DAO prepress abstract  -  DOI: https://doi.org/10.3354/dao03210

Two new myxosporean species parasitising Phractocephalus hemioliopterus from the Brazilian Amazon: morphology, ultrastructure and SSU-rDNA sequencing

Juliana Naldoni*, Antônio A. M. Maia, Lincoln L. Correa, Marcia R. M. da Silva, Edson A. Adriano

*Email: jnaldoni@gmail.com

ABSTRACT: Myxozoans are a diverse group of parasitic cnidarians, with some species recognized as serious pathogens to their hosts. The present study, describes two new myxobolid species (Myxobolus figueirae sp. nov. and Henneguya santarenensis sp. nov.) infecting skin and gill filaments of the Amazonian pimelodid fish Phractocephalus hemioliopterus, based on ultrastructural, histology and phylogenetic analysis. The fish were caught in the Amazonas river, Pará, Brazil. The plasmodial development of M. figueirae sp. nov. was in the dermis and those of H. santarenensis sp. nov. were of the intralamellar type. For both species, the plasmodia were surrounded by connective tissue layer but there was no inflammatory infiltrate. For M. figueirae sp. nov., mature spores were ovoid measuring 9.1-10 (9.5±0.3) µm in length, 5.8–6.9 (6.4±0.3) µm in width and 4.4–4.5 (4.5±0.1) µm in thickness. Two polar capsules were elongated and with unequal size. For H. santarenensis n. sp., mature spores were ellipsoidal in the frontal view, measuring 26.3−36.1  (31.9±3) μm in total length, 9.6-11.9  (10.8±0.5) μm in body length, 3.7-4.9 (4.3±0.3) μm in width, and 16.6-25.6  (21±3.1) μm in caudal process. The polar capsules were elongated and with equal size. Phylogenetic analysis, based on partial SSU rDNA sequences and using the closest myxozoan sequences to each one of the species studied here based on previous GenBank data, showed M. figueirae n. sp. and H. santarenensis sp. nov. clustering in distinct lineages. While H. santarenensis sp. nov. clustered in a well-supported subclade composed by Henneguya species that infect gills of South American pimelodid host, M. figueirae sp. nov. clustered in a weakly-supported subclade containing parasites species of bryconids hosts.