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1.
Rao D Ceballos Fernandez O Castañeda-Barbosa E Díaz-Fleischer F 《Die Naturwissenschaften》2011,98(8):699-703
Most orb-web spiders face downwards in the web. A downward orientation has been proposed to be the optimal strategy because
spiders run faster downwards and thus can catch prey quicker. Consequently, orb-web spiders also extend their web in the lower
part, leading to top-down web asymmetry. Since the majority of orb-web spiders face downwards, it has been difficult to test
the effect of orientation on prey capture and web asymmetry. In this study, we explored the influence of reverse orientation
on foraging efficiency and web asymmetry in Verrucosa arenata, a neotropical orb-web spider that faces upwards in the web. We show that reverse orientation does not imply reverse web
asymmetry in this species. V. arenata spiders captured more prey in the lower part of the web but more prey per area on the upper part. The average running speeds
of spiders did not differ between upward and downward running, but heavier spiders took longer to capture prey while running
upwards. We discuss these findings in the context of foraging efficiency and web asymmetry. 相似文献
2.
Nakata K 《Die Naturwissenschaften》2007,94(10):853-857
Animals obtain information from past foraging experience to adjust their foraging activity according to their environment.
The ability of spiders to obtain information from unsuccessful predation experiences was investigated by examining the effects
on web building, a significant foraging investment, of prey detection without successful capture in the orb-web spider Cyclosa octotuberculata. Four treatments were employed: (1) successful capture and feeding: one syrphid fly was allowed to be captured and consumed
by the spider on the web; (2) single prey-item detection: a syrphid fly was placed on the web to lure the spider, but was
removed before capture; (3) five prey-item detection: above prey-item detection stimulus was given five times; and, (4) control:
neither prey nor feeding on the web. While control spiders decreased the total thread length and capture area of their webs,
prey-item detection spiders in both conditions increased them, indicating that the spider obtained information from unsuccessful
predation experience to adjust their foraging investment. The fed spiders exhibited a significantly greater increase than
the prey-detection-only spiders, suggesting that prey detection alone and prey detection with consumption had different informational
effects. Total thread length did not differ between single and five prey-item detection spiders, but distance between two
adjacent sticky spirals increased only in the former spiders, possibly because five times unsuccessful predations prevented
spiders to reduce web stickiness. It suggests that the spider changed web morphology according to the number of prey detection. 相似文献
3.
Leg loss is a common phenomenon in spiders, and according to the species 5% to 40% of the adults can present at least one
missing leg. There is no possibility of regeneration after adult moult and the animal must manage with its missing appendages
until its death. With the loss of one or more legs, female orb-weaving spiders can be penalized twice: firstly, because the
legs are necessary for web construction and secondly, the legs are essential for the control of the prey after its interception
by the web. During development, spiders may be also penalized because regeneration has energetic costs that take away resources
for survival, growth and reproduction. All these consequences should influence negatively the development of the spider and
thus its fitness. We investigated the impact of leg loss in the orb-weaving spider, Zygiella x-notata by studying its frequency in a natural population and web building and prey capture behaviours in laboratory. In field populations,
9.5% to 13%, of the adult females presented the loss of one or more legs; the majority of individuals had lost only one leg
(in 48% of cases, a first one). Leg loss seems to affect all the adult spiders, as there is no difference of mass between
intact spiders and those with missing leg. Data obtained with laboratory-reared spiders, showed that the loss of legs due
to the moult is rare (less than 1%). Considering changes in web design, spiders with missing legs decreased their silk investment,
increased the distance between spiral turns but did not change the capture surface of the web. Under our laboratory experimental
conditions, spiders with one or two lost legs did not present any difference in prey capture efficiency. In laboratory conditions,
spiders with lost leg(s) did not show any difference in egg sac production or in longevity (adult lifespan) compared to intact
spiders. 相似文献
4.
