Specimens of three little-known species of Rhabdochona (Nematoda: Rhabdochonidae) were collected during occasional examinations of some freshwater fishes in India: R. (Rhabdochona) hellichi turkestanica (Skryabin, 1917) in Schizothorax sp. (Cyprinidae, Cypriniformes) from the Lodhomakhola and Rangit Rivers, West Bengal and Sikkim, respectively; R. (R.) hospeti Thapar, 1950 in Tor sp. (Cyprinidae) from the Rangit River; and R. (Globochona) mazeedi Prasad et Sahay, 1965 in Clupisoma garua (Hamilton) (Schilbeidae, Siluriformes) from the Farakka Dam Lake, West Bengal. Their detailed light and electron microscopical studies revealed some taxonomically important, previously not observed features and made possible their redescription. Fourth-stage larvae of R. hospeti are described for the first time. Rhabdochona hellichi turkestanica (syns. R. denudata filamentosa Bykhovskaya-Pavlovskaya, 1936, R. kashmirensis Thapar, 1950, R. schizothoracis Siddiqi et Khattak, 1984) is proposed as a subspecies, differing from the nominotypical subspecies R. hellichi hellichi (Šrámek, 1901) mainly in the shape of the distal end of the left spicule, molecular data and geographical distribution. Rhabdochona moraveci Katoch et Kalia, 1991 (a homonym to R. moraveci Duggal et Kaur, 1987) is renamed R. indica nom. n. The following six species are considered new junior synonyms of R. hospeti: Comephronema [sic] mackiewiczi Malhotra et Rautela, 1984, Rhabdochona moraveci Duggal et Kaur, 1987, R. bifidum Kakar et Bilqees, 2007, R. uvaginus Kakar et Bilqees, 2007, R. bolani Kakar, Bilqees et Ahmad, 2008 and R. cephalodiverticula Kakar, Bilqees et Ahmad, 2008. Rhabdochona edentati Paul et Majumdar, 1994 is considered a species incertae sedis.
Specimens of the nematode genus Rhabdochona Railliet, 1916 (Rhabdochonidae) were collected during helminthological examination of four species of cyprinid fishes in two rivers of the Amur River basin in the Russian Far East (Primorsky Region) in June 2011. Detailed light microscopical (LM) and scanning electron microscopical (SEM) examinations (the latter used for the first time for the reported nematode species) of the available material revealed the presence of three inadequately described nominal species of this genus: R. (Rhabdochona) denudata (Dujardin, 1845) from the spotted steed Hemibarbus maculatus Bleeker (Gobioninae), and R. (Rhabdochona) longispicula Belous in Roytman, 1963 and R. (Globochonoides) coronacauda Belous, 1965 from Culter alburnus Basilewsky (Cultrinae) in the Ilistaya River. Detailed morphological study of these worms, especially SEM examination, made it possible to reveal some previously unreported morphological features (e.g., the presence of sublabia or the character of ventral precloacal ridges) and to confirm other taxonomically important characters such as the shape of deirids, number of anterior prostomal teeth, number and situation of lateral preanal and postanal papillae or the detailed structure of the crown-like formation on the female tail tip in R. coronacauda. Unidentifiable Rhabdochona (Rhabdochona) gravid females were recorded from the humpback Chanodichthys dabryi (Bleeker) (Cultrinae) in the Ilistaya River and from the Amur minnow Rhynchocypris lagowskii (Dybowski) (Leuciscinae) in the Komissarovka River.