Poster Presentation ESA-SRB-ANZBMS 2024 in conjunction with ENSA

Investigating the existence and nature of the prostate gland in monotreme species (#447)

Yolande Campbell 1 2 , Chiara Palmieri 2 , Jo Gordon 2 , Peter Temple-Smith 3 , Marilyn Renfree 4 , Brett Nixon 5 , Jackson Boyd 1 2 , Stephen Johnston 1 2
  1. School of Environment, University of Queensland, Birsbane , QLD, Australia
  2. School of Veterinary Science, University of Queensland, Gatton, QLD, Australia
  3. Department of Medicine, Nursing and Health Sciences, Monash University , Melbourne, VIC, Australia
  4. School of BioSciences, The University of Melbourne, Melbourne, VIC, Australia
  5. School of Environmental and Life Sciences, The University of Newcastle, Newcastle, NSW, Australia

In therian mammals, male accessory sex glands are fundamental to the production of seminal fluid and fertility[1], but little is known about their function in monotremes. Furthermore, the existence of a definitive prostate gland in the echidna and platypus remains controversial[2]. Understanding the presence and nature of sex accessory glands in monotremes will not only provide new insights into their reproductive biology but also to the evolution of the prostate gland.

This study describes the peri-urethral tissue and secretory material in the short-beaked echidna (Tachyglossus aculeatus) and the platypus (Ornithorhynchus anatinus). Sexually mature male echidnas, euthanized for welfare reasons, were obtained from wildlife hospitals both outside (n = 3) and during the mating season (n=3). Platypus tissue samples (n = 3) were sourced from breeding males from an earlier study. Tissue sections were prepared for histology, histochemistry (Masson's trichrome, Alcian Blue, Period Acid Schiff) and immunohistochemistry using basal cell (tumour protein63 and cytokeratin14) and luminal cell (cytokeratin8/18, prostate specific antigen and androgen receptor) markers.

The platypus showed a morphologically and histologically distinctive prostate gland surrounded by a thick band of stroma, encapsulated in collagen fibres. The glands were tubulo-alveolar, lined by pseudo-stratified tall columnar cells and embedded into fibromuscular stroma with minimal collagen fibres. The secretory material was strongly positive for polysaccharides and acidic mucosubstances.

Echidnas collected outside of breeding season had limited or no obvious development of peri-urethral glands. However, breeding males demonstrated glandular epithelial tissue that was more disseminate in nature and ranged from stratified squamous to pseudostratified columnar cells.

Further immunohistochemical analysis of cell types will be used to determine if this peri-urethral tissue in echidnas and platypuses represents a primitive prostate, homologous to the definitive prostate glands of marsupials and placental mammals. This will provide insight into the evolutionary origins of this key accessory sex gland.

  1. 1. Evans, T. J. (2007). Chapter 14 - Reproductive toxicity and endocrine disruption. In R.C. Gupta (Eds.), Veterinary Toxicology (pp. 206-244). Academic Press. https://doi.org/10.1016/B978-0-12-811410-0.00017-9
  2. 2. Temple-Smith, P. & Grant, T. (2001). Uncertain breeding: a short history of reproduction in monotremes. Reproduction, Fertility and Development, 13, 487-497.