Eur J Anat, 21 (2): 125-139 (2017)

Apteryx spp. (Kiwi) possess an uropygial gland: Anatomy and pathology

Sian M. Reynolds^1,2, Isabel Castro¹, Maurice R. Alley³, Susan J. Cunningham4

¹P.O. Box 11222, Institute of Agriculture and Environment, Massey University, Palmerston North, New Zealand, ²New Zealand Department of Conservation, Haast Awarua Field Centre. P.O. Box 50, Haast 7844, New Zealand, ³P.O. Box 11222, Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, New Zealand, ⁴Percy FitzPatrick Institute, DST/NRF Centre of Excellence, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa

ABSTRACT The uropygial gland is a prominent feature of the avian anatomy but there is limited information on its structure and function. The gland is of current interest because it provides a source for volatile chemicals that can be used by birds in communication. We examined the anatomy of uropygial glands in Apteryx for the first time. The gland was located immediately caudal to the cloaca and surrounding the coccygeal bone rather than rostral to the coccygeal bone and above the posterior free caudal vertebrae as in other birds. This may explain why it has not been recognised until relatively recently. Like most uropygial glands Apteryxâ??s were bilobar but possessed eight primary sinuses, each opening through its own orifice in the glandâ??s papilla. Primary ducts were compact and branches of connective tissue extending from the capsule internally formed interfollicular septae that were thicker in some areas, grouping follicles into discrete lobules. Striated muscle was present in the capsule, a characteristic so far unique to Apteryx that may be used in controlling the expulsion of secretion. There were significant differences in the architecture of the follicles between species and sexes that suggest differences in the production, storage and availability of uropygial gland secretion. This was supported by variations in live birdâ??s gland volume between two years of sampling. Atrophy of the uropygial gland was seen in two birds in poor condition suggesting that health impacts the functioning of the gland. This finding suggests an adaptive significance for the gland and offers a possible way for birds to communicate their health status through the production or composition of the secretion. More research is needed to fully understand the relationship between the anatomy of the gland in Apteryx and its function, but we propose that it plays roles in both feather maintenance and sociality.

Keywords: Holocrine â?? Oil gland â?? Rump gland â?? Preen gland â?? Integumentary gland â?? Apterygidae