Evolution; international journal of organic evolution, Jan 19, 2015
Predation exerts strong selection on mimetic butterfly wing colour patterns, which also serve oth... more Predation exerts strong selection on mimetic butterfly wing colour patterns, which also serve other functions such as sexual selection. Therefore, specific selection pressures may affect the sexes and signal components differentially. We tested three predictions about the evolution of mimetic resemblance by comparing wing colouration of aposematic butterflies and their Batesian mimics: (a) females gain greater mimetic advantage than males and therefore are better mimics, (b) due to intersexual genetic correlations, sexually monomorphic mimics are better mimics than female-limited mimics, and (c) mimetic resemblance is better on the dorsal wing surface which is visible to predators in flight. Using a physiological model of avian colour vision, we quantified mimetic resemblance from predators' perspective, which showed that female butterflies were better mimics than males. Mimetic resemblance in female-limited mimics was comparable to that in sexually monomorphic mimics, suggestin...
No animals are known to possess both ultraviolet (UV) reflectance and fluorescence that are sex-s... more No animals are known to possess both ultraviolet (UV) reflectance and fluorescence that are sex-specific. We provide evidence for this separation in the jumping spider Cosmophasis umbratica, which has UV reflectance and UV-induced green fluorescence restricted to males and females, respectively. During courtship, many of the studied pairs failed to show typical display posturing when UV light was blocked. Occluding the UV component of sunlight to only one of each pair also caused atypical behavior: Females showed no interest in non‐UV-reflective courting males, and males either ignored or were lackluster in courting nonfluorescing females. These results demonstrate the importance of both sex-specific hues as sexual signals for effective intraspecific communication.
Proceedings of the Royal Society B: Biological Sciences, 2007
Recent studies have shown for birds that females sometimes choose mates on the basis of condition... more Recent studies have shown for birds that females sometimes choose mates on the basis of condition-dependent variation in ultraviolet (UV, less than 400 nm) ornamentation, but there have been few comparable studies on invertebrates. Yet many invertebrates have UV structural coloration. Here, we investigate Cosmophasis umbratica , a jumping spider (Araneae: Salticidae) that has sexually dimorphic UV-iridescent ornamentation, and we provide evidence that male UV coloration is condition dependent in this species. Spectral-reflection patterns change with male age and prior feeding history. The position of the UV band (i.e. UV hue) of the carapaces of younger (field-collected as subadults and matured as adults in laboratory) males shifted, relative to older (field-collected as adults) males, significantly towards longer wavelengths. Food deprivation significantly decreased the spectral intensity of the abdomen, but not the carapace. Questions concerning the mechanisms by which UV ornament...
Animal colour signals used in intraspecies communications can generally be attributed to a compos... more Animal colour signals used in intraspecies communications can generally be attributed to a composite effect of structural and pigmentary colours. Notably, the functional role of iridescent coloration that is 'purely' structural (i.e., absence of pigments) is poorly understood. Recent studies reveal that iridescent colorations can reliably indicate individual quality, but evidence of iridescence as a pure structural coloration indicative of male quality during contests and relating to an individual's resource-holding potential (RHP) is lacking. In age-and size-controlled pairwise male-male contests that escalate from visual displays of aggression to more costly physical fights, we demonstrate that the ultraviolet-green iridescence of Cosmophasis umbratica predicts individual persistence and relates to RHP. Contest initiating males exhibited significantly narrower carapace band separation (i.e., relative spectral positions of UV and green hues) than non-initiators. Asymmetries in carapace and abdomen brightness influenced overall contest duration and escalation. As losers retreated upon having reached their own persistence limits in contests that escalated to physical fights, losers with narrower carapace band separation were significantly more persistence. We propose that the carapace UV-green iridescence of C. umbratica predicts individual persistence and is indicative of a male's RHP. As the observed UV-green hues of C. umbratica are 'pure' optical products of a multilayer reflector system, we suggest that intrasexual variations in the optical properties of the scales' chitinair-chitin microstructures are responsible for the observed differences in carapace band separations.
