The biology of Euryattus sp. indet., a web-building jumping spider (Araneae, Salticidae) from Queensland: utilization of silk, predatory behaviour and intraspecific interactions

The biology of an aberrant saltioid spider, Euryattus Thorell sp. indet., is described from observations in a Queensland rain forest and the laboratory. Pronounced morphological and behavioural changes occur during post-embryological development. Juveniles spin webs, but adult females make 'suspension nests' by suspending a curled-up leaf by heavy guylines from a rock ledge or vegetation. Adult males spin neither webs nor suspension nests. Females oviposit inside their suspension nests, but if denied access to leaves for suspension, they spin and oviposit in webs similar to those spun by juveniles. The flat, papery egg sacs of Euryattus are atypical for a salticid, being more like the egg sacs of many of the Gnaphosidae. Intraspecific display behaviour has characteristics in common with typical salticids, but also includes unique features. Male courtship includes vibratory displays performed on the surface of the suspended leaf. Mating occurs inside the curled-up leaf. Males co-habit with sub-adult females in suspension nests. Females take over suspension nests of other females and eat each other's eggs. Normal locomotion, intraspecific interactions, and predatory behaviour are characterized by frequent leaping. Euryattus routinely makes long and accurate leaps on to prey, including flying insects intercepted in mid-air and spiders and insects located in alien webs. The phylogenetic implications of the unusual characteristics of Euryattus are considered.     

The biology of ant-like jumping spiders: intraspecific interactions of Myrmarachne lupata (Araneae, Salticidae)

Myrmarachne lupata is an ant-like salticid in which males have very large chelicerae. The display repertoire of this species is unusually large and complex for a salticid spider. Each individual male uses one of three different mating tactics depending on the female's maturity and location. With adult females outside nests type 1 courtship occurs which seems to be a form of visual communication and includes specialized movements and postures of the legs, palps and body. With adult females inside nests, males use type 2 courtship, which seems to be a form of non-visual communication and consists primarily of probing with the legs on the silk; males mate with receptive females inside the nests. With subadult females, males first use type 2 courtship then spin an adjacent silken chamber and cohabit. After she moults and matures, mating occurs inside the nest. Vacant nests of conspecific females, but not those of another sympatric salticid species, elicit courtship behaviour from males. During male-male interactions, embracing occurs with the large chelicerae spread apart. Females and subadults also display, and different displays occur in interactions depending on the sex/age classes of the spiders involved. Despite the unusual morphology of these spiders, their individual displays are similar to those of more typical salticids. During copulation males stand beside the female instead of over or on her as occurs with typical salticids.     

Predator-prey interactions between web-invading jumping spiders and two species of tropical web-building pholcid spiders, Psilochorus sphaeroides and Smeringopus pallidus

Psilochorus sphaeroides from Queensland, Australia and Smeringopus pallidus from Sri Lanka are long-legged, web-building pholcid spiders with a special defence behaviour, whirling. The efficiency of whirling as a defence against web-invading jumping spiders (Salticidae) was examined in the laboratory. Three salticid species were used in these tests- Euryattus sp., Portia fimbriata and Portia labiata. Euryattus leapt into webs, but Portia fimbriata and Portia labiata walked slowly into webs and practised aggressive mimicry. Portia fimbriata was more consistent at using aggressive mimicry and more efficient at capturing Psilochorus sphaeroides and Smeringopus pallidus than was Portia labiata . Both species of Portia were more efficient at catching pholcids than was Euryattus. Portia , especially Portia fimbriata , was less inclined than Euryattus to stimulate pholcids to whirl. In an experiment in which pholcids were artificially induced to whirl whenever a salticid was near, salticids never captured pholcids, providing additional evidence that whirling is an effective defence of Psilochorus sphaeroides and Smeringopus pallidus against web-invaders. Results from this study are compared to those from a study of another pholcid that whirls, Pholcus phalangioides .     

Cross-modality effects during male-male interactions of jumping spiders

An important prediction from game theory is that the value of a resource influences the level to which male-male conflict escalates. Earlier experimental studies have shown that the seven salticid species we study here (Bavia aericeps, Euryattus sp., Hypoblemum albovittatum, Jacksonoides queenslandicus, Marpissa marina, Portia africana and Simaetha paetula) determine by sight whether a female is a conspecific or a heterospecific and then escalate the intensity with which they interact (i.e., they adopt behaviour that is likely to put them at greater risk of injury after detecting the presence of a conspecific female). Here the earlier studies are extended by using the odour of conspecific females (experimental tests) and heterospecific females (control tests), and by presenting each male with his mirror image as well as having two males interact with each other. Findings from this study suggest that, for J. queenslandicus and P. africana, the odour of conspecific females, more than the odour of heterospecific females, primes the male to escalate conflict with a potential rival. However, this was not found for the other five species tested.     

