Meeting Abstract
P3.28 Tuesday, Jan. 6 The anterior orbital glands in Sminthopsis crassicaudatis: a nomenclatural conundrum REHOREK, S.J.; HILLENIUS, W.J.*; LEIGH, C.; FIRTH, B.T.; Slippery Rock Univ.; College of Charleston; Univ. of Adelaide; Univ. of Adelaide hilleniusw@cofc.edu
The anterior orbital glands of tetrapods include the Harderian and nictitans glands, both located in the nictitating membrane. Usually these can 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 of these glands. For example, of the two studies on Sminthopsis crassicaudata (Dasyuridae; Marsupiala), one failed to note any anterior ocular glands and the other used no histochemical analyses. This study reexamined the structure of this glandular complex of S. crassicaudata. Histological examination revealed a well-developed, two-part (anterior vs posterior) glandular structure in the nictitating membrane. Histochemically and ultrastructurally it was shown that secretions of both glandular portions are mainly serous with sparse lipid droplets. The nomenclature of this complex depends upon the definition used. According to the anatomical definition, S. crassicaudata would have two glands: an anterior nictitans and a posterior Harderian gland. Fetal examination will be required to confirm that distinction. In contrast, the histochemical definition holds that both masses are Harderian glands, as both produce lipid and appear to use a merocrine secretory mechanism. However, the histochemical definition faces problems with respect to the mechanism of secretion, multiple secretions and glandular plasticity. Alternatively, the unitary definition refers only to the medial position of this gland and allows for multiple unconnected ducts. Based on this definition, S. crassicaudata would have one bilobed gland with an anterior and a posterior lobe. This last definition is broad enough to account the level of anatomical variation in the anterior ocular glands of tetrapods.