Phytotelmata (plant-held waters) are useful ecological models for studying predator-prey interact... more Phytotelmata (plant-held waters) are useful ecological models for studying predator-prey interactions. However, the ability of terrestrial predators to influence organism abundance within phytotelmata remains poorly studied. We investigated the predation of two pitcher-dwelling spiders, the red crab spider Misumenops nepenthicola and the yellow crab spider Thomisus nepenthiphilus (Araneae: Thomisidae) on dipteran larval abundance by manipulating their presence in the pitcher Nepenthes gracilis. Lower abundance in the larvae of the mosquito Tripteriodes spp. and increased spider mass were recorded after M. nepenthicola was introduced into laboratory-maintained pitchers (n = 10); T. nepenthiphilus did not affect larval abundance and a decrease in spider mass was recorded. Further investigations on two other dipteran larval species, the scuttle fly Endonepenthia schuitemakeri and gall midges Lestodiplosis spp., reported reduced numbers with the introduction of M. nepenthicola. We further tested this predation on dipteran larval abundance by its introduction, removal, and re-introduction to pitchers in the field (n = 42) over 1 mo. The spider's absence and presence significantly influenced larval numbers: all four dipteran species reported a significant decrease in numbers after M. nepenthicola was introduced. These results are one of the first to demonstrate the influence of a terrestrial phytotelm forager on the abundance of pitcher organisms via direct predation, reiterating the ecological importance of terrestrial phytotelm predators on phytotelm community structure and dynamics.
Journal of Experimental Marine Biology and Ecology, 2011
Bright colours are a key visual signal in many animal communication systems. Here we examine the ... more Bright colours are a key visual signal in many animal communication systems. Here we examine the function of the blue-green facial bands found in two species of mangrove crabs, Perisesarma eumolpe (De Man) and P. indiarum (Tweedie). Food (mangrove leaves) ...
Jumping spiders are known to possess ultraviolet (UV) receptors in the retinas of their large-pri... more 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-speciWc interactions. In the study reported herein, we performed behavioural experiments to test whether a UV¡reXecting jumping spider, Cosmophasis umbratica, is sensitive to UV wavelengths and whether UV cues are important in intra-speciWc communication. The absence of UV cues not only aVected intra-speciWc behaviour by signiWcantly reducing the frequency of agonistic displays, but also elicited unprecedented courtship displays in males towards their own mirror images and conspeciWc opponents. Furthermore, C. umbratica males were able to respond rapidly to changes in UV cues of conspeciWc mirror images by switching between agonistic and courtship displays. These Wndings clearly demonstrate that C. umbratica males are capable of seeing UV wavelengths and that UV cues are necessary and suYcient for this species to enable the agonistic displays. Hence, UV light may have an important role to play in intra-speciWc communication in jumping spiders.
Although there are numerous examples of animals having photoreceptors sensitive to UVA (315-400 n... more Although there are numerous examples of animals having photoreceptors sensitive to UVA (315-400 nm) [1] and relying on UVA-based mate-choice cues [2-5], here we provide the first evidence of an animal using UVB (280-315 nm) for intraspecific communication. An earlier study showed that Phintella vittata, a jumping spider (Salticidae) from China, reflects UVB . By performing six series of binary matechoice experiments in which we varied lighting conditions with filters (UVB+ [no filter] versus UVB2, UVB+ versus ND1, UVB+ versus ND2, UVB2 versus ND1, UVB2 versus ND2, and UVB2 versus UVA2), we show that significantly more UVB + males than UVB2 males are chosen by females as preferred mates. Female preference for UVB-reflective males is not affected by differences in brightness or by UVA.
