scholarly journals Optics of the ultraviolet reflecting scales of a jumping spider

2007 ◽  
Vol 274 (1618) ◽  
pp. 1583-1589 ◽  
Author(s):  
Michael F Land ◽  
Julia Horwood ◽  
Matthew L.M Lim ◽  
Daiqin Li
Keyword(s):  
Air Gap ◽  
Sexually Dimorphic ◽  
Peak Wavelength ◽  
Jumping Spider ◽  
Quarter Wavelength ◽  
Reflection Maximum ◽  
Colour Signals ◽  
Reflectance Peak

The jumping spider Cosmophasis umbratica from Singapore is strongly sexually dimorphic. The males, but not the females, reflect ultraviolet as well as green–orange light. The scales responsible for this are composed of a chitin–air–chitin sandwich in which the chitin layers are three-quarters of a wavelength thick and the air gap a quarter wavelength (where λ =600 nm, the peak wavelength of the principal reflection maximum). It is shown that this configuration produces a second reflectance peak at approximately 385 nm, accounting for the observed reflection in the ultraviolet. Other scales have a similar thickness of chitin but lack the air gap and thus produce a dull purple reflection. This novel mechanism provides the spiders with two colour signals, both of which are important in mating displays.

scholarly journals Sexually dimorphic dorsal coloration in a jumping spider: testing a potential case of sex-specific mimicry

2021 ◽  
Vol 8 (6) ◽  
pp. 210308
Author(s):  
Collette Cook ◽  
Erin C. Powell ◽  
Kevin J. McGraw ◽  
Lisa A. Taylor
Keyword(s):  
Colour Pattern ◽  
Sexually Dimorphic ◽  
Sham Control ◽  
Jumping Spider ◽  
Negative Results ◽  
Potential Case ◽  
Opposite Sex ◽  
Colour Patterns ◽  
Hymenopteran Insects ◽  
Predation Rates

To avoid predation, many animals mimic behaviours and/or coloration of dangerous prey. Here we examine potential sex-specific mimicry in the jumping spider Habronattus pyrrithrix . Previous work proposed that males' conspicuous dorsal coloration paired with characteristic leg-waving (i.e. false antennation) imperfectly mimics hymenopteran insects (e.g. wasps and bees), affording protection to males during mate-searching and courtship. By contrast, less active females are cryptic and display less leg-waving. Here we test the hypothesis that sexually dimorphic dorsal colour patterns in H. pyrrithrix are most effective when paired with sex-specific behaviours. We manipulated spider dorsal coloration with makeup to model the opposite sex and exposed them to a larger salticid predator ( Phidippus californicus ). We predicted that males painted like females should suffer higher predation rates than sham-control males. Likewise, females painted like males should suffer higher predation rates than sham-control females. Contrary to expectations, spiders with male-like coloration were attacked more than those with female-like coloration, regardless of their actual sex. Moreover, males were more likely to be captured, and were captured sooner, than females (regardless of colour pattern). With these unexpected negative results, we discuss alternative functional hypotheses for H. pyrrithrix colours, as well as the evolution of defensive coloration generally.

scholarly journals A Predator's Perspective of the Accuracy of Ant Mimicry in Spiders

2012 ◽  
Vol 2012 ◽  
pp. 1-5 ◽  
Author(s):  
Ximena J. Nelson
Keyword(s):  
Batesian Mimicry ◽  
Sexually Dimorphic ◽  
Oecophylla Smaragdina ◽  
Jumping Spider ◽  
Behavioural Characteristics ◽  
Ant Mimicry ◽  
Signal Accuracy

Among spiders, resemblance of ants (myrmecomorphy) usually involves the Batesian mimicry, in which the spider coopts the morphological and behavioural characteristics of ants to deceive ant-averse predators. Nevertheless, the degree of resemblance between mimics and ants varies considerably. I usedPortia fimbriata,a jumping spider (Salticidae) with exceptional eyesight that specialises on preying on salticids, to test predator perception of the accuracy of ant mimicry.Portia fimbriata’s response to ants (Oecophylla smaragdina), accurate ant-like salticids (Synageles occidentalis), and inaccurate ant-like salticids (females ofMyrmarachne bakeriand sexually dimorphic males ofM. bakeri, which have enlarged chelicerae) was assessed.Portia fimbriataexhibited graded aversion in accordance with the accuracy of resemblance to ants (O. smaragdina>S. occidentalis> femaleM. bakeri> maleM. bakeri). These results support the hypothesis that ant resemblance confers protection from visual predators, but to varying degrees depending on signal accuracy.

scholarly journals Effects of age and feeding history on structure-based UV ornaments of a jumping spider (Araneae: Salticidae)

2006 ◽  
Vol 274 (1609) ◽  
pp. 569-575 ◽  
Author(s):  
Matthew L.M Lim ◽  
Daiqin Li
Keyword(s):  
Mate Choice ◽  
Food Deprivation ◽  
Spectral Intensity ◽  
Sexually Dimorphic ◽  
Jumping Spider ◽  
Structural Coloration ◽  
Spectral Reflection ◽  
Male Age ◽  
Uv Coloration

