Eye Size Research Articles

A taxonomic revision and a review of the biology of the North American seed-harvester ant genus Veromessor (Hymenoptera: Formicidae: Myrmicinae).

This paper provides a taxonomic revision and a review of the biology for the 10 species of North American seed-harvester ants in the genus Veromessor. Two new synonomies are proposed: V. julianus subsp. clarior W.M. Wheeler and Creighton 1934 new synonym and V. julianus subsp. manni W.M. Wheeler and Creighton 1934 new synonym are synonomized under V. julianus (Pergande, 1894). One new species is described: V. pseudolariversi new species (worker, queen, male), as a result of splitting V. lariversi Smith into two species based on morphological and genetic differences. We also diagnose previously undescribed queens and males for the following species: V. andrei (male), V. chamberlini (queen, male), V. chicoensis (queen, male), V. julianus (queen, male), and V. stoddardi (queen, male). Information on biology of each species is summarized, along with distribution maps and keys to workers, queens, and males. We then discuss the biology for species of Veromessor, focusing on several morphological and ecological traits that display strong variation across the relatively low number of species (10) in the genus. Morphological traits include degree of psammophore development, propodeal spine length, eye size and structure, and worker polymorphism and worker body size, while ecological traits include colony size and foraging method, seasonality of mating flights, mating frequency, and queen size and colony founding strategy.

The Basic VRS-Effect Study: Clinical Trial Outcomes and Cost-Effectiveness of Low Vision Rehabilitation in Portugal.

The aim of this study was twofold: (1) to investigate the clinical impact of vision rehabilitation in patients with vision impairment and (2) to investigate the cost-effectiveness of a basic vision rehabilitation service in Portugal. The trial recruited patients diagnosed with age-related macular degeneration or diabetic retinopathy (DR) and visual acuity in the range 0.4-1.0logMAR in the better-seeing eye. Participants were randomised to one of the study arms consisting of immediate intervention and delayed intervention. The intervention included: new refractive correction, optical reading aids, in-office training and advice about modifications at home. Visual ability, health-related quality of life and costs were measured. Economic analysis was performed to evaluate whether the intervention was cost-effective. The trial compared the outcomes 12 weeks after the start in both arms. Of the 46 participants, 34 (74%) were diagnosed with DR, 25 (54%) were female, and mean age was 70.08 years (SD = 8.74). In the immediate intervention arm visual ability increased a mean of 0.523 logits (SE = 0.11) (p < 0.001). Changes in the delayed intervention arm were not statistically significant (p = 0.95). Acuity in the better-seeing eye, near acuity and critical print size also improved during the study. The mean cost of the intervention was €118.79 (SD = 24.37). The incremental cost-effectiveness ratio using the EQ-5D-5L was 30,421€/QALY and 1186€/QALY when using near acuity. The current study gives evidence of positive clinical impact of a basic vision rehabilitation intervention and shows that a basic vision rehabilitation service is cost-effective. These findings are important to clinical and rehabilitation practices and for planning vision rehabilitation services. Retrospectively registered, 21/01/2019. ISRCTN10894889, https://www.isrctn.com/ISRCTN10894889.

Adverse effects of thyroid-hormone-disrupting chemicals 6-propyl-2-thiouracil and tetrabromobisphenol A on Japanese medaka (Oryzias latipes)

Thyroid-hormone-disrupting chemicals are increasingly attracting attention because of their potential harmful effects on animal health, including on fishes. Here, we investigated the effects of exposure to the thyroid-hormone-disrupting chemicals 6-propyl-2-thiouracil (PTU) and tetrabromobisphenol A (TBBPA) on swim bladder inflation, eye development, growth, swimming performance, and the expression of thyroid-related genes in Japanese medaka (Oryzias latipes). PTU exposure resulted in reductions in eye size, growth, and swim bladder inflation, and these effects led to poorer swimming performance. These phenotypic effects were accompanied by increased expression of the thyroid-stimulating hormone subunit beta (tshβ) paralog tshβ-like, but there were no significant changes in expression for tshβ, deiodinase 1 (dio1), deiodinase 2 (dio2), and thyroid hormone receptor alpha (trα) and beta (trβ). For PTU exposure, we identified the key event (swim bladder inflation reduction) and an adverse outcome (swimming performance reduction). No significant effects from TBBPA exposure were seen on swim bladder inflation, eye development, growth, or swimming performance. However, expression of tshβ-like and tshβ (significantly enhanced) and trα and trβ (significantly reduced) were affected by TBBPA exposure albeit not in dose-dependent manners. There were no effects of TBBPA on the expression of dio1 and dio2. We thus show that the two thyroid-hormone-disrupting chemicals PTU and TBBPA differ in their effect profiles with comparable effects on the studied phenotypes and thyroid-related gene expression to those reported in zebrafish.

