Is Fasciola monospecies? : Cross experiments between Fasciola hepatica and F.gigantica

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The first purpose of the study is to find small experimental animals susceptible to Fasciola hepatica and F.gigantica through experimental infections. Rats, gerbils (Meriones unguiculatus), and the rat-like hamster, Tscherskia triton were orally inoculated with 2 to 10 metacercariae of the two species, and then sacrificed after 2 to 3 months. The animals were checked for the presence of flukes in the liver parenchyma and bile duct, infection rate and damage of the liver. The flukes obtained were fixed in 70% ethanol, stained with Carmin solution, and measured on the body length and width. F.hepatica had high recovery rate and matured in the three animal species, while F.gigantica had low rate and did not matured in all the hosts. These findings showed that these three animals could not play the role of suitable hosts of both Fasciola species.Cross experiments between bisexual F.hepatica (Fh) and parthenogenic diploid (2n) or triploid (3n) were carried out using rodent hosts, and the fi … More rst filial generations (F1) were genetically characterized by analyzes of chromosomes and DNA sequences. In the first experiments, single metacercariae of both Fh and 2n were orally inoculated to the rat-like hamster, Tscherskia triton. A 2n fluke recovered from the host was confirmed to conjugate with a Fh fluke by morphological observation. F1 produced from the 2n fluke was allopolyploid (triploid) and this suggested that Fh and 2n were different species each other. In the second experiments, 10 metacercariae each of Fh and 3n were inoculated to Wistar rats. The 3n flukes recovered from the rats and confirmed to conjugate with a Fh fluke were provided for production of F1. Genetic observation showed that the F1 was a tetraploid and had 10 univalent chromosomes and 10 trivalent chromosomes in reproductive cells. Furthermore, the F1 had abnormal spermatogenesis. These findings suggested that F.hepatica and parhtenogenic triploid were different species each other. The F1 tetraploid was sterile.Cross experiments between Fh and Fg, and Fg and parthenogenic diploid (2n) or triploid (3n) were carried out using goat hosts. Unfortunately, the goat infected with both Fh and Fg was dead by the time the flukes have matured and therefore the F1 flukes between the two species could not be obtained. While the F1s between Fg and the parthenogenic plolpoids have not been obtained by the time the experimental period expired. However, these findings suggest that F.hepatica, F.gigantica and parthenogenic Fasciola sp. are different species each other. Less