Iris Coloration Research Articles

A songbird can detect the eyes of conspecifics under daylight and artificial nighttime lighting

Eyes convey important information about the external and internal worlds of animals. Individuals can follow the gaze of others to learn about the location of salient objects as well as assess eye qualities to evaluate the health, age or other internal states of conspecifics. Because of the increasing prevalence of artificial lighting at night (ALAN), urbanized individuals can potentially garner information from conspecific eyes under both daylight and ALAN. We tested this possibility using a visual modeling approach in which we estimated the maximum distance at which individuals could detect conspecific eyes under daylight and high levels of ALAN. We also estimated the minimum light level at which individuals could detect conspecific eyes. Great-tailed grackles (Quiscalus mexicanus) were used as our study species because they are highly social and are unusual among birds in that they regularly gather at nocturnal roosts in areas with high levels of ALAN. This visual modelling approach revealed that grackles can detect conspecific eyes under both daylight and ALAN, regardless of iris coloration. The grackles could detect conspecific eyes at farther distances in daylight compared to ALAN. Our results highlight the potential importance of lighting conditions in shaping social interactions.

Integrative taxonomy reveals a new species of Leptobrachella (Anura: Megophryidae) from the mountains of northern Thailand.

The genus Leptobrachella is one of the most speciose and taxonomically troubling groups of Asian anurans. Herein, we describe a new species of Leptobrachella from Doi Inthanon, Chiang Mai Province, Thailand based on the integration of morphological, acoustic and molecular data. The new species, Leptobrachella murphyi sp. nov., is morphologically distinguished from its congeners on the basis of body size, dorsal skin texture and coloration, ventral coloration and pattern, degree of webbing and fringing on the fingers and toes, iris coloration in life, pattern of markings on flanks and pattern of body macroglands. It also differs from its phylogenetically close congeners by an uncorrected p-distance of >9.6% for a fragment of 16S rRNA. The advertisement call of the new species consists of 4.54.7 kHz (at 15 C) and without a distinct introductory note. Leptobrachella murphyi sp. nov. likely occurs across the Thanon Thong Chai Range and analyses provide evidence of unknown biodiversity and species composition on Doi (mountain) Inthanon. In addition, the congeneric species L. minima was also confirmed in Doi Inthanon. The coexistence pattern of Leptobrachella in Doi Inthanon deserves further study. As Thailands highest mountain and biodiversity reservoir, the need for further biological exploration is urgent given ongoing habitat loss and degradation.

Two Genomic Loci Control Three Eye Colors in the Domestic Pigeon (Columba livia).

The iris of the eye shows striking color variation across vertebrate species, and may play important roles in crypsis and communication. The domestic pigeon (Columba livia) has three common iris colors, orange, pearl (white), and bull (dark brown), segregating in a single species, thereby providing a unique opportunity to identify the genetic basis of iris coloration. We used comparative genomics and genetic mapping in laboratory crosses to identify two candidate genes that control variation in iris color in domestic pigeons. We identified a nonsense mutation in the solute carrier SLC2A11B that is shared among all pigeons with pearl eye color, and a locus associated with bull eye color that includes EDNRB2, a gene involved in neural crest migration and pigment development. However, bull eye is likely controlled by a heterogeneous collection of alleles across pigeon breeds. We also found that the EDNRB2 region is associated with regionalized plumage depigmentation (piebalding). Our study identifies two candidate genes for eye colors variation, and establishes a genetic link between iris and plumage color, two traits that vary widely in the evolution of birds and other vertebrates.

The genetics and evolution of eye color in domestic pigeons (Columba livia).