Leocrates ernstehlersi n. sp. (Polychaeta: Hesionidae), a new species from Juan Fernández Archipelago, Chile

The genus Leocrates is currently made up of 11 nominal species, of which Leocrates chinensis Kinberg, 1866 is the type species. Kinberg's original description is brief, and the diagnostic morphological characters are poorly defined. Therefore, numerous subsequent records in different world regions have been considered doubtful. Numerous specimens of Leocrates collected by SCUBA diving in various locations of Robinson Crusoe Island (33°37'S, 78°51'W) in the Juan Fernández Archipelago, between 4 and 10 m depth were examined and determined as a new species herein named Leocrates ernstehlersi n. sp. It is characterized by the size of anterior and posterior eyes, the median chaetigers with scarce notochaetae and neurochaetae per bundle; neurochaetal blades are 4-14 times longer than wide and neuracicular lobes slightly longer than wide. A key to identifying species of Leocrates having large anterior eyes and anterior eyes/prostomial width ratio between 1/4 to 1/8 is also included.

Biogeography and eye size evolution of the ogre-faced spiders

Net-casting spiders (Deinopidae) comprise a charismatic family with an enigmatic evolutionary history. There are 67 described species of deinopids, placed among three genera, Deinopis, Menneus, and Asianopis, that are distributed globally throughout the tropics and subtropics. Deinopis and Asianopis, the ogre-faced spiders, are best known for their giant light-capturing posterior median eyes (PME), whereas Menneus does not have enlarged PMEs. Molecular phylogenetic studies have revealed discordance between morphology and molecular data. We employed a character-rich ultra-conserved element (UCE) dataset and a taxon-rich cytochrome-oxidase I (COI) dataset to reconstruct a genus-level phylogeny of Deinopidae, aiming to investigate the group’s historical biogeography, and examine PME size evolution. Although the phylogenetic results support the monophyly of Menneus and the single reduction of PME size in deinopids, these data also show that Deinopis is not monophyletic. Consequently, we formally transfer 24 Deinopis species to Asianopis; the transfers comprise all of the African, Australian, South Pacific, and a subset of Central American and Mexican species. Following the divergence of Eastern and Western deinopids in the Cretaceous, Deinopis/Asianopis dispersed from Africa, through Asia and into Australia with its biogeographic history reflecting separation of Western Gondwana as well as long-distance dispersal events.

Sensory evolution in a cavefish radiation: patterns of neuromast distribution and associated behaviour in Sinocyclocheilus (Cypriniformes: Cyprinidae).

The genus Sinocyclocheilus, comprising a large radiation of freshwater cavefishes, are well known for their presence of regressive features (e.g. variable eye reduction). Fewer constructive features are known, such as the expansion of the lateral line system (LLS), which is involved in detecting water movements. The precise relationship between LLS expansion and cave adaptation is not well understood. Here, we examine morphology and LLS-mediated behaviour in Sinocyclocheilus species characterized by broad variation in eye size, habitat and geographical distribution. Using live-staining techniques and automated behavioural analyses, we examined 26 Sinocyclocheilus species and quantified neuromast organ number, density and asymmetry within a phylogenetic context. We then examined how these morphological features may relate to wall-following, an established cave-associated behaviour mediated by the lateral line. We show that most species demonstrated laterality (i.e. asymmetry) in neuromast organs on the head, often biased to the right. We also found that wall-following behaviour was distinctive, particularly among eyeless species. Patterns of variation in LLS appear to correlate with the degree of eye loss, as well as geographical distribution. This work reveals that constructive LLS evolution is convergent across distant cavefish taxa and may mediate asymmetric behavioural features that enable survival in stark subterranean microenvironments.

