# Testicular Morphology and Spermatogenesis in Potamotrygon motoro: Insights Into Reproduction of Freshwater Stingrays

## TL;DR

This study describes how freshwater stingrays develop and produce sperm, revealing unique features of their reproductive biology.

## Contribution

The paper provides the first detailed description of spermatogenesis in Potamotrygon motoro.

## Key findings

- Testes of P. motoro contain germinal zones, a degenerated zone, and the epigonal organ.
- Spermatogenesis follows a cystic pattern maintained by Sertoli cells.
- Spermiogenesis involves nuclear compaction and structural modifications.

## Abstract

This study investigated the spermatogenesis of the freshwater stingray Potamotrygon motoro using microscopic analyses. The testes of this species were described as being composed of germinal zones, a degenerated zone, and the epigonal organ, consisting of connective tissue and lymphomyeloid cells. A cystic pattern of spermatogenesis was observed, in which each cyst is formed and maintained by Sertoli cells that undergo morphological and positional changes throughout the process. After the release of spermatozoa into the duct, the peripheral cysts formed a degenerating layer. Spermiogenesis, the final phase of sperm development and differentiation, was identified as a complex process in P. motoro, involving nuclear compaction and structural modifications. This study presents, for the first time, a detailed description of the germ cell development process in P. motoro, contributing to the understanding of spermatogenesis in freshwater stingrays.

Electron microscopy of Potamotrygon motoro spermatozoa. a – Illustration of a schematic sperm cell depicting the helical head, intermediate piece (midpiece), and flagellum. b ‐ Helical heads (Hh) of spermatozoa inserted into the cytoplasm of Sertoli cells (S) through openings in the plasma membrane. Scales: 10 μm.