The eye color of birds, generally referring to the color of the iris, results from both pigmentation and structural coloration. Avian iris colors exhibit striking interspecific and intraspecific variations that correspond to unique evolutionary and ecological histories. Here, we identified the genetic basis of pearl (white) iris color in domestic pigeons (Columba livia) to explore the largely unknown genetic mechanism underlying the evolution of avian iris coloration. Using a genome-wide association study (GWAS) approach in 92 pigeons, we mapped the pearl iris trait to a 9 kb region containing the facilitative glucose transporter gene SLC2A11B. A nonsense mutation (W49X) leading to a premature stop codon in SLC2A11B was identified as the causal variant. Transcriptome analysis suggested that SLC2A11B loss of function may downregulate the xanthophore-differentiation gene CSF1R and the key pteridine biosynthesis gene GCH1, thus resulting in the pearl iris phenotype. Coalescence and phylogenetic analyses indicated that the mutation originated approximately 5,400 years ago, coinciding with the onset of pigeon domestication, while positive selection was likely associated with artificial breeding. Within Aves, potentially impaired SLC2A11B was found in six species from six distinct lineages, four of which associated with their signature brown or blue eyes and lack of pteridine. Analysis of vertebrate SLC2A11B orthologs revealed relaxed selection in the avian clade, consistent with the scenario that during and after avian divergence from the reptilian ancestor, the SLC2A11B-involved development of dermal chromatophores likely degenerated in the presence of feather coverage. Our findings provide new insight into the mechanism of avian iris color variations and the evolution of pigmentation in vertebrates.

A new species of Leptobrachella (Anura, Megophryidae) from Guizhou Province, China.

This study describes a new species of the genus Leptobrachella, Leptobrachella suiyangensissp. nov. from the Huoqiuba Nature Reserve, Suiyang County, Guizhou Province, China, based on morphological data and phylogenetic analyses (16S rRNA mtDNA). The new species can be distinguished from other congeners by the molecular divergence and by a combination of morphological characters, including body size, dorsal and ventral patterns, dorsal skin texture, size of the pectoral and femoral glands, degree of webbing and fringing on the toes and fingers, dorsum coloration, and iris coloration in life. Currently, the genus Leptobrachella contains 75 species, 21 of which are found in China, including seven species reported from Guizhou Province. The uncorrected sequence divergence percentage between Leptobrachella suiyangensissp. nov. and all homologous DNA sequences available for the 16S rRNA gene was found to be >4.7%. The new record of the species and its relationships with others in the same genus imply that species distribution, habitat variation, environmental adaptation, and diversity of the genus Leptobrachella in southwest China need to be further investigated.

Integrative evidence confirms new endemic island frogs and transmarine dispersal of amphibians between Madagascar and Mayotte (Comoros archipelago).

Previous genetic studies of frogs from Mayotte Island (a French Overseas Department in the Comoros Archipelago) in the Western Indian Ocean have provided evidence for oceanic dispersal in amphibians, which is a rare phenomenon due to the osmotic intolerance of amphibians to saline water. Using an integrative approach including morphological, bioacoustic, and genetic evidence, we here confirm that these frogs correspond to two new species and are the only representatives of the family Mantellidae not endemic to Madagascar. Blommersia transmarina sp. nov. differs from its sister taxon, B. wittei, by several morphological differences including larger body size (snout-vent length up to 34.5mm) and by slight differences in advertisement calls. Boophis nauticus sp. nov. differs from its closest relatives, B. tephraeomystax and B. doulioti, by slight morphological differences (including larger body size), a reddish (vs. silvery or golden) iris coloration in life, and slightly different advertisement calls. The two new species differ from their closest relatives by a substantial genetic differentiation, with pairwise genetic distances > 5% in the mitochondrial 16S rRNA gene, and based on the limited available data, also by distinct differences in nuclear DNA. They also are both larger than their closest relatives from Madagascar and B. transmarina sp. nov. is the largest Blommersia species, suggesting a moderate form of island gigantism. The Madagascan sister species B. wittei and B. doulioti are among the relatively few amphibian species occurring in the arid western biomes of the island, are adapted to open landscape, and reproduce in stagnant water bodies, which we hypothesizemay represent important preadaptations for successful overseas colonization.

