R.J. Tarpley, DVM, PhD; S.H. Ridgway, DVM, PhD
Gross dissection of the orbital gland of the bottlenose dolphin
(Tursiops truncatus) has revealed a large, finely lobulated, belt-like structure
complete-Ty surrounding the ocular globe with ductular connections directly into the
conjunctival sac between the globe and eyelids. Correlative light microscopic (LM) and electron
microscopic (EM) analysis utilizing a special embedding plastic (LR White) has been used which
allows adjacent sections to be examined from the same block using both techniques. This
approach has confirmed the composition of both major types of intracytoplasmic vesicles in the
acinar cells as acid and neutral glycosaminoglycans through Alcian blue/periodic acid Schiff
histochemistry. While these appear both from structural and histochemical evidence to represent
the major components of the tear product in the dolphin, exposure of paraffin sections to Sudan
Black stain indicate the presence of some secretary lipid vesicles as well. The predominance of
glycosaminoglycans, however, represents a departure from the findings in terrestrial
mammals.