Pheromonal discriminations of sex,reproductive condition,and species by the lacertid lizard Podarcis hispanica

In some vertebrate taxa, pheromones provide important information about species, sex, reproductive condition, kinship, and even individual identity. Because they possess highly developed nasal chemosensory systems, lizards are capable of many chemical discriminations, but many aspects of their pheromonal communication remain poorly understood even in major families. We report that males of a lacertid lizard, Podarcis muralis, are capable of differential response to surface chemical cues from conspecific males and females, from gravid and nongravid females, and from conspecific females and females of the closely related sympatric congener, P. bocagei carbonelli. In 60 sec trials in which stimuli from the femoral, cloacal, lateral, and upper body surfaces were presented to males on cotton swabs, males tongue-flicked at significantly higher rates to stimuli from conspecific females than males, from conspecific nongravid than gravid females, and from conspecific than heterospecific females. Responses to stimuli from conspecific males did not differ from those to distilled water. Together with previous findings that males can distinguish between chemical cues from familiar and unfamiliar males, these findings suggest that pheromones provide male P. hispanica important information regarding the presence of sexual rivals and the reproductive condition of potential mates without visually encountering other lizards. A growing body of literature indicates that lacertids are capable of sophisticated pheromonal discriminations that may play important roles in their social behavior.     

Lack of species discrimination based on chemical cues by male sailfin mollies, <Emphasis Type="Italic">Poecilia latipinna</Emphasis>

When making mating decisions, individuals may rely on multiple cues from either the same or multiple sensory modalities. Although the use of visual cues in sexual selection is well studied, fewer studies have examined the role of chemical cues in mate choice. In addition, few studies have examined how visual and/or chemical cues affect male mating decisions. Male mate choice is important in systems where males must avoid mating with heterospecific females, as is found in a mating complex of Poecilia. Male sailfin mollies, Poecilia latipinna, are sexually parasitized by gynogenetic Amazon mollies, P. formosa. Little is known about the mechanism by which male sailfin mollies base their mating decisions. Here we tested the hypothesis that male sailfin mollies from an allopatric and a sympatric population with Amazon mollies use multiple cues to distinguish between conspecific and heterospecific females. We found that male sailfin mollies recognized the chemical cues of conspecific females, but we found no support for the hypothesis that chemical cues are by themselves sufficient for species discrimination. Lack of discrimination based on chemical cues alone may be due to the close evolutionary history between P. latipinna and P. formosa. Males from populations sympatric with Amazon mollies did not differentially associate with females of either of the two species when given access to both visual and chemical cues of the females, yet males from the allopatric population did associate more with conspecific females than with heterospecific females in the presence of both chemical and visual cues. The lack of discrimination by males from the sympatric population between conspecific and heterospecific females based on both chemical and visual cues suggests that these males require more complex combinations of cues to distinguish species, possibly due to the close relatedness of these species.     

Population and Species Divergence of Chemical Cues that Influence Male Recognition of Females in Desmognathine Salamanders

Growing evidence indicates that males may be more discriminating of mating partners than often has been assumed. In the North American Ocoee dusky salamander, Desmognathus ocoee (Plethodontidae: Desmognathinae), sexual incompatibility among conspecific populations is high in encounters staged in the laboratory, at least in part because males fail to recognize ‘other’ females as appropriate targets for courtship. I used Y-mazes to test the hypothesis that males of D. ocoee discriminate between substrate-borne chemical cues produced by ‘own’ (homotypic) and ‘other’ (heterotypic) females. Males of four populations discriminated in favor of substrates soiled by homotypic females over clean (control) substrates (expt 1), suggesting that females produce chemical cues of sociosexual significance to males. Furthermore, males from these populations discriminated in favor of substrates soiled by homotypic females vs. substrates soiled by heterotypic females (expt 2), both conspecific and heterospecific (D. carolinensis and D. orestes). Thus, differences among populations and species in female chemical cues appear to affect the chemotactic responses of males. I suggest that, together with differences in behavioral signals and responses exhibited during courtship, differences in female chemical cues likely contribute to sexual incompatibility among populations and taxa of desmognathine salamanders.     