The evolution of iris colour in relation to nocturnality in owls

Birds, due to their multiple colourful displays, constitute a classic paradigm for the study of colour evolution. Although avian eyes are remarkably coloured, the functional basis behind inter‐specific variability in iris colouration remains poorly understood. Owls are an ideal system to shed light on the role of ecology in promoting iris colour evolution as they show inter‐specific variation in iris colour and in niche specialization with some species being strictly nocturnal and others active during the day. Owls perching for hunting at night might be unnoticed by both predators and their prey if they had dark irises, which would predict that dark irises were more likely to evolve in strictly nocturnal species than in diurnal ones. Using phylogenetic comparative models, we tested the camouflage hypothesis for eye colour. The proportion of dark‐eyed owl species is higher among strictly nocturnal owls than among diurnal ones. Ancestral state reconstruction revealed that the owl ancestor of the family Strigidae was more likely bright‐irided whereas the ancestor of the family Tytonidae was more likely dark‐irided. Our results show robust support for the coevolution of iris coloration and nocturnality in the owls, and suggest that shifting to a nocturnal niche would be a prerequisite leading to the evolution of dark eyes in owls. The specific evolutionary pathway by which iris coloration and activity rhythm coevolve, however, remains to be investigated further as we have found only partial support for the idea that dark irises in birds might be an adaptive feature evolved due to the selective advantage of concealment from undesired visual receptors.

A new minute Pristimantis (Amphibia: Anura: Strabomantidae) from the Andes of southern Ecuador.

We describe a new rainfrog species (Pristimantis), from the wetland complex Oña, Nabón, Saraguro and Yacuambi, in the Andes of southern Ecuador, at altitudes ranging between 3000–3400 m a.s.l. Pristimantis tiktik sp. nov. is a small frog, displaying sexual dimorphism (the males with dorsum of various shades of gray, brown, orange or green and a whitish or pinkish yellow venter; females with brownish gray or gray dorsum and a reticulated white and black venter), with SVL ranging between 19.7–20.4 mm in females (n = 3) and 16.1–18.4 mm in males (n = 6). The skin on dorsum is tuberculated, that on venter is coarsely areolate, dorsolateral folds are absent, tympanic membrane is absent but the tympanic annulus is evident, cranial crests are absent, discs on fingers just slightly expanded, heel is lacking enlarged tubercles, inner edge of tarsus is bearing a long fold, Toe V is slightly longer than Toe III and the iris coloration is bronze with fine black reticulations. The males have a large subgular vocal sac that extends onto the chest and vocal slits but lack nuptial pads. The unique advertisement call consists of long duration series of periodically repeated clicks: “tik”. Molecular analyses place the new species in the recently resurrected P. orestes group, as the sister species of the assemblage that contains P. bambu, P. mazar, P. simonbolivari and an undescribed species.

Description of two new sympatric species of the genus Leptolalax (Anura: Megophryidae) from western Yunnan of China.

The Asian leaf litter toads of the genus Leptolalax represent a highly diverse species group and currently contain 53 recognized species. During herpetological surveys in Yingjiang County, western Yunnan of China, we collected series of Leptolalax specimens from an isolated small fragment of montane evergreen forest. Subsequent study based on acoustic, morphological and molecular data reveals that there were three different species among the specimens sampled: while one of them belongs to Leptolalax ventripunctataus, the other two species represent unknown taxa and are described herein: Leptolalax purpurus sp. nov. and Leptolalax yingjiangensis sp. nov. The two new species can be distinguished from other congeners by the molecular divergences, acoustic data, and by a combination of morphological characters including: body size, dorsal and ventral patterns, dorsal skin texture, sizes of pectoral and femoral glands, degree of webbing and fringing on the toes and fingers, dorsum coloration and iris coloration in life. Our results further reveal that species diversity of the genus Leptolalax still remains highly underestimated and warrants further attention.