Scleral PERK and ATF6 as targets of myopic axial elongation of mouse eyes

Axial length is the primary determinant of eye size, and it is elongated in myopia. However, the underlying mechanism of the onset and progression of axial elongation remain unclear. Here, we show that endoplasmic reticulum (ER) stress in sclera is an essential regulator of axial elongation in myopia development through activation of both PERK and ATF6 axis followed by scleral collagen remodeling. Mice with lens-induced myopia (LIM) showed ER stress in sclera. Pharmacological interventions for ER stress could induce or inhibit myopia progression. LIM activated all IRE1, PERK and ATF6 axis, and pharmacological inhibition of both PERK and ATF6 suppressed myopia progression, which was confirmed by knocking down above two genes via CRISPR/Cas9 system. LIM dramatically changed the expression of scleral collagen genes responsible for ER stress. Furthermore, collagen fiber thinning and expression of dysregulated collagens in LIM were ameliorated by 4-PBA administration. We demonstrate that scleral ER stress and PERK/ATF6 pathway controls axial elongation during the myopia development in vivo model and 4-PBA eye drop is promising drug for myopia suppression/treatment.

The subfamily Pachyotominae in Mexico (Collembola: Isotomidae) with description of a new Pachyotoma species

Pachyotoma primamexicana sp. nov, from Popocatépetl, Mexico is described; it is similar to Pachyotoma alpa (Christiansen & Bellinger, 1980) and P. muskegis (Guthrier, 1903). It can be distinguished from all other the members of the genus by the small size of PAO (about half the size of closest eye) and the formula (2,3,3) of the slightly capitate tenent hairs. An identification key for Nearctic Pachyotominae and a table with diagnostic morphological characters to the Nearctic species of the genus with integument clearly granulated is given. Three new records of species from Mexico are listed: Pachyotoma crassicauda (Tullberg, 1871), Coloburella octogenaria (Mills & Schmidt, 1957) and Bonetrura boneti (Yosii, 1962). A discussion on the distribution of the subfamily Pachyotominae and some notes on the biogeography of the subfamily are provided.

Genomic insight into the nocturnal adaptation of the black-crowned night heron (Nycticorax nycticorax)

BackgroundThe black-crowned night heron (Nycticorax nycticorax) is an ardeid bird successfully adapted to the nocturnal environment. Previous studies had indicated that the eyes of the night herons have evolved several specialized morphological traits favoring nocturnal vision. However, the molecular mechanisms of the nocturnal vision adaptation of night herons remained inattentions. In this study, the whole genome of N. nycticorax was sequenced and comparative analyses were performed on the vision-related and olfactory receptor (OR) genes to understand the molecular mechanisms of the visual and olfactory adaptation of night herons.ResultsThe results indicated that a number of vision genes were under positive or relaxed selection in N. nycticorax, whereas a number of other vision genes were under relaxed or intensified selection in the boat-billed heron (Cochlearius cochlearius), which suggested that the two species adapt to nocturnality with different genetic mechanisms. The different selections acting on vision genes are probably associated with the enlargement of eye size and the enhancement of visual sensitivity in night herons. The analyses on olfactory receptor (OR) genes indicated that the total number of OR genes in the genomes of N. nycticorax and C. cochlearius were about half those in the little egret (Egretta garzetta), whereas the diversity of their OR genes was not remarkably different. Additionally, the number of expressed OR genes in the transcriptomes of N. nycticorax was also fewer than that in E. garzetta. These results suggest a reduced olfactory capability in night herons compared with E. garzetta.ConclusionsOur results provided evidence that several vision genes of the night herons were subjected to different natural selections, which can contribute to a better understanding of the genetic mechanisms of visual adaptions of the night heron. In addition, the finding of the reduced number of total and expressed OR genes in night herons may reflect a trade-off between olfaction and vision.

Fast-growing growth hormone transgenic coho salmon (Oncorhynchus kisutch) show a lower incidence of vaterite deposition and malformations in sagittal otoliths.

In fish otoliths, CaCO3 normally precipitates as aragonite, and more rarely as vaterite or calcite. A higher incidence of vaterite deposition in otoliths from aquaculture-reared fish has been reported and it is thought that high growth rates under farming conditions might promote its deposition. To test this hypothesis, otoliths from growth hormone (GH) transgenic coho salmon and non-transgenic fish of matching size were compared. Once morphometric parameters were normalized by animal length, we found that transgenic fish otoliths were smaller (-24%, -19%, -20% and -30% for length, width, perimeter and area, respectively; P<0.001) and rounder (-12%, +13.5%, +15% and -15.5% in circularity, form factor, roundness and ellipticity; P<0.001) than otoliths from non-transgenic fish of matching size. Interestingly, transgenic fish had smaller eyes (-30% eye diameter) and showed a strong correlation between eye and otolith size. We also found that the percentage of otoliths showing vaterite deposition was significantly smaller in transgenic fish (21-28%) than in non-transgenic fish (69%; P<0.001). Likewise, the area affected by vaterite deposition within individual otoliths was reduced in transgenic fish (21-26%) compared with non-transgenic fish (42.5%; P<0.001). Our results suggest that high growth rates per se are not sufficient to cause vaterite deposition in all cases, and that GH overexpression might have a protective role against vaterite deposition, a hypothesis that needs further investigation.