Discrimination of conspecific sex and reproductive condition using chemical cues in axolotls (<Emphasis Type="Italic">Ambystoma mexicanum</Emphasis>)

Chemosensory cues play an important role in the daily lives of salamanders, mediating foraging, conspecific recognition, and territorial advertising. We investigated the behavioral effects of conspecific whole-body odorants in axolotls, Ambystoma mexicanum, a salamander species that is fully aquatic. We found that males increased general activity when exposed to female odorants, but that activity levels in females were not affected by conspecific odorants. Although males showed no difference in courtship displays across testing conditions, females performed courtship displays only in response to male odorants. We also found that electro-olfactogram responses from the olfactory and vomeronasal epithelia were larger in response to whole-body odorants from the opposite sex than from the same sex. In males, odorants from gravid and recently spawned females evoked different electro-olfactogram responses at some locations in the olfactory and vomeronasal epithelia; in general, however, few consistent differences between the olfactory and vomeronasal epithelia were observed. Finally, post hoc analyses indicate that experience with opposite-sex conspecifics affects some behavioral and electrophysiological responses. Overall, our data indicate that chemical cues from conspecifics affect general activity and courtship behavior in axolotls, and that both the olfactory and vomeronasal systems may be involved in discriminating the sex and reproductive condition of conspecifics.Abbreviations EOG electro-olfactogram - VNO vomeronasal organ     

Behavioural evidence of UV sensitivity in jumping spiders (Araneae: Salticidae)

Jumping spiders are known to possess ultraviolet (UV) receptors in the retinas of their large-principal eyes. The existence of UV visual cells, however, does not prove that jumping spiders can see into the UV part of spectrum (300–400 nm) or whether such an ability plays any role in salticid intra-specific interactions. In the study reported herein, we performed behavioural experiments to test whether a UV−reflecting jumping spider, Cosmophasis umbratica, is sensitive to UV wavelengths and whether UV cues are important in intra-specific communication. The absence of UV cues not only affected intra-specific behaviour by significantly reducing the frequency of agonistic displays, but also elicited unprecedented courtship displays in males towards their own mirror images and conspecific opponents. Furthermore, C. umbratica males were able to respond rapidly to changes in UV cues of conspecific mirror images by switching between agonistic and courtship displays. These findings clearly demonstrate that C. umbratica males are capable of seeing UV wavelengths and that UV cues are necessary and sufficient for this species to enable the agonistic displays. Hence, UV light may have an important role to play in intra-specific communication in jumping spiders.     

A new mechanism of sound production by courting male jumping spiders (Araneae: Salticidae, Saitis michaelseni Simon)

Male Saitis michaelseni Simon (Araneae: Salticidae) produce sounds during courtship which can be heard several metres away. Courting males stridulate on dead leaves and are positioned on the opposite side of the leaf from the female. The courtship display contains both visual and acoustic elements. Courtship consists of three phases. In the first two phases, the male stridulates, and in the third phase, in which he makes tactile contact with the female, he alternates bursts of stridulatory sound with bouts of percussive sound in which the first pair of legs strikes the substratum. Stridulation apparently results from the thickened bases of short hairs on the anterior part of the abdomen moving over two files on the posterior part of the carapace. This stridulatory mechanism has not been previously reported for salticid spiders. The frequency spectra and amplitude modulation patterns of sounds produced by stridulation and percussion are presented.     

同种雄性竞争对手的存在对星豹蛛雄蛛求偶和交配行为的影响

越来越多的研究发现,雄性产生精子(精液)也需付出代价。雄性除了依据配偶质量和竞争对手的竞争强度适应性调整生殖投入外,雄性在求偶和交配行为上也相应产生适应性反应,求偶和交配行为具有可塑性。目前雄性求偶和交配行为可塑性研究主要集中于雌性多次交配的类群中,在雌性单次交配的类群中研究甚少。以雌蛛一生只交配一次而雄蛛可多次交配的星豹蛛为研究对象,比较:(1)前一雄性拖丝上信息物质对后续雄蛛求偶和交配行为的影响,(2)雌雄不同性比对雄蛛求偶和交配行为的影响。研究结果表明,星豹蛛前一雄蛛拖丝上的信息物质对后续雄蛛求偶潜伏期、求偶持续时间和交配持续时间都没有显著影响,但前一雄蛛拖丝上的信息物质对后续雄蛛求偶强度有显著抑制作用。同时,性比对星豹蛛雄蛛求偶和交配行为都没有显著影响。可见,星豹蛛雄蛛对同种雄性拖丝上的化学信息可产生求偶行为的适应性调整,而对性比不产生适应性反应。     

Influence of optical cues from conspecific females on escalation decisions during male-male interactions of jumping spiders

An important prediction from game theory is that the value of a resource influences the level to which male-male conflict escalates. An earlier experimental study showed that males of Hypoblemum albovittatum, a common salticid in New Zealand, can discern by sight alone whether a female is in the vicinity and that, having detected a female's presence, males escalate (i.e., adopt behaviour that is likely to put them at greater risk of injury). Seeing a bare moving cork, a conspecific male or a prey item also elicits escalation, but not to the level elicited by seeing a conspecific female. Here the earlier study is extended by using non-conspecific females in control tests and by undertaking experiments with an additional six salticid species. Findings from these experiments suggest that the ability of interacting males to detect by sight alone that a conspecific, instead of a non-conspecific, female is present is widespread in the family Salticidae and that it may be routine for salticid males to use information about the presence of conspecific females when making strategic decisions related to escalation during encounters with other males.     

