Comparative Histology of the Cornea and Palisades of Vogt in the Different Wild Ruminants (Bovidae, Camelidae, Cervidae, Giraffidae, Tragulidae)

SIMPLE SUMMARY: In this study, for the first time, we performed a detailed histological analysis of the cornea and palisades of Vogt in the different wild ruminant species. The material for the research was taken from 49 adult wild ruminants (Bovidae, Camelidae, Cervidae, Giraffidae and Tragulidae) constituting 13 species coming from the Wroclaw Zoological Garden (Poland), the Warsaw Zoological Garden (Poland) and own collection of the Division of Animal Anatomy (Wroclaw). Our results showed that the number of layers of the cornea, i.e., five layers (anterior corneal epithelium, anterior limiting membrane (Bowman’s layer), the proper substance of the cornea, the posterior limiting membrane (Descemet’s membrane) and posterior corneal epithelium) or four layers (no Bowman’s layer) is not constant within even the same genus that includes the given species of the tested animal. The results of this study can form the basis for further research on the immunohistochemistry of the cornea in the maintenance of structural integrity and fluid balance in wild ruminants that can be used in veterinary ophthalmology diagnostics. ABSTRACT: In the study, we data concerning the histological and morphometrical examination of the cornea and palisades of Vogt in the different species of ruminants from the families Bovidae, Camelidae, Cervidae, Giraffidae and Tragulidae, coming from the Warsaw Zoological Garden, the Wroclaw Zoological Garden and the Division of Animal Anatomy. The following ruminant species were investigated: common wildebeest, Kirk’s dik-dik, Natal red duiker, scimitar oryx, sitatunga, Philippine spotted deer, Père David’s deer, moose, reindeer, reticulated giraffe, okapi, Balabac mouse-deer and alpaca. The cornea of ruminant species such as the common wildebeest, Kirk’s dik-dik, Natal red duiker, scimitar oryx, reindeer and Balabac mouse-deer consisted of four layers (not found in the Bowman’s layer): the anterior corneal epithelium, the proper substance of the cornea, the posterior limiting membrane (Descemet’s membrane) and the posterior corneal epithelium (endothelium). The anterior corneal epithelium was composed of a multilayer keratinizing squamous epithelium, which was characterized in the studied ruminants with a variable number of cell layers but also with a different thickness both in the central epithelium part and in the peripheral part. Moreover, the proper substance of cornea was thinnest in Balabac mouse-deer, Kirk’s dik-dik, Natal red duiker, scimitar oryx, Philippine spotted deer, alpaca, reindeer and sitatunga and was thickest in the reticulated giraffe. The thickest Descemet’s membrane was observed in the Père David’s deer. The corneal limbus is characterized by a large number of pigment cell clusters in Kirk’s dik-dik, scimitar oryx, moose, Balabac mouse-deer and alpaca. In the common wildebeest, Père David’s deer, moose, reticulated giraffe, okapi and alpaca, the palisades of Vogt were marked in the form of a crypt-like structure. The corneal limbus epithelium in the examined ruminants was characterized by a variable number of cell layers but also a variable number of melanocytes located in different layers of this epithelium. The detailed knowledge of the corneal structure of domestic and wild animals can contribute to the even better development of methods for treating eye diseases in veterinary medicine.