The complete mitochondrial genome of 3 species of allocreadiids (Digenea, Allocreadiidae): characterization and phylogenetic position within the order Plagiorchiida.

Trematodes of the family Allocreadiidae are primarily found in the intestines of freshwater fishes around the world. The family includes 15 genera and c. 130 species. The last 2 decades have witnessed an increase in the genetic library of its species. Molecular data have been crucial for species delimitation and species description within Allocreadiidae and for understanding their evolutionary and biogeographical history and classification. Here, the mitogenomes of 3 species of allocreadiids were obtained using high throughput sequencing methods. Mitogenomes were compared with other members of the order Plagiorchiida to determine their molecular composition, gene rearrangement and phylogenetic interrelationships. The complete circular mitogenomes of Allocreadium lobatum, Creptotrematina aguirrepequenoi and Wallinia mexicana were 14 424, 13 769 and 13 924 bp long respectively, comprising 12 protein-coding genes, 22 transfer RNA genes, 2 ribosomal RNA genes and 2 non-coding regions. Gene arrangements were identical to other Xiphidiatan trematodes. Phylogenetic analyses using the mitogenomes revealed Allocreadiidae as a monophyletic group closely related to other members of the suborder Xiphidiata; A. lobatum was yielded as the sister taxon of C. aguirrepequenoi + W. mexicana. Our study increases the complete mitochondrial genome library of trematodes and strengthens our understanding of the phylogenetic relationships and classification of this parasite group.

Phylogenetic assessment of some Palearctic Allocreadium spp. (Trematoda, Gorgoderoidea: Allocreadiidae).

The genus Allocreadium is a group of digenetic trematodes whose adult representatives mainly parasitize the intestines of freshwater fishes. The aim of this research is to reconstruct the phylogeny of four Palearctic species of this genus, Allocreadium dogieli, Allocreadium isoporum, Allocreadium papilligerum, and Allocreadium sp. ex Oreoleuciscus potanini from Mongolia. The DNA sequences of the 28S rRNA gene and the rDNA ITS2 region were obtained and then analyzed for phylogenetic inference. The analysis is complemented with the morphological descriptions for all four species. Phylogenetic analyses show that the newly obtained isolate of A. isoporum appeared to be genetically similar to previously obtained isolates of A. isoporum. Allocreadium dogieli probably belongs to the same evolutionary lineage of Allocreadium as A. crassum, while A. papilligerum to the same evolutionary lineage as Alocreadium transversale ex Cobitis taenia from Lithuania, but the detailed species composition of these lineages requires further elucidation. Allocreadium sp. was genetically close to Allocreadium sp. ex P. phoxinus from Primorski Krai, Russia, and a group of these Allocreadium had a sister relationship with Allocreadium khankaiensis. Our findings contradict some recent hypotheses about the phylogeography of Allocreadium spp.

Allocreadium khankaiensis sp.nov. and Allocreadium hemibarbi Roitman, 1963 (Trematoda: Allocreadiidae) from the Russian Far East: Morphological, molecular, and phylogenetic studies.

Three species of the genus Allocreadium were collected from cyprinid fish in the territory of the Russian Far East: Allocreadium khankaiensis sp.nov; Allocreadium hemibarbi Roitman, 1963, and Allocreadium sp. 1. It is established that, according to morphometric values, the species A. khankaiensis sp.nov. has high morphological similarity with Allocreadium elongatum Achmerov, 1960; Allocreadium erythroculteris Achmerov, 1960; and Allocreadium aburahaya Shimazu, 2003. However, A. khankaiensis sp.nov. differs from A. elongatum and A. erythroculteris by vitellaria extension and size of cirrus pouch. In addition, A. khankaiensis sp.nov. differs from A. erythroculteris by the smaller size of the body and ventral sucker. A. khankaiensis sp.nov. and A. aburahaya have similar metrical values but A. khankaiensis sp.nov. differs by the shape of the testes: rounded vs. lobed. Species affiliation of another Allocreadium species is based on the morphometric identity with the species A. hemibarbi. Phylogenetic tree reconstruction using partial sequences of the 28S rRNA gene revealed a clear resolution of all Allocreadium species, excluding Allocreadium lobatum and Allocreadium neotenicum. The genetic analysis detected Allocreadium sp. 1 as a presumably independent species from the Razdolnaya River basin.

Histopathology of the liver of Mastacembelus armatus (Lecepede, 1800) due to trematode parasite, Allocreadium khami n.sp.

The trematode parasite, Allocreadium khami n.sp. cyst is found infected to the liver of freshwater fish, Mastacembelus armatus (Lecepede, 1800). Histopathological studies have been made to access the extent of damage caused by the parasite. The changes that have witnessed in the liver includes inflammation of liver, change of colour and formation of cysts. The histopathological changes include disarray in the arrangement of hepatochords, arrangement and rupture of hepatocytes.