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1. Carnivores are often food and/or macronutrient limited in their natural habitats, but whether they are limited mostly by protein or lipid is still a matter of controversy. As many predators and carnivorous scavengers also include plant material in their diet (omnivory), carbohydrate limitation is also possible. 2. The authors used a recently described double-test procedure to test for food and macronutrient limitation in five co-existing species of predators and omnivorous scavengers from Uruguay (two crickets: Gryllus sp. and Miogryllus verticalis; two cockroaches: Blatta orientalis and Blaptica dubia and a harvestman: Acanthopachylus aculeatus). 3. The authors found that the two crickets and one cockroach were food limited and one cockroach was non-protein (lipid) limited in the field. The harvestman showed a dramatic change in food limitation between two dates separated by only 3 weeks, but was non-protein (lipid) limited over both dates. From all species, the harvestman showed the highest self-selected intake of carbohydrates (27%), indicating a high level of omnivory. In contrast, the two cockroaches selected a surprisingly low proportion of carbohydrates (13–14%), while the crickets were intermediate (14–19%). The authors hypothesize that these omnivores are more carnivorous in the wild than expected from studies of laboratory populations. 4. Though individuals were collected from the same habitats and all species self-selected macronutrient ratios characteristic of omnivorous carnivores, they showed different patterns of food and macronutrient limitation, reflecting species' niche segregation and individual differences in foraging success.

Fear of animals is an important issue to consider in order to increase knowledge about nature and foster positive attitudes for nature conservation. Spiders are a challenging group, because...

Background When males are selective, they can either reject low-quality females or adjust their reproductive investment in response to traits that indicate female quality (e.g., body size or condition). According to the differential allocation hypothesis, males increase their reproductive investment when paired with high-quality females (positive differential allocation) or increase their reproductive investment when paired with low-quality females (negative differential allocation). This hypothesis has been proposed for monogamous species with biparental care, and most empirical studies focus on birds. Here we used the polygamous spider Paratrechalea ornata, in which males offer prey wrapped in silk as nuptial gifts, to test whether males adjust their reproductive investment in gift size, pre-copulatory and copulatory courtship, and sperm transfer in response to female body condition. Results Males exposed to females in good body condition added more flies to the gift, stimulated these females longer with abdominal touches during pre-copulatory courtship, and had longer pedipalp insertions than males exposed to females in poor body condition. Female condition affected neither silk investment in nuptial gift wrapping nor the quantity of sperm transferred by males. Finally, females in good body condition oviposited faster after copulation and laid more eggs than females in poor body condition. Conclusions We provide experimental evidence that males of a gift-giving spider exhibit positive differential allocation in three key aspects of their reproductive investment: the size of the nutritious gift, duration of pre-copulatory courtship, and duration of pedipalp insertions, which is regarded as a form of copulatory courtship in spiders. This positive differential allocation is likely associated with the benefits of copulating with females in good body condition. These females are more fecund and oviposit faster after copulation than females in poor body condition, which under natural field conditions probably reduces the risk of multiple matings and thus the level of sperm competition faced by the males. As a final remark, our findings indicate that the hypothesis of differential allocation also applies to species with a scramble competition mating system, in which males heavily invest in nuptial gift construction, but not in parental care.

Male sensory exploitation of female gustatory pre-existing bias has been proposed for the origin of nuptial gifts in insects and spiders. This sexual trait may have been beneficial to both sexes, giving mating and survival advantages to males and providing nutritional resources for females. However, the evolution of deceptive worthless gifts is against females’ interests and may trigger a co-evolutionary change in females’ preferences. We evaluated females’ preferences for nuptial gifts and the adaptive function of the gift in the spider Trechaleoides keyserlingi. The genus belongs to the understudied Neotropical family Trechaleidae in which nuptial gifts are widespread. The family is composed of only two species, and the gift seems to be absent in the sister species, creating a relevant scenario for understanding co-evolutionary processes. In the laboratory, we found that although males invested more in nuptial gifts when encountering mated females compared to unmated, they had similar mating access and duration than males lacking a gift. We also found an absence of female choice between males offering nutritive and worthless gifts. Few females were aggressive and cannibalized males, and we did not find evidence that the gift protected males from cannibalism. In the field, 50% of the gifts were worthless items. This is congruent with the laboratory findings where males offering worthless gifts seem to better attract females, which we discuss in the context of exploitation of female gustatory bias. We therefore propose that females may have evolved indifference for the gift and that gift-giving in this species represents a currently non-functional remnant of a behaviour. Nutritive nuptial gifts can exploit female gustatory preferences, with mutual benefits for both sexes: males can increase mating success and survival, while females increase their fecundity. But males can offer worthless gifts leading females to suboptimal matings, and in turn females can evolve indifference for the trait. The spider genus Trechaleoides is ideal to examine this process because gift-giving behaviour is present in one species and absent in the other. We examined females’ preferences for nuptial gifts and its function for males in the gift-giving species T. keyserlingi. We found that males invest in a gift but gain no reproductive advantage, as females were equally likely to mate with them regardless of whether they offered a gift or whether the gift was nutritive or worthless. We propose that females may have changed their preferences and that the gift is a remnant non-functional trait.