Spider dragline silk is of practical interest because of its excellent mechanical properties. How... more Spider dragline silk is of practical interest because of its excellent mechanical properties. However, the structure of this material is still largely unknown. In this article, we report what we believe is a new model of the hierarchical structure of silk based on scanning electron microscope and atomic force microscope images. This hierarchical structure includes b-sheet, polypeptide chain network, and silk fibril. It turns out that an exceptionally high strength of the spider dragline silk can be obtained by decreasing the size of the crystalline nodes in the polypeptide chain network while increasing the degree of orientation of the crystalline nodes. Based on this understanding, how the reeling speed affects mechanical properties of spider dragline silk can be understood properly. Hopefully, the understanding obtained in this study will shed light on the formation of spider silk, and consequently, on the principles for the design of ultrastrong silk. AFM imaging was performed by standard procedures in taping mode by Nanoscope III (Veeco, Woodbury, NY) scanning force microscope. Scanning electron microscope (SEM) measurements were carried out on a JEOL (Tokyo, Japan) JSM6700F. The wide angle x-ray scattering (WAXS) patterns of a bundle of 800 spider dragline silk filaments were collected using Bruker GADDS XRD with beam size 0.5 mm. The radiation wavelength is 1.5418 A ˚for Cu Ka. The sample-to-detector distance was 6 cm and the exposure time was 30 min. The small angle x-ray scattering (SAXS) experiments were performed with a Bruker NanoSTAR small angle x-ray scattering system. The generator was
Jumping spiders (Salticidae) have acute vision with some cells in the retina that are sensitive t... more Jumping spiders (Salticidae) have acute vision with some cells in the retina that are sensitive to ultraviolet (UV) spectra ( < 400 nm). However, no study has documented the use of UV signals in salticids. To appreciate the function of UV vision, it is necessary to characterize the UV colours of salticids. In the present study, the UV and humanvisible wavelengths of a tropical ornate salticid spider, Cosmophasis umbratica , were analysed using reflectance spectrometry to obtain evidence of sex-specific UV colours. An absolute sexual dimorphism in the UV colours of this salticid species was found. All of the body parts of adult males that are displayed to conspecifics during intra-specific interactions reflected UV (300-400 nm) light, whereas the adult females and juveniles did not reflect UV light from any body part. A great deal of variation was also found in the UV wavebands among males. This is the first full UV characterization of a salticid spider and the first study to demonstrate an extreme sexual UV dimorphism in jumping spiders. The findings obtained provide evidence that UV reflectance may comprise important sexual signals in jumping spiders.
In the literature on animal use of ultraviolet (UV) vision and UV reflectance, it has usually bee... more In the literature on animal use of ultraviolet (UV) vision and UV reflectance, it has usually been UV-A (315-400 nm) that is considered. Animals are generally assumed to be unable to discriminate UV-B (280-315 nm) from other wavelengths in natural sunlight. Recently, some animals are known to be able to detect and respond directly to UV-B in order to avoiding exposure to it. However, there is no evidence that the hue corresponding to UV-B is salient to an animal during intraspecies communication. Using Phintella vittata, an ornate jumping spider from two geographically different populations in China, we investigated geographical, intersexual, intrasexual, and interpopulation variation in UV reflectance. We found that both the males and the females of P. vittata reflect UV light, and that the reflection bands are located in UV-B, a part of reflectance spectrum never previously investigated. We also found a great deal of population variation in the UV-B spectral reflectance. Furthermore, two colour morphs, the 'green' and 'yellow' morphs, are identified for adult males for both populations, and both morphs differ greatly in both UV-B and human-visible wavelengths. This is the first demonstration of a UV-B reflecting salticid and UV-B sexual dichromatism.
... such as shuttling, dropping, and pumping (A. argen-tata: Robinson &amp;amp; Robinson, 197... more ... such as shuttling, dropping, and pumping (A. argen-tata: Robinson &amp;amp; Robinson, 1970; A. appensa: Jackson et al., 1993; re-view: Cloudsley-Thompson, 1995; Rayor, 1996; Blackledge &amp;amp; Pickett, 2000; Blackledge &amp;amp; Wenzel, 2001). However, unlike many other orb-weaving spi ...
Earlier studies have shown that Cosmophasis umbratica, a jumping spider from Singapore, is sexual... more Earlier studies have shown that Cosmophasis umbratica, a jumping spider from Singapore, is sexually dimorphic in the reflectance of ultraviolet (UV) (males, but not females, have UV-reflecting markings). Here we present the first experimental evidence that the male's UV markings influence mate choice of C. umbratica females. When presented with males whose appearance was manipulated by the use of a UV-blocking filter, females spent more time watching UV1 males (i.e., males with UV present) and less time watching UVÿ males (UV absent). We also manipulated the levels of male brightness by using 2 UV-transmitting neutral density filters and showed that UV reflectance was used specifically for hue discrimination instead of being used for detecting differences in brightness alone. This is not only the first strong evidence of UV influence on female mate-choice decisions for a spider but also the best experimental demonstration of color vision, whatever the wavelength.
