Still Waiting for Mister Right? Asymmetric Information, Abortion Laws and the Timing of Marriage

Previous studies have suggested that more liberal abortion laws should lead to a decrease in marriage rates among young women as 'shotgun weddings' are no longer necessary. Empirical evidence from the United States lends support to that hypothesis. This paper presents an alternative theory of abortion access and marriage based on asymmetric information, which suggests that more liberal abortion laws may actually promote young marriage. An empirical examination of marriage data from Eastern Europe shows that countries that liberalized their abortion laws saw an increase in marriage rates among non-teenage women.abortion, marriage asymmetric information

Developmental dynamics of cone photoreceptors in the eel

Background: Many fish alter their expressed visual pigments during development. The number of retinal opsins expressed and their type is normally related to the environment in which they live. Eels are known to change the expression of their rod opsins as they mature, but might they also change the expression of their cone opsins?Results: The Rh2 and Sws2 opsin sequences from the European Eel were isolated, sequenced and expressed in vitro for an accurate measurement of their lambda(max) values. In situ hybridisation revealed that glass eels express only rh2 opsin in their cone photoreceptors, while larger yellow eels continue to express rh2 opsin in the majority of their cones, but also have <5% of cones which express sws2 opsin. Silver eels showed the same expression pattern as the larger yellow eels. This observation was confirmed by qPCR (quantitative polymerase chain reaction).Conclusions: Larger yellow and silver European eels express two different cone opsins, rh2 and sws2. This work demonstrates that only the Rh2 cone opsin is present in younger fish (smaller yellow and glass), the sws2 opsin being expressed additionally only by older fish and only in <5% of cone cells

Isolation of chick retina cones and study of their diversity based on oil droplet colour and nucleus position

The chick retina has four morphological cone types that differ not only in shape, but also in the visual pigment in the outer segment, in the colour of the oil droplet in the inner segment and in synaptic connectivity. Neither the type of droplet nor the visual pigment has been definitively established for the four cone types. The main aim of the present work has been the isolation of entire live photoreceptors in order to study the oil droplet colour in each cone type and to quantify each type. We have improved an earlier retinal cell isolation method and obtained large numbers of entire cones. Principal cones (27% of the cones) possess a yellow or colourless droplet. Accessory cones (27% of the cones) all contain a small pale green droplet. Straight cones (44% of the cones) have a red, orange, yellow, or colourless droplet. Oblique cones (1.66% of the cones) all have a colourless droplet. We have found that straight cones with a red, orange, or yellow droplet differ in terms of the position of the nucleus and their percentage and conclude that they are distributed in three rows in the outer nuclear layer (ONL) of the central retina. Our study of 4,6-diamidino-2-phenylindole-stained retinal sections has revealed three rows of nuclei instead of the two currently thought to form the ONL. Together, our results show a larger cone diversity than previously known, suggest a larger functional diversity and provide an efficient method for isolating entire chick photoreceptors

Di-μ-thio­cyanato-bis­[bis­(tri-p-tolyl­phosphine)silver(I)] 0.35-hydrate

In the binuclear centrosymmetric title compound, [Ag2(NCS)2(C21H21P)4]·0.35H2O, a pseudo-polymorph of [Ag2(NCS)2(C21H21P)4]·2CH3CN, the Ag atom is coordinated by two phosphine ligands and two bridging thio­cyanate ligands in a distorted tetra­hedral configuration. The crystal structure exhibits inter­molecular C—H⋯π inter­actions

Bird pollination of Canary Island endemic plants

The Canary Islands are home to a guild of endemic, threatened bird pollinated plants. Previous work has suggested that these plants evolved floral traits as adaptations to pollination by flower specialist sunbirds, but subsequently they appear to be have co-opted passerine birds as sub-optimal pollinators. To test this idea we carried out a quantitative study of the pollination biology of three of the bird pollinated plants, Canarina canariensis (Campanulaceae), Isoplexis canariensis (Veronicaceae) and Lotus berthelotii (Fabaceae), on the island of Tenerife. Using colour vision models, we predicted the detectability of flowers to bird and bee pollinators. We measured pollinator visitation rates, nectar standing crops, as well as seed set and pollen removal and deposition. These data showed that the plants are effectively pollinated by non-flower specialist passerine birds that only occasionally visit flowers. The large nectar standing crops and extended flower longevities (&#x3e;10days) of Canarina and Isoplexis suggests that they have evolved bird pollination system that effectively exploits these low frequency non-specialist pollen vectors and is in no way suboptimal. Seed set in two of the three species was high, and was significantly reduced or zero in flowers where pollinator access was restricted. In L. berthelotii, however, no fruit set was observed, probably because the plants were self incompatible horticultural clones of a single genet. We also show that, while all three species are easily detectable for birds, the orange Canarina and the red Lotus (but less so the yellow-orange Isoplexis) should be difficult to detect for insect pollinators without specialised red receptors, such as bumblebees. Contrary to expectations if we accept that the flowers are primarily adapted to sunbird pollination, the chiffchaff (Phylloscopus canariensis) was an effective pollinator of these species

RT-qPCR reveals opsin gene upregulation associated with age and sex in guppies (Poecilia reticulata) - a species with color-based sexual selection and 11 visual-opsin genes