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 ornaments change are highlighted, as are hypotheses concerning the role of condition-dependent UV variation in male–male competition and as a criterion used by females when making mate-choice decisions.

scholarly journals The jumping spider Saitis barbipes lacks a red photoreceptor to see its own sexually dimorphic red coloration

2021 ◽  
Vol 109 (1) ◽  
Author(s):  
Mateusz Glenszczyk ◽  
David Outomuro ◽  
Matjaž Gregorič ◽  
Simona Kralj-Fišer ◽  
Jutta M. Schneider ◽  
...  
Keyword(s):  
Reasonable Assumption ◽  
Sexually Dimorphic ◽  
Sexual Signaling ◽  
Jumping Spider ◽  
Maximal Sensitivity ◽  
Green Sensitivity ◽  
Ill Posed ◽  
Human Eyes ◽  
Black Color ◽  
Red Coloration

AbstractExamining the role of color in mate choice without testing what colors the study animal is capable of seeing can lead to ill-posed hypotheses and erroneous conclusions. Here, we test the seemingly reasonable assumption that the sexually dimorphic red coloration of the male jumping spider Saitis barbipes is distinguishable, by females, from adjacent black color patches. Using microspectrophotometry, we find clear evidence for photoreceptor classes with maximal sensitivity in the UV (359 nm) and green (526 nm), inconclusive evidence for a photoreceptor maximally sensitive in the blue (451 nm), and no evidence for a red photoreceptor. No colored filters within the lens or retina could be found to shift green sensitivity to red. To quantify and visualize whether females may nevertheless be capable of discriminating red from black color patches, we take multispectral images of males and calculate photoreceptor excitations and color contrasts between color patches. Red patches would be, at best, barely discriminable from black, and not discriminable from a low-luminance green. Some color patches that appear achromatic to human eyes, such as beige and white, strongly absorb UV wavelengths and would appear as brighter “spider-greens” to S. barbipes than the red color patches. Unexpectedly, we discover an iridescent UV patch that contrasts strongly with the UV-absorbing surfaces dominating the rest of the spider. We propose that red and black coloration may serve identical purposes in sexual signaling, functioning to generate strong achromatic contrast with the visual background. The potential functional significance of red coloration outside of sexual signaling is discussed.

scholarly journals Predatory response to changes in camouflage in a sexually dimorphic jumping spider

2013 ◽  
Vol 41 (3) ◽  
pp. 381-386 ◽  
Author(s):  
Maciej Bartos ◽  
Katarzyna Szczepko ◽  
Marzena Stanska
Keyword(s):  
Sexually Dimorphic ◽  
Jumping Spider ◽  
Predatory Response

Determination of the Effects of Air Gap and Hind Support on the Sound Absorption Coefficient of Biobased and Foam Materials

2012 ◽  
Author(s):  
N. V. David ◽  
M. N. Zainal ◽  
M. J. M. Nor
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Low Frequency ◽  
Air Gap ◽  
High Density ◽  
Sound Absorption Coefficient ◽  
Sound Waves ◽  
Fibrous Media ◽  
Rigid Foam ◽  
Quarter Wavelength

The sound absorption characteristics of wooden and porous materials including fibrous media and porous foams vary with the nature of their surface porosity. The low frequency absorption, which is of interest in noise control engineering, of these material types is generally enhanced by introducing an air gap of a certain width or a flexible support at the rear face of the material posterior to the impinging sound waves. This study investigates the effect of air gap with and without hind support on the low frequency absorption of a kenaf/epoxy composite, a Meranti wood, a low-density rigid foam and a high-density rigid foam. The sound absorption coefficient of these materials are determined using the two-microphone impedance tube transfer-function method according to ISO 10534-2 standard in the frequency range between 20 Hz and 1600 Hz. In this study, 5-mm, 10-mm, 50-mm and 100-mm wide air gaps are introduced at the posterior of the specimens to measure the influence of the quarter-wavelength absorption on sound absorption coefficient. Backing panels made from polyethylene are used to study the effect of hind support on sound absorption coefficient at different frequencies. The dBFA Suite 4.8.1 program is used to acquire and process the acoustic signals and the SCS8100 software package is employed for the computation of sound absorption coefficient. The sound absorption coefficient and characteristics of each material within the range of frequency tested are discussed based on the width of air gap (i.e., the quarter-wavelength effect) in tandem with the presence or absence of the hind support. It is found that the low frequency absorption of the high-density foam with the hind support improved the absorption by 50% as the air gap is increased from 0 to 100 mm. The opposite effect is observed for the other materials tested whereby the sound absorption coefficient is reduced by 30 to 40% with the hind support.

