The Harderian gland of the Cheesman's gerbil (Gerbillus cheesmani) of the Kuwaiti Desert

The Harderian gland is a large orbital structure. Several functions have be en ascribed to the gland such as lubrication of the eye, a source of pherom ones, thermoregulartory lipids and photoprotective secretions and a part of the retinal-pineal axis. In the present study, the Harderian gland of the Cheesman's gerbil, Gerbillus cheesmani, is described for the first time. Th e gland is located around the posterior portion of the eyeball. The gland i s compound tubular, surrounded by a thin connective tissue capsule. Only on e secretory epithelial cell type was recognized, characterized by the prese nce of lipid vacuoles and cytoplasmic slashes in high numbers; the former b eing more concentrated towards the apical part while the latter being more concentrated towards the central and basal parts. Some of the cytoplasmic s lashes contained electron dense filamentous structures. Similar structures were observed in the lipid vacuoles. Thus, a functional relationship betwee n the cytoplasmic slashes and the lipid vacuoles is suggested. A unique str ucture was observed, termed dome-like cells, located between the epithelial cells and the basement membrane. These cells were characterized by the ext ensive presence of pleomorphic mitochondria and compact lamellae of granula r endoplasmic reticulum (GER) in the form of finger prints. The gland was f ound to be actively secreting porphyrins as well as lipids. Cellular debris was also seen in the tubular lumina. Myoepithelial cells with their spindl e shape and elongated nuclei were evident between the basement membrane and the secretory epithelium. Sparse interstitial tissue was observed in-betwe en the gland tubules of both male and female gerbils. Macrophages, dendriti c melanocytes and lymphocytes are the most represented cellular components of che interstitium. Further studies are required to investigate the functi on of the dome-like cells as well as the role of lymphocytes in the rodents Harderian gland.