<p>Abstract</p> <p>Background</p> <p>PCR-based surveys have shown that guppies (<it>Poecilia reticulata</it>) have an unusually large visual-opsin gene repertoire. This has led to speculation that opsin duplication and divergence has enhanced the evolution of elaborate male coloration because it improves spectral sensitivity and/or discrimination in females. However, this conjecture on evolutionary connections between opsin repertoire, vision, mate choice, and male coloration was generated with little data on gene expression. Here, we used RT-qPCR to survey visual-opsin gene expression in the eyes of males, females, and juveniles in order to further understand color-based sexual selection from the perspective of the visual system.</p> <p>Results</p> <p>Juvenile and adult (male and female) guppies express 10 visual opsins at varying levels in the eye. Two opsin genes in juveniles, <it>SWS2B </it>and <it>RH2-2</it>, accounted for >85% of all visual-opsin transcripts in the eye, excluding <it>RH1</it>. This relative abundance (RA) value dropped to about 65% in adults, as <it>LWS-A180 </it>expression increased from approximately 3% to 20% RA. The juvenile-to-female transition also showed <it>LWS-S180 </it>upregulation from about 1.5% to 7% RA. Finally, we found that expression in guppies' <it>SWS2-LWS </it>gene cluster is negatively correlated with distance from a candidate locus control region (LCR).</p> <p>Conclusions</p> <p>Selective pressures influencing visual-opsin gene expression appear to differ among age and sex. <it>LWS </it>upregulation in females is implicated in augmenting spectral discrimination of male coloration and courtship displays. In males, enhanced discrimination of carotenoid-rich food and possibly rival males are strong candidate selective pressures driving <it>LWS </it>upregulation. These developmental changes in expression suggest that adults possess better wavelength discrimination than juveniles. Opsin expression within the <it>SWS2-LWS </it>gene cluster appears to be regulated, in part, by a common LCR. Finally, by comparing our RT-qPCR data to MSP data, we were able to propose the first opsin-to-λ_maxassignments for all photoreceptor types in the cone mosaic.</p

Surface science of soft scorpionates

The chemisorption of the soft scorpionate Li[PhTmMe] onto silver and gold surfaces is reported. Surface enhanced Raman spectroscopy in combination with the Raman analysis of suitable structural models, namely, [Cu(κ3-S,S,S-PhTmMe)(PCy3)], [Ag(κ3-S,S,S-PhTmMe)(PCy3)], [Ag(κ2-S,S-PhTmMe)(PEt3)], and [Au(κ1-S-PhTmMe)(PCy3)], are employed to identify the manner in which this potentially tridentate ligand binds to these surfaces. On colloidal silver surface-enhanced Raman spectroscopy (SERS) spectra are consistent with PhTmMe binding in a didentate fashion to the surface, holding the aryl group in close proximity to the surface. In contrast, on gold colloid, we observe that the species prefers a monodentate coordination in which the aryl group is not in close proximity to the surface

Pattern of the Divergence of Olfactory Receptor Genes during Tetrapod Evolution

The olfactory receptor (OR) multigene family is responsible for the sense of smell in vertebrate species. OR genes are scattered widely in our chromosomes and constitute one of the largest gene families in eutherian genomes. Some previous studies revealed that eutherian OR genes diverged mainly during early mammalian evolution. However, the exact period when, and the ecological reason why eutherian ORs strongly diverged has remained unclear. In this study, I performed a strict data mining effort for marsupial opossum OR sequences and bootstrap analyses to estimate the periods of chromosomal migrations and gene duplications of OR genes during tetrapod evolution. The results indicate that chromosomal migrations occurred mainly during early vertebrate evolution before the monotreme-placental split, and that gene duplications occurred mainly during early mammalian evolution between the bird-mammal split and marsupial-placental split, coinciding with the reduction of opsin genes in primitive mammals. It could be thought that the previous chromosomal dispersal allowed the OR genes to subsequently expand easily, and the nocturnal adaptation of early mammals might have triggered the OR gene expansion

Human Wavelength Discrimination of Monochromatic Light Explained by Optimal Wavelength Decoding of Light of Unknown Intensity

We show that human ability to discriminate the wavelength of monochromatic light can be understood as maximum likelihood decoding of the cone absorptions, with a signal processing efficiency that is independent of the wavelength. This work is built on the framework of ideal observer analysis of visual discrimination used in many previous works. A distinctive aspect of our work is that we highlight a perceptual confound that observers should confuse a change in input light wavelength with a change in input intensity. Hence a simple ideal observer model which assumes that an observer has a full knowledge of input intensity should over-estimate human ability in discriminating wavelengths of two inputs of unequal intensity. This confound also makes it difficult to consistently measure human ability in wavelength discrimination by asking observers to distinguish two input colors while matching their brightness. We argue that the best experimental method for reliable measurement of discrimination thresholds is the one of Pokorny and Smith, in which observers only need to distinguish two inputs, regardless of whether they differ in hue or brightness. We mathematically formulate wavelength discrimination under this wavelength-intensity confound and show a good agreement between our theoretical prediction and the behavioral data. Our analysis explains why the discrimination threshold varies with the input wavelength, and shows how sensitively the threshold depends on the relative densities of the three types of cones in the retina (and in particular predict discriminations in dichromats). Our mathematical formulation and solution can be applied to general problems of sensory discrimination when there is a perceptual confound from other sensory feature dimensions