The spider family Trechaleidae includes 17 genera and 131 species distributed throughout the Neotropical region. Most of them are semiaquatic spiders living adjacent to streams and rivers. Very few species of the family have been studied for their natural history or behavior; however four genera (ParatrechaleaCarico, 2005, Trechalea Thorell, 1869, Paradossenus F. O. Pickard-Cambridge, 1903 and TrechaleoidesCarico, 2005) are already known to have males that offer wrapped nuptial gifts to females. Here we describe a new species from the genus Enna O. Pickard-Cambridge, 1897, namely E. gloriae sp. nov. from Quindio, Colombia. We additionally report the presence of males of this species offering nuptial gifts to females during courtship, being the first record of this sexual trait for the genus.

In the spider families Trechaleidae and Pisauridae, males offer nuptial gifts to females during courtship. Nutritive gifts contain recently caught prey wrapped in silk, while worthless gifts contain prey leftovers or plant parts. The presence of wrapped gifts is known in three out of 16 genera (ParatrechaleaCarico, 2005, Trechalea Thorell, 1869 and TrechaleoidesCarico, 2005) in Trechaleidae, suggesting that this sexual trait is of widespread occurrence in the family. Here, we report the presence of wrapped nuptial gifts in the genus Paradossenus F.O. Pickard-Cambridge, 1903. Males of P. longipes (Taczanowski, 1874) produce prey-gifts following the same sequence of behavioral units as described for other species of the family. More surprisingly, these males may also produce empty gifts consisting of a silken structure lacking contents. This is the first record of empty nuptial gifts in spiders. This novel male tactic may have evolved from worthless gifts as a further step in the evolution of deception in gift-giving spiders.

Sexes' roles in post-copulatory processes have important effects on individual fitness and are promising to study in species showing complex mating behaviours. In the spider Schizocosa malitiosa, males perform two different copulatory patterns, pattern 1 includes 80% of total pedipalp insertions and pattern 2 includes 20%. Both patterns produce similar number of offspring, but pattern 1 induces higher female reluctance to remating than pattern 2. We hypothesised that the complex copulatory patterns are linked to post-copulatory sexual selection, affecting males' sperm transfer and the resulting sperm storage by females. First, we examined amounts of sperm in males and live females from uninterrupted (pattern 1 + 2) and interrupted matings (pattern 1, pattern 2). Second, in order to disentangle male and female actions, we induced males to mate with dead females and examined amounts of sperm. Males transfer in total 71% of the sperm available in their pedipalps, being higher but not significant in pattern 1 than in pattern 2. Females drastically reduced the amount of sperm stored in their spermathecae and such control is stronger in pattern 1 compared to pattern 2 matings. We propose that cryptic female control is a main factor driving males to strengthen sperm transfer. Active female reduction in ejaculate most probably diminished her reluctance to remate.

Pisauridae, Trechaleidae, and Lycosidae constitute part of the Lycosoidea clade that includes a diverse range of wandering spider species that inhabit terrestrial and semi-aquatic environments. Phylogenetic studies of these three families based on morphological and behavioural traits have produced contradictory results on their evolutionary relationships. To resolve their relationship, we constructed a molecular phylogeny based on five mitochondrial and three nuclear genes. We found support for the sister group relationship between Lycosidae and Trechaleidae. In contrast to previous findings, our results suggest that Pisauridae is not monophyletic, and that Dolomedes forms its own group. Both Pisauridae and Trechaleidae contain species that provide nuptial gifts. In combination with sampling of more species for this trait, our results provide a phylogenetic framework for assessing the evolution of nuptial gift giving in spiders.

