Germinal Development in the Mother Sporocyst and Redia of Halipegus eccentricus Thomas, 1939

Abstract

H. eccentricus, a hemiurid trematode from the eustachian tubes of the frog, has its mother sporocyst and one generation of rediae in spp. of Physa in the Douglas Lake region, Michigan. Development of germinal masses was observed in a large series of immature stages of mother sporocysts and rediae from both exptl. and natural infections. A morula-like germinal mass consisting only of unicellular components is present in the miracidium and youngest mother sporocyst. In a stage 0.1 mm. in length, the body cavity is almost completely filled with germinal masses composed of both unicellular and multicellular components. In later stages these produce large numbers of embryos, and in almost mature mother sporocysts all the germinal masses have broken down into embryos except one attached near the posterior end. This was still present in the oldest mother sporocyst seen. In very immature redial embryos a morula-like germinal mass of unicellular components is present near the posterior end. In older embryos germinal masses are found all along the body cavity. In later stages these break up into cercarial embryos, leaving finally a single large germinal mass in the posterior end which is still present and giving off embryos in mature rediae. It was estimated that in natural infections as many as 30,000 to 40,000 embryos were present, and that the total cercarial production would be many times that number.