The aim of study is to report for the first time the occurrence of Rhinoxenus bulbovaginatus infesting the nasal cavity of Salminus hilarii from the Taquari River, São Paulo State, Brazil. Rhinoxenus bulbovaginatus was originally described parasitizing the nasal cavities of Salminus brasiliensis from the Paraná River. Rhinoxenus spp. are monogenean parasites from the nasal cavities of Characiformes fishes in the Neotropical region. To date, eight species of Rhinoxenus were described in seven different hosts. This study broadens the range of hosts parasitized with monogeneans of nasal cavities.

A new species of Monogenea - Trinibaculum pinctiarum n. sp. is described from the gills of Astyanax fasciatus known as "lambari do rabo vermelho", sampled in the Paranapanema River, Jurumirim reservoir, São Paulo State, Brazil. The new species is allocated to the genus Trinibaculum because it has a double ventral bar and dextro-lateral vagina. It is the second species (first species is Trinibaculum altiparanae) belonging to this genus that parasitizes the gills of the fish genus Astyanax. This monogenean is similar to T. altiparanae regarding the haptor structures and the bulbous distal vagina. However, Trinibaculum pinctiarum n. sp. differs in having: (1) coiled male copulatory organ, (2) accessory structure shaped as tweezers, (3) absence of postmedian process in the ventral bar, and (4) hooks with depressed thumb. The phylogenetic hypothesis of the genus Trinibaculum (Consistency ind...