Gross and microanatomy of the male reproductive duct system of the saltwater crocodile Crocodylus porosus

Information on the morphology and histology of the male reproductive system of the Crocodylia species is necessary to determine the role of these tissues in the production of functional spermatozoa. Accordingly, in this study we examined the gross morphology and microanatomy of the testis and the male excurrent duct system through which spermatozoa pass before ejaculation. The data demonstrate that the reproductive system in male saltwater crocodiles comprises paired testes, which convey spermatozoa distally via the rete testis into an excurrent duct system comprising ductuli efferentes, ductuli epididymides, ductus epididymidis and ductus deferens. The epithelium delineating the male tract was dominated by non-ciliated and ciliated cells structured into a simple columnar lining of the ductuli efferentes and ductuli epididymides, through to the high pseudostratified columnar epithelium of the ductus epididymidis and ductus deferens. The morphology and histochemical staining of these ducts suggest their involvement in seminal fluid production and/or its modification, which likely contributes to the nourishment, protection and/or storage of crocodile spermatozoa. As a reflection of their common Archosaurs ancestry, the overall structural characteristics we describe for the crocodile male excurrent duct system share closer similarities to those of the Aves than other clades within the Reptilia class or Mammalia.

Automated summary

This study investigated the morphology and histology of the male reproductive system of crocodiles, focusing on the role of the excurrent duct system in sperm production and modification. The findings suggest that the ducts are involved in seminal fluid production and/or modification, contributing to the nourishment, protection, and storage of crocodile sperm. The structural characteristics of the crocodile male excurrent duct system share closer similarities with birds than with other groups within the Reptilia class or Mammalia, reflecting their common Archosaurs ancestry.