Morphology and Morphometry of the Ovaries and Uteri of the Amazonian Freshwater Stingrays (Potamotrygonidae: Elasmobranchii).

The reproductive biology of South American freshwater stingrays (family Potamotrygonidae) is still poorly studied compared to other marine species. In the present study, we examined the gross anatomy and histology of six species of potamotrygonids from the Amazon basin and described the structural asymmetry of the ovaries and their relationship between ovarian and uterine fecundities. Stereological techniques were used to quantify the volume of ovarian and epigonal organ tissue associated with the left and right sides of the Potamotrygon wallacei, a recently described species, locally known as the cururu ray. This species presented ovarian asymmetry; the left epigonal organ-ovary complex was 55 times larger than the right side. The right side was composed of, volumetrically, 7.3% ovarian tissue and 92.7% epigonal organ tissue whereas the left side was 51.2% of ovarian tissue and 48.8% epigonal organ tissue. In all species, six types of follicles were identified in both right and left ovaries. Uteri were symmetrical and the fecundity ratio between the right and left sides was 0.9:1.1, respectively. Despite the volumetric difference of ovarian tissue between the two sides, the uterine fecundity shows that both ovaries are functional and that ovarian fecundity alone is not an accurate measure to determine the reproductive potential of freshwater stingrays. Anat Rec, 300:265-276, 2017. © 2016 Wiley Periodicals, Inc.