Female responses to isolated signals from multimodal male courtship displays in the wolf spider genus Schizocosa (Araneae: Lycosidae)

Male wolf spiders within the genus Schizocosa display considerable variation in foreleg ornamentation as well as in courtship communication. Multiple modes of male signalling have evolved in a number of species. Divergence in courtship signals among species within this genus may be directly associated with variation in the sensory sensitivities of conspecific females. We isolated the visual and vibratory courtship cues of four species of Schizocosa and recorded conspecific female receptivity to each isolated cue. We also examined female receptivity to complete multimodal courtship signals. We found that the sensory sensitivities of conspecific females were associated with the predominant modes of male courtship communication. Species in which females use mostly stridulatory cues in assessing conspecific males tended to have stridulation-based male courtship displays (S. duplex and S. uetzi) while the opposite was true for species in which females used more visual cues in male assessment (S. stridulans and S. crassipes). This study suggests coevolution between male signal design and female sensory design. We discuss possible scenarios that could be driving this coevolution, including hypotheses of sensory bias and environmental constraints. Copyright 1999 The Association for the Study of Animal Behaviour.     

Mutual Mate Assessment in Wolf Spiders: Differences in the Cues Used by Males and Females

When males engage in conspicuous courtship displays, it seems obvious that females would use characteristics of that display in mating decisions. However, males must also have a way to identify and evaluate females prior to engaging in what might be a costly mating ritual. Although it was known that female wolf spiders of the species Pardosa milvina (Araneae; Lycosidae) attract males using volatile chemical cues, the nature of the cues used by males and females in mate selection had not been investigated. Specifically we determined whether males could detect the mating status of the female and if chemotactile cues from the female played a role in that process. In addition, we quantified conspicuous aspects of the male courtship (leg raises and body shakes) to determine if courtship intensity was related to female choice. Although repeated mating occurred in our studies, males were more likely to court and mate with virgin females. Males used substrate‐borne cues deposited by females to discriminate between mated and virgin females. Females used the conspicuous behaviors of males during courtship, body shakes and leg raises, in mate selection. Thus males and females use different kinds of information and different sensory modalities to assess the suitability of a potential mate.     

Pheromonal and behavioral cues trigger male-to-female aggression in Drosophila

Appropriate displays of aggression rely on the ability to recognize potential competitors. As in most species, Drosophila males fight with other males and do not attack females. In insects, sex recognition is strongly dependent on chemosensory communication, mediated by cuticular hydrocarbons acting as pheromones. While the roles of chemical and other sensory cues in stimulating male to female courtship have been well characterized in Drosophila, the signals that elicit aggression remain unclear. Here we show that when female pheromones or behavior are masculinized, males recognize females as competitors and switch from courtship to aggression. To masculinize female pheromones, a transgene carrying dsRNA for the sex determination factor transformer (traIR) was targeted to the pheromone producing cells, the oenocytes. Shortly after copulation males attacked these females, indicating that pheromonal cues can override other sensory cues. Surprisingly, masculinization of female behavior by targeting traIR to the nervous system in an otherwise normal female also was sufficient to trigger male aggression. Simultaneous masculinization of both pheromones and behavior induced a complete switch in the normal male response to a female. Control males now fought rather than copulated with these females. In a reciprocal experiment, feminization of the oenocytes and nervous system in males by expression of transformer (traF) elicited high levels of courtship and little or no aggression from control males. Finally, when confronted with flies devoid of pheromones, control males attacked male but not female opponents, suggesting that aggression is not a default behavior in the absence of pheromonal cues. Thus, our results show that masculinization of either pheromones or behavior in females is sufficient to trigger male-to-female aggression. Moreover, by manipulating both the pheromonal profile and the fighting patterns displayed by the opponent, male behavioral responses towards males and females can be completely reversed. Therefore, both pheromonal and behavioral cues are used by Drosophila males in recognizing a conspecific as a competitor.     

