Functional anatomy of the ocular circulatory system: vascular corrosion casts of the cetacean eye

Ninomiya, Hiroyoshi; Yoshida, Emi

doi:10.1111/j.1463-5224.2007.00544.x

Cited by 26 publications

(45 citation statements)

References 23 publications

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“…The vascularization of the eyeball and its accessory structures similar to a rete mirabile in several vertebrates proved to be complex; according to some authors (Dawson ; Zhu et al . ; Ninomiya and Yoshida ; Ninomiya et al . ), the vascular networks may act to prevent heat loss from the retina to the optic nerve and contribute to the retention of oxygen during deep dives.…”

Section: Discussionmentioning

confidence: 99%

Morphology of accessory structures of the humpback whale (Megaptera novaeangliae) eye

et al. 2014

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Rodrigues, F.M., Silva, F.M.O., Trompieri-Silveira, A.C., Vergara-Parente, J.E., Miglino, M.A. and Guimarães, J.P. 2015. Morphology of accessory structures of the humpback whale (Megaptera novaeangliae) eye. -Acta Zoologica (Stockholm) 96: 328-334.The humpback whale (Megaptera novaeangliae) has a cosmopolitan distribution and inhabits coastal and oceanic habitats, being present in polar and tropical waters. In aquatic mammals, vision has an important role in the perception of photoperiod changes. Due to lack of information on the morphology of Mysticetes, this study aimed to provide a morphological description of the adnexal structures of the humpback whale eye. Three newborn female specimens, stranded on the coast of Sergipe, Brazil, were used. Samples were fixed in a 10% formalin solution, dissected and photographed, and all the structures were collected and analysed using different light microscopy techniques. Eyelids were characterized by a palpebral fissure, a palpebral opening, two grooves (dorsal and ventral) and the presence of mechanoreceptors in the dermis. Some fibres of the four recti muscles had palpebral, scleral and glandular insertions. The Harderian gland filled the area between the orbit wall and the eyeball. Two vascular networks separated the extraocular retractor muscle of the eye and surround the optic nerve. The morphology of the accessory structures of the humpback whale eye was similar to that of other cetaceans, which suggests an adaptation to diving during migration, contributing to the perception of temperature difference in different regions.Juliana P. Guimarães, N ucleo de Estudo dos Efeitos Antropogênicos nos Recursos Marinhos/Fundac ßão Mam ıferos Aqu aticos, Av. Tancredo Neves,

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Section: Discussionmentioning

confidence: 99%

Morphology of accessory structures of the humpback whale (Megaptera novaeangliae) eye

et al. 2014

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“…The operculum can extend far enough to touch a similar, smaller proturbance extending from the inferior aspect. Due to this unique pupil, during miosis, the cetacean eye only has two small slits on the nasal and temporal aspect visible on complete constriction of the pupil, but on complete dilation is ellipsoid (longer in the horizontal direction …”

Section: Discussionmentioning

confidence: 99%

Anatomic features of the cetacean globe

Miller

Samuelson

Dubielzig

2013

Veterinary Ophthalmology

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The horizontal diameter of the globe was longer than the vertical diameter. The posterior sclera was thick, causing the internal axial length (and therefore the optical axis) to be shorter than the vertical diameter. The cornea was composed of an epithelium, Bowman's layer, collagenous stroma, thin Descemet's membrane and endothelial layer. Bowman's layer was present in all specimens except one Kogia breviceps. The thickness was variable, with the acellular layer thickest in Tursiops truncatus and thinnest in Kogia sp. The iris was well vascularized and muscled while the ciliary body lacked musculature, but retained vasculature. Single and clustered ESC were found in the anterior uvea, sclera surrounding the anterior uvea, trabecular meshwork, or some combination of these locations. They were often regionally grouped and varied from 0 to 21. There were three species where no ESC were found, L. borealis, D. capensis, and S. bredanensis, but the presence of these corpuscles cannot be ruled as only one section of the globe was analyzed.

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“…Cold‐adapted animals have several thermoregulatory strategies to retain or release heat 4 . In cetaceans, the multivessel plexuses covering the large posterior area of the orbit act as a radiator to prevent heat loss from the retina and optic nerve 5,6 . The blubber effectively insulates most of the body surface, and the counter‐current heat exchangers in the vascular system of the tongue, fins and flukes of whales, dolphins 7 and manatees 8 serve to conserve core body temperature.…”

Section: Introductionmentioning

confidence: 99%

Functional anatomy of the footpad vasculature of dogs: scanning electron microscopy of vascular corrosion casts

Ninomiya

Akiyama

Simazaki

et al. 2011

Veterinary Dermatology

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Dogs are well adapted to cold climates and they can stand, walk and run on snow and ice for long periods of time. In contrast to the body trunk, which has, dense fur, the paws are more exposed to the cold due to the lack of fur insulation. The extremities have a high surface area-to-volume ratio, so they lose heat very easily. We offer anatomical evidence for a heat-conserving structure associated with dog footpad vasculature. Methylmethacrylate vascular corrosion casts for scanning electron microscopy, Indian ink-injected whole-mount and histological specimens were each prepared, in a series of 16 limbs from four adult dogs. Vascular casts and Indian ink studies showed that abundant venules were arranged around the arteries supplying the pad surface and formed a vein-artery-vein triad, with the peri-arterial venous network intimately related to the arteries. In addition, numerous arteriovenous anastomoses and well-developed venous plexuses were found throughout the dermal vasculature. The triad forms a counter-current heat exchanger. When the footpad is exposed to a cold environment, the counter-current heat exchanger serves to prevent heat loss by recirculating heat back to the body core. Furthermore, the arteriovenous anastomoses shift blood flow, draining blood to the skin surface, and the venous plexuses retain warm blood in the pad surface. Hence, the appropriate temperature for the footpad can be maintained in cold environments.

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Functional anatomy of the ocular circulatory system: vascular corrosion casts of the cetacean eye

Cited by 26 publications

References 23 publications

Morphology of accessory structures of the humpback whale (Megaptera novaeangliae) eye

Morphology of accessory structures of the humpback whale (Megaptera novaeangliae) eye

Anatomic features of the cetacean globe

Functional anatomy of the footpad vasculature of dogs: scanning electron microscopy of vascular corrosion casts

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