New nematode species, Orientatractis mekongensis n. sp. (Atractidae) and Neosynodontisia suratthaniensis n. g., n. sp. (Pharyngodonidae) from freshwater fishes in Thailand

Abstract

Based on light and scanning electron microscopical studies, two new species of nematode parasites are described from freshwater fishes in Thailand: Orientatractis mekongensis n. sp. (Atractidae) from the intestine of Pangasius bocourti Sauvage (type-host) and Helicophagus leptorhynchus Ng & Kottelat (both Pangasiidae, Siluriformes), and Neosynodontisia suratthaniensis n. sp. (Pharyngodonidae) from the intestine of Labiobarbus siamensis (Sauvage) (Cyprinidae, Cypriniformes), for which a new genus Neosynodontisia n. g. is established. Orientatractis mekongensis is mainly characterised by the number and distribution of caudal papillae (2 preanal, 1 adanal and 5 postanal pairs), the length of the left spicule (306-384 µm) and large body sizes (length of males and gravid females 5.4-6.7 mm and 7.8-9.0 mm, respectively). Neosynodontisia differs from other pharyngodonid genera with representatives parasitic in fishes not only by some morphological features (mouth withdrawn into the cephalic end with inflated cuticle, structure of the male caudal end, filamented eggs), but mainly by the occurrence of males inside the body of females. A key to the genera of the Pharyngodonidae with representatives parasitising fishes is provided.

Orientatractis moravecin. sp. andRondonia rondoniTravassos, 1920 (Nematoda: Atractidae), parasites ofPimelodus blochii(Osteichthyes, Pimelodidae) from the Acre and Xapuri Rivers, Western Amazon, Brazil

“…Species of the genus Orientatractis have been reported parasitizing fish, reptiles and anurans from Mexico, Thailand, Vietnam, Costa Rica and New Guinea (Petter, 1966; Buckley, 1969; González-Solís and Moravec, 2004; Gibbons and Platt, 2006; Bursey et al 2014; Moravec et al 2015). Currently, this genus comprises the species Orientatractis levanhoai Petter, 1966, Orientatractis leiperi Buckley, 1969, Orientatractis campechensis González-Solís and Moravec, 2004, Orientatractis chiapasensis González-Solís and Moravec, 2004, Orientatractis asymmetrica Gibbons and Platt, 2006, Orientatractis hamabatrachos Bursey et al .…”

“…2014 and Orientatractis mekongensis Moravec et al . 2015. Only three of these species parasitize fishes: O. chiapasensis from Vieja intermedia and Tomocichla tuba , and O. campechensis from Vieja bifasciata , all cichlid fishes from México, and O. mekongensis from Helicophagus leptorhynchus , a pangasiid fish from Thailand.…”

“…Species of the genus Orientatractis have been reported parasitizing fish, reptiles and anurans from Mexico, Thailand, Vietnam, Costa Rica and New Guinea (Petter, 1966;Buckley, 1969;González-Solís and Moravec, 2004;Gibbons and Platt, 2006;Bursey et al 2014;Moravec et al 2015). Currently, this genus comprises the species Orientatractis levanhoai Petter, 1966…”

“…confirms the position of this species within the Atractidae, with the Cosmocercidae as a sister group and the Kathlaniidae as a basal group. However, Pereira et al (2015) found that the kathlaniid C. americana nested within the Cosmocercidae, and the inconsistent position of this species was also pointed out by Nadler et al (2007) when analyzing the same 18S rDNA region. Raillietnema sp., C. pulcher and N. bakeri grouped within the Cosmocercidae with high Bpp support (0.0.93), but much less so for the bootstrap analysis (68%).…”

A new species of Orientatractis (Nematoda: Cosmocercoidea: Atractidae) parasite of Yellow-Spotted Amazon River Turtle, Podocnemis unifilis Troschel, 1848 (Testudines: Podocnemididae) in Brazilian Amazon

“…Orientatractis Petter, 1966 comprises nematodes parasitic in fishes, amphibians, and reptiles. Currently, the genus includes 10 valid species, namely: Orientatractis levanhoai Petter (1966) (type-species), Orientatractis leiperi Buckley (1969) , Orientatractis campechensis González-Solís and Moravec (2004) , Orientatractis chiapasensis González-Solís and Moravec (2004) , Orientatractis asymmetrica Gibbons and Platt (2006) , Orientatractis hamabatrachos Bursey et al, 2014 , Orientatractis mekongensis Moravec et al, 2015 , Orientatractis brycini González-Solís and Mariaux (2017) , Orientatractis moraveci Cavalcante et al (2017) and Orientatractis longicaudata Liu et al, 2018 ; Jesus et al (2020) . Among these, four species were described from chelonians, O. asymmetrica and O .…”