Cranial Courtship Glands of Eurycea chamberlaini

Besides studies on mental glands, research regarding cranial integumentary glands potentially involved in courtship of plethodontid salamanders is scarce. In this study, we examined the cranial glands of Eurycea chamberlaini. Scattered amongst typical mucous and serous glands of the integument, we found simple alveolar glands that reacted positively with the periodic acid-Schiff procedure along the lateral sides of the heads of only male E. chamberlaini during the putative mating season. These glands were identical to the lateral head courtship glands previously described in E. bislineata. External nasal glands of E. chamberlaini were also identical in morphology and histology to those previously described in E. bislineata, with the bulk of the secretory terminals residing behind the orbital cavities and extending anteriorly to where their excretory ducts empty through the integument dorsal to the external nares. We measured external nasal gland length, width, height, and volume and found that the means were greater in males when compared to females except for width, which was not sexually dimorphic. We compared external nasal gland tubular diameter to mental gland tubular diameter (a known secondary sexual structure) throughout the year and found a direct correlation that was significant in males but not for females; thus, hypertrophy of external nasal glands occurs at the same time pheromone production increases in mental glands, supporting a previously proposed hypothesis that external nasal glands are also secondary sexual structures in Eurycea. In culmination, Eurycea from two different complexes possess the same suite of cranial integumentary glands that may be involved in courtship, providing evidence that these glands are possibly ubiquitous across Eurycea.