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

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.

Keywords: cornea; histology; palisades of Vogt; wild ruminants.

Figure 1

The photomicrograph of the cornea in the examined ruminants. H&E stain. (a)—common wildebeest, (b)—Kirk’s dik-dik, (c)—Natal red duiker, (d)—scimitar oryx, (e)—sitatunga, (f)—Philippine spotted deer, (g)—Père David’s deer, (h)—moose, (i)—reindeer, (j)—reticulated giraffe, (k)—okapi, (l)—Balabac mouse-deer, (m)—alpaca. Scale bar: (a,k) = 20 µm; (b–j,l–m) = 10 µm. ace—anterior corneal epithelium, alm—anterior limiting membrane (Bowman layer—blue arrow), ker—keratocytes (black arrow), psc—the proper substance of the cornea.

Figure 2

The photomicrograph of the cornea in the examined ruminants. H&E stain. (a)—common wildebeest, (b)—Kirk’s dik-dik, (c)—Natal red duiker, (d)—scimitar oryx, (e)—sitatunga, (f)—Philippine spotted deer, (g)—Père David’s deer, (h)—moose, (i)—reindeer, (j)—reticulated giraffe, (k)—okapi, (l)—Balabac mouse-deer, (m)—alpaca. Scale bar: (a,h) = 50 µm; (d,f–m) = 20 µm; (b,c,e) = 10 µm. plm—posterior limiting membrane (Descemet’s membrane), psc—proper substance of cornea.

Figure 3

The photomicrograph of the palisades of Vogt in the examined ruminants. H&E stain. (a,b)—common wildebeest; (c,d)—Kirk’s dik-dik; (e,f)—Natal red duiker; (g,h)—scimitar oryx; (i,j)—sitatunga; (k,l)—Philippine spotted deer. Scale bar: (a,c,e,g,i,k) = 50 µm; (b,d,f,h,j,l) = 10 µm. cle—corneal limbus epithelium, psc—the proper substance of the cornea, pss—the proper substance of the sclera, pV—palisades of Vogt (black arrows).

Figure 4

The photomicrograph of the palisades of Vogt in the examined ruminants. H&E stain (c–h,k–n); Picro-Mallory stain (a,b,i,j). (a,b)—Père David’s deer; (c,d)—moose; (e,f)—reindeer; (g,h)—reticulated giraffe; (i,j)—okapi; (k,l)—Balabac mouse-deer; (m,n)—alpaca. Scale bar: (a,c,e,g,i,k,m) = 50 µm; (b,d,j,h) = 20 µm; (f,l,n) = 10 µm. cle—corneal limbus epithelium, psc—the proper substance of the cornea, pss—the proper substance of the sclera, pV—palisades of Vogt (black arrows).