In the gift-giving spider Paratrechalea ornata, females mate multiple times and apparently may bias the paternity according to the nuptial gift content (nutritive or worthless). Paternity studies using microsatellite markers would, therefore, be ideal for studying male fertilization success for female offspring. We genotyped four microsatellites previously reported in one species of the genus using 43 individuals from four different localities in Uruguay. We describe the allelic and genotypic variation in all loci, and compare the findings to the reported variation for the genus. Except for one locus, all loci showed significant departure from the Hardy-Weinberg equilibrium due to heterozygote deficit. This could possibly be explained by the mixed nature of the sample and the effect of the population structure. These loci, and especially those that are highly hypervariable, are an important tool for paternity assessment and would allow a better understanding of the role of post-copulatory processes in P. ornata.

Alternative mating tactics are expected to occur predominantly when mate competition is intense, resources are in short supply, or as a result of asymmetric power relationships between individuals. Males of the nuptial gift-giving spider Pisaura mirabilis use a prevailing tactic of offering a nutritive gift (insect prey) and a deceptive tactic of offering a worthless gift (consumed prey) to prospective mates. If the male’s tactic depends on precopulatory male–male competition, worthless gifts should occur primarily late in the season, when the operational sex ratio (OSR) becomes male-biased. If it depends on resource availability and/or postcopulatory sexual selection (sperm competition), worthless gifts should occur mostly early in the mating season, when prey availability is low and most females are unmated (i.e., postcopulatory sexual selection is weak). Nuptial gift construction correlated positively with prey availability and negatively with OSR, suggesting that males increase reproductive effort when resource and mate availability increase. We did not find evidence for body condition affecting male tactic use. Male size had a marked effect on the reproductive tactic employed. Males that matured early in the season were very small and employed mostly the nutritive gift tactic during their short life. Among the males that matured later and persisted through the season, relatively small males employed the worthless gift tactic whereas large males employed the nutritive gift tactic. We suggest that the existence of 2 distinct life-history strategies among males (early small and late large size) interacts with environmental and demographic conditions to maintain the deceptive tactic.

Male exploitation of female sensory or motivational biases has been proposed to account for the early evolution of nuptial gift-giving behaviour. The hypothesis is supported if females of a species positioned early in a clade respond positively to sexual signals from males of more recent species in the clade, and if these signals are not included in the courtship repertoire of its conspecific males. We tested whether such a scenario may apply to the evolution of gift-giving behaviour in the spider family Pisauridae. Presumably, the Canarian endemic Cladycnis insignis diverged on an early branch from the clade that includes the well-known nuptial gift-giving species Pisaura mirabilis. We first showed that the natural courtship and mating in C. insignis does not include gift-giving behaviour. Second, by staging female C. insignis with gift-carrying males of P. mirabilis, we found that these females accepted the gift and allowed the males to attempt mating. The duration of heterospecific ‘matings’ was much longer than conspecific matings (45–50 min versus ca. 1 min). Thus, there is scope for exploitation of the females' foraging motivation through a behavioural switch from courting without a prey gift to courting with a prey gift. Such a switch would initially have brought huge fitness benefits to these males in terms of greatly increased mating duration (advantage in sperm competition) and protection against aggressive females (shield effect), and also a benefit to the females from increased food supply.

Polyandry is commonly maintained by direct benefits in gift-giving species, so females may remate as an adaptive foraging strategy. However, the assumption of a direct benefit fades in mating systems where male gift-giving behaviour has evolved from offering nutritive to worthless (non-nutritive) items. In the spider Paratrechalea ornata, 70% of gifts in nature are worthless. We therefore predicted female receptivity to be independent of hunger in this species. We exposed poorly-fed and well-fed females to multiple males offering nutritive gifts and well-fed females to males offering worthless gifts. Though the treatments strongly affected fecundity, females of all groups had similar number of matings. This confirms that female receptivity is independent of their nutritional state, i.e. polyandry does not prevail as a foraging strategy.ConclusionsIn the spider Pisaura mirabilis, in which the majority (62%) of gifts in nature are nutritive, female receptivity depends on hunger. We therefore propose that the dependence of female receptivity on hunger state may have evolved in species with predominantly nutritive gifts but is absent in species with predominantly worthless gifts. Fil: Pandulli Alonso, Irene. Laboratorio de Etología, Ecología y Evolución. Instituto de Investigaciones Biológicas Clemente Estable; Uruguay Fil: Quaglia, Agustín Ignacio Eugenio. Universidad Nacional de Cordoba. Facultad de Medicina. Instituto de Virologia "Dr. J.M. Vanella". Laboratorio de Arbovirus; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Albo, Maria J.. Laboratorio de Etología, Ecología y Evolución. Instituto de Investigaciones Biológicas Clemente Estable; Uruguay