ABSTRACT Highlights ► We blocked reflections from Argiope versicolor web decorations at different... more ABSTRACT Highlights ► We blocked reflections from Argiope versicolor web decorations at different wavelengths. ► Only blocking UV reflections reduced number of Portia approaching webs. ► Thus UV is more important than other wavelengths for Portia to locate Argiope.
Stabilimenta, the conspicuous, ultraviolet (UV)-reflecting, white silk structures around the hub ... more Stabilimenta, the conspicuous, ultraviolet (UV)-reflecting, white silk structures around the hub of orb webs, are thought to increase a spider's foraging success by attracting prey (prey attraction hypothesis). No studies, however, have yet investigated the function of nonlinear and noncruciform stabilimenta and the stabilimenta of juvenile spiders. We examined whether the discoid stabilimenta spun by juvenile Argiope versicolor, an orb-spinning spider, function to attract prey. When we measured the UV reflectance of the web silks of A. versicolor juveniles, we found that the discoid stabilimentum silk, but not spiral silk or radial silk or the joint where the two types of silk met, reflected UV light. We then carried out two series of choice experiments in the laboratory to determine whether the webs with discoid stabilimenta attract more fruit flies than undecorated webs when UVC white light (300-700 nm) is present. We also examined whether the discoid stabilimenta still attract insects when the UV section of the spectrum (300-400 nm) is eliminated (UVÿ). Webs with discoid stabilimenta attracted more fruit flies than the webs without stabilimenta in UVC white light. However, in UVÿ light, fewer fruit flies flew to the webs, even when they were decorated with discoid stabilimenta. In a field experiment, significantly more insects were intercepted by webs with discoid stabilimenta than by webs without stabilimenta. We suggest that the discoid stabilimenta of A. versicolor juveniles act as a visual signal that attracts insects, supporting the prey attraction hypothesis.
The courtship and male-male agonistic behaviour of Cosmophasis umbratica Simon, an iridescent jum... more The courtship and male-male agonistic behaviour of Cosmophasis umbratica Simon, an iridescent jumping spider from Singapore, was studied for the first time. Exhibiting sexual colour and size dimorphism, C. umbratica is frequently found on leaves and flowers of tropical plants in open areas. Males are generally larger than females and dominantly green and black with silvery white markings; females are generally a mixture of green, brown, white and black. Sixteen major displays are described for C. umbratica. Skittering, vibrating of palps, arching of legs and flexed up abdomens are dominant male behaviours during courtship. Females almost always decamp on first sight of males, although males are very persistent in their courtship. A large repertoire of male-male agonistic displays is observed, with males either decamping after a clash, being lifted up and thrown down, or while embracing are chased away after being pushed back. Drumming is also displayed in both male-female and male-male interactions. This vibratory communication channel during inter-(male-female) and intra-sexual (male-male) interactions away from nests is discussed in regards to the evolution of salticids.
1. We review the mechanisms behind ecosystem functions, the processes that facilitate energy tran... more 1. We review the mechanisms behind ecosystem functions, the processes that facilitate energy transfer along food webs, and the major processes that allow the cycling of carbon, oxygen and nitrogen, and use case studies to show how these have already been, and will continue to be, altered by global warming. 2. Increased temperatures will affect the interactions between heterotrophs and autotrophs (e.g. pollination and seed dispersal), and between heterotrophs (e.g. predators-prey, parasites ⁄ pathogens-hosts), with generally negative ramifications for important ecosystem services (functions that provide direct benefit to human society such as pollination) and potential for heightened species co-extinction rates. 3. Mitigation of likely impacts of warming will require, in particular, the maintenance of species diversity as insurance for the provision of basic ecosystem services. Key to this will be long-term monitoring and focused research that seek to maintain ecosystem resilience in the face of global warming. 4. We provide guidelines for pursuing research that quantifies the nexus between ecosystem function and global warming. These include documentation of key functional species groups within systems, and understanding the principal outcomes arising from direct and indirect effects of a rapidly warming environment. Localized and targeted research and monitoring, complemented with laboratory work, will determine outcomes for resilience and guide adaptive conservation responses and long-term planning.
