Skeletal elements of the penguin eye and their functional and phylogenetic implications (Aves: Sphenisciformes: Spheniscidae)

Autor: Charles N J McGhee, Dane Gerneke, Jie Zhang, Peter W Hadden
Jazyk: angličtina
Rok vydání: 2021
Předmět:
Zdroj: Journal of Morphology
ISSN: 1097-4687
0362-2525
Popis: Scleral ossicles and other bony elements are present in the eyes of many vertebrates, including birds. In this study, the skeletal elements present in the penguin eye and orbit were imaged using macro photographs and micro‐computed tomography (micro‐CT), to help elucidate their function and significance. A total of 36 scleral rings and three whole skulls were imaged. King (Aptenodytes patagonicus), Fiordland crested (Eudyptes pachyrhynchus), Snares crested (Eudyptes robustus), royal (Eudyptes schlegeli) and yellow‐eyed (Megadyptes antipodes) penguins had between 12 and 14 elements in their scleral ring while the gentoo (Pygoscelis papua) had 14 and 17; little penguins (Eudyptula sp.) consistently had between 10 and 12 elements. All had at least two elements that overlapped, usually totally, each neighbour, and two that were overlapped by each neighbour. The interior structure of all ossicles revealed a lattice‐like arrangement of struts typical of cancellous bone, the whole being surrounded by thick cortical bone. The scleral ring of a 10 week gentoo chick was not completely ossified but rather had multiple small holes within it on micro‐CT. A large os opticus was present in one king penguin but in another bird of the same age and gender there was no such bone. Much smaller accessory bones were found in the posterior pole of one Snares crested and one little penguin. We conclude that the penguin scleral ring not only maintains the shape of the eye but also provides protection and a site of insertion for rectus muscles. However, the extreme variability in the os opticus suggests that it is not essential to normal function.
Micro‐CT of the scleral ring of a Snares crested penguin (Eudyptes robustus) surrounding a gentoo penguin (Pygoscelis papua) skull. In penguins the scleral ring contains 10–17 overlapping ossicles, maintaining the shape of the eye and providing an attachment for the rectus muscles. Its position within the skull suggests a role in globe protection also. The ossicle ring is 23.3 mm in external diameter and the part of the head imaged is 80 mm long.
Databáze: OpenAIRE
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