In numerous spider species, reproductive success of adult females has been shown to be positively correlated with their body mass. We suggest, however, that spiders may incur greater foraging costs as their body mass increases due to the numerous and complex locomotor bouts needed to build an orb-web. Such a body-mass-dependent cost should, in turn, affect the web-building decisions of spiders. In the laboratory, we tested the influence of body mass on energetic expenditure (measured as mass loss) during web-building behavior in Zygiella x-notata. Our results showed (1) that energetic costs associated with web-building were closely related to body mass and to web-building activity, and (2) that as their body mass increased, spiders reduced the amount of silk used per web, while their foraging effort simultaneously increased. This work gives new insights into web-building behavior and energy allocation strategies of weaving spiders. 相似文献
5.
Orb web spiders sit at the centre of their approximately circular webs when waiting for prey and so face many of the same
challenges as central-place foragers. Prey value decreases with distance from the hub as a function of prey escape time. The
further from the hub that prey are intercepted, the longer it takes a spider to reach them and the greater chance they have
of escaping. Several species of orb web spiders build vertically elongated ladder-like orb webs against tree trunks, rather
than circular orb webs in the open. As ladder web spiders invest disproportionately more web area further from the hub, it
is expected they will experience reduced prey gain per unit area of web investment compared to spiders that build circular
webs. We developed a model to investigate how building webs in the space-limited microhabitat on tree trunks influences the
optimal size, shape and net prey gain of arboricolous ladder webs. The model suggests that as horizontal space becomes more
limited, optimal web shape becomes more elongated, and optimal web area decreases. This change in web geometry results in
decreased net prey gain compared to webs built without space constraints. However, when space is limited, spiders can achieve
higher net prey gain compared to building typical circular webs in the same limited space. Our model shows how spiders optimise
web investment in sub-optimal conditions and can be used to understand foraging investment trade-offs in other central-place
foragers faced with constrained foraging arenas. 相似文献
6.
Why do kleptobiotic spiders of the genus Argyrodes seem to be associated with spiders of the genus Nephila worldwide? Observations following introduction of experimental insect prey of different sizes and weights on to host webs revealed that: (1) small prey are more effectively retained on the web of Nephila clavipes than on the web of another common host, Leucauge venusta. (2) N. clavipes did not consume small prey that accumulated on the web whereas larger, heavier prey were enveloped and stored. (3) We observed clear partitioning of prey items between N. clavipes and Argyrodes spp.; diet selection by Argyrodes did not overlap with that of N. clavipes but closely overlapped with that of L. venusta. (4) L. venusta responds very quickly to prey impact whereas N. clavipes is slower, offering a temporal window of opportunity for Argyrodes foraging. (5) The ability of L. venusta to detect and respond to small items also means that it acts aggressively to Argyrodes spp., whereas N. clavipes does not. Consequently, food-acquisition behaviours of Argyrodes were clearly less risky with N. clavipes compared with L. venusta. We conclude that when a kleptobiotic organism has a choice of various host species, it will opt for the least risky host that presents the highest rate of availability of food items. The fact that Nephila species present such characteristics explains the worldwide association with Argyrodes kleptobiotic spiders. 相似文献
7.
Bjorkman-Chiswell BT Kulinski MM Muscat RL Nguyen KA Norton BA Symonds MR Westhorpe GE Elgar MA 《Die Naturwissenschaften》2004,91(5):245-248
The orb-weaving spider Nephila edulis incorporates into its web a band of decaying animal and plant matter. While earlier studies demonstrate that larger spiders utilise these debris bands as caches of food, the presence of plant matter suggests additional functions. When organic and plastic items were placed in the webs of N. edulis, some of the former but none of the latter were incorporated into the debris band. Using an Y-maze olfactometer, we show that sheep blowflies Lucilia cuprina are attracted to recently collected debris bands, but that this attraction does not persist over time. These data reveal an entirely novel foraging strategy, in which a sit-and-wait predator attracts insect prey by utilising the odours of decaying organic material. The spiders habit of replenishing the debris band may be necessary to maintain its efficacy for attracting prey. 相似文献
8.