Thyroid hormone disruption by bis-(2-ethylhexyl) phthalate (DEHP) and bis-(2-ethylhexyl) adipate (DEHA) in Japanese medaka Oryzias latipes

Pollution of water bodies with plasticizers is a serious environmental problem worldwide. In this study, we investigated the effects of plasticizers bis-(2-ethylhexyl) phthalate (DEHP) and bis-(2-ethylhexyl) adipate (DEHA) in Japanese medaka (Oryzias latipes). DEHP significantly increased the expression of all the genes tested: thyroid stimulating hormone beta subunit (tshβ-like), tshβ, deiodinase 1 (dio1), deiodinase 2 (dio2), and thyroid hormone receptor alpha (trα) and beta (trβ). However, DEHA only significantly increased tshβ at 7.4 µg/L but significantly decreased dio2 expression at 25.8, 111.1, and 412.6 4 µg/L, while other genes were not significantly affected. Both chemicals reduced eye size and total body length, but did not affect embryo development, hatching time and rate, and swimming performance. DEHA alone affected swim bladder inflation and not DEHP. This is the first report that not only DEHP but also DEHA disrupt thyroid hormone activity in fish. DEHP contamination (13.2 μg/L) was detected in tap water from Kobe, Japan; thus, tap water itself may disrupt thyroid hormone activity in Japanese medaka. Importantly, the effective concentration of DEHP for thyroid hormone–related gene expression and growth was close to or lower than DEHP concentrations reported in surface water elsewhere, indicating that DEHP contamination is a serious aquatic pollution.

In vivo depth-resolved morphological analysis of compound eye dioptric system using full-field optical coherence tomography

Presence of a range of insects with different shape, size, and structural morphology of compound eye reveals the diverse pathways adopted by the nature striving to develop a flawless vision under given set of constraints. Exploration of various compound eyes allows researchers to understand better the various stages of visual system development in insects. By far, the most frequently used techniques for the investigation of structural morphology of a compound eye are scanning electron microscopy, transmission electron microscopy, microcomputed tomography, and histology. The nature of implementation of these techniques restricts in vivo studies, and also the requirements for a complicated and costly setup put limitations on its availability at small research facilities. Despite the widespread acceptance of the optical coherence tomography (OCT) as a standard tool for the various ophthalmological investigations, reports on compound eye study using OCT are uncommon. We demonstrate the application of a full-field OCT (FF-OCT) system for depth-resolved structural imaging and morphological analysis of the compound eye dioptric system. We report the application of a time-domain FF-OCT system for depth-resolved en face and three dimensional in vivo imaging of dragonfly’s prominent compound eye with resolutions of 2.8 and 7.2 μm in lateral and axial directions, respectively. The study shows the effectiveness of the FF-OCT approach for label-free and rapid structural morphology analysis of compound eyes. The results have been compared with the histology results reported in literature.

Diversity and evolution of amphibian pupil shapes

Abstract Pupil constriction has important functional consequences for animal vision, yet the evolutionary mechanisms underlying diverse pupil sizes and shapes are poorly understood. We aimed to quantify the diversity and evolution of pupil shapes among amphibians and to test for potential correlations to ecology based on functional hypotheses. Using photographs, we surveyed pupil shape across adults of 1294 amphibian species, 74 families and three orders, and additionally for larval stages for all families of frogs and salamanders with a biphasic ontogeny. For amphibians with a biphasic life history, pupil shape changed in many species that occupy distinct habitats before and after metamorphosis. In addition, non-elongated (circular or diamond) constricted pupils were associated with species inhabiting aquatic or underground environments, and elongated pupils (with vertical or horizontal long axes) were more common in species with larger absolute eye sizes. We propose that amphibians provide a valuable group within which to explore the anatomical, physiological, optical and ecological mechanisms underlying the evolution of pupil shape.

