Characterizing Two New Henneguya Species in the Respiratory Organs of African Sharptooth Catfish.

Henneguya species are myxozoans, a suborder of Cnidaria, which can affect the gills and extrarespiratory organs of the African sharptooth catfish, Clarias gariepinus. This research describes natural infection-induced histological alterations caused by the Henneguya species present. The Henneguya species were also identified molecularly using DNA sequenced from infected tissue cysts, and phylogenetically analyzed. Clinical investigations revealed cyst-like nodules on the fish gill filaments and extrarespiratory organs. Within a milky fluid inside the cysts were several Henneguya-like spores. Henneguya sp. infested 27.5% of the fish, with the highest prevalence in the gills compared to the extrarespiratory organs. The Henneguya species parasitized the gill and the dendritic tissues, resulting in histopathological characteristics. The plasmodia's developmental stages resulted in destructive damage which manifested as marked necrosis, which was replaced by a focal aggregation of inflammatory cells. Amplification of the 18S ribosomal DNA from the fish parasites was followed by sequencing, which confirmed their identities as new species Henneguya qenabranchiae n. sp. and Henneguya qenasuprabranchiae n. sp. with 99.53 and 99.64% identities, respectively, to Henneguya sp. 1 HS-2015. The two C. gariepinus myxozoans shared some characteristics based on morphologic and phylogenetic analysis as previously published, where it was proposed that they were a sister lineage to Henneguya species in Egypt, and it is now proposed that they are new species.

Henneguya species infecting the gastrointestinal tract of Clarias gariepinus from the Nile River.

As part of a study on parasitic infection in the African sharptooth catfish Clarias gariepinus, we found cysts of varying sizes in the stomach and intestine that contained myxospores with morphological features resembling those of the genus Henneguya. The present investigation was carried out with data on spore morphology and histopathology. Additionally, the myxozoan was identified using a molecular-based approach with 18S small subunit rDNA sequences. Based on the morphological characterization and tissue specificity of Myxozoa, 2 species of Henneguya were identified in the catfish stomach and intestine. Several histopathological changes were observed in the intestine which may affect fish performance and survival. The phylogenetic position of nucleotide sequences of the Henneguya species identified here were clustered with other fish-infecting Henneguya species. These sequences were deposited in GenBank. It appears that they potentially represent 2 species, denominated Henneguya sp. 1 and Henneguya sp. 2 according to the samples originating from the stomach and intestine, respectively. Although future investigations are needed for detailed morphological and molecular descriptions, this study documents the likely occurrence of infection with Henneguya noted for the first time, to our knowledge, in the digestive system of C. gariepinus in Egypt.