Evolution; international journal of organic evolution, Jan 19, 2015
Predation exerts strong selection on mimetic butterfly wing colour patterns, which also serve oth... more Predation exerts strong selection on mimetic butterfly wing colour patterns, which also serve other functions such as sexual selection. Therefore, specific selection pressures may affect the sexes and signal components differentially. We tested three predictions about the evolution of mimetic resemblance by comparing wing colouration of aposematic butterflies and their Batesian mimics: (a) females gain greater mimetic advantage than males and therefore are better mimics, (b) due to intersexual genetic correlations, sexually monomorphic mimics are better mimics than female-limited mimics, and (c) mimetic resemblance is better on the dorsal wing surface which is visible to predators in flight. Using a physiological model of avian colour vision, we quantified mimetic resemblance from predators' perspective, which showed that female butterflies were better mimics than males. Mimetic resemblance in female-limited mimics was comparable to that in sexually monomorphic mimics, suggestin...
No animals are known to possess both ultraviolet (UV) reflectance and fluorescence that are sex-s... more No animals are known to possess both ultraviolet (UV) reflectance and fluorescence that are sex-specific. We provide evidence for this separation in the jumping spider Cosmophasis umbratica, which has UV reflectance and UV-induced green fluorescence restricted to males and females, respectively. During courtship, many of the studied pairs failed to show typical display posturing when UV light was blocked. Occluding the UV component of sunlight to only one of each pair also caused atypical behavior: Females showed no interest in non‐UV-reflective courting males, and males either ignored or were lackluster in courting nonfluorescing females. These results demonstrate the importance of both sex-specific hues as sexual signals for effective intraspecific communication.
Proceedings of the Royal Society B: Biological Sciences, 2007
Recent studies have shown for birds that females sometimes choose mates on the basis of condition... more Recent studies have shown for birds that females sometimes choose mates on the basis of condition-dependent variation in ultraviolet (UV, less than 400 nm) ornamentation, but there have been few comparable studies on invertebrates. Yet many invertebrates have UV structural coloration. Here, we investigate Cosmophasis umbratica , a jumping spider (Araneae: Salticidae) that has sexually dimorphic UV-iridescent ornamentation, and we provide evidence that male UV coloration is condition dependent in this species. Spectral-reflection patterns change with male age and prior feeding history. The position of the UV band (i.e. UV hue) of the carapaces of younger (field-collected as subadults and matured as adults in laboratory) males shifted, relative to older (field-collected as adults) males, significantly towards longer wavelengths. Food deprivation significantly decreased the spectral intensity of the abdomen, but not the carapace. Questions concerning the mechanisms by which UV ornament...
Animal colour signals used in intraspecies communications can generally be attributed to a compos... more Animal colour signals used in intraspecies communications can generally be attributed to a composite effect of structural and pigmentary colours. Notably, the functional role of iridescent coloration that is 'purely' structural (i.e., absence of pigments) is poorly understood. Recent studies reveal that iridescent colorations can reliably indicate individual quality, but evidence of iridescence as a pure structural coloration indicative of male quality during contests and relating to an individual's resource-holding potential (RHP) is lacking. In age-and size-controlled pairwise male-male contests that escalate from visual displays of aggression to more costly physical fights, we demonstrate that the ultraviolet-green iridescence of Cosmophasis umbratica predicts individual persistence and relates to RHP. Contest initiating males exhibited significantly narrower carapace band separation (i.e., relative spectral positions of UV and green hues) than non-initiators. Asymmetries in carapace and abdomen brightness influenced overall contest duration and escalation. As losers retreated upon having reached their own persistence limits in contests that escalated to physical fights, losers with narrower carapace band separation were significantly more persistence. We propose that the carapace UV-green iridescence of C. umbratica predicts individual persistence and is indicative of a male's RHP. As the observed UV-green hues of C. umbratica are 'pure' optical products of a multilayer reflector system, we suggest that intrasexual variations in the optical properties of the scales' chitinair-chitin microstructures are responsible for the observed differences in carapace band separations.
