The vertebrate retina is said to be inverted because the photoreceptors are oriented in the posterior direction and are thus unable to maximize photodetection under conditions of low illumination. The tapetum lucidum is a photoreflective structure located posterior to the photoreceptors in the eyes of some fish and terrestrial animals. The tapetum reflects light forward, giving incident photons a "second chance" to collide with a photoreceptor, substantially enhancing retinal photosensitivity in dim light. Across vertebrates (and arthropods), there are a wide variety of tapeta that vary in structure, chemical composition, and even tissue architecture, indicating repeated convergent evolution. To date, the tapetum has not been observed in any cephalopod, however, which also possess a camera-like eye, but with the retinal photoreceptors oriented in the anterior direction. We therefore hypothesize that the tapetum lucidum is a compensatory adaptation for the suboptimal design of the inverted retina of vertebrates.
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http://dx.doi.org/10.1002/bies.202200003 | DOI Listing |
Pol J Vet Sci
June 2024
Department and Clinic of Animal Surgery, Faculty of Veterinary Medicine, University of Life Sciences in Lublin, Głęboka 30, 20-612 Lublin, Poland.
The aim of the study was to determine the thickness of choroidal layers in mixed breed dogs suffering from retinal atrophy (RA) and showing symptoms of progressive retinal atrophy (PRA), with the use of SD-OCT. The study was performed on 50 dogs divided into two groups: 25 dogs diagnosed with retinal atrophy (RA) with PRA symptoms aged 1.5-14 years and 25 healthy dogs aged 2-12 years.
View Article and Find Full Text PDFFront Vet Sci
September 2024
Anatomy and Embryology Department, Faculty of Veterinary Medicine, Alexandria University, Alexandria, Egypt.
Sci Adv
September 2024
School of Electrical Engineering and Computer Science, Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Republic of Korea.
Cryst Growth Des
August 2024
School of Chemistry, Cardiff University, Cardiff, Wales CF10 3AT, U.K.
J Biol Phys
December 2024
Independent Researcher, Waalre, The Netherlands.
The evolutionary origin of the inverted retina in the vertebrate eye is unknown. This paper explores a hypothetical evolutionary scenario that explains the unique orientation of the photoreceptors in the vertebrate retina. The proposed scenario follows the scientific accepted scenario for eye evolution and gradually builds up towards an eye prototype by considering light direction detection and increase in achievable spatial resolution as the driving forces.
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