Kensuke Nakata 《Die Naturwissenschaften》2010,97(11):1029-1032
Most orb web spiders face downward on the web hub, and their webs are vertically asymmetrical, that is, the lower part of
the web is larger than the upper part and the ratio of the lower part to the whole web area increases as the spider grows.
This phenomenon may reflect biogenetic law such that young animals exhibit a general ancestral trait whereas adults exhibit
specific and derived traits. An alternative explanation is that vertical asymmetry may arise from the difference in time required
by spiders to move up or down the web to capture prey. The present study tested these two hypotheses for Eriophora sagana. Subadults of this species build their webs with reverse asymmetry in that the upper part of the web area is larger than
the lower part. In both subadults and adults, the upper proportion decreased with spider weight, and adult spiders built more
symmetric webs. These results support the capture time difference hypothesis. 相似文献
9.
Orb-web building spiders (Araneae: Araneoidea, Uloboridae) can be considered as territorial central place foragers. In territorial
central place foragers, the optimal foraging arena is circular, with the forager sitting in its centre. In orb webs, the spider’s
orientation (head up or head down) whilst waiting for prey on the hub of its web and the downwards–upwards asymmetry of its
running speeds are the probable causes for the observed deviation of the hub from the web’s centre. Here, we present an analytical
model and a more refined simulation model to analyse the relationships amongst the spider’s running speeds, its orientation
whilst waiting for prey and the vertical asymmetry of orb webs. The results of our models suggest that (a) waiting for prey
head down is generally favourable because it allows the spider to reach the prey in its web on average quicker than spiders
waiting head up, (b) the downwards–upwards running speed asymmetry, together with the head-down orientation of most spiders,
are likely causes for the observed vertical asymmetry of orb webs, (c) waiting head up can be advantageous for spiders whose
downwards–upwards running speed asymmetry is small and who experience high prey tumbling rates and (d) spiders waiting head
up should place their hub lower than similar spiders waiting head down. 相似文献
10.
The architecture of vertical aerial orb webs may be affected by spider size and gravity or by the available web space, in
addition to phylogenetic and/or developmental factors. Vertical orb web asymmetry measured by hub displacement has been shown
to increase in bigger and heavier spiders; however, previous studies have mostly focused on adult and subadult spiders or
on several size classes with measured size parameters but no mass. Both estimations are suboptimal because (1) adult orb web
spiders may not invest heavily in optimal web construction, whereas juveniles do; (2) size class/developmental stage is difficult
to estimate in the field and is thus subjective, and (3) mass scales differently to size and is therefore more important in
predicting aerial foraging success due to gravity. We studied vertical web asymmetry in a giant orb web spider, Nephila pilipes, across a wide range of size classes/developmental stages and tested the hypothesis that vertical web asymmetry (measured
as hub displacement) is affected by gravity. On a sample of 100 webs, we found that hubs were more displaced in heavier and
larger juveniles and that spider mass explained vertical web asymmetry better than other measures of spider size (carapace
and leg lengths, developmental stage). Quantifying web shape via the ladder index suggested that, unlike in other nephilid
taxa, growing Nephila orbs do not become vertically elongated. We conclude that the ontogenetic pattern of progressive vertical web asymmetry in
Nephila can be explained by optimal foraging due to gravity, to which the opposing selective force may be high web-building costs
in the lower orb. Recent literature finds little support for alternative explanations of ontogenetic orb web allometry such
as the size limitation hypothesis and the biogenetic law. 相似文献
11.
We show that uloborid spiders, which lack the poison glands typical of nearly all other spiders, employ thousands of wrapping movements with their hind legs and up to hundreds of meters of silk line to make a shroud that applies substantial compressive force to their prey. Shrouds sometimes break the prey’s legs, buckle its compound eyes inward, or kill it outright. The compressive force apparently results from the summation of small tensions on sticky lines as they are applied to the prey package. Behavioral details indicate that wrapping is designed to compact prey; in turn, compaction probably functions to facilitate these spiders’ unusual method of feeding. This is the first demonstration that prey wrapping by spiders compacts and physically damages their prey, rather than simply restraining them. 相似文献
12.