Drosophila melanogaster males respond differently at the behavioural and genome‐wide levels to Drosophila melanogaster and Drosophila simulans females

Drosophila melanogaster are found in sympatry with Drosophila simulans, and matings between the species produce nonfertile hybrid offspring at low frequency. Evolutionary theory predicts that females choose mates, so males should alter their behaviour in response to female cues. We show that D. melanogaster males quickly decrease courtship towards D. simulans females. Courtship levels are reduced within 5 min of exposure to a heterospecific female, and overall courtship is significantly lower than courtship towards conspecific females. To understand changes at the molecular level during mate choice, we performed microarray analysis on D. melanogaster males that courted heterospecific D. simulans females and found nine genes have altered expression compared with controls. In contrast, males that court conspecific females alter expression of at least 35 loci. The changes elicited by conspecific courtship likely modulate nervous system function to reinforce positive conspecific signals and dampen the response to heterospecific signals.     

Release of chemicals by prostaglandin-treated female fathead minnows, Pimephales promelas, that stimulate male courtship

Intramuscular injection of PGF2 alpha tromethamine salt (Sigma) did not induce sexual behavior in female fathead minnows, Pimephales promelas, when in the presence of male conspecific. However, coresident males exhibited an increased frequency of courtship behavior, consisting of approach and leading, to females following PGF2 alpha treatment. When presented with both saline-injected and PGF2 alpha-injected females, males showed increased courtship only to PGF2 alpha-treated females. Isolated males also showed increased leading behavior following the introduction of water exposed to PGF2 alpha-treated females, but not with water exposed to PGF2 alpha-treated males, untreated females or males, or PGF2 alpha alone. Hence, PGF2 alpha appears to induce the release of a female-specific chemical in P. promelas that triggers courting behavior in conspecific males.     

Predator-prey interactions between web-invading jumping spiders and a web-building spider, Holocnemus pluchei (Araneae, Pholcidae)

Three species of web-invading salticid spiders, with different predatory strategies, were tested with Holocnemus pluchei in the laboratory: Portia fimbriata and Portia labiata , which practise aggressive mimicry, and Euyattus sp., which leaps from outside on to spiders in webs but does not practise aggressive mimicry. Portia was shown to be more efficient than Euryattus at catching H. pluchei. Portia fimbriata from Queensland was more consistent at using aggressive mimicry than was Portia labiata and was also more efficient at catching H. pluchei . The web-invaders that were more efficient at catching H. pluchei were also better able to avoid setting off bouncing, a special defence behaviour used by H. pluchei . An experiment, in which H. pluchei was artificially induced to bounce whenever the predator was near, provided additional evidence that bouncing is effective in defending H. pluchei against web-invaders.     

Conspecific and heterospecific pheromone effects on female receptivity

Courtship pheromones play an important role in salamander reproductive behaviour. In salamanders of the family Plethodontidae, males deliver specialized pheromones to females during courtship interactions. These courtship pheromones increase female receptivity and may be involved in mate discrimination. In order to test hypotheses related to mate discrimination, we staged courtship encounters between male-female Plethodon shermani pairs in which the female received pheromones obtained from either conspecific (P. shermani) or heterospecific (P. yonahlossee orP. montanus ) males. Both conspecific and heterospecific pheromones increased female receptivity. Moreover, pheromones from both heterospecific species were as effective as the conspecific pheromone in increasing female receptivity inP. shermani females. Our results suggest that the courtship pheromone signal and function may be conserved across related species, with mate discrimination occurring before pheromone delivery. Copyright 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.     

The biology of Portia fimbriata, a web-building jumping spider (Araneae, Salticidae) from Queensland: intraspecific interactions

Portia fimbriata (Doleschall) is an unusual salticid because it spins webs and uses its own webs and those of other species in predation. However, the courtship and threat displays of this species are more like those of typical, cursorial salticids than like typical web-building spiders. During male-female interactions, males perform leg-waving and leg-shaking displays, with legs I and II extended stiffly forward, while distant from the females. Before mounting they tap the females with their legs; and after mounting they tap, scrape and stroke the females' abdomens. Copulation takes place on or near the female's web or on the webs of other species. Hunched-legs displays, with legs I–III highly flexed and held to the side of the body, occur in male-male interactions. Also, during male-female and female-female interactions, females perform hunched-legs displays, strike, charge, ram, embrace, grapple with and leap at conspecifics. Sometimes they lose legs while grappling. After female-female interactions associated with maternal webs, if the resident decamps, the intruder eats the eggs left behind on a suspended leaf, spins a new egg-case over the destroyed one, and oviposits. Adult and sub-adult males co-habit in webs with sub-adult females for as long as 48 days and mate when the spiders mature.