New data on Thelohanellus. sanagaensis Fomena, Marques, Bouix & Njine, 1994 (Cnidaria: Myxosporea): host, histopathology, molecular data and molecular phylogeny

Thelohanellus sanagaensis Fomena, Marques, Bouix & Njine, 1994 was described in the gills and fins of Labeo sp. in Cameroon based on morphometric characteristics of the spores. However, spore characteristics are insufficient to determine the validity of morphologically similar myxosporeans. The present study aims to supplement this species diagnosis with information on histology and molecular characterization. Fresh specimens of Labeo batesii were captured and transported to the laboratory. For histological studies, gills were fixed in 10% neutral buffered formalin and cut into 3μm-thick sections after embedding in paraffin wax and processed for histology. Sections were stained with Hematoxylin and Eosin, examined and photographed using an Olympus BH-2 microscope equipped with camera. For molecular analysis, mature spores were fixed in absolute ethanol and genomic DNA was extracted using the Livak optimized method (Lekeufack et al., 2020) follow by the amplification of the 18S rDNA gene using the primers MC5F and MC3R. PCR products were electrophoresed on 1.5 % agarose gel stained with midori green, and visualized using an Ultraviolet-transilluminator system. Afterward, PCR products were purified and sequenced. The sequences obtained were visualized, assembled, edited, and clarified using BioEdit software. The myxozoan nature of the corrected sequence was verified by BLAST search. Nucleotide sequences were aligned and exported as fasta and nexus files. DNA sequence similarities were calculated. Phylogenetic relationships determined through Bayesian inference and maximum likelihood methods were performed. Labeo batesii Boulenger, 1911 was identified as Thelohanellus sanagaensis host. Histologically, the development of T. sanagaensis plasmodia deformed and pushed sideways some gill lamellae of the fish host on both sides. Molecular analysis of the 18S rDNA of Thelohanellus sanagaensis resulted in a 933 bp sequence which showed genetic similarity between 70.3-85.4% with previously described Myxobolidae species. Phylogenetically, Thelohanellus sanagaensis was placed with the highest bootstrap value within clade compound twenty-five Myxobolidae species parasites of different organs of Cyprinid fish.
Keys words: Thelohanellus sanagaensis, Labeo batesii, histology, molecular data, phylogeny