Genetic characterization and phylogenetic relationships of Phyllodistomum parasites in Indian subcontinent: insights from freshwater fish and shrimp hosts.

Phyllodistomum is the large digenean group of fish parasites, with 25 species described so far in the Indian subcontinent. Here, we redescribed two adult species of Phyllodistomum (P. srivastava Rai 1964 and P. parorchium Jaiswal 1957) collected from freshwater fish Heteropneustes fossilis Bloch, 1974 and Glossogobius giuris Ham, 1822, respectively, and an unknown Phyllodistomum metacercaria from shrimp (Macrobrachium dayanum Henderson, 1893). These parasites were genetically characterized using 28S and first and second internal transcribed spacers (ITS1 and ITS2) regions of the nuclear ribosomal DNA and CoxI region of the mitochondrial (mt) DNA to establish the link between metacercaria and adult. Morphologically, both the unknown metacercaria in shrimp and adult Phyllodistomum srivastava in fish, resembled in terms of crenulated margin of hind body, arrangement of diagonal testes, bipartite seminal vesicle, and compact paired vitelline masses. The two adult parasite species, P. srivastava from P. parorchium, were different in terms of shape and size of the body, ratio of suckers, the absence of crenulated margin of hind body, a single chambered seminal vesicle, and deeply lobed paired vitelline masses, in the former species. Comparison of the 28S, ITS, and mtCoxI sequence data suggested P. srivastava and Phyllodistomum metacercaria belong to the same species, and supported the distinction between P. srivastava and P. parorchium. Exploring the potential impact of Phyllodistomum infection on host behaviour and health would be prospective areas for future research.

Characterization of Clinostomum (Digenea: Clinostomidae) spp. in India.

Platyhelminths belonging to the family Clinostomidae (Digenea) have a worldwide distribution and are known to infect piscivorous birds through their intermediate hosts, usually fish species. In the present study, clinostome metacercariae were collected from fish hosts, including Channa punctata (Bloch 1793) (n = 25) and Trichogaster fasciata Bloch and Schneider 1801 (n = 25), from a freshwater system in India. The experimental infection of cattle egrets, Ardea (Bubulcus) ibis Linnaeus 1758, with some of the live metacercariae found in the present study was successful. Live adult parasites were obtained from the buccal cavity of the birds. Both metacercaria and adult specimens were subjected to molecular studies to obtain the sequences of 28S, ITS1, and ITS2 (nuclear rDNA) regions. The parasites were found to belong to three species, Clinostomum giganticum Agarwal 1959; C. piscidium Southwell and Prashad 1918; and Euclinostomum heterostomum (Rudolphi 1809). Phylogenetic analyses of the sequences obtained from the adults and metacercariae established a link between the metacercariae in the fish hosts and adults in the avian host, which is essential to elucidate their partial life cycle and specify morphological characteristics in the metacercarial stage.

Morphological and molecular characterization of six Indian Tetracotyle type metacercariae (Digenea: Strigeidae Railliet, 1919), using ribosomal and mitochondrial DNA.

Strigeids have a cup-shaped fore body, containing a holdfast organ with two lobes and hind body. The species diversity of strigeids remains incomplete, especially in the Indian sub-continent. Here, we described six Tetracotyle type metacercariae (T. muscularis, T. fausti, T. lucknowensis, T. xenentodoni, T. mathuraensis and T. glossogobii) from five fresh water fish, collected at Lucknow (India). Next, we characterized these metacercariae using ribosomal (18S, 28S, ITS2) and mitochondrial DNA (COI) to determine their systematic and phylogenetic position. Molecular identification using inter-specific variation range for all four molecular markers revealed 1.9-4.9% (18S); 3.3-8.8% (28S); 6.8-12.9% (ITS2), and 3.5-9.4% (COI) among six Tetracotyle type metacercariae. In phylogenetic analysis, constructed by neighbour-joining (NJ) and maximum likelihood (ML) methods, T. fausti, T. glossogobii, T. xenentodoni, T. lucknowensis and T. mathuraenis nested as sister groups with the member of strigeids for all four markers used; T. muscularis, however, formed a basal clade. Furthermore, phylogenetic placement states the monophyly of the Tetracotyle type of metacercariae in all the markers (18S, 28S, COI), except ITS2.

A new species of an interesting amphistome Pseudodiplodiscoides Murty, 1970 in Bellamya bengalensis Lamarck, 1882 from water bodies near district Barabanki, U.P.

A new species of an interesting trematode genus Pseudodiplodiscoides (Murty, Zool Anz 185:312-317, 1970), is described from the gut of the snail Bellamya bengalensis Lamarck, 1882, collected from the fresh water bodies near district Barabanki, U.P. After careful examination of several freshly collected specimens, the genus is validated and another species described under the genus Diplodiscus viz., D. minutus (Saksena et al., Indian J Helminthol 4:37-54, 1987) from Indoplanorbis exustus Deshayes has also been transferred to the genus Pseudodiplodiscoides as P. mimutus (1987). The new species is characterised by the shape and size of non operculated eggs, extension of vitellaria and position of genital pore.