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

This study aimed to describe the morphology and sperm quality of free-living adult males of cururu stingray Potamotrygon wallacei, endemic from the Rio Negro basin, Brazilian Amazon. The sperm was collected in loco from 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 × 1010 spermatozoa/ml of semen. These observations are unprecedented for potamotrygonid species and will serve as a basis for future management and conservation strategies.

Effects of exposure to cadmium in sperm cells of zebrafish, Danio rerio.

Cadmium is a natural element found in the earth's crust; it is usually associated with other metals, but due to the impacts caused by human activity, its concentration has increased in the aquatic environment. This metal may damage aquatic animal reproduction, decreasing the rate of fertilization of organisms such as fish. Thus, this study aimed to evaluate the in vitro toxicity of different concentrations of cadmium (0 (control), 0.5, 5, and 10 µg/L) using sperm cells of model organism zebrafish, Danio rerio. Structural parameters, including integrity and fluidity of the plasma membrane, concentration of oxygen species, mitochondrial function and DNA fragmentation were measured by flow cytometry. The following sperm movement parameters were also measured using the computer assisted sperm analysis (CASA) system: motility, time of motility, curvilinear velocity, average path velocity and straight line velocity in µm/s. Significant effects were observed on path speed, straight speed, curvilinear velocity, motility time, progressive and total motility, and plasma and DNA integrity. The results showed that cadmium can negatively affect some reproductive parameters in D. rerio, which may reduce the fertility rate of these animals.