title: Morphology and phylogeny of Thelohanellus marginatus n. sp. (Myxozoa: Myxosporea), a parasite infecting the gills of the fish Hypophthalmus marginatus (Teleostei: Pimelodidae) in the Amazon River.
abstract: Thelohanellus marginatus n. sp., a new myxosporean parasite infecting the primary gill filaments of the teleost fish Hypophthalmus marginatus (Pimelodidae) in the Amazon River, is described on the basis of microscopic and molecular procedures. The parasite forms whitish and ellipsoidal cysts up to 250 μm in diam. Myxospores ellipsoidal with a slightly more pointed anterior end, measuring 17.1 ± 0.6 μm in length, 6.9 ± 0.4 μm in width, and 5.1 ± 0.5 μm in thickness. A single pyriform polar capsule, 9.0 ± 0.3 μm long and 6.1 ± 0.4 μm wide, positioned slightly right to the medial plane in valvular view, contains a polar filament arranged in 4-5 coils. Molecular analysis of the SSU rRNA gene by Maximum Parsimony, Neighbor-Joining, and Maximum Likelihood revealed the parasite clustering among other myxobolids, namely Henneguya and Myxobolus. Host affinity is supported as an important evolutionary signal for the phylogeny of myxobolids. The parasite here described represents the first record of the genus Thelohanellus Kudo, 1933 from the South American fauna.
authors.affiliation: Laboratory of Cell Biology, Institute of Biomedical Sciences (ICBAS/UP), University of Porto, Porto, Portugal; Laboratory of Animal Pathology, Interdisciplinary Centre of Marine and Environmental Research (CIIMAR/UP), University of Porto, Porto, Portugal.
authors.forename: Sónia
authors.initials: S
authors.lastname: Rocha
authors.forename: Graça
authors.initials: G
authors.lastname: Casal
authors.forename: Michele
authors.initials: M
authors.lastname: Velasco
authors.forename: Angela
authors.initials: A
authors.lastname: Alves
authors.forename: Edilson
authors.initials: E
authors.lastname: Matos
authors.forename: Saleh
authors.initials: S
authors.lastname: Al-Quraishy
authors.forename: Carlos
authors.initials: C
authors.lastname: Azevedo
mesh_terms: D000818:Animals; D005393:Fish Diseases / Q000469:parasitology*; D005880:Gills / Q000469:parasitology*; D058507:Host Specificity; D046529:Microscopy, Electron, Transmission; D055764:Myxozoa / Q000145:classification* / Q000166:cytology* / Q000235:genetics / Q000648:ultrastructure; D010273:Parasitic Diseases, Animal / Q000469:parasitology*; D010802:Phylogeny; D045483:Rivers
keywords: Brazil; SSU rRNA; fish-infecting; host affinity; ultrastructure