Males from gift-giving species attempt to obtain food to offer to females. Therefore, food access may affect both their body condition and their reproductive success. In some species, males reduce the costs associated with giving gifts by reusing gifts, or by offering inedible items. Males from the spider Paratrechalea ornata (Trechaleidae) offer fresh prey or ‘genuine gifts’ to females, but also offer prey leftovers or ‘worthless gifts’. We examined gift weight and content, and their relation to male condition in the field. We also investigated how gift content, male condition and female reproductive status (virgin/mated) affect male mating success. In the field, most gifts were worthless; genuine gifts were heavier than worthless ones; and gift weights (both genuine and worthless gifts combined) were positively correlated with male condition. In the laboratory, males in good condition had higher mating success than males in poor condition. Males offering gifts (genuine or worthless) to virgin females enjoyed similar mating success and duration; neither differed significantly when compared to males without gift. In contrast, mated females behaved differently. Males without gifts were consistently rejected by mated females, while those that offered worthless gifts achieved matings. The interplay between male condition, prey access, female mating history and female preferences for gifts can favour the evolution of worthless gifts under certain conditions. Females do not penalize males with non-nutritive items by not mating or by reducing mating duration, but penalties may be potentially exerted via postcopulatory process.

In some spiders, nuptial gifts consist of prey or inedible items wrapped in silk by males and offered to females during courtship. Such gifts occur in the Neotropical family Trechaleidae, of which most species are semi-aquatic, associated with watercourses in riparian habitats. Here, we describe the sexual behaviour of the South American species Trechaleoides keyserlingi and report the presence of nuptial gift-giving behaviour for the first time in the genus.

In many species the function and evolution of nuptial gifts have been explained by the male mating effort hypothesis; i.e., males increase their fertilization success by donating gifts to females. The gift size may determine copulation duration and consequently affects male fertilization rate. In the well-known spider Pisaura mirabilis, previous studies suggested that the brightness of the gift (a prey wrapped in silk) affects female acceptance and larger gifts promote longer matings, but little is known from other gift-giving spider species. In this paper we test if gift size affects mating and remating success in the Neotropical and semi-aquatic spider Paratrechalea ornata (Trechaleidae). We exposed virgin females to males offering one fly (OF group) or four flies (FF group) wrapped in silk, and afterwards mated females were exposed to remating. Males from FF showed both longer courtship and mating than males from OF. We found a positive linear relationship between insertion duration of male intromitten...

Spiders have long been noted as classic examples of sexual behavior among arachnids, including extreme sexual dimorphism in some groups, and behavioral adaptations to diverse mating patterns. In recent decades, studies on the biology of Neotropical spiders have offered novel information on processes related to reproductive biology, including sexual selection. The present chapter synthesizes the large amount of knowledge on sexual selection and associated subjects in spiders from the Neotropics. Some of the groups considered in this review are mygalomorphs, lycosids and related, orb-weaving species, tetragnathids, social species, pholcids, and oonopids, among others. Concepts, patterns, mechanisms, and prospects on different areas of sexual selection are shown in detail for all these groups. In particular, here we highlight selected examples of the different contexts in which male–female interactions occur, such as mate choice, sexual cannibalism, sperm competition, and cryptic female choice. We outline the potential evolutionary consequences according to those contexts, with a final selection of model groups for specific experimental and comparative investigations.

In many species, condition-dependent secondary sexual traits are important for female choice. In the spider Pisaura mirabilis, males offer females a nuptial gift (prey wrapped in silk) during courtship. Gift construction may involve high costs for males, and those in low condition invest less time and silk in wrapping the prey. We investigated how male condition and gift wrapping affect male reproductive success and whether females use the wrapped gift as an honest indicator of male condition. We experimentally manipulated male condition (satiated and starved males) and gift wrapping (well- and poorly wrapped gifts) and carried out experiments in a fully factorial design. We found that males in good condition were more successful in obtaining matings and obtained longer copulations than males in poor condition. In contrast, gift wrapping did not affect female mate choice. Only good-condition males obtained offspring. Gift wrapping is an honest indicator of male condition, but in spite of this females did not use this information in mate choice. We argue that because gift wrapping mainly functions to promote male interests, good-condition males would also be better at cheating the female, for example using wrapping to hide a worthless gift. Females should therefore evolve to ignore the wrapping information and instead base their mate choice decision on male traits that unequivocally benefit their own reproductive success. Our results are consistent with this prediction, as females discriminated males based only on their actual feeding condition, and this choice provided them with direct reproductive benefits.

