Development of the reproductive system of Echinostoma paraensei in Mesocricetus auratus analyzed by light and confocal scanning laser microscopy

► The maturation of the reproductive system of Echinostoma paraensei after infection of hamsters was observed by confocal microscopy. ► Primordium testis and ovary as a cluster of primordial cells from day 3 onward. ► The testes, ovary, cirrus sac and uterus organs were already present during the first week. ► Cells at different stages of development on ovary and few bundles of functional spermatozoa in 10 day-old worms. ► Eggs in the uterus, spermatozoa in the seminal vesicle, oocytes as fertilized eggs in the ootype were seen on day 14 p.i.