Comparative Histology, Histochemistry, and Ultrastructure of Rathke's Glands in Hatchlings of Two Species of North American Box Turtles (Terrapene carolinaandTerrapene ornata)

Abstract

We examined the histology, histochemistry, and ultrastructure of Rathke's glands in hatchlings of the three-toed box turtle, Terrapene carolina triunguis, and the desert box turtle, Terrapene ornata luteola. Both species possess one pair (axillary) of Rathke's glands, which are similar anatomically and histochemically to one another. Each gland is composed of a single, highly vascularized secretory lobule, which is surrounded by a thick sheath of striated muscle. Two types of large secretory vacuoles characterize most of the holocrine cells produced by a relatively thin glandular secretory epithelium. Analysis of our results suggests that the chief secretory material of the smaller dark-staining type 1 secretory vacuole appears to be a glycoprotein complex. The larger, mostly translucent type 2 secretory vacuole contains multilayered and variously sized lamellar bodies, whose structural design is reminiscent of an epidermal lipid delivery system in vertebrates. The functional role of Rathke's glands in Terrapene and in other turtles remains unclear at the present time.