Morphology of Rathke's Glands in the Snapping Turtle, Chelydra serpentina, with Comments on the Presence of Multilaminar Lamellar Bodies in Turtles

Abstract

I examined the histology and ultrastructure of Rathke’s glands in hatchling, juvenile, and adult snapping turtles (Chelydra serpentina). This species possesses four pairs of Rathke’s glands (i.e., one axillary and three inframarginals) that are embedded beneath marginal bones and are named primarily according to the anatomical location of their orifices. These integumentary glands are similar anatomically and ultrastructurally to one another. Each gland is comprised of a single, highly vascularized, secretory lobule, which is surrounded by a thick tunic of asymmetrically arranged, striated muscle. Two types of large secretory vacuoles characterize most of the holocrine cells produced by a relatively thin secretory epithelium. My results support previous studies that suggest that the chief secretory material of the mostly larger, dark-staining Type 1 secretory vacuole is a glycoprotein complex. The mostly translucent Type 2 secretory vacuole may contain osmiophilic granules that exhibit variously sized lamellar bodies, whose multilaminar structural design is reminiscent of an epidermal lipid delivery system in many vertebrates. The functional role of Rathke’s gland secretions in Chelydra serpentina and in other turtles remains unknown.