Morphology of Rathke’s Glands in the Alligator Snapping Turtle, Macrochelys temminckii (Chelonia: Chelydridae)

I examined the morphology of Rathke’s glands (RG) in the Alligator Snapping Turtle, Macrochelys temminckii, using light microscopy and scanning electron microscopy. This species possesses 4 pairs of RG (i.e., an axillary and three inframarginals) that are embedded beneath marginal bones and are named primarily according to the anatomical location of their orifices. These holocrine-type, exocrine, integumentary glands are anatomically and ultrastructurally similar to one another. Each gland contains a single and highly vascularized secretory lobule, which is bounded by a thick tunic of asymmetrically-arranged striated muscle bundles. Two types of secretory vacuoles were identified within the holocrine cells of the glandular epithelium. The results of this study generally support my previous findings on RG in Chelydra serpentina, the Snapping Turtle; however, some lack of cellular and structural conformity was evident compared to glands in this close relative as well as to RG in other turtle species. For example, epithelial cell layer depth and configuration and glandular lumen composition were inconsistent with prior observations. Moreover, the dearth of secretory cells and their products within the lumen of glands suggests that storage or temporary retention of glandular materials differs markedly from the conditions found in RG of other cryptodiran turtles. The functional role of RG secretions in all turtles remains speculative.