”

“…The female always opened her chelicerae wide as the male approached (usually with his own The endites and labium of female, before (e) and after (f) setae, were shaved off. The setae along the margins of both the chelicerae and the endites, which presumably function when the spider bites and ingests prey, were left intact (figure from Aisenberg et al 2015) chelicerae closed) and then grasped the distal portions of the basal segments of the male's chelicerae by closing her fangs. The inner surface of her fang grasped the posterior surface of the male's chelicerae rather than his endites (Fig.…”

Potential for CFC in Black Widows (Genus Latrodectus): Mechanisms and Social Context

“…Since males typically move the embolus across the epigynum multiple times before insertion is achieved, repeated contact between the pedipalps and these hairs is common ( 5,6,7 Kaston 1970) and may serve a stimulatory function ('copulatory courtship,' e.g., Huber 2005;Eberhard and Huber 2010). Whether the fertilization valve is activated during copulation, is linked to stimulation of the epigynal hairs, and whether paternity is affected could be studied with a combination of mating trials, sensory-hair ablation (e.g., Aisenberg et al 2015), muscle physiology, and freeze-fixation (Huber 1993).…”