On the life cycle of Brachylecithum orfi Kingston and Freeman, 1959 (Trematoda: Dicrocoeliidae), from the liver of the ruffed grouse, Bonasa umbellus L. infections in the vertebrate and molluscan hosts

MOLECULAR AND MORPHOLOGICAL DISCRIMINATION OF DICROCOELIID LARVAE (TREMATODA: DIGENEA) FROM TERRESTRIAL MOLLUSKS IN JAPAN

Trematodes of the family Dicrocoeliidae commonly use terrestrial mollusks as the first intermediate host. Despite the abundant studies on the adult worms in birds and mammals, few reports exist on their larval stage in snail intermediate hosts. A present survey of mollusks in Japan led us to the discovery of dicrocoeliid sporocysts with cercariae in 16 out of 303 individuals, encompassing eight snail species and one slug species. A DNA barcoding based on sequencing of mitochondrial cytochrome c oxidase subunit 1 showed that the larvae consisted of five species. Phylogenetic trees of nuclear 18S and 28S ribosomal DNAs confirmed the five species to be members of the Dicrocoeliidae. These were temporarily termed dicrocoeliid spp. 1 to 5, since conclusive identification was impossible without adult worms. These unknown species were phylogenetically related to each other, except sp. 5. The phylogenetic trees demonstrated close genetic relationships between sp. 3 and the genus Lutztrema, and between sp. 5 and the genus Lyperosomum. The phylogenetic analysis also suggested that a division into the subfamilies Dicrocoeliinae and Leipertrematinae is a wrong classification due to the paraphyly of the Dicrocoeliinae. Morphological characterization of the cercariae and their DNA barcodes provide a primary platform for differentiating dicrocoeliids from various mollusks in Japan. The DNA barcodes, in particular, will enable tracing the parasite life cycles, in case of finding metacercariae and adults from presently unknown hosts.

Molecular characteristics of representatives of the genus Brachylecithum Shtrom, 1940 (Digenea, Dicrocoeliidae) with comments on life cycle and host specificity

The genus Brachylecithum was for the first time subject to molecular taxonomic phylogenetic analysis in order to ascertain relationships among its component taxa. We used two markers—the nuclear ribosomal 28S ribosomal DNA (rDNA) gene and the mitochondrial cox1 gene, for six species of the genus; 11 sequences of partial 28S rDNA and partial cox1 were obtained from adult B. capilliformis, B. glareoli, B. kakea, B. laniicola, B. lobatum, and B. strigis, and from larval stages obtained from snails of the genus Cepaea. We propose to synonymize B. strigis with B. lobatum, while the genetic differences in the 28S rDNA gene and mitochondrial cox1 gene confirm the species status of B. capilliformis and indicate a distinct group within Brachylecithum, including B. kakea and B. laniicola. Cercarial and metacercarial isolates from the snails showed 100 % similarity to B. lobatum; thus, it is the first record of Cepaea snails as intermediate hosts of this species and the first report on life cycle abbreviation within the Dicrocoeliidae.