Microscopic anatomy of the eye of the deep‐diving Antarctic Weddell seal <i>(Leptonychotes weddellii)</i>

Welsch, Ulrich; Ramdohr, Sven; Riedelsheimer, Bernd; Hebel, Rudolf; Eisert, Regina; Plötz, Joachim

doi:10.1002/jmor.1027

Cited by 26 publications

(34 citation statements)

References 28 publications

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“…Many cetaceans, such as the common dolphin Delphinus delphis (Dral, 1983), bottlenose dolphin Tursiops truncatus (Dral, 1977;Mass and Supin, 1995), harbor porpoise Phocoena phocoena (Mass and Supin, 1986), Chinese river dolphin Lipotes vexillifer (Gao and Zhou, 1987), gray whale Eschrichtius gibbosus ), Dall's porpoise, and Minke whale Balaenoptera acutorostrata (Murayama et al, 1992(Murayama et al, , 1995, have two spots of high cell density, one in the nasal and the other in the temporal retinal quadrants. In pinnipeds, a high cell density area occurs as either a discrete spot (the northern fur seal, Mass and Supin, 1992; the Weddel seal, Welsch et al, 2001) or a streak (the walrus, Mass, 1992) or a combination of both (the sea otter Enhydra lutris, Mass and Supin, 2000; the harbor seal, Hanke et al, 2009; the Caspian Seal, Mass and Supin, 2010). All these patterns are different from that found in the manatee.…”

Section: Ganglion Cell Number and Distributionmentioning

confidence: 92%

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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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Section: Ganglion Cell Number and Distributionmentioning

confidence: 92%

“…Using this method, retinal resolution has been estimated in many terrestrial (rev. Pettigrew et al, 1988) and marine mammals (Landau and Dawson, 1970;Murayama et al, 1992Murayama et al, , 1995Supin et al, 2001;Welsch et al, 2001;Mass and Supin, 2003, 2010Hanke et al, 2009). To date, however, there is no investigation of this kind on manatee retinae.…”

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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“…6A,B) generally corresponds to that of terrestrial mammals (Landau and Dawson, 1970;Ronald, 1970, 1975;Jamieson and Fisher, 1971;Welsch et al, 2001;Mass and Supin, 2005). However, there are several features unique to aquatic mammals.…”

Section: Pinnipedsmentioning

confidence: 96%

“…Those authors studied transverse retinal sections. Later topographic mapping of ganglion cells in retinal whole-mounts, however, revealed high-density areas in five pinniped species belonging to different families, including Odobenidae: the walrus (Odobenus rosmarus) (Mass, 1992), Otariidae: northern fur seal (Callorhinus ursinus) (Mass and Supin, 1992) and Steller sea lion (Eumetopias jubatus) (Mass and Supin, 2005), and Phocidae: harp seal (Pagophilus groenlandicus) (Mass and Supin, 2003) and Weddell seal (Leptonychotes weddellii) (Welsch et al, 2001). Figure 10 presents typical examples of high-and low-density areas in a whole-mount of the harp seal's retina (Mass and Supin, 2003).…”

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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“…Although the retina of true seals was investigated in several studies [Landau and Dawson, 1970;Ronald, 1970, 1975;Jamieson and Fisher, 1971;Peichl and Moutairou, 1998;Welsh et al, 2001], their retinal topography was not investigated with the use of the retinal wholemount method. The only attempt was made in the Weddell seal [Welsch et al, 2001] by counting ganglion cell density in a limited number of sites, and some differences in the cell density were found among different sites, but there was no attempt to compose a complete retinal topographic map. In the present study, we examined the retinal topography in a phocid species, the harp seal Pagophilus groenlandicus Erxleben, 1777, in order to compose a complete ganglioncell distribution map and evaluate the retinal resolution.…”

Section: Introductionmentioning

confidence: 99%

Retinal Topography of the Harp Seal <i>Pagophilus groenlandicus</i>

Mass

Supin

2003

Brain Behav Evol

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The total number, size, topographic distribution, and cell density of ganglion cells were studied in retinal wholemounts of the harp seal Pagophilus groenlandicus. Ganglion cell size varied from 10 to 60 µm. A distinct group were large ganglion cells more than 30–35 µm in diameter which were similar to α-cells known in terrestrial mammals. The number of α-cells constituted 5.3–5.9% of the total ganglion cell population. The cell size distribution was bimodal, with the second mode composed of α-cells. The topographic distribution of ganglion cells showed a definite area of high cell density similar to area centralis of terrestrial carnivores. This area was located in the temporal retinal quadrant, 7–8 mm (16–18°) from the optic disk. In this area, the peak cell densities in two wholemounts were 2,500 and 1,650 (mean 2,075) cells/mm². With a posterior nodal distance of 25.5 mm (underwater), this density corresponded to 495 and 327 (mean 411) cells/deg². These values predict a retinal resolution of 2.7–3.3′ (11.1–9.0 cycles/deg) in water and 3.6–4.4′ (8.3–6.8 cycles/deg) in air. Topographic distributions of α-cells was qualitatively similar to that of the total ganglion cell population, but the density of α-cells constituted only a few percent (mostly 3–7.5%) of the total ganglion cell density.

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Microscopic anatomy of the eye of the deep‐diving Antarctic Weddell seal (Leptonychotes weddellii)

Cited by 26 publications

References 28 publications

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

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

Adaptive features of aquatic mammals' eye

Retinal Topography of the Harp Seal <i>Pagophilus groenlandicus</i>

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