Nematodes from the squeaker fishes Synodontis nigromaculatus and S. vanderwaali from the Okavango River, Botswana, including three new species

Camallanid nematodes from Clarias gariepinus (Burchell, 1822) in the Crocodile River, Gauteng, South Africa: Exploring diversity and divergence in an acid-mine drainage impacted environment

Clarias gariepinus collected from Lake Heritage, Crocodile River, were found to harbour camallanid nematodes. Previously, Boomker (1982) surveyed the Hartbeespoort Dam, downstream of the current study site, and identified a high prevalence of Procamallanus (Procamallanus) laeviconchus and Paracamallanus cyathopharynx. Since then, Procamallanus (Procamallanus) pseudolaeviconchus was described from C. gariepinus suggesting reconsideration of the identifications of Procamallanus species in historical studies from clariids. The aim of the current study was to definitively identify the nematodes collected from C. gariepinus in Lake Heritage, using morphological and molecular analyses. Morphological study consisted of light and scanning electron microscopy which confirmed the identity P. (P.) pseudolaeviconchus and P. cyathopharynx. This included descriptions of the detailed morphology of isolated buccal capsules for both species using soft tissue digestion, notably for the first time for P. (P.) pseudolaeviconchus. The morphology of isolated spiculae of both species was described for the first time using SEM. Molecular analyses included genetic characterisation of the small ribosomal subunit (18S) rDNA and cytochrome oxidase 1 (CO1) mtDNA. Genetic data supported the morphological identification of both species, however, divergence was detected in CO1 mtDNA data for P. cyathopharynx indicating two distinct lineages. Due to this variation, the morphometry of P. cyathopharynx specimens were revisited including statistical re-evaluation. No robust morphological traits were identified to support CO1 mtDNA lineages and all specimens were considered conspecific. In terms of camallanid biodiversity in the Crocodile River system, it is similar to that in Boomker (1982), despite the altered water quality from past acid mine pollution in the river.

Some nematodes from freshwater fishes in central Africa

Twenty species (sixteen adult and four larval) of parasitic nematodes belonging to the Ascaridoidea, Camallanoidea, Cosmocercoidea, Dioctophymatoidea, Habronematoidea, Oxyuroidea, Seuratoidea, and Thelazioidea were collected from freshwater fishes of the Congo River basin in the Democratic Republic of the Congo and the Central African Republic in 2008 and 2012, respectively. Based on light and scanning electron microscopical examination, many species are redescribed in detail. This material also contained four previously unknown species, Labeonema longispiculatum sp. n. from Synodontis acanthomias Boulenger, Gendria longispiculata sp. n. from Schilbe grenfelli (Boulenger), G. sanghaensis sp. n. from Schilbe marmoratus Boulenger, and Cucullanus congolensis sp. n. from Auchenoglanis occidentalis (Valenciennes). The new species L. longispiculatum is mainly characterised by conspicuously long (210-228 µm) spicules, approximately twice as long as those in other congeners, the length (45-48 µm) of the gubernaculum and the host family