Pisaura mirabilis males offer a prey wrapped in silk as a nuptial gift that functions as a male mating effort. If nuptial gift construction is costly, males in poor feeding condition would invest less in this behaviour than males in good condition. We investigated frequencies and characteristics of gift construction in males under different sexual stimuli and different feeding conditions. We analysed gift construction behaviours of 17 males exposed sequentially to three treatments: female silk (S), female silk plus female (SF) and no female cues (control; C). The same individuals were first tested when in good feeding condition (young/satiated) and subsequently in poor feeding condition (old/starved). A separate group in good feeding condition controlling for effects of male age was also tested (old/satiated). Presence of female cues (S and SF) elicited much stronger gift construction response in males compared with the control group. Both groups of satiated males constructed nuptial gifts more frequently than starved males, spending more time on gift construction and using more silk. Our findings show that poor feeding condition affects pre-copulatory gift construction behaviour. Nuptial gift construction may be an honest indicator of male condition and therefore a target of female choice.

The occurrence of nuptial gifts is rare in spiders, being well known only for a single species, Pisaura mirabilis (Pisauridae), whose males offer females a prey wrapped in silk during courtship. Although some males can mate without offering a prey, the gift in this species is thought to represent male mating effort. Male gift offering has been recently described in Paratrechalea ornata , a Neotropical spider belonging to another family, Trechaleidae. We investigated the function of the gift in this species by testing the mating effort hypothesis and two other nonexclusive hypotheses, sexual cannibalism avoidance and paternal investment. Two groups of males were exposed to virgin females: 23 males with no prey (NP group) and 21 males carrying a prey (CP group). Mating success, courtship, copulation and first oviposition were recorded. Males from group CP had better mating success, longer copulations and longer palpal insertions than those from NP. Longer copulations were associated with earlier eggsac construction and oviposition. Some unmated males from NP wrapped prey carrion when they returned to their breeding jars after the trial. Our findings suggest that nuptial gift giving represents male mating effort for P. ornata . Nuptial gifts would allow males to control copulation duration and to accelerate female oviposition, improving sperm supply and paternity, and minimizing possible costs of remating with polyandrous

By wrapping prey and offering it as a nuptial gift, males can obtain mating and/or parental benefits despite some costs. Males of the Neotropical semiaquatic spider Paratrechalea ornata (Trechaleidae) offer females a nuptial gift consisting of a prey item wrapped in silk. What stimulus inhibits males from feeding and elicits gift construction? We hypothesized that signals associated with female silk threads could affect decision-making by males. We investigated three groups of males carrying a captured prey under different experimental treatments. In the treatment S, males were exposed to an arena with female silk; in SF, males were exposed to both silk and a female confined in a cell, and in the control group, males were exposed to a clean arena. Gift construction was observed only in the S and SF groups, with a similar occurrence rate. After touching females (SF group), males did not change their pattern of gift construction. Gift construction occurrence increased with male and female age. The results lead us to assume that the existence of chemical cues associated with female silk elicits male searching behaviour and gift construction, allowing males to decide between eating or wrapping prey according to the possibility of a sexual encounter. Anticipating gift construction, males are ready to mate, diminishing the risks of predation, female desertion or male–male scramble competition. The effect of age on behavioural variation and the rate of construction is discussed.

Most sexual preference studies test female choice between different males or test male choice between females with different reproductive status, but few studies test male preference towards females of different ages within the same reproductive status. In subsocial spiders, males can share the nest with subadult and adult females of different ages. We exposed a male of Anelosimus cf. studiosus to three kinds of females simultaneously: a subadult female, a recently moulted female and a mature adult female (both virgins) comparing male preferences and female interactions. Males courted mature and recently moulted females indiscriminably, but preferentially mated with mature females, while subadult females were not courted. Mature females did not interfere with male courtship towards other females whereas some recently moulted females unsuccessfully attempted to interfere with male courtship towards mature females. In spite of these interferences, no female-female fighting was observed. Taking into account ...