Molt strategy and aging of Rufous-collared Sparrow (Zonotrichia capensis) in Bogotá, Colombia

La muda es un proceso importante de la historia natural de las aves y aprender sobre este proceso permite entender varios aspectos de su vida. En zonas templadas, el conocimiento sobre las estrategias de muda, las características de cada tipo de plumaje y su relación con la edad del ave, son bien conocidas. Por el contrario, en el neotrópico, este conocimiento no está bien desarrollado. Una especie con bastantes estudios sobre muda en varias localidades es el ampliamente distribuido Copetón (Zonotrichia capensis). Esos estudios cubren localidades de su ámbito geográfico facilitando comparaciones entre poblaciones y proveyendo un excelente modelo para estudiar la variación del plumaje y la muda. En este estudio, determiné el alcance y la estrategia de muda de Z. capensis costaricensis mediante muestreos durante un año en dos localidades de Bogotá. Capturé y anillé individuos de Z. capensis y tomé información de características como los límites de muda, osificación del cráneo y color del iris que me permitieron identificar el tipo de plumaje/muda y relacionarlo con una categoría de edad del sistema de clasificación de edad basado en los ciclos de muda. Encontré que Z. capensis tiene una estrategia de muda básica compleja, donde todas las mudas prebásicas, incluida la prejuvenil, son completas y la muda preformativa es parcial. Estos resultados son congruentes con los de otras regiones. Sin embargo, la muda de Z. capensis varía mucho, e individuos lejos de los trópicos tienen una muda alterna parcial-incompleta adicional y aún desconocemos por qué.

A new morphologically cryptic species of Phyllomedusa (Anura: Phyllomedusidae) from Amazonian forests of northern Peru revealed by DNA sequences.

We describe and name Phyllomedusa chaparroi sp. nov., a medium-sized species (snout-vent length in adult males 67.9-77.5 mm) of monkey frog from Amazonian rainforests of northern Peru. Although morphologically most similar to P. boliviana and P. camba (indistinguishable from the latter in external qualitative and quantitative traits), phylogenetic analysis of combined mitochondrial and nuclear markers place the new species sister to a clade containing P. neildi, P. tarsius, and P. trinitatis. Phyllomedusa chaparroi can be readily differentiated from these species by having a dark reddish-brown iris with indistinct tiny orange spots versus an orange iris with marked dark reticulation found in P. neildi, P. tarsius, and P. trinitatis. Furthermore, genetic distances for a 532 bp sequence of the 16S gene between the new species and its sister species are 2.8-4.1 %, whereas distances are 4.5-5.5 % to the morphologically cryptic P. camba. We briefly discuss the importance of DNA sequences in revealing morphologically cryptic species and modify the content of the P. tarsius species group based on phylogenetic analyses and observations on iris coloration.

Cross-spectral Iris Recognition for Mobile Applications using High-quality Color Images

With the recent shift towards mobile computing, new challenges for biometric authentication appear on the horizon. This paper provides a comprehensive study of cross-spectral iris recognition in a scenario, in which high quality color images obtained with a mobile phone are used against enrollment images collected in typical, near-infrared setups. Grayscale conversion of the color images that employs selective RGB channel choice depending on the iris coloration is shown to improve the recognition accuracy for some combinations of eye colors and matching software, when compared to using the red channel only, with equal error rates driven down to as low as 2%. The authors are not aware of any other paper focusing on cross-spectral iris recognition is a scenario with near-infrared enrollment using a professional iris recognition setup and then a mobile-based verication employing color images.

What colour are newborns' eyes? Prevalence of iris colour in the Newborn Eye Screening Test (NEST) study.

This study aims to assess the birth prevalence of iris colour among newborns in a prospective, healthy, full-term newborn cohort. The Newborn Eye Screening Test (NEST) study is a prospective cohort study conducted at Lucile Packard Children's Hospital at Stanford University School of Medicine. A paediatric vitreoretinal specialist (DMM) reviewed images sent to the Byers Eye Institute telemedicine reading centre and recorded eye colour for every infant screened. Variables were graphed to assess for normality, and frequencies per subject were reported for eye colour, sex, ethnicity and race. Among 192 subjects screened in the first year of the NEST study with external images of appropriate quality for visualization of the irides, the birth prevalence of iris colour was 63.0% brown, 20.8% blue, 5.7% green/hazel, 9.9% indeterminate and 0.5% partial heterochromia. The study population was derived from a quaternary care children's hospital. We report the birth prevalence of iris colour among full-term newborns in a diverse prospective cohort. The study demonstrates a broad range of iris colour prevalence at birth with a predominance of brown iris coloration. Future studies with the NEST cohort will assess the change in iris colour over time and whether the frequencies of eye colour change as the child ages.

