Lizards occupy both scotopic (light-limited) and photopic (light-rich) environments, thereby making this clade ideal for analyses of eye morphology adaptations. This study examines how in lizards the ...morphology of the eye varies according to activity in these different light environments. Measurements were collected on corneal diameters and axial lengths of the eye for 239 specimens of 116 lizard species (including Sphenodon) that include both species with scotopic and photopic visual adaptations. I show that the light level available to a lizard for vision has a significant effect on eye shape and size. Scotopic lizards have eye shapes that are optimized for visual sensitivity, with larger corneal diameters relative to axial lengths. However, photopic lizards do not exhibit absolutely larger axial lengths than do scotopic lizards, and the groups have the same absolute axial lengths of the eye. Results also indicate that the light level the lizard functions under is a more significant influence on eye shape, as defined by the relationship between corneal diameter and axial length of the eye, than is phylogeny.
This paper summarizes our findings on the eye morphology, visual perception, learning abilities, navigation system and recruitment strategy of three Myrmica species, pointing out the agreement ...between each species’ morphological, physiological and behavioral characters as well as the accordance between these characters and each species’ environmental preferences. We also draw biological generalities and report other similar studies. Myrmica sabuleti workers have small eyes, perceive the dimension, number of basic elements and orientation of a visual cue but do not distinguish shapes from one another. They see the colors, perceive UV light and the perspective, and adapt their vision to the light intensity. They learn odors better than visual cues and essentially use odors to navigate. Myrmica ruginodis workers have large eyes, distinguish shapes, small see-through forms as well as patterns of luminous points located above them. They have no olfactory memory but a very long lasting visual one. They exclusively use visual cues located above them while travelling, relying on odors only when they no longer see. Myrmica rubra workers have eyes of middle size and distinguish filled shapes but not hollow forms. Their olfactory and visual conditioning lead to equivalent learning in the course of time and they use all available olfactory and visual elements for navigating.
Sensory information plays a critical role in determining an animal's behavior on both proximate and evolutionary timescales. Butterflies, like many other insects, use vision extensively over their ...lifetimes, and yet relatively little work has been published to date on their visual capabilities. We describe the visual system of a pierid butterfly,
Colias eurytheme, with the ultimate goal of better understanding its role in shaping the behavior of this animal. We made several measurements: visual field dimensions, eye surface area, interommatidial angle (Δ
ϕ), facet diameter (
D), and eye parameter (
p).
C. eurytheme had a large visual field and considerable regional variation in visual acuity, as inferred by Δ
ϕ and
D. When compared to females, males had larger eye surface areas, smaller Δ
ϕ, and larger
D in all regions except ventrally. Both sexes had proportionally large eye surface areas compared to other butterflies. Minimum
p in males was small, indicating that some regions of their eyes may operate close to the diffraction limit. Finally, we found that both eye surface area and
D scaled positively, but with negative allometry to body size. We discuss the relevance of these visual characteristics to the biology and behavior of
C. eurytheme.
Male Empress Leilia butterflies ( Asterocampa leilia) use a sit-and-wait tactic to locate mates. To see how vision might influence male behavior, we studied the morphology, optics, and receptor ...physiology of their eyes and found the following. (1) Each eye's visual field is approximately hemispherical with at most a 10 degrees overlap in the fields of the eyes. There are no large sexual differences in visual field dimensions. (2) In both sexes, rhabdoms in the frontal and dorsal ommatidia are longer than those in other eye regions. (3) Interommatidial angles are smallest frontally and around the equator of the eye. Minimum interommatidial angles are 0.9-1 degrees in males and 1.3-1.4 degrees in females. (4) Acceptance angles of ommatidia closely match interommatidial angles in the frontal region of the eye. We conclude that vision in these butterflies is mostly monocular and that males have more acute vision than females, especially in the frontal region (large facets, small interommatidial angles, small acceptance angles, long rhabdoms, and a close match between interommatidial angles and acceptance angles). This study also suggests that perched males direct their most acute vision where females are likely to appear but show no eye modifications that appear clearly related to a mate-locating tactic.
