Description of Metagonimus pusillus sp. nov. (Trematoda: Heterophyidae): phylogenetic relationships within the genus

Abstract

As a result of experimental studies conducted in the Russian southern Far East, adult worms from the genus Metagonimus were obtained. A comparative analysis of the morphometry of these worms with other Metagonimus representatives showed that they are most similar to M. katsuradai Izumi, 1935 and M. otsurui Shimazu & Urabe, 2002 found in Japan, due to the ratio of suckers and the positions of the testicle, uterus and vitellaria. However, Russian worms differ from species in Japan by other metric characters: they differ from M. otsurui by the maximum size of most organs and from M. katsuradai by body width, pharynx length, and maximum size of testes and ovary. At the same time, they are identical to a trematode from the Russian southern Far East, which was previously identified as M. katsuradai. The validity of this species was also confirmed by genetic data. According to the 28S gene and the internal transcribed spacer 2 (ITS2) region of rDNA, as well as the cytochrome c oxidase I (cox1) gene of mtDNA, the Metagonimus specimens found in Russia differ from published genetic data for other members of this genus. However, both morphological similarity and molecular data showed that M. pusillus sp. nov., M. katsuradai and M. otsurui are most likely cryptic species. Furthermore, additional data based on a mitochondrial marker were provided for M. suifunensis Shumenko, Tatonova & Besprozvannykh, 2017 from Russia.

Three species of Exorchis Kobayashi, 1921 (Digenea: Cryptogonimidae) in the East-Asian region: morphological and molecular data

“…n. (7.1–7.4%), which is located at a basal position of the tree. These values are comparable to interspecies genetic distances between representatives of related families, namely Opisthorchiidae Looss, 1899 and Heterophyidae Leiper, 1909 (Tatonova et al ., 2018; Besprozvannykh et al ., 2019). Fixed amino acid substitutions have also been identified between analysed species (Fig.…”

Infection characteristics of Metagonimus species (Digenea: Heterophyidae) metacercariae in fish from major rivers of Korea

“…Fluke members in the genus Metagonimus Katsurada, 1912 (Digenea: Heterophyidae) included more than 7 nominal species; i.e., M. yokogawai Katsurada, 1912, M. takahashii Suzuki, 1930, M. minutus Katsuta, 1932, M. katsuradai Izumi, 1935, M. otsurui Saito and Shimizu, 1968, M. miyatai Saito et al, 1997, and M. hakubensis Shimazu, 1999 [ 10 , 11 ]. Recently, 2 species, M. suifunensis Shumenko et al, 2017 and M. pusillus Tatonova et al, 2018, were additionally reported in Russia [ 12 , 13 ]. Among these 9 Metagonimus species, 3 ones, i.e., M. yokogawai , M. takahashii , and M. miyatai , are distributed in this country.…”

Molecular evidence of the absence of Metagonimus yokogawai (Katsurada, 1912) in Europe: report of Metagonimus sp. in cyprinoid fish from the River Danube in Hungary

“…This species was described by Katsurada (1912) in Japan as Heterophyes yokogawai and then reported from other Asian countries (South Korea, Taiwan, and India), as well as Russia, Israel and several European countries (Bulgaria, Czech Republic, Hungary, Serbia, and Spain) (Yu and Mott 1994 ; Rácz and Zemankovics 2002 ; Chai et al 2009 ; Pornruseetairatn et al 2016 ). However, the global distribution of M. yokogawai has yet to be confirmed, as other species of Metagonimus have a limited geographical distribution, with most species described from East Asia (Shimazu 1999 , 2002 ; Chai and Lee 2002 ; Shimazu and Urabe 2002 ; Kino et al 2006 ; Shumenko et al 2017 ; Tatonova et al 2018 ; Nakao et al 2022 ).…”