Phytotelmata (plant-held waters) are useful ecological models for studying predator-prey interact... more Phytotelmata (plant-held waters) are useful ecological models for studying predator-prey interactions. However, the ability of terrestrial predators to influence organism abundance within phytotelmata remains poorly studied. We investigated the predation of two pitcher-dwelling spiders, the red crab spider Misumenops nepenthicola and the yellow crab spider Thomisus nepenthiphilus (Araneae: Thomisidae) on dipteran larval abundance by manipulating their presence in the pitcher Nepenthes gracilis. Lower abundance in the larvae of the mosquito Tripteriodes spp. and increased spider mass were recorded after M. nepenthicola was introduced into laboratory-maintained pitchers (n = 10); T. nepenthiphilus did not affect larval abundance and a decrease in spider mass was recorded. Further investigations on two other dipteran larval species, the scuttle fly Endonepenthia schuitemakeri and gall midges Lestodiplosis spp., reported reduced numbers with the introduction of M. nepenthicola. We further tested this predation on dipteran larval abundance by its introduction, removal, and re-introduction to pitchers in the field (n = 42) over 1 mo. The spider's absence and presence significantly influenced larval numbers: all four dipteran species reported a significant decrease in numbers after M. nepenthicola was introduced. These results are one of the first to demonstrate the influence of a terrestrial phytotelm forager on the abundance of pitcher organisms via direct predation, reiterating the ecological importance of terrestrial phytotelm predators on phytotelm community structure and dynamics.
Journal of Experimental Marine Biology and Ecology, 2011
Bright colours are a key visual signal in many animal communication systems. Here we examine the ... more Bright colours are a key visual signal in many animal communication systems. Here we examine the function of the blue-green facial bands found in two species of mangrove crabs, Perisesarma eumolpe (De Man) and P. indiarum (Tweedie). Food (mangrove leaves) ...
Jumping spiders are known to possess ultraviolet (UV) receptors in the retinas of their large-pri... more 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-speciWc interactions. In the study reported herein, we performed behavioural experiments to test whether a UV¡reXecting jumping spider, Cosmophasis umbratica, is sensitive to UV wavelengths and whether UV cues are important in intra-speciWc communication. The absence of UV cues not only aVected intra-speciWc behaviour by signiWcantly reducing the frequency of agonistic displays, but also elicited unprecedented courtship displays in males towards their own mirror images and conspeciWc opponents. Furthermore, C. umbratica males were able to respond rapidly to changes in UV cues of conspeciWc mirror images by switching between agonistic and courtship displays. These Wndings clearly demonstrate that C. umbratica males are capable of seeing UV wavelengths and that UV cues are necessary and suYcient for this species to enable the agonistic displays. Hence, UV light may have an important role to play in intra-speciWc communication in jumping spiders.
Although there are numerous examples of animals having photoreceptors sensitive to UVA (315-400 n... more Although there are numerous examples of animals having photoreceptors sensitive to UVA (315-400 nm) [1] and relying on UVA-based mate-choice cues [2-5], here we provide the first evidence of an animal using UVB (280-315 nm) for intraspecific communication. An earlier study showed that Phintella vittata, a jumping spider (Salticidae) from China, reflects UVB . By performing six series of binary matechoice experiments in which we varied lighting conditions with filters (UVB+ [no filter] versus UVB2, UVB+ versus ND1, UVB+ versus ND2, UVB2 versus ND1, UVB2 versus ND2, and UVB2 versus UVA2), we show that significantly more UVB + males than UVB2 males are chosen by females as preferred mates. Female preference for UVB-reflective males is not affected by differences in brightness or by UVA.
