Anatomy, histology, histochemistry and fine structure of the Harderian gland in the South American armadillo Chaetophractus villosus (Xenarthra, Mammalia)

Abstract

The anatomical, histological, histochemical and ultrastructural characteristics of the Harderian gland of the armadillo Chaetophractus villosus were described. The gland is the largest structure in the bony orbit. It is situated in the anteroventral region of the orbit. Obvious structural differences are not observed between males and females. The gland is compound-branched tubulo-alveolar, being characterized by a single layer of columnar cells surrounded by myoepithelial cells. It possesses a single excretory duct opened into the inner canthus. All glandular cells show yellow-green autofluorescence and additionally some glandular lumen may contain dense autofluorescent solid accretions. There are two peculiar and outstanding cytoplasmic features. One is represented by the smooth endoplasmic reticulum (SER), forming a closely woven meshwork. The other one is represented by "membranous bodies" apparently derived from the SER, RER and cytoskeleton with a "Star of David" configuration situated in the supranuclear region. Three types of vesicles are detected in the cytoplasm. Histochemical staining methods reveal lipids, proteins, neutral and acidic containing glycoconjugates in secretory vesicles. The mechanism of secretion appears either merocrine or apocrine. The epithelium of the intra- and inter-lobular excretory ducts suggests secretory activity. Tubulo-acinar glands similar to those seen in the lacrimal gland and nictitans glands are found related to the intralobular and main excretory ducts. The capillary network is characterized by fenestrated endothelium. The stroma possesses unmyelinated axons and plasma cells. The normal secretion of the secretory endpieces, particularly lipids, proteins and glycoconjugates, is complemented by mucous and serous secretions released by ductal cells and glands associated to the ducts.

Development of the nasolacrimal apparatus in the Mongolian gerbil (Meriones unguiculatus), with notes on network topology and function

“…The number of secretory ducts of the AOG varies within tetrapods (Rehorek et al, ). A single exiting duct has been described for a variety of tetrapods, including rodents (Payne et al, ; Shirama and Hokano, ; Theissen, ; Djeridane, ; this study), rabbits (Rehorek et al, 2011), deer (Rehorek et al, ), tree shrews (Pradidarcheep et al, ), armadillos (Weaker, ; Aldana Marcos and Affani, ), opossums (Krause and McMenamin, ), birds (Burns, ), and frogs (Chieffi et al, ). However, multiple exiting ducts have been described in dolphins (Tarpley and Ridgway, ) and reptiles (Saint‐Girons, ).…”

The organ of vision morphology of the southern two‐toed sloth (Choloepus didactylus Linnaeus, 1758; Pilosa, Choloepodidae)

“…Because there are a few study about the eye anatomy in the sloth, we compared our results with American armadillo Chaetophractus villosus . According to Aldana Marcos and Affani (2005), the lacrimal and superficial gland of the third eyelid in the South American Armadillo histologically and histochemically was identical because of the type of cells of the secretory endpieces (mucous, seromucous and serous cells). Our study, as well as the study in armadillos (Aldana Marcos, 1996; Aldana Marcos & Affani, 2005; Aldana Marcos et al, 1995, 2002; Cavagnari et al, 2001; Cavangnari et al, 1988; Weaker, 1981), confirms the presence of the deep gland of the third eyelid, what was opposite to the results obtained in the brown‐throated sloth by Sena et al (2021).…”

Ocular lens morphology is influenced by ecology and metamorphosis in frogs and toads

“…The association between spherical lenses and fossorial habits in frogs is distinct from what has been observed in some fossorial mammals such as the South American armadillo ( Chaetophractus villosus ), which appears to have flattened lenses [46]. However, previous work has shown that fossorial adult caecilian amphibians (Gymnophonia) with aquatic larvae have only slightly flattened lenses as adults [47].…”