Donacides are distributed at sandy beaches all over the world except the Polar Regions, whereas the number of total species is 64. Many species of this family are demonstrating a valuable source for the artisanal fisheries. D. marincovichi and D. obesulus inhabit beaches from Northern Chile to Northern Ecuador in dense populations. The taxonomy of D. marincovichi and D. obesulus are controversially discussed. Sperm morphology is useful for taxonomic identification, frequently applied for mollusk taxonomy. Therefore samples of D. obesulus were taken from a Northern Chilean beach in Arica (Chinchorro) and D. marincovichi sampled in Central Peru south of Lima (Jahuya). Male gonads were elaborated and analyzed by transmission electron microscopy (TEM). Both putative species demonstrate a primitive sperm type, structured in acrosome, nucleus and tail (9+2 axoneme). In both cases the total number of mitochondria is four. The apex of the acrosome of both species shows a characteristic arrowhead, which was not observed from other species of this family yet. No differences in sperm morphology were found between both putative species. This supports our genetic study indicating that we rather deal with one single instead of two distinct Donax species.