Spider dragline silk is of practical interest because of its excellent mechanical properties. How... more Spider dragline silk is of practical interest because of its excellent mechanical properties. However, the structure of this material is still largely unknown. In this article, we report what we believe is a new model of the hierarchical structure of silk based on scanning electron microscope and atomic force microscope images. This hierarchical structure includes b-sheet, polypeptide chain network, and silk fibril. It turns out that an exceptionally high strength of the spider dragline silk can be obtained by decreasing the size of the crystalline nodes in the polypeptide chain network while increasing the degree of orientation of the crystalline nodes. Based on this understanding, how the reeling speed affects mechanical properties of spider dragline silk can be understood properly. Hopefully, the understanding obtained in this study will shed light on the formation of spider silk, and consequently, on the principles for the design of ultrastrong silk. AFM imaging was performed by standard procedures in taping mode by Nanoscope III (Veeco, Woodbury, NY) scanning force microscope. Scanning electron microscope (SEM) measurements were carried out on a JEOL (Tokyo, Japan) JSM6700F. The wide angle x-ray scattering (WAXS) patterns of a bundle of 800 spider dragline silk filaments were collected using Bruker GADDS XRD with beam size 0.5 mm. The radiation wavelength is 1.5418 A ˚for Cu Ka. The sample-to-detector distance was 6 cm and the exposure time was 30 min. The small angle x-ray scattering (SAXS) experiments were performed with a Bruker NanoSTAR small angle x-ray scattering system. The generator was
Jumping spiders (Salticidae) have acute vision with some cells in the retina that are sensitive t... more Jumping spiders (Salticidae) have acute vision with some cells in the retina that are sensitive to ultraviolet (UV) spectra ( < 400 nm). However, no study has documented the use of UV signals in salticids. To appreciate the function of UV vision, it is necessary to characterize the UV colours of salticids. In the present study, the UV and humanvisible wavelengths of a tropical ornate salticid spider, Cosmophasis umbratica , were analysed using reflectance spectrometry to obtain evidence of sex-specific UV colours. An absolute sexual dimorphism in the UV colours of this salticid species was found. All of the body parts of adult males that are displayed to conspecifics during intra-specific interactions reflected UV (300-400 nm) light, whereas the adult females and juveniles did not reflect UV light from any body part. A great deal of variation was also found in the UV wavebands among males. This is the first full UV characterization of a salticid spider and the first study to demonstrate an extreme sexual UV dimorphism in jumping spiders. The findings obtained provide evidence that UV reflectance may comprise important sexual signals in jumping spiders.
In the literature on animal use of ultraviolet (UV) vision and UV reflectance, it has usually bee... more In the literature on animal use of ultraviolet (UV) vision and UV reflectance, it has usually been UV-A (315-400 nm) that is considered. Animals are generally assumed to be unable to discriminate UV-B (280-315 nm) from other wavelengths in natural sunlight. Recently, some animals are known to be able to detect and respond directly to UV-B in order to avoiding exposure to it. However, there is no evidence that the hue corresponding to UV-B is salient to an animal during intraspecies communication. Using Phintella vittata, an ornate jumping spider from two geographically different populations in China, we investigated geographical, intersexual, intrasexual, and interpopulation variation in UV reflectance. We found that both the males and the females of P. vittata reflect UV light, and that the reflection bands are located in UV-B, a part of reflectance spectrum never previously investigated. We also found a great deal of population variation in the UV-B spectral reflectance. Furthermore, two colour morphs, the 'green' and 'yellow' morphs, are identified for adult males for both populations, and both morphs differ greatly in both UV-B and human-visible wavelengths. This is the first demonstration of a UV-B reflecting salticid and UV-B sexual dichromatism.
... such as shuttling, dropping, and pumping (A. argen-tata: Robinson &amp;amp; Robinson, 197... more ... such as shuttling, dropping, and pumping (A. argen-tata: Robinson &amp;amp; Robinson, 1970; A. appensa: Jackson et al., 1993; re-view: Cloudsley-Thompson, 1995; Rayor, 1996; Blackledge &amp;amp; Pickett, 2000; Blackledge &amp;amp; Wenzel, 2001). However, unlike many other orb-weaving spi ...
Earlier studies have shown that Cosmophasis umbratica, a jumping spider from Singapore, is sexual... more Earlier studies have shown that Cosmophasis umbratica, a jumping spider from Singapore, is sexually dimorphic in the reflectance of ultraviolet (UV) (males, but not females, have UV-reflecting markings). Here we present the first experimental evidence that the male's UV markings influence mate choice of C. umbratica females. When presented with males whose appearance was manipulated by the use of a UV-blocking filter, females spent more time watching UV1 males (i.e., males with UV present) and less time watching UVÿ males (UV absent). We also manipulated the levels of male brightness by using 2 UV-transmitting neutral density filters and showed that UV reflectance was used specifically for hue discrimination instead of being used for detecting differences in brightness alone. This is not only the first strong evidence of UV influence on female mate-choice decisions for a spider but also the best experimental demonstration of color vision, whatever the wavelength.