A Compact Single-Ended Inverter-Based Transceiver With Swing Improvement for Short-Reach Links

This paper presents a compact single-ended inverter-based transceiver with swing improvement for short-reach links. The low output impedance of the transmitter enlarges the output swing and the eye size to overcome large single-ended noise while relaxed impedance matching provides good signal integrity. For good area efficiency, the proposed transmitter utilizes an inverter driver which is much smaller than the conventional source-series termination driver and thus occupies only <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$42.5 ~\mu \text{m}^{2}$ </tex-math></inline-formula> . By taking the advantage of a large signal swing, the receiver consists of only four slicers and latches to minimize area overhead and to simplify the design. The transceiver was fabricated in 28-nm CMOS technology and tested at supply voltage of 1.13 V. The transmitter achieved a large output swing of 850 mV, which is 50.4 % larger than the conventional source-series termination transmitter. At the far-end of a channel consisting of a 1 m SMA cable and a 17 mm printed circuit board trace, the transmitter achieved eye openings of 440 mV and 234 mV at 16 Gb/s (−2.7 dB) and 20 Gb/s (−8 dB), respectively. Even with a large switching noise of 100 mV, the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in-situ</i> eye at the receiver was measured 114 mV with 7.4 dB loss.

Environmentally relevant concentrations of F–53B induce eye development disorders-mediated locomotor behavior in zebrafish larvae

The perfluorooctane sulfonate alternative, F–53B, induces multiple physiological defects but whether it can disrupt eye development is unknown. We exposed zebrafish to F–53B at four different concentrations (0, 0.15, 1.5, and 15 μg/L) for 120 h post-fertilization (hpf). Locomotor behavior, neurotransmitters content, histopathological alterations, morphological changes, cell apoptosis, and retinoic acid signaling were studied. Histology and morphological analyses showed that F–53B induced pathological changes in lens and retina of larvae and eye size were significantly reduced as compared to control. Acridine orange (AO) staining revealed a dose-dependent increase in early apoptosis, accompanied by upregulation of p53, casp-9 and casp-3 genes. Genes related to retinoic acid signaling (aldh1a2), lens developmental (cryaa, crybb, crygn, and mipa) and retinal development (pax6, rx1, gant1, rho, opn1sw and opn1lw) were significantly downregulated. In addition, behavioral responses (swimming speed) were significantly increased, while no significant changes in the neurotransmitters (dopamine and acetylcholine) level were observed. Therefore, in this study we observed that exposure to F–53B inflicted histological and morphological changes in zebrafish larvae eye, induced visual motor dysfunctions, perturbed retinoid signaling and retinal development and ultimately triggering apoptosis.

Correlated expression of phenotypic and extended phenotypic traits across stingless bee species: worker eye morphology, foraging behaviour, and nest entrance architecture

Stingless bees are the most species-rich group of eusocial bees and show great diversity in behaviour, ecology, nest architecture, colony size, and worker morphology. How this variation relates to varying selection pressures and constraints is not well understood. Variation can be caused by selection acting on behavioural or morphological traits, both alone and in correlation across traits. Here we tested whether behavioural and morphological traits important for foraging and defence are linked to nest-entrance architecture, an extended phenotype relevant to both foraging and nest defence. Using 23 species we investigated whether eye size, nest entrance size, landing behaviour and foraging method show cross-species correlations. A phylogenetically-controlled comparative analysis revealed that species with relatively smaller eyes build relatively larger entrances, which in turn are associated with faster landing approaches and fewer landing errors by foragers, both of which could reduce predation risk. Concerning foraging, mass-recruiting species have c. 10-times larger entrance holes than species with a solitary foraging strategy. Larger entrances could help species with mass recruitment to rapidly increase forager traffic or mount a strong defensive response when under attack. Our results show that studying correlations among different traits helps understand phenotypic diversity in species rich groups.

Quantification and comparison of teleost scleral cartilage development and growth.

The ocular skeleton is composed of the scleral cartilage and the scleral ossicles. Teleost scleral cartilage is composed of a single layer of chondrocytes embedded in the sclera of the eye. The teleost scleral cartilage ring can vary in depth across teleost families and species, from a narrow ring a few cells wide to a deeper ring that resembles a cup and surrounds the entire sclera. However, very little research has been conducted on the development and morphology of teleost scleral cartilage. Thus, this study aims to characterize the development of the scleral cartilage in the zebrafish and Mexican tetra, with respect to the timing of emergence, depth throughout development, and positioning within the eye. We hypothesized that the scleral cartilage would first emerge in the scleral tissue closely abutting the ora serrata, and that growth would proceed in an anterior-to-posterior direction, resulting in differences in scleral cartilage depth between different fish species. We found that the scleral cartilage ring does not develop uniformly along its circumference, and that its relationship to the ora serrata varies between the rostral and caudal regions. Furthermore, distinct differences in the growth trajectory of the scleral cartilage indicate that the deep scleral cartilage of the Pachón cavefish is the result of both decreased eye size and prolonged cartilage growth. A significant difference in the size of the scleral chondrocytes was also noted. Overall, this study provides the first characterization of early scleral cartilage development in teleost fish and indicates that some aspects of scleral cartilage development and morphology are highly conserved while others are not.

