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

Examining 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.

Behaviour-based Pricing in the Green Product Supply Chain

We study the pricing strategies of supply chains of green products under behaviour-based pricing. Considering consumer preferences for green product functional attributes and environmental attributes, we construct a two-stage supply chain. The optimal behaviour pricing of green products is solved, and the effects of green sensitivity and the cost coefficient on the optimal price are analysed. We find that when consumers are less sensitive to the greenness, with the increase in the market share of green products, green product retailers will increase the loyalty price. An increase in greenness sensitivity and a decrease in the greenness cost coefficient will increase the wholesale prices and retail prices of green products. Consumer attention to the greenness and a decrease in the initial market share of green products will be conducive to promoting the greenness and improving the environment. Consumers' emphasis on the greenness of their products will lead to higher profits for the manufacturers and retailers of green products.

Spectral sensitivity of the horse fly Tabanus nigrovittatus (Diptera: Tabanidae)

Spectral sensitivity functions were calculated from electroretinograms recorded from dark-adapted compound eyes of male and female horse flies (Tabanus nigrovittatus Macquart). Females had a broad sensitivity in the violet to green area of the spectrum; their spectral sensitivity was fitted by a theoretical mixture containing 20% of 440-nm and 80% 520-nm rhodopsins. Older females (8–18 days) were 93 times more sensitive than 1-day-old females. Males showed a narrower sensitivity function with more blue and less green sensitivity. Older males (8–18 days) were the most blue-sensitive of all groups; their spectral sensitivity was best fitted by a mixture containing 10% 440-nm, 70% 480-nm, and 20% 520-nm rhodopsins. Older males that were light-adapted to red light showed an apparent decline in the contribution of the 520-nm rhodopsin to overall sensitivity, as expected if this pigment is present in a separate system. The sensitivity function of 1-day-old males was best fitted by a mixture of 55% 480-nm and 45% 520-nm rhodopsins. The absolute sensitivity of both groups of males was close to that of the older females. All flies had substantial ultraviolet sensitivity, averaging 67% of the sensitivity at the longer wavelength maximum. The role of the differing sensitivities in males and females, and in young and old females, is discussed in relation to the visual behavior and sexual dimorphism of horse flies.

Rotgrün-Blindheit bei einem heterogametischen Schein-Mädchen, zugleich ein Beitrag zur Genetik der heterogametischen Pseudofemininität

SUMMARYBy cytological diagnosis of chromosomal sex it has been shown, that about 80 per cent of all cases of gonadal dysgenesis are genetically male. In about 8 per cent of male individuals various defects of red-green sensitivity may be expected. Deuteranopia was observed in a hetero-gametic pseudo-female with testicular dysgenesis. Tests for colour vision should be made in all patients with the syndrome of testicular feminization. From such tests a decision may be expected between sex- linked recessive and autosomal dominant transmission with sex limitation.