Several not mutually exclusive functions have been ascribed to nuptial gifts across different taxa. Although the idea that a nuptial prey gift may protect the male from pre-copulatory sexual cannibalism is attractive, it has previously been considered of no importance based on indirect evidence and rejected by experimental tests. We reinvestigated whether nuptial gifts may function as a shield against female attacks during mating encounters in the spider Pisaura mirabilis and whether female hunger influences the likelihood of cannibalistic attacks. The results showed that pre-copulatory sexual cannibalism was enhanced when males courted without a gift and this was independent of female hunger. We propose that the nuptial gift trait has evolved partly as a counteradaptation to female aggression in this spider species.

In spider species with first male sperm priority, males guard subadult females as a tactic for improving their paternity. Preliminary observations in Anelosimus cf. studiosus, a subsocial species from Uruguay, showed that males court and guard subadult females. To elucidate the sexual tactics of this species, we placed two adult males with one adult female, and two other males with one subadult (penultimate) female under laboratory conditions (20 trials for each female status/group). Males courted both adult and subadult females, and subadult females were as receptive as adults, adopting the acceptance posture and pseudocopulating with males. Males performed conspicuous fights under both situations. Winner males copulated (or pseudocopulated), while the losers remained as satellites. Some females remated with satellite males. Subadult female behaviour simulating the adult receptive display could be a cheating tactic for retaining males and eliciting combats. Male-male fights and the guarding of subadult females suggest the occurrence of first male sperm priority, but the persistence of satellite males also suggests second males have some degree of paternity success. Competition could be caused by an asynchrony in female maturation at the beginning of the reproductive season, turning adult females in to the scarce resource.

For many spiders, sex pheromones associated with female silk are important stimuli that elicit male searching and courtship behaviors. In that context, female sexual receptivity and chemical attractiveness can depend on age and reproductive status. In Paratrechalea ornata (Mello-Leitao 1943) (Araneae: Trechaleidae), males offer females a nuptial gift (a prey wrapped in silk) during courtship. Gift construction is elicited by the presence of female silk, and silk attractiveness is influenced by female age, increasing from 20 days after the female reaches adulthood. Our goal was to investigate whether female age affects female sexual receptivity and to discuss the relationship between receptivity and silk attractiveness. We exposed 26 virgin females, from 2 to 28 days after the final molt, to males offering a nuptial gift. Female sexual receptivity was age dependent and increased with adult female age. Females over 15 days from adulthood accepted more gifts than younger females, but the latency of ...

In species where females gain a nutritious nuptial gift during mating, the balance between benefits and costs of mating may depend on access to food. This means that there is not one optimal number of matings for the female but a range of optimal mating numbers. With increasing food availability, the optimal number of matings for a female should vary from the number necessary only for fertilization of her eggs to the number needed also for producing these eggs. In three experimental series, the average number of matings for females of the nuptial gift-giving spider Pisaura mirabilis before egg sac construction varied from 2 to 16 with food-limited females generally accepting more matings than well-fed females. Minimal level of optimal mating number for females at satiation feeding conditions was predicted to be 2-3; in an experimental test, the median number was 2 (range 0-4). Multiple mating gave benefits in terms of increased fecundity and increased egg hatching success up to the third mating, and it had costs in terms of reduced fecundity, reduced egg hatching success after the third mating, and lower offspring size. The level of polyandry seems to vary with the female optimum, regulated by a satiation-dependent resistance to mating, potentially leaving satiated females in lifelong virginity.

In nuptial gift-giving species females sometimes select their potential mates based on the presence and size of the gift. But in some species, such as the Neotropical polyandrous spider Paratrechalea ornate male gifts vary in quality, from nutritive to worthless, and this male strategy can be in conflict with female nutritional benefits. In this species, males without gifts experience a reduction in mating success and duration, while males that offer worthless or genuine nutritive gifts mate with similar frequencies and durations. The female apparently controls the duration of copulation. Thus, there is scope for females to favour males offering gifts and further if these are nutritious, via post-copulatory processes. We first tested whether females differentially store sperm from males that offer the highest nutritional benefits by experimentally presenting females with males that offer either nutritive or worthless gifts (uninterrupted matings). Second, we carried out another set of experiments to examine whether females can select sperm based only on gift presence. This time we interrupted matings after the first pedipalp insertion, thus matching number of insertions and mating duration for males that: offered and did not offer gift. Our results showed that the amount of sperm stored is positive related to mating duration in all groups, except in matings with worthless gifts. Gift presence itself did not affect the sperm stored by females, while they store similar number of sperm in matings with males offering either nutritive or worthless gifts. We discuss whether females prefer males with gifts regardless, if content, because it represents an attractive and/or reliable signal. Or alternatively, they prefer nutritive nuptial gifts, as they are an important source of food supply and/or signal of male donor ability.