Postnatal eye size in mice is controlled by SREBP2-mediated transcriptional repression of Lrp2 and Bmp2.

ABSTRACTEye size is a key parameter of visual function, but the precise mechanisms of eye size control remain poorly understood. Here, we discovered that the lipogenic transcription factor sterol regulatory element-binding protein 2 (SREBP2) has an unanticipated function in the retinal pigment epithelium (RPE) to promote eye size in postnatal mice. SREBP2 transcriptionally represses low density lipoprotein receptor-related protein 2 (Lrp2), which has been shown to restrict eye overgrowth. Bone morphogenetic protein 2 (BMP2) is the downstream effector of Srebp2 and Lrp2, and Bmp2 is suppressed by SREBP2 transcriptionally but activated by Lrp2. During postnatal development, SREBP2 protein expression in the RPE decreases whereas that of Lrp2 and Bmp2 increases as the eye growth rate reduces. Bmp2 is the key determinant of eye size such that its level in mouse RPE inversely correlates with eye size. Notably, RPE-specific Bmp2 overexpression by adeno-associated virus effectively prevents the phenotypes caused by Lrp2 knock out. Together, our study shows that rapid postnatal eye size increase is governed by an RPE-derived signaling pathway, which consists of both positive and negative regulators of eye growth.

Multiple Invagination Patterns and Synaptic Efficacy in Primate and Mouse Rod Synaptic Terminals.

PurposeOptical retina images are scaled based on eye size, which results in a linear scale ratio of 10:1 for human versus mouse and 7:1 for macaque monkey versus mouse. We examined how this scale difference correlates with the structural configuration of synaptic wiring in the rod spherule (RS) between macaque and mouse retinas compared with human data.MethodsRod bipolar cell (BC) dendrites and horizontal cell (HC) axonal processes, which invaginate the RS to form synaptic ribbon-associated triads, were examined by serial section transmission electron microscopy.ResultsThe number of rod BC invaginating dendrites ranged 1∼4 in the macaque RS but only 1∼2 in the mouse. Approximately 40% of those dendrites bifurcated into two central elements in the macaque, but 3% of those dendrites did in the mouse. Both factors gave rise to 10 invagination patterns of BC and HC neurites in the macaque RS but only two in the mouse. Five morphological parameters: the lengths of arciform densities and ribbons, the area of the BC–RS contact, and the surface areas of BC and HC invaginating neurites, were all independent of the invagination patterns in the macaque RS. However, those parameters were significantly greater in the macaque than in the mouse by ratios of 1.5∼1.8.ConclusionsThe primate RS provides a more expansive BC–RS interface associated with the longer arciform density and more branched invaginating neurites of BCs and HCs than the mouse RS. The resulting greater synaptic contact area may contribute to more efficient signal transfer.

Large irides enhance the facial attractiveness of Japanese and Chinese women

Since large eyes are often perceived to enhance facial attractiveness, many individuals are motivated to change their eyes' appearance. Colored contact lenses are often used by young women to darken the limbal rings of their irides, to increase their facial attractiveness. Among Westerners, wearing contact lenses with limbal rings enhances facial attractiveness; a similar effect might exist for East Asians whose irides are darker; although, the mechanism underlying these preferences in Westerners and East Asians might differ. In this study, we investigated whether larger irides increased the attractiveness of Japanese and Chinese women, and whether this effect was accompanied by changes in perceived friendliness or youthfulness. We manipulated eye size by enlarging only the iris or the whole eye, and asked participants to rate face stimuli in terms of facial attractiveness, friendliness, and youthfulness. We found that larger irides enhanced not only attractiveness but also perceived youthfulness and friendliness, and that there was a significant correlation between attractiveness and friendliness. Further, iris-enlarged faces were perceived as more attractive even when the iris was originally dark, as enlarged dark irides were confused with dilated pupils, which are often perceived as a sign of attraction.