Integrative taxonomy provides evidence for the species status of the Ibero-Maghrebian grass snakeNatrix astreptophora

The grass snake (Natrix natrix) is Europe's most widely distributed and, in many regions, most common snake species, with many morphologically defined subspecies. Yet, the taxonomy of grass snakes is relatively little studied and recent work has shown major conflicts between morphologically defined subspecies and phylogeographical differentiation. Using external morphology, osteological characters, and information from 13 microsatellite loci and two mitochondrial markers, we examine differentiation of the subspecies N. n. astreptophora from the North African Maghreb region, the Iberian Peninsula and neighbouring France. According to previous studies, N. n. astreptophora corresponds to a deeply divergent mitochondrial clade and constitutes the sister taxon of all remaining grass snakes. In the French Pyrenees region, there is a contact zone of N. n. astreptophora with another subspecies, N. n. helvetica. Our analyses of microsatellites and mitochondrial DNA reveal that the distribution ranges of the two taxa abut there, but both hybridize only exceptionally. Even though many morphological characters are highly variable and homoplastic in grass snakes, N. n. astreptophora differs consistently from all other grass snakes by its reddish iris coloration and in having significantly fewer ventral scales and another skull morphology. Considering further the virtual absence of gene flow between N. n. astreptophora and N. n. helvetica, and acknowledging the morphological distinctiveness of N. n. astreptophora and its sister group relationship to all remaining subspecies of grass snakes, we conclude that Natrix astreptophora (Seoane, 1884) should be recognized as a distinct species. Further research is needed to explore whether N.astreptophora is polytypic because a single sample of N.astreptophora from Tunisia turned out to be genetically highly distinct from its European conspecifics.

Phenotypic Characterization of Native Chickens (Gallus gallus domesticus) in Eastern Samar, Philippines

The study characterized native chickens based on phenotypic traits, measuring 13 morphometric and describing 7 discrete characters of 228 randomly-selected native chickens from three arbitrary districts (North District [ND], Central District [CD] and South District [SD]) in the province of Eastern Samar. Results show that significant difference was observed in drumstick length and beak length (p<0.05) across districts but most of the morphometric traits were dominant in chickens of CD. Although there were more than 2 traits observed for each of the 7 discrete characters, traditional chickens from both sexes across districts were found to have R/W earlobe, white skin, gray shank, single comb, red wattles and yellow / orange iris coloration. Sexual dimorphism was only observed in plumage color, having mahogany red and brown as dominant plumage colors in roosters and hens, respectively. Based on the morphometric data, discriminant analysis revealed that 52%, 47% and 73% of traditional chickens from ND, CD and SD were classified as member of their respective localities, respectively while dendrogram showed that most native chickens from neighboring municipalities under each district clustered together. The study concluded that there is a considerable variation in the phenotypic characters of native chickens in the province of Eastern Samar. Keywords - Phenotypic characterization, native chickens and traditional chickens, Eastern Samar, Philippines

A New Species ofHyloscirtus(Anura: Hylidae) from Colombia, with a Rediagnosis ofHyloscirtus larinopygion(Duellman, 1973)

Abstract: Hyloscirtus larinopygion is rediagnosed, and a new species formerly confused with that species is described from the highlands of the Central Cordillera in the Andes Mountains of Colombia. The new species differs from the other species of the H. larinopygion group by its color pattern, iris coloration, and presence of a nuptial pad with dark-brown epidermal projections. We discuss variation and diversity of nuptial pads, the calcar tubercle, and some aspects related to the swollen cloacal region in the H. larinopygion group. Finally, we discuss reproductive biology and problems involving the definition of a putative synapomorphy of Hyloscirtus.