Marija Majer Ingi Agnarsson Jens-Christian Svenning Trine Bilde 《Die Naturwissenschaften》2013,100(11):1031-1040
Latitude, rainfall, and productivity have been shown to influence social organisation and level of sociality in arthropods on large geographic scales. Social spiders form permanent group-living societies where they cooperate in brood care, web maintenance, and foraging. Sociality has evolved independently in a number of unrelated spider genera and may reflect convergent evolutionary responses to common environmental drivers. The genus Anelosimus contains a third of approximately 25 described permanently social spider species, eight to nine species that all occur in the Americas. To test for environmental correlates of sociality in Anelosimus across the Americas, we used logistic regression to detect effects of annual rainfall, productivity, and precipitation seasonality on the relative likelihood of occurrence of social and non-social Anelosimus spiders. Our analyses show that social species tend to occur at higher annual rainfall and productivity than non-social species, supporting the hypothesised effects of these environmental variables on the geographical distribution of social species. We did not find support for the hypothesis that permanently social species occur in areas with low precipitation seasonality. High annual precipitation and, to less extent, high productivity favour the occurrence of permanently group-living Anelosimus spiders relative to subsocial and solitary species. These results are partially consistent with previous findings for the Old World spider genus Stegodyphus, where a link between high habitat productivity and sociality was also found. Unlike Anelosimus, however, Stegodyphus typically occur in dry habitats negating a general importance of high precipitation for sociality. Sociality in spiders thus seems to be strongly linked to productivity, probably reflecting the need for relatively high availability of large prey to sustain social colonies. 相似文献
13.
Spiders have been suspected to be one of the most important groups of natural enemies of insects worldwide. To document the impact of the global spider community as insect predators, we present estimates of the biomass of annually killed insect prey. Our estimates assessed with two different methods suggest that the annual prey kill of the global spider community is in the range of 400–800 million metric tons (fresh weight), with insects and collembolans composing >90% of the captured prey. This equals approximately 1‰ of the global terrestrial net primary production. Spiders associated with forests and grasslands account for >95% of the annual prey kill of the global spider community, whereas spiders in other habitats are rather insignificant contributors over a full year. The spider communities associated with annual crops contribute less than 2% to the global annual prey kill. This, however, can be partly explained by the fact that annual crop fields are “disturbed habitats” with a low buildup of spider biomass and that agrobiont spiders often only kill prey over short time periods in a year. Our estimates are supported by the published results of exclusion experiments, showing that the number of herbivorous/detritivorous insects and collembolans increased significantly after spider removal from experimental plots. The presented estimates of the global annual prey kill and the relative contribution of spider predation in different biomes improve the general understanding of spider ecology and provide a first assessment of the global impact of this very important predator group. 相似文献
14.
Kazuhiro Tanaka 《Die Naturwissenschaften》2001,88(10):431-433
The influence of prey animals on the supercooling ability of the house spider, Achaearanea tepidariorum, was studied by feeding spiders with field-collected and laboratory-cultured prey animals. Irrespective of the prey species supplied, spiders given field-collected prey had a higher supercooling point than those given laboratory-cultured counterparts. This means that (1) the field prey animals contained some efficient ice nucleators, whereas the laboratory animals were free from such substances and (2) the ice nucleators must be of external origin. Several lines of evidence also suggest that, under natural conditions, potential prey animals for the house spider are highly contaminated with ice nucleators. 相似文献
15.
