Editing Tapetum lucidum (section)

== Variation across species ==

=== Primates ===
Humans like [[Haplorhini|haplorhine primates]]  lack a tapetum lucidum as they are [[Diurnality|diurnal]].<ref name="Ollivier+2004">{{cite journal |vauthors=Ollivier FJ, Samuelson DA, Brooks DE, Lewis PA, Kallberg ME, Komáromy AM |title=Comparative morphology of the tapetum lucidum (among selected species) |journal=Veterinary Ophthalmology |volume=7 |issue=1 |pages=11–22 |year=2004 |pmid=14738502 |doi=10.1111/j.1463-5224.2004.00318.x }}</ref> [[Strepsirrhini|Strepsirrhine]] primates are mostly nocturnal and, with the exception of several diurnal ''[[Eulemur]]'' species, have a tapetum lucidum of riboflavin crystals.<ref name="Ankel-Simons2007">{{cite book | last = Ankel-Simons | first = Friderun | title= Primate Anatomy | edition = 3rd | publisher = Academic Press | year = 2007 |isbn= 978-0-12-372576-9 | page = 375}}</ref>

=== Dogs ===
In canids, the tapetum lucidum is found in the dorsal half of the eye's fundus. It consists of 9-20 layers of specialized rectangular cells between the choroid and retinal pigment epithelium, thinning towards the periphery. The cells contain zinc-rich rodlets arranged in parallel. The structure appears yellow-green in adults, though blue in puppies until four months of age. Zinc concentration varies among species, with red foxes showing highest levels, followed by Arctic foxes, then domestic dogs. A hereditary zinc-deficiency condition in some beagles results in degenerated tapetal cells with disrupted rodlet arrangement.<ref name="a165">{{cite book |last1=Mowat |first1=Freya M. |title=Wild and Exotic Animal Ophthalmology |last2=Peichl |first2=Leo |publisher=Springer International Publishing |year=2022 |isbn=978-3-030-81272-0 |pages=181–214 |chapter=Ophthalmology of Canidae: Foxes, Wolves, and Relatives |doi=10.1007/978-3-030-81273-7_11}}</ref>

=== Cats ===
The tapetum lucidum in cats is renowned for its brilliance, even inspiring ancient Egyptians to believe it reflected the sun at night. This reflective layer is composed of 15-20 layers of cells arranged in a central pattern. This structure, denser than that of dogs, results in high reflectance, nearly 130 times that of humans. Its color is heterogeneous, varying with age and species due to factors like rodlet spacing, refractive index, and light interactions. Young cats exhibit a blue appearance, which shifts to yellow with age, with adult coloration ranging from light orange to green. While enhancing night vision, increased light scatter within the tapetum slightly compromises visual acuity.<ref name="g085">{{cite book |last1=Corsi |first1=Francesca |title=Wild and Exotic Animal Ophthalmology |last2=Guandalini |first2=Adolfo |last3=Rossi |first3=João Luiz |last4=Ben-Shlomo |first4=Gil |last5=Montiani-Ferreira |first5=Fabiano |last6=Moore |first6=Bret A. |publisher=Springer International Publishing |isbn=978-3-030-81272-0 |pages=155–180 |chapter=Ophthalmology of Felidae: Cats |date=2022 |doi=10.1007/978-3-030-81273-7_10}}</ref>

===Birds===
[[Kiwi (bird)|Kiwi]]s, [[stone-curlew]]s, the [[boat-billed heron]], the flightless [[kākāpō]], and many [[nightjar]]s, [[owl]]s, and other night birds such as the [[swallow-tailed gull]] possess a tapetum lucidum.<ref>Gill, Frank, B (2007) "Ornithology", Freeman, New York</ref> Nightjars use a retinal tapetum lucidum composed of lipids.<ref>{{cite journal |title=Tapeta lucida in the eyes of goatsuckers (Caprimulgidae) |journal=Proceedings of the Royal Society of London. Series B. Biological Sciences |date=5 November 1974 |volume=187 |issue=1088 |pages=349–352 |doi=10.1098/rspb.1974.0079|pmid=4154455 |last1=Nicol |first1=J. A. |last2=Arnott |first2=H. J. |bibcode=1974RSPSB.187..349N |s2cid=43626885 }}</ref>

===In spiders===
Most species of spider also have a tapetum, which is located only in their smaller, lateral eyes; the larger central eyes have no such structure. This consists of reflective crystalline deposits and is thought to have a similar function to the structure of the same name in vertebrates. Four general patterns can be distinguished in spiders:<ref name="BoS">{{cite book |author=Rainer F. Foelix |url=https://archive.org/details/biologyofspiders00foel_0/page/84 |title=Biology of Spiders, 2nd ed. |publisher=Oxford University Press |year=1996 |isbn=978-0-19-509594-4 |pages=[https://archive.org/details/biologyofspiders00foel_0/page/84 84–85]}}</ref>
# Primitive type (e.g. [[Mesothelae]], [[Orthognatha]]){{Snd}}a simple sheet behind the retina
# Canoe-shape type (e.g. [[Araneidae]], [[Theridiidae]]){{Snd}}two lateral walls separated by a gap for the nerve fibres
# Grated type (e.g. [[Lycosidae]], [[Pisauridae]]){{Snd}}a relatively complex, grill-shaped structure
# No tapetum (e.g. [[Salticidae]])

=== Animals lacking a tapetum lucidum ===
Animals without tapetum lucidum include haplorhine primates, squirrels, some birds, [[red kangaroo]], and pigs.<ref name="Charnock1896">Orlando Charnock Bradley, 1896, ''Outlines of Veterinary Anatomy. Part I. The Anterior and Posterior Limbs,'' Baillière, Tindall & Cox, p. 224. [https://books.google.com/books?id=ZQOq9yYDK1AC Free full text on Google Books]</ref>