An extensive diversity of nuptial gifts is known in invertebrates, but prey wrapped in silk is a unique type of gift present in few insects and spiders. Females from spider species prefer males offering a gift accepting more and longer matings than when males offered no gift. Silk wrapping of the gift is not essential to obtain a mating, but appears to increase the chance of a mating evidencing a particularly intriguing function of this trait. Consequently, as other secondary sexual traits, silk wrapping may be an important trait under sexual selection, if it is used by females as a signal providing information on male quality. We aimed to understand whether the white color of wrapped gifts is used as visual signal during courtship in the spider Paratrechalea ornata. We studied if a patch of white paint on the males’ chelicerae is attractive to females by exposing females to males: with their chelicerae painted white; without paint; and with the sternum painted white (paint control). Females contacted males with white chelicerae more often and those males obtained higher mating success than other males. Thereafter, we explored whether silk wrapping is a condition-dependent trait and drives female visual attraction. We exposed good and poor condition males, carrying a prey, to the female silk. Males in poor condition added less silk to the prey than males in good condition, indicating that gift wrapping is an indicator of male quality and may be used by females to acquire information of the potential mate.

Nuptial gifts are an intriguing male sexually selected trait that has evolved in a wide range of forms among different animals. Wrapped prey gifts have been intensively studied in two spiders: Paratrechalea ornata (Trechaleidae), a neotropical species, and Pisaura mirabilis (Pisauridae), a Palearctic species. Interestingly, these species experience differences in their ecology but show remarkable similarities in sexual behavior, suggesting convergent evolution of the male trait. The origin of nuptial gifts probably was derived from a fecundity advantage to females and a mating advantage to males. However, the benefits to each sex might be sensitive to fluctuations in food availability, leading to antagonistic co-evolution. When food is scarce, males may deceive females by providing worthless gifts and females may counter this exploitation by limiting sperm transfer. We review studies on the function and evolution of nuptial gifts, particularly comparing the neotropical with the Palearctic species, and discuss evolutionary implications of nuptial gifts for males and females.

Polyandrous females are expected to discriminate among males through postcopulatory cryptic mate choice. Yet, there is surprisingly little unequivocal evidence for female-mediated cryptic sperm choice. In species in which nuptial gifts facilitate mating, females may gain indirect benefits through preferential storage of sperm from gift-giving males if the gift signals male quality. We tested this hypothesis in the spider Pisaura mirabilis by quantifying the number of sperm stored in response to copulation with males with or without a nuptial gift, while experimentally controlling copulation duration. We further assessed the effect of gift presence and copulation duration on egg-hatching success in matings with uninterrupted copulations with gift-giving males. We show that females mated to gift-giving males stored more sperm and experienced 17% higher egg-hatching success, compared with those mated to no-gift males, despite matched copulation durations. Uninterrupted copulations resulted in both increased sperm storage and egg-hatching success. Our study confirms the prediction that the nuptial gift as a male signal is under positive sexual selection by females through cryptic sperm storage. In addition, the gift facilitates longer copulations and increased sperm transfer providing two different types of advantage to gift-giving in males.

The relative force of direct and indirect selection underlying the evolution of polyandry is contentious. When females acquire direct benefits during mating, indirect benefits are often considered negligible. Although direct benefits are likely to play a prominent role in the evolution of polyandry, post-mating selection for indirect benefits may subsequently evolve. We examined whether polyandrous females acquire indirect benefits and quantified direct and indirect effects of multiple mating on female fitness in a nuptial gift-giving spider (Pisaura mirabilis). In this system, the food item donated by males during mating predicts direct benefits of polyandry. We compared fecundity, fertility and survival of singly mated females to that of females mated three times with the same (monogamy) or different (polyandry) males in a two-factorial design where females were kept under high and low feeding conditions. Greater access to nutrients and sperm had surprisingly little positive effect on fitness, apart from shortening the time until oviposition. In contrast, polyandry increased female reproductive success by increasing the probability of oviposition, and egg hatching success indicating that indirect benefits arise from mating with several different mating partners rather than resources transferred by males. The evolution of polyandry in a male-resource-based mating system may result from exploitation of the female foraging motivation and that indirect genetic benefits are subsequently derived resulting from co-evolutionary post-mating processes to gain a reproductive advantage or to counter costs of mating. Importantly, indirect benefits may represent an additional explanation for the maintenance of polyandry.

