Fax: +724 738 4782
Is It or Isn't It? A Reexamination of the Anterior Orbital Glands of the Fat-Tailed Dunnart Sminthopsis Crassicaudata (Dasyuridae: Marsupiala) and a Reevaluation of Definitions for the Harderian Gland
Article first published online: 22 JUL 2010
Copyright © 2010 Wiley-Liss, Inc.
The Anatomical Record
Volume 293, Issue 8, pages 1449–1454, August 2010
How to Cite
Rehorek, S.J., Hillenius, W.J., Leigh, C. and Firth, B.T. (2010), Is It or Isn't It? A Reexamination of the Anterior Orbital Glands of the Fat-Tailed Dunnart Sminthopsis Crassicaudata (Dasyuridae: Marsupiala) and a Reevaluation of Definitions for the Harderian Gland. Anat Rec, 293: 1449–1454. doi: 10.1002/ar.21111
- Issue published online: 22 JUL 2010
- Article first published online: 22 JUL 2010
- Manuscript Accepted: 15 DEC 2009
- Manuscript Received: 9 JUL 2009
- Harderian gland;
- nictitans gland;
- anterior orbital gland
The anterior orbital glands of tetrapods, which include the Harderian and nictitans glands, can usually be differentiated either anatomically (nictitans gland is more anterior) or histochemically (Harderian gland secretes lipids). However, conflicting statements exist in the literature about the presence and identity of these glands. Two previous studies on Sminthopsis crassicaudata (Dasyuridae: Marsupiala) either failed to note any anterior ocular glands or used no histochemical analyses. This study reexamined the structure of the anterior orbital glands of S. crassicaudata. Histological, histochemical, and ultrastructural examination revealed three glandular units: two of which are located superficially in the nictitating membrane, the third lying deeper in the connective tissue. The ducts of these three glandular units all open onto the corneal aspect of the nictitating membrane. These cells contain mainly serous granules with sparse intracellular lipid droplets. The nomenclature of these structures depends upon the definition used. According to the anatomical definition, S. crassicaudata has two glands: anteriorly the nictitans and posteriorly the Harderian gland. In contrast, if the histochemical definition is used, there is only one gland, but its precise identity cannot be confirmed until the role of the lipid droplets is established. Moreover, the histochemical definition poses additional problems with respect to the mechanism of secretion, multiple secretions, and glandular plasticity. Finally, the unitary definition identifies one deeply subdivided gland with an anterior and a posterior lobe in S. crassicaudata. This last definition is broad enough to accommodate a wide level of anatomical variation in the anterior ocular glands of tetrapods. Anat Rec 293:1449–1454, 2010. © 2010 Wiley-Liss, Inc.