A comparative study of the anatomy of the iris and ciliary body in aquatic mammals

West, Judith A.; Sivak, J. G.; Murphy, Christopher J.; Kovacs, Kit M.

doi:10.1139/z91-366

Cited by 26 publications

(35 citation statements)

References 25 publications

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“…An interesting work could be a validation or adaptation of the iris deformation model against monkeys (CLARKE; ZHANG; GAMLIN, 2003a,b;MAGOUN et al, 1936), cats (HAM-MOND; MOUAT, 1985;SCHAEPPI;KOELLA, 1964;MITCHELL, 2006), rabbits (YA-MAJI et al, 2003), pigeons (PILAR; VAUGHAN, 1971) or other animals (WEST et al, 1991). This thesis can be used as a guideline to create PLR and iris deformation models for other species.…”

Section: Discussion and Future Workmentioning

confidence: 99%

Photorealistic models for pupil light reflex and iridal pattern deformation

2009

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We introduce a physiologically-based model for pupil light reflex (PLR) and an image-based model for iridal pattern deformation. Our PLR model expresses the pupil diameter as a function of the lighting of the environment, and is described by a delay-differential equation, naturally adapting the pupil diameter even to abrupt changes in light conditions. Since the parameters of our PLR model were derived from measured data, it correctly simulates the actual behavior of the human pupil. Another contribution of our work is a model for realistic deformation of the iris pattern as a function of pupil dilation and constriction. Our models produce high-fidelity appearance effects and can be used to produce real-time predictive animations of the pupil and iris under variable lighting conditions. We assess the predictability and quality of our simulations through comparisons of modeled results against measured data derived from experiments also described in this work. Combined, our models can bring facial animation to new photorealistic standards.

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Section: Discussion and Future Workmentioning

confidence: 99%

Photorealistic models for pupil light reflex and iridal pattern deformation

2009

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“…The ciliary muscle is poorly developed in all dolphins and is absent from most whales (Waller, 1984;West et al, 1991;Bjerager et al, 2003), suggesting that accommodation cannot be achieved by a change of the lens shape (Dral, 1972). This suggestion is supported by ophthalmoscopic observations (Dawson et al, 1987b), which revealed no significant accommodative changes.…”

Section: Eye Anatomy and Optics Cetaceansmentioning

confidence: 99%

“…The ciliary muscle in pinnipeds is much better developed than in cetaceans (Jamieson and Fisher, 1972;Sivak et al, 1989;West et al, 1991), although accommodation is weak or absent (Sivak et al, 1989).…”

Section: Pinnipedsmentioning

confidence: 99%

Adaptive features of aquatic mammals' eye

Mass¹,

Supin²

2007

The Anatomical Record

112

129

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The eye of aquatic mammals demonstrates several adaptations to both underwater and aerial vision. This study offers a review of eye anatomy in four groups of aquatic animals: cetaceans (toothed and baleen whales), pinnipeds (seals, sea lions, and walruses), sirenians (manatees and dugongs), and sea otters. Eye anatomy and optics, retinal laminar morphology, and topography of ganglion cell distribution are discussed with particular reference to aquatic specializations for underwater versus aerial vision. Aquatic mammals display emmetropia (i.e., refraction of light to focus on the retina) while submerged, and most have mechanisms to achieve emmetropia above water to counter the resulting aerial myopia. As underwater vision necessitates adjusting to wide variations in luminosity, iris muscle contractions create species-specific pupil shapes that regulate the amount of light entering the pupil and, in pinnipeds, work in conjunction with a reflective optic tapetum. The retina of aquatic mammals is similar to that of nocturnal terrestrial mammals in containing mainly rod photoreceptors and a minor number of cones (however, residual color vision may take place). A characteristic feature of the cetacean and pinniped retina is the large size of ganglion cells separated by wide intercellular spaces. Studies of topographic distribution of ganglion cells in the retina of cetaceans revealed two areas of ganglion cell concentration (the best-vision areas) located in the temporal and nasal quadrants; pinnipeds, sirenians, and sea otters have only one such area. In general, the visual system of marine mammals demonstrates a high degree of development and several specific features associated with adaptation for vision in both the aquatic and aerial environments. Anat Rec 290: 701-715, 2007. 2007 Key words: vision; ocular optics; retina; ganglion cells; retinal topography; aquatic mammalsComparative studies of the visual system in animals adapted to various living conditions have revealed new specific features of neuronal structures, have aided our understanding of mechanisms of visual perception, and have described the many ways in which sensory systems show adaptations to various environments. In recent years, there has been a great interest in the visual system of aquatic mammals: cetaceans (dolphins, porpoises, and whales), pinnipeds (seals, sea lions, and walruses), sirenians (manatees and dugongs), and sea otters. These species demonstrate various extents of adaptation to the aquatic environment. Many aquatic mammals (cetaceans, sirenians) spend their entire life in the water; however, air-breathing confines them to a near-surface layer of water. Other marine mammals (pinnipeds, sea otters) spend a significant part of their life on land. As a result, the visual systems of these groups feature remarkable morphological and functional specializations for both

