Sperm characterization of the Amazonian freshwater cururu stingrayPotamotrygon wallacei(Potamotryogonidae): basic knowledge for reproduction and conservation plans

Abstract

SummaryThis study aimed to describe the morphology and sperm quality of free-living adult males of cururu stingrayPotamotrygon wallacei, endemic from the Rio Negro basin, Brazilian Amazon. The sperm was collectedin locofrom the seminal vesicle region and fixed in buffered saline formaldehyde solution for further evaluation of morphometry, sperm plasma membrane integrity and sperm concentration. The spermatozoa presented a total length of 138.25 ± 1.82 μm with a helical shape and a long head. A high percentage of cells with intact membrane (98 ± 2%) and normal spermatozoa (92 ± 1%) were observed. The cell concentration was 0.34 ± 0.05 × 1010spermatozoa/ml of semen. These observations are unprecedented for potamotrygonid species and will serve as a basis for future management and conservation strategies.