Observations were made on eyes from 46 bowhead whales, Balaena mysticetus, taken in the subsistence harvest near Barrow, Point Hope, Savoonga, and Kaktovik, Alaska. Data reported here include ...palpebral, eyeball, corneal, scleral, pupillary, and lens dimensions. These quantitative data have allowed us to compare structures relative to one another and sometimes to compare them with similar structures in other species. We found, for example, that the cornea is almost three times as thick at its periphery as at its center; that when the ratio of scleral thickness and eyeball size are compared, the ratio, in the bowhead whale, is twice that of any other cetacean for which data were available; and that the corneal and pupillary width to height ratios indicate a less elongated cornea and pupil than has been reported in other cetaceans. We also found a strong correlation between body length and eyeball size indicating that within the species, unlike what is seen between species, larger animals have larger eyes. Novel observations include the presence of three periorbital fatty layers, 112 ciliary processes, the presence of scleral canals, the absence of an obvious fovea or macular region in the retina, a holangiotic pattern of fundic vessels, the presence of zonular fibers and a lens sheath, and the absence of an obvious pupillary operculum. Anatomical features like the wide angle of divergence and the palpebral dimensions suggest the absence of binocular vision while features like the size of the palpebral sac, abundant conjuctival fat, and the prominence of the retractor bulbi muscle suggest mechanisms for the protrusion and retraction of the eyeball.
Qualitative taxonomic characters based on differences in linear eye measurements were converted to qualitative scores for Efferia group species, and statistical analyses of intraspecific and ...interspecific variation were perfomed. Sexual dimorphism noted for E. albibarbis is the first documented for an eye morphology character in Asilidae, and may be analogous to sexual dimorphism described in a holoptic-dichoptic context for other species of Diptera. Interspecific variation in E. albibarbis Macquart and E. aestuans (Linnaeus) demonstrates that robust comparisons among species cannot rely on single exemplars, and differences among specimens based on sex and geography should be considered during subsequent eye morphology studies in Asilidae. The variables identified in this study demonstrate that a wide variation in eye morphology exists among Efferia group species that can be examined in a quantitative context. Detailed accounts of intraspecific variation are considered crucial for comparisons among species of Asilidae, and interspecific comparisons of eye morphology are likely to demonstrate biologically significant results in studies of monophyletic taxa and ecological guilds.
Optic morphology (Om) mutations in Drosophila ananassae map to at least 22 loci, which are scattered throughout the genome. Om mutations are all semidominant, neomorphic, nonpleiotropic, and ...associated with the insertion of a retrotransposon, tom. We have found that the Om(2D) gene encodes a novel protein containing histidine/proline repeats, and is ubiquitously expressed during embryogenesis. The Om(2D) RNA is not detected in wild-type eye imaginal discs, but is abundantly found in the center of the eye discs of Om(2D) mutants, where excessive cell death occurs. Drosophila melanogaster flies transformed with the Om(2D) cDNA under control of the hsp70 promoter display abnormal eye morphology when heat-shocked at the third larval instar stage. These results suggest that the Om(2D) gene is not normally expressed in the eye imaginal discs, but its ectopic expression, induced by the tom element, in the eye disc of third instar larvae results in defects in adult eye morphology.
We found a specific eye morphology designated as Square, which is induced when some Drosophila melanogaster strains harboring P elements are crossed with the delta 2-3 strain carrying a modified P ...element, Pry(+), delta 2-3, which produces transposase in somatic tissue. This phenotype was dominant and also induced in the reciprocal crosses. Square was induced when the delta 2-3 strain was crossed with Q and M' strains such as the sn(w) (M) strain carrying three small P elements but not with P strains. Inheritance of Square was also tested and its phenotype was not transmitted to the next generation. These results suggest that Square is caused by the transposition of P elements in somatic cells.
