The Eyes of an African Penguin (Spheniscus demersus): General Morphology and Ophthalmopathology

Evaluation of the common pauraque (Nyctidromus albicollis) cornea using light and scanning electron microscopy

“…The Common pauraque corneal epithelium consisted of stratified, squamous and non-keratinized cells, similar to that found in other bird species (Collin & Collin, 2021;Monção-Silva et al, 2016;Pinto et al, 2016;Sokolenko et al, 2021). Centrally the epithelium consisted of 3 to 4 layers and measured 10.2 ± 3.4 μm thick, whereas peripherally only two to three layers were detected measuring 8 ± 3.9 μm thick.…”

“…The present study is the first to describe the characteristics of the common pauraque ( Nyctidromus albicollis ) cornea. Light microscopic evaluation showed similarities to most avian species previously studied, it is formed predominantly by collagen tissue, and composed of five layers from outside to inside: epithelium, Bowman's layer, stroma, Descemet's membrane and endothelium (Bayón et al., 2008; Collin & Collin, 2021; de Carvalho et al., 2018; Kafarnik et al., 2007; Pinto et al., 2016; Sokolenko et al., 2021; Werther et al., 2017).…”

“…Centrally the epithelium consisted of 3 to 4 layers and measured 10.2 ± 3.4 μm thick, whereas peripherally only two to three layers were detected measuring 8 ± 3.9 μm thick. Such dimensions are noticeably thinner in relation to other avian species (Collin & Collin, 2021;Murphy & Dubielzig, 1993;Sokolenko et al, 2021). For instance, the corneal F I G U R E 1 Histology of Common pauraque cornea.…”

“…In most other avian species, considerably higher values can be seen than in the Common pauraque cornea (Chard & Gundlach, 1938;Collin & Collin, 2021;Gonçalves et al, 2016;Gonzalez-Alonso-Alegre et al, 2015;Liu et al, 2016;Montiani-Ferreira et al, 2004;Moraes, 2018;Murphy & Dubielzig, 1993;Sokolenko et al, 2021;Werther et al, 2017) (Table 1). Species smaller than the Common pauraque have been shown to have thinner corneas, such as in the Anna's and Black-Chinned Hummingbirds (Moore et al, 2019), and in the Japanese Quail (Mayakkannan et al, 2018) (Table 1).…”

“…For instance, the corneal epithelium of Little Penguins Eudyptula minor has a thickness of 26 ± 7 μm and is composed of five to six rows of stratified squamous cells (Collin & Collin, 2021). Yet, the African Penguin Spheniscus demersus presented values closer to the common pauraque, demonstrating four layers of cells and 15 μm of thickness in the epithelium (Sokolenko et al., 2021). In the Golden Eagle Aquila chrysaetos , Murphy and Dubielzig (1993), found an epithelium with eight layers and 50 μm thick.…”