The Influence of Chemical vs. Visual Cues From Females on Male Courtship Behavior in a Wolf Spider (Araneae: Lycosidae)

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Animal communication is often multimodal as signals may involve multiple sensory modes (chemical, visual, and seismic) simultaneously. Multimodal signals may contain redundant messages (e.g., ‘backup signals’ contain the same information about a trait), or different messages (e.g., each signal conveys information about a different trait). Multimodal communication is common in many contexts, including territory defense, alarm signals, and predator deterrence, but its role in mate attraction and courtship is most frequently studied.

Wolf spiders (Lycosidae) of the genus Schizocosa provide a model system for investigating multimodal communication (Hebets & Uetz 1999, 2000; Uetz 2000; Uetz & Roberts 2002). While the role of multimodal male signals in species recognition and mate choice have been studied extensively (Stratton & Uetz 1981, 1983, 1986; Scheffer et al. 1996; McClintock & Uetz 1996), few studies has looked at the influence of female cues on the courtship of males (Balsby & Dabelsteen 2002). Males of several species initiate courtship upon encounter with chemical cues in female silk (Roberts 2003), but the role of visual cues in mediating male behavior is unknown. In this study, we examine male responses to isolated and combined visual and chemical cues from females to determine if females use multimodal signals.

	The Brush-legged Wolf Spider Schizocosa ocreata (Hentz) (Araneae: Lycosidae) inhabits the leaf litter of deciduous forests throughout the eastern United States . Previous research has shown that S. ocreata communicate through chemical, seismic, and visual modes (Stratton & Uetz 1983, 1986; Scheffer et al. 1996).
Schizocosa ocreata - Male
	Female S. ocreata can distinguish conspecific males based on visual and seismic communication (Stratton & Uetz 1983,1986), and respond with equal frequency to both modes in isolation or combined. Whether males rely more on chemical or visual cues (or combined cues) from the female to initiate courtship has not been tested.
Schizocosa ocreata - Female

The experiment was cond uc ted using both laboratory-reared and field caught (juveniles brought from field into laboratory to mature) spiders. All spiders were housed individually and maintained in controlled conditions with ad libitum water and a regular feeding schedule.

Males and females were randomly paired and assigned to stimulus treatment groups (Visual, Chemical, or Visual & Chemical stimuli). Twelve hours prior to experimentation, all females were placed in clear plastic experimental chambers (7 x 13 x 5cm) lined with paper to collect silk. Males were placed in containers with or without silk, and/or a visual barrier obscuring the female. All trials were video recorded for five min. in a cue isolation apparatus providing stimuli from a live female and/or her silk (Fig. 1).

Male behaviors (chemo-exploratory, and jerky-tapping) were scored for each five minute trial using The Observer, ver. 4.1 (®Noldus). Occurrence of courtship (jerky-tapping) across stimulus treatments was analyzed with a contingency test. Three aspects of the scored behaviors: (1) latency, (2) frequency, and (3) mean duration were analyzed using Two-Way ANOVA with stimulus and rearing treatment as factors.

Figure 1 - Cue isolation apparatus

Courtship of male S. ocreata is not independent of stimulus (X2 = 13.376; p = 0.0012). Males rely on chemical cues to initiate courtship behavior (jerky-tapping) more than visual cues. Furthermore, males seem to respond with the same amount of courtship vigor when given either chemical cues or chemical and visual cues combined (Figures 2-4). Except for one measurement, all behaviors measured showed significant effects for sensory cues and rearing environment (Table 1). Despite both factors being statistically significant, there was no interaction between them.

Table 1: Results of Two-Way ANOVA for male behavior parameters in cue isolation studies. Level of significance: * < 0.05, ** < 0.01, *** < 0.001

Figure 2 - Latency to observation (mean + SEM)

Figure 3 - Frequency of observation (mean + SEM)

Figure 4 - Mean duration of behaviors (mean +SEM)

Our results also indicate that there are behavioral differences between lab-reared and field-caught spiders. Spiders that were field caught generally courted more frequently and had shorter latencies for initiating courtship (Figures 2-4).

From this study we conclude that female S. ocreata do not use multimodal communication, as males primarily use chemical cues from females for recognition and courtship initiation.

Balsby, T.J.S. and Dabelsteen, T. 2002. Female behaviour affects male courtship in

whitethroats, Sylvia communis: An interactive experiment using visual and acoustic cues. Animal Behaviour, 63(2):251-257.

Hebets, E.A. and Uetz, G.W. 1999. Female responses to isolated signals from multimodal

male courtship displays in the wolf spider genus Schizocosa (Araneae: Lycosidae). Animal Behaviour, 57(4):865-872.

Hebets, E.A. and Uetz, G.W. 2000. Leg ornamentation and the efficacy of courtship

display in four species of wolf spider (Araneae: Lycosidae). Behavioral Ecology and Sociobiology, 47(4):280-286.

McClintock, W.J. and Uetz, G.W. 1996. Female choice and pre-existing bias: Visual cues during courtship in two Schizocosa wolf spiders (Araneae: Lycodidae). Animal Behaviour, 52:167-181.

Roberts, J.A. 2003. Multi-modal communication in spiders: information content and consequences of signal apparency. Ph.D. Dissertation, University of Cincinnati , Cincinnati , Ohio .

Scheffer, S.J., Uetz, G.W. and Stratton, G.E. 1996. Sexual selection, male morphology,

and the efficacy of courtship signaling in two wolf spiders (Araneae: Lycodidae). Behavioral Ecology and Sociobiology, 38:17-23.

Stratton, G.E. and Uetz, G.W. 1981. Acoustic communication and reprod uc tive isolation

in 2 species of wolf spiders. Science, 214:4520, 575-577.

Stratton, G.E. and Uetz, G.W. 1983. Communication via substratum-coupled stridulation

and reprod uc tive isolation in wolf spiders (Araneae: Lycosidae). Animal Behaviour, 31:164-172.

Stratton, G.E. and Uetz, G.W. 1986. The inheritance of courtship behavior and its role as

a reprod uc tive isolating mechanism in two species of Schizocosa wolf spiders (Araneae: Lycosidae). Evolution, 40(1):129-141.

Uetz, G.W. 2000. Signals and multi-modal signaling in spider communication. In: Animal Signals: Signaling and signal design is animal communication in animal communication (Ed. By Espmark, Y., Amundesen, T. & Rosenqvist, G.), pp. 387-405. Trondheim , Norway : Tapir Publishers.

Uetz, G.W. and Roberts, J.A. 2002. Multisensory cues and multimodal communication in

spiders: Insights from video/audio playback studies. Brain Behavior and Evolution, 59:4, 222-230.