Comparative ultrastructural studies on uterus-egg interrelations in some species of hymenolepidids [Cestoda] with aquatic life cycles

Adult specimens of four hymenolepidid species with aquatic life cycle: Microsomacanthus paracompressa (Czapliński, 1956) Spasskaya et Spasskii, 1961, Diorchis parvogenitalis (Skryabin et Matevosyan, 1945), Fimbriaria fasciolaris (Pallas, 1781) and Fimbriaria czaplinskii Grytner-Zięcina, 1994 were used to study and compare uterus-egg interrelation at the ultrastructural level (TEM and SEM). Results of the presented studies showed that in none of the species examined was the uterus merely a simple sac filled with eggs. At the final stage of development of infective eggs which was available for analysis, several tapeworms displayed significant differences in: (1) general architecture of uterus, (2) the ultrastructure of the uterine wall at the lumenal side, (3) the extent of connections between the uterine wall and the eggs, and (4) the ultrastructure of the outermost envelope surrounding the oncospheres. Details of ultrastructure of uterus-egg interrelations are presented and discussed.