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“…Contrary to the majority of mammals that have avascular corneae, blood vessels have been reported throughout the manatee cornea (Harper et al, 2005). Another unusual feature of the manatee's visual system is that the ciliary body contains no muscle fibers (West et al, 1991;Samuelson et al, 1994;Natiello et al, 2005). Further, the angioarchitecture of the ciliary body of the manatee is unique compared to those examined in terrestrial mammals.…”

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confidence: 99%

“…The manatee's eye is reported to lack a definite tapetum (West et al, 1991). However, manatees have eyes equipped with a rod-dominant retina (Cohen et al, 1982), which may provide good sensitivity despite the lack of a tapetum (Griebel and Schmidt, 1997).…”

mentioning

confidence: 99%

Ganglion Cell Distribution and Retinal Resolution in the Florida Manatee, Trichechus Manatus Latirostris

Mass

Ketten

Odell

et al. 2011

The Anatomical Record

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The topographic organization of retinal ganglion cells was examined in the Florida manatee (Trichechus manatus latirostris) to assess ganglion cell size and distribution and to estimate retinal resolution. The ganglion cell layer of the manatee's retina was comprised primarily of large neurons with broad intercellular spaces. Cell sizes varied from 10 to 60 lm in diameter (mean 24.3 lm). The retinal wholemounts from adult animals measured 446-501 mm 2 in area with total ganglion cell counts of 62,000-81,800 (mean 70,200). The cell density changed across the retina, with the maximum in the area below the optic disc and decreasing toward the retinal edges and in the immediate vicinity of the optic disc. The maximum cell density ranged from 235 to 337 cells per millimeter square in the adult retinae. Two wholemounts obtained from juvenile animals were 271 and 282 mm 2 in area with total cell numbers of 70,900 and 68,700, respectively (mean 69,800), that is, nearly equivalent to those of adults, but juvenile retinae consequently had maximum cell densities that were higher than those of adults: 478 and 491 cells per millimeter square. Calculations indicate a retinal resolution of $19 0 (1.6 cycles per degree) in both adult and juvenile retinae. Anat Rec, 295:177-186, 2012. V V C 2011 Wiley Periodicals, Inc.Key words: manatee; Trichechus manatus; eye; retina; ganglion cells; cell topography; cell size; retinal resolution; visual acuityThe Sirenia order includes the manatee, dugong, and the extinct Steller cow. Sirenians are adapted to salt and fresh water habitats and, unlike other marine mammals, are exclusively herbivorous. Consequently, they have a range of unique anatomical, physiological, and behavioral adaptations. Further, all species of the order are endangered. The West Indian manatee is a slow grazer that inhabits the coastal areas and rivers of the Caribbean basin (Bertram and Bertram, 1962;Hartman, 1979; Nowak, 1991). The Florida manatee, Trichechus manatus latirostris, is a subspecies of the West Indian manatee, T. manatus. Knowing more about their sensory abilities, including their visual abilities, is of interest not only for basic evolutionary research but also for planning strategies for conserving this highly endangered species.

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A comparative study of the anatomy of the iris and ciliary body in aquatic mammals

Cited by 26 publications

References 25 publications

Photorealistic models for pupil light reflex and iridal pattern deformation

Photorealistic models for pupil light reflex and iridal pattern deformation

Adaptive features of aquatic mammals' eye

Ganglion Cell Distribution and Retinal Resolution in the Florida Manatee, Trichechus Manatus Latirostris

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