The origin of viscid capture silk in orb webs, from cribellate silk-spinning ancestors, is a key innovation correlated with significant diversification of web-building spiders. Ancestral cribellate silk consists of dry nanofibrils surrounding a stiff, axial fiber that adheres to prey through van der Waals interactions, capillary forces, and physical entanglement. In contrast, viscid silk uses chemically adhesive aqueous glue coated onto a highly compliant and extensible flagelliform core silk. The extensibility of the flagelliform fiber accounts for half of the total work of adhesion for viscid silk and is enabled by water in the aqueous coating. Recent cDNA libraries revealed the expression of flagelliform silk proteins in cribellate orb-weaving spiders. We hypothesized that the presence of flagelliform proteins in cribellate silk could have allowed for a gradual shift in mechanical performance of cribellate axial silk, whose effect was masked by the dry nature of its adhesive. We measured supercontraction and mechanical performance of cribellate axial silk, in wet and dry states, for two species of cribellate orb web-weaving spiders to see if water enabled flagelliform silk-like performance. We found that compliance and extensibility of wet cribellate silk increased compared to dry state as expected. However, when compared to other silk types, the response to water was more similar to other web silks, like major and minor ampullate silk, than to viscid silk. These findings support the punctuated evolution of viscid silk mechanical performance. 相似文献
16.
In a predator–prey system where both intervenients come from the same taxon, one can expect a strong selection on behavioural
and morphological traits involved in prey capture. For example, in specialised snake-eating snakes, the predator is unaffetced
by the venom of the prey. We predicted that similar adaptations should have evolved in spider-eating (araneophagous) spiders.
We investigated potential and actual prey of two Palpimanus spiders (P. gibbulus, P. orientalis) to support the prediction that these are araneophagous predators. Specific behavioural adaptations were investigated using
a high-speed camera during staged encounters with prey, while morphological adaptations were investigated using electron microscopy.
Both Palpimanus species captured a wide assortment of spider species from various guilds but also a few insect species. Analysis of the potential
prey suggested that Palpimanus is a retreat-invading predator that actively searches for spiders that hide in a retreat. Behavioural capture adaptations
include a slow, stealthy approach to the prey followed by a very fast attack. Morphological capture adaptations include scopulae
on forelegs used in grabbing prey body parts, stout forelegs to hold the prey firmly, and an extremely thick cuticle all over
the body preventing injury from a counter bite of the prey. Palpimanus overwhelmed prey that was more than 200% larger than itself. In trials with another araneophagous spider, Cyrba algerina (Salticidae), Palpimanus captured C. algerina in more than 90% of cases independent of the size ratio between the spiders. Evidence indicates that both Palpimanus species possesses remarkable adaptations that increase its efficiency in capturing spider prey. 相似文献
17.
Spiders are fascinating model species to study information-acquisition strategies, with the web acting as an extension of the animal’s body. Here, we compare the strategies of two orb-weaving spiders that acquire information through vibrations transmitted and filtered in the web. Whereas Araneus diadematus monitors web vibration directly on the web, Zygiella x-notata uses a signal thread to remotely monitor web vibration from a retreat, which gives added protection. We assess the implications of these two information-acquisition strategies on the quality of vibration information transfer, using laser Doppler vibrometry to measure vibrations of real webs and finite element analysis in computer models of webs. We observed that the signal thread imposed no biologically relevant time penalty for vibration propagation. However, loss of energy (attenuation) was a cost associated with remote monitoring via a signal thread. The findings have implications for the biological use of vibrations by spiders, including the mechanisms to locate and discriminate between vibration sources. We show that orb-weaver spiders are fascinating examples of organisms that modify their physical environment to shape their information-acquisition strategy. 相似文献
18.
