A new species of Raphidascaris (Nematoda: Raphidascarididae) infecting the fish Gymnogeophagus balzanii (Cichlidae) from the Pantanal wetlands, Brazil and a taxonomic update of the subgenera of Raphidascaris based on molecular phylogeny and morphology

Abstract

Raphidascaris (Sprentascaris) andersoni n. sp. (Nematoda: Raphidascarididae) collected in the intestine of the humphead cichlid Gymnogeophagus balzanii (Perugia) from the Pantanal wetlands, State of Mato Grosso do Sul (Brazil) is described and genetically characterized. The new species differs from its congeners mainly by having a conspicuous papilla-like formation slightly anterior to the cloacal aperture. Furthermore, males of R. (S.) lanfrediae and R. (S.) mahnerti have caudal alae, and R. (S.) hypostomi and R. (S.) pimelodi lack lateral alae, whereas in the new species caudal alae are absent and lateral alae present. The remaining congeners, namely, R. (S.) marano and R. (S.) saltaensis differ from Raphidascaris (Sprentascaris) andersoni n. sp. mainly because males have three pairs of postcloacal papillae (vs five pairs). In the phylogenetic reconstructions, using three nuclear genetic markers (18S, ITS1-5.8S-ITS2 and 28S rDNA) and one mitochondrial (cox1 mtDNA), the new species was separated from other representatives of Raphidascarididae, and the absence of monophyly in Hysterothylacium and Raphidascaroides was confirmed. Moreover, the subgenera Sprentascaris and Ichthyascaris appeared to be monophyletic. Therefore, even though Raphidascaris (Raphidascaris) was apparently not monophyletic, the subgenera of Raphidascaris should be re-erected as valid genera. The updated diagnoses of Ichthyascaris, Raphidascaris and Sprentascaris are given. The present study represents the first parasitological survey in G. balzanii.

First description of aRaphidascarisspecies (Nematoda: Raphidascarididae) in a mudskipperApocryptes bato(Actinopterygii: Gobiidae) from West Bengal, India

“…The genus Raphidascaris was previously subdivided on morphological grounds into three subgenera – namely, Ichthyascaris Wu, 1949, Raphidascaris Railliet & Henry, 1915 and Sprentascaris Petter & Cassone, 1984 (Moravec et al ., 1990; Moravec & Nagasawa, 2002; Li et al ., 2012, 2016). Recent integrative taxonomic analyses have shown that Sprentascaris can be considered a separate valid genus (Malta et al ., 2018, 2020), a conclusion supported by our analyses (see fig. 3).…”

“…The interrelationships of various ascaridoid taxa including the genus Raphidascaris are controversial, and the taxonomy and systematics of raphidascaridids are still in flux; the monophyly of Raphidascaris and Hysterothylacium remains doubtful (Malta et al ., 2018, 2020; this study). The genus Raphidascaris was previously subdivided on morphological grounds into three subgenera – namely, Ichthyascaris Wu, 1949, Raphidascaris Railliet & Henry, 1915 and Sprentascaris Petter & Cassone, 1984 (Moravec et al ., 1990; Moravec & Nagasawa, 2002; Li et al ., 2012, 2016).…”

“…Previous phylogenetic analyses of raphidascaridids varied in their taxon sampling (Pereira et al ., 2015; Malta et al ., 2018, 2020) and included two or more genes (18S, 28S) and regions (ITS1, 5.8S, ITS2) of the rRNA gene array. Consequently, direct comparisons between our analysis and those in previous studies have their limitations.…”

“…Our results did not find Ichthyascaris to be monophyletic as in Malta et al . (2018, 2020). Because of the different number of taxa used in this study, we cannot address this discrepancy.…”

“…Parasitic nematodes from fishes of the Indian subcontinent have been studied since the early 20th century (Baylis & Daubney, 1922; Soota, 1983; Sood, 1988, 2017), with over 600 species recorded to date. Of these, ascaridoids are reportedly represented by species in the following genera: Aliascaris Kalyankar, 1971; Alibagascaris Kalyankar, 1970; Hysterothylacium Ward & Magath, 1917; Iheringascaris Pereira, 1935; Lappetascaris Rasheed, 1965; Mehdiascaris Kalyankar, 1969; Paranisakis Baylis, 1923; Raphidascaris Railliet & Henry, 1915; and Raphidascaroides Yamaguti, 1914 (Soota, 1983; Malta et al ., 2018, 2020). During a long-term survey of parasites of fishes from West Bengal, worms belonging to a previously unknown species of ascaridoid were collected from the gastrointestinal tract of a unique fish host, Apocryptes bato (Hamilton, 1822) (Actinopterygii: Gobiidae: Oxydercinae), a mudskipper, and the only species in its monotypic genus (Murdy & Jaafar, 2017).…”