scholarly journals Shaping communicative colour signals over evolutionary time

2016 ◽  
Vol 3 (11) ◽  
pp. 160728 ◽  
Author(s):  
Alison G. Ossip-Drahos ◽  
José R. Oyola Morales ◽  
Cuauhcihuatl Vital-García ◽  
J. Jaime Zúñiga-Vega ◽  
Diana K. Hews ◽  
...  
Keyword(s):  
Spectrophotometric Analysis ◽  
Sexually Dimorphic ◽  
Relative Timing ◽  
Evolutionary Time ◽  
Evolutionary Forces ◽  
History Of ◽  
Long Term Impact ◽  
Communicative Signals ◽  
Colour Signals

Many evolutionary forces can shape the evolution of communicative signals, and the long-term impact of each force may depend on relative timing and magnitude. We use a phylogenetic analysis to infer the history of blue belly patches of Sceloporus lizards, and a detailed spectrophotometric analysis of four species to explore the specific forces shaping evolutionary change. We find that the ancestor of Sceloporus had blue patches. We then focus on four species; the first evolutionary shift (captured by comparison of S. merriami and S. siniferus ) represents an ancient loss of the belly patch by S. siniferus , and the second evolutionary shift, bounded by S. undulatus and S. virgatus , represents a more recent loss of blue belly patch by S. virgatus . Conspicuousness measurements suggest that the species with the recent loss ( S. virgatus ) is the least conspicuous. Results for two other species ( S. siniferus and S. merriami ) suggest that over longer periods of evolutionary time, new signal colours have arisen which minimize absolute contrast with the habitat while maximizing conspicuousness to a lizard receiver. Specifically, males of the species representing an ancient loss of blue patch ( S. siniferus ) are more conspicuous than are females in the UV, whereas S. merriami males have evolved a green element that makes their belly patches highly sexually dimorphic but no more conspicuous than the white bellies of S. merriami females. Thus, our results suggest that natural selection may act more immediately to reduce conspicuousness, whereas sexual selection may have a more complex impact on communicative signals through the introduction of new colours.

Androgen-induced plasticity at a “vocal” neuromuscular synapse

1994 ◽  
Vol 52 ◽  
pp. 32-33
Author(s):  
Darcy B. Kelley ◽  
Martha L. Tobias ◽  
Mark Ellisman
Keyword(s):  
Xenopus Laevis ◽  
Motor Neurons ◽  
Sexual Differentiation ◽  
Molecular Basis ◽  
Neuromuscular Synapse ◽  
Sexually Dimorphic ◽  
Intracellular Protein ◽  
Developmental Program ◽  
Androgen Action ◽  
Clawed Frog

Brain and muscle are sexually differentiated tissues in which masculinization is controlled by the secretion of androgens from the testes. Sensitivity to androgen is conferred by the expression of an intracellular protein, the androgen receptor. A central problem of sexual differentiation is thus to understand the cellular and molecular basis of androgen action. We do not understand how hormone occupancy of a receptor translates into an alteration in the developmental program of the target cell. Our studies on sexual differentiation of brain and muscle in Xenopus laevis are designed to explore the molecular basis of androgen induced sexual differentiation by examining how this hormone controls the masculinization of brain and muscle targets.Our approach to this problem has focused on a highly androgen sensitive, sexually dimorphic neuromuscular system: laryngeal muscles and motor neurons of the clawed frog, Xenopus laevis. We have been studying sex differences at a synapse, the laryngeal neuromuscular junction, which mediates sexually dimorphic vocal behavior in Xenopus laevis frogs.

The Relationship of Digit Ratio (2D:4D) and Gender-Role Orientation in Four National Samples

2007 ◽  
Vol 28 (2) ◽  
pp. 78-87 ◽  
Author(s):  
Stefan J. Troche ◽  
Nina Weber ◽  
Karina Hennigs ◽  
Carl-René Andresen ◽  
Thomas H. Rammsayer
Keyword(s):  
Gender Role ◽  
Sex Role ◽  
Role Orientation ◽  
Sexually Dimorphic ◽  
Gender Role Orientation ◽  
Left Hand ◽  
Fourth Finger ◽  
And Gender ◽  
Relationship Of ◽  
The Relationship

Abstract. The ratio of second to fourth finger length (2D:4D ratio) is sexually dimorphic with women having higher 2D:4D ratio than men. Recent studies on the relationship between 2D:4D ratio and gender-role orientation yielded rather inconsistent results. The present study examines the moderating influence of nationality on the relationship between 2D:4D ratio and gender-role orientation, as assessed with the Bem Sex-Role Inventory, as a possible explanation for these inconsistencies. Participants were 176 female and 171 male university students from Germany, Italy, Spain, and Sweden ranging in age from 19 to 32 years. Left-hand 2D:4D ratio was significantly lower in men than in women across all nationalities. Right-hand 2D:4D ratio differed only between Swedish males and females indicating that nationality might effectively moderate the sexual dimorphism of 2D:4D ratio. In none of the examined nationalities was a reliable relationship between 2D:4D ratio and gender-role orientation obtained. Thus, the assumption of nationality-related between-population differences does not seem to account for the inconsistent results on the relationship between 2D:4D ratio and gender-role orientation.

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