D. Rodríguez-Morales V. Rico-Gray J. G. García-Franco H. Ajuria-Ibarra L. T. Hernández-Salazar L. E. Robledo-Ospina D. Rao 《Die Naturwissenschaften》2018,105(5-6):36
Many animals use body coloration as a strategy to communicate with conspecifics, prey, and predators. Color is a trade-off for some species, since they should be visible to conspecifics but cryptic to predators and prey. Some flower-dwelling predators, such as crab spiders, are capable of choosing the color of flowers where they ambush flower visitors and pollinators. In order to avoid being captured, visitors evaluate flowers visually before landing. The crab spider Mecaphesa dubia is a polymorphic species (white/purple color morphs), which inhabits the flower heads of a dune plant, Palafoxia lindenii. Using full-spectrum photography of spiders and flowers, we evaluated how honeybees perceived the spiders at different distances. Using visual modeling, we obtained the chromatic and achromatic contrasts of the spiders on flower heads as perceived by honeybees. Purple morphs were found mainly on the receptacle area and white morphs were equally likely to be found in the flowers and receptacle. According to theoretical modeling, white morphs were visible to honeybees from a distance of 10 cm in receptacle area but appeared to be cryptic in the flower area. Purple morphs were cryptic on the receptacle and less so when they were on the flowers. Spiders on flower heads are predicted to be more easily detected by honeybees using chromatic contrast. Our study shows that the conspicuousness of flower dwelling spiders to honeybees depends on the color morph, the distance of observation, and the position of spider on the flower head. 相似文献
19.
Chris R. Pavey Chris J. Burwell Gerhard Körtner Fritz Geiser 《Die Naturwissenschaften》2009,96(6):679-683
One of the energetic benefits of daily torpor over prolonged hibernation is that it enables animals to regularly forage and,
therefore, replenish food reserves between bouts of torpor. However, little is known about the diet of predators undergoing
torpor or whether differences in prey composition among individuals influence torpor characteristics. Here, we test the hypothesis
that prey composition affects winter torpor use and patterns of a population of carnivorous marsupial, the brush-tailed mulgara
(Dasycercus blythi), in the Great Sandy Desert, Australia. Mulgaras in the study population captured a wide range of prey including vertebrates
(mammals, reptiles, birds), seven insect orders, spiders and centipedes. The proportion of vertebrates in the diet was negatively
correlated with both frequency of torpor use and maximum bout duration. This variation in torpor use with diet can be explained
by the higher energetic content of vertebrates as well as their larger size. Even assuming uniform intake of prey biomass
among individuals, those that subsisted on an invertebrate-dominated diet during winter apparently suffered energetic shortages
as a result of the scarcity of invertebrate taxa with high energy content (such as insect larvae). Our study is the first
to demonstrate a link between diet composition and daily torpor use in a free-ranging mammal. 相似文献
20.
Alain Dejean Nicolas Labrière Axel Touchard Frédéric Petitclerc Olivier Roux 《Die Naturwissenschaften》2014,101(4):323-330
We tested if nesting habits influence ant feeding preferences and predatory behavior in the monophyletic genus Pseudomyrmex (Pseudomyrmecinae) which comprises terrestrial and arboreal species, and, among the latter, plant-ants which are obligate inhabitants of myrmecophytes (i.e., plants sheltering so-called plant-ants in hollow structures). A cafeteria experiment revealed that the diet of ground-nesting Pseudomyrmex consists mostly of prey and that of arboreal species consists mostly of sugary substances, whereas the plant-ants discarded all the food we provided. Workers forage solitarily, detecting prey from a distance thanks to their hypertrophied eyes. Approach is followed by antennal contact, seizure, and the manipulation of the prey to sting it under its thorax (next to the ventral nerve cord). Arboreal species were not more efficient at capturing prey than were ground-nesting species. A large worker size favors prey capture. Workers from ground- and arboreal-nesting species show several uncommon behavioral traits, each known in different ant genera from different subfamilies: leaping abilities, the use of surface tension strengths to transport liquids, short-range recruitment followed by conflicts between nestmates, the consumption of the prey’s hemolymph, and the retrieval of entire prey or pieces of prey after having cut it up. Yet, we never noted group ambushing. We also confirmed that Pseudomyrmex plant-ants live in a kind of food autarky as they feed only on rewards produced by their host myrmecophyte, or on honeydew produced by the hemipterans they attend and possibly on the fungi they cultivate. 相似文献