Iris colour as an indicator of age feature in female Brazilian tanagers (Passeriformes: Emberizidae) confirmed by a molecular sexing technique

The Brazilian tanager, Ramphocelus bresilius is an endemic species from Brazil that is sexually dimorphic in adult plumage. Young males are similar to adult and young females until their second year. Adults and young females are not distinguishable in plumage. We tested whether iris colour can be used to separate adult females from immature females. We used for the first time the molecular sexing technique based on CHD-genes to confirm the sex of the individuals classified as "female plumage with red iris", and to identify the sex of individuals classified as "female plumage and brown iris". The adult males were used as a positive control. DNA samples from 190 individuals were analysed. The sizes of the PCR products were identified as 350 base pairs (bp) for CHD-Z and 388 bp for CHD-W. We confirmed that adult females have a red iris and the young females a brown iris. We could also separate young males and females which present the same iris colour and plumage. Although there are indications that the iris colour can be used by birds to identify the adults in co-operative breeding species such as the Brazilian tanager, more behavioural data are required to understand the role of iris coloration in this species.

Evolutionary trends in southern African glossy starlings (Lamprotornis)

Craig, A.J.F.K. 2000. Evolutionary trends in southern African glossy starlings (Lamprotornis). Ostrich 71 (1 & 2): 244–245. In southern African six Lamprotornis species occur in savanna woodland. Locally up to five species may be sympatric, dependent on similar food sources and sharing roost sites. All are obligate tree-hole nesters. Morphological differences concern signal structures (tail length and shape, iris coloration, wing notches) rather than adaptations for feeding. There is very little sexual dimorphism, and when body size is accounted for, there are no significant inter- or intra-specific differences in bill dimensions. The long-tailed L. mevesii and L. australis are probably sister taxa, which evolved in southern Africa. L. nitens and L. acuticaudus are also likely to be southern African in origin, whereas L. chalybaeus and L. chloropterus may have evolved to the north, with their current distribution in southern Africa a consequence of later range expansion. Similar modifications of signal structures in sympatric species are evident in northern glossy starlings.

Different Iris Coloration and Uptake of a Fluoroquinolone Agent into the Iris Ciliary Body of Rabbit Eyes

In order to know the correlation of a drug with high affinity to melanin in the iris ciliary body with the amount of melanin contained in the iris ciliary tissues, an in vivo study was performed on pigmented rabbits with brown or blue irises and albino rabbits. The melanin concentrations in the iris ciliary bodies of pigmented rabbits with brown and blue irises and nonpigmented rabbit eyes with whitish irises were determined. The mean concentrations of melanin in the eyes with brown-, blue- and whitish-colored irises were 47.43, 34.73 and below 0.2 microgram/mg tissue, respectively. The amount of sparfloxacin uptake in the iris ciliary bodies of eyes with brown, blue and whitish irises administered as 40 microliters of 0.3% solution 5 times every 5 min was 15.46 +/- 2.07, 8.53 +/- 1.87 and 1.9 micrograms/g, respectively. The results may be useful for intraocular drug dynamics studies.

A Pupillographic Evaluation of a Phenylephrine HC1 5% - Tropicamide 0.8% Combination Mydriatic

A continuously recording high-resolution pupillometer was used to measure changes in pupil size and pupil reactivity to temporally modulated light, following topical application of a phenylephrine HCl 5%-tropicamide 0.8% combination mydriatic (Phenyltrope). A controlled light stimulus induced pupillary changes in the left eye while changes in the consensual pupillary responses were measured in the mydriatic-treated right eye. The effects on pupil light reactivity of a single drop of the combination mydriatic were also compared to those caused by one drop of tropicamide 1% alone. Phenyltrope was introduced onto the ophthalmic market ostensibly offering faster mydriasis because of its combined effect of both the parasympathetic and sympathetic innervation to the pupil. In the present study, we looked for any differences in the pupil reaction times and amplitudes as a function of time after drug administration, iris coloration and type of mydriatic instilled. Our results show that while the combination is a fast acting mydriatic providing a large and stable pupillary dilation in subjects with either blue or brown irides, it does not differ appreciably in efficacy from the mydriatic effect of tropicamide 1% alone in healthy subjects between 20 to 36 years of age. Applications of our findings to the clinical environment are presented.