ABSTRACT Highlights ► We blocked reflections from Argiope versicolor web decorations at different... more ABSTRACT Highlights ► We blocked reflections from Argiope versicolor web decorations at different wavelengths. ► Only blocking UV reflections reduced number of Portia approaching webs. ► Thus UV is more important than other wavelengths for Portia to locate Argiope.
Stabilimenta, the conspicuous, ultraviolet (UV)-reflecting, white silk structures around the hub ... more Stabilimenta, the conspicuous, ultraviolet (UV)-reflecting, white silk structures around the hub of orb webs, are thought to increase a spider's foraging success by attracting prey (prey attraction hypothesis). No studies, however, have yet investigated the function of nonlinear and noncruciform stabilimenta and the stabilimenta of juvenile spiders. We examined whether the discoid stabilimenta spun by juvenile Argiope versicolor, an orb-spinning spider, function to attract prey. When we measured the UV reflectance of the web silks of A. versicolor juveniles, we found that the discoid stabilimentum silk, but not spiral silk or radial silk or the joint where the two types of silk met, reflected UV light. We then carried out two series of choice experiments in the laboratory to determine whether the webs with discoid stabilimenta attract more fruit flies than undecorated webs when UVC white light (300-700 nm) is present. We also examined whether the discoid stabilimenta still attract insects when the UV section of the spectrum (300-400 nm) is eliminated (UVÿ). Webs with discoid stabilimenta attracted more fruit flies than the webs without stabilimenta in UVC white light. However, in UVÿ light, fewer fruit flies flew to the webs, even when they were decorated with discoid stabilimenta. In a field experiment, significantly more insects were intercepted by webs with discoid stabilimenta than by webs without stabilimenta. We suggest that the discoid stabilimenta of A. versicolor juveniles act as a visual signal that attracts insects, supporting the prey attraction hypothesis.
The courtship and male-male agonistic behaviour of Cosmophasis umbratica Simon, an iridescent jum... more The courtship and male-male agonistic behaviour of Cosmophasis umbratica Simon, an iridescent jumping spider from Singapore, was studied for the first time. Exhibiting sexual colour and size dimorphism, C. umbratica is frequently found on leaves and flowers of tropical plants in open areas. Males are generally larger than females and dominantly green and black with silvery white markings; females are generally a mixture of green, brown, white and black. Sixteen major displays are described for C. umbratica. Skittering, vibrating of palps, arching of legs and flexed up abdomens are dominant male behaviours during courtship. Females almost always decamp on first sight of males, although males are very persistent in their courtship. A large repertoire of male-male agonistic displays is observed, with males either decamping after a clash, being lifted up and thrown down, or while embracing are chased away after being pushed back. Drumming is also displayed in both male-female and male-male interactions. This vibratory communication channel during inter-(male-female) and intra-sexual (male-male) interactions away from nests is discussed in regards to the evolution of salticids.
1. We review the mechanisms behind ecosystem functions, the processes that facilitate energy tran... more 1. We review the mechanisms behind ecosystem functions, the processes that facilitate energy transfer along food webs, and the major processes that allow the cycling of carbon, oxygen and nitrogen, and use case studies to show how these have already been, and will continue to be, altered by global warming. 2. Increased temperatures will affect the interactions between heterotrophs and autotrophs (e.g. pollination and seed dispersal), and between heterotrophs (e.g. predators-prey, parasites ⁄ pathogens-hosts), with generally negative ramifications for important ecosystem services (functions that provide direct benefit to human society such as pollination) and potential for heightened species co-extinction rates. 3. Mitigation of likely impacts of warming will require, in particular, the maintenance of species diversity as insurance for the provision of basic ecosystem services. Key to this will be long-term monitoring and focused research that seek to maintain ecosystem resilience in the face of global warming. 4. We provide guidelines for pursuing research that quantifies the nexus between ecosystem function and global warming. These include documentation of key functional species groups within systems, and understanding the principal outcomes arising from direct and indirect effects of a rapidly warming environment. Localized and targeted research and monitoring, complemented with laboratory work, will determine outcomes for resilience and guide adaptive conservation responses and long-term planning.
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Papers by Matthew Lim