Preliminary genetic studies in Trechaleidae spider family show high variation in sex chromosomes and high heterocigocity, suggesting high chromatin plasticity. The trechaleids Paratrechalea ornata, Trechalea bucculenta and Trechaleoides biocellata are present in Uruguay. Males offering nuptial gifts during courtship have been reported in P. ornata and T. bucculenta but not in T. biocellata. Nuptial gifts are an inherited trait probably highly affected by environmental factors, which play an important role in gene expression. We hypothesize that this trait could be associated with tissue-specific genes existing in G-bands. We investigate the male meiosis in these 3 species, their sex chromosome system and the effects of G-banding on their chromosomes, and elucidate genetic differences among them. Meiotic stages of the 3 species were submitted to Giemsa-staining and G-banding treatments. We observed a haploid number of n= 11 in P. ornata and n= 13 in both T. bucculenta and T. biocellata. Males from the 3 species presented an X(1) X(2) 0 sex chromosome system, which is suggested as ancestral in Araneae. In P. ornata and T. bucculenta, both sex chromosomes were together and aligned in parallel until the segregation during anaphase I. In contrast to these species, sex chromosomes of T. biocellata usually remained distant from each other until diakinesis when they were observed associated in parallel disposition. Interstitial G-bands were similar in P. ornata and T. bucculenta, and they both differed from those in T. biocellata. The special behavior of sex chromosomes in T. biocellata as well as the different G-banding pattern of this species suggests the existence of novel modifications in this species.

Background In nuptial gift-giving species, benefits of acquiring a mate may select for male deception by donation of worthless gifts. We investigated the effect of worthless gifts on mating success in the spider Pisaura mirabilis. Males usually offer an insect prey wrapped in silk; however, worthless gifts containing inedible items are reported. We tested male mating success in the following experimental groups: protein enriched fly gift (PG), regular fly gift (FG), worthless gift (WG), or no gift (NG). Results Males that offered worthless gifts acquired similar mating success as males offering nutritional gifts, while males with no gift experienced reduced mating success. The results suggest that strong selection on the nuptial gift-giving trait facilitates male deception by donation of worthless gifts. Females terminated matings faster when males offered worthless donations; this demonstrate a cost of deception for the males as shorter matings lead to reduced sperm transfer and thus give the deceiving males a disadvantage in sperm competition. Conclusion We propose that the gift wrapping trait allows males to exploit female foraging preference by disguising the gift content thus deceiving females into mating without acquiring direct benefits. Female preference for a genuine prey gift combined with control over mating duration, however, counteracts the male deception.

Males of the nursery web spider Pisaura mirabilis usually offer an insect prey wrapped in white silk as a nuptial gift to facilitate copulation. Males exploit female foraging preferences in a sexual context as females feed on the gift during copula- tion. It is possible for males to copulate without a gift, however strong female preference for the gift leads to dramatically higher mating success for gift-giving males. Females are polyandrous, and gift-giving males achieve higher mating success, longer copulations, and increased sperm transfer that confer advantages in sperm competition. Intriguingly, field studies show that ap- proximately one third of males carry a worthless gift consisting of dry and empty insect exoskeletons or plant fragments wrapped in white silk. Silk wrapping disguises gift content and females are able to disclose gift content only after accepting and feeding on the gift, meanwhile males succeed in transferring sperm. The evolution of deceit by worthless gift donation may be favoured by strong intra-sexual competition and costs of gift-construction including prey capture, lost foraging opportunities and investment in silk wrapping. Females that receive empty worthless gifts terminate copulation sooner, which reduces sperm transfer and likely disadvantages males in sperm competition. The gift-giving trait may thus become a target of sexually antagonistic co-evolution, where deceit by worthless gifts leads to female resistance to the trait. We discuss factors such as female mating rate and intensity of sperm competition that may shape the evolution of male deception, and how ecological factors may influence the evolution and maintenance of worthless gifts as an evolutionarily stable alternative mating strategy by frequency dependent selection (Cur- rent Zoology 60(1): 4351, 2014). Keywords Sexual selection, Sexual conflict, Nuptial gift, Worthless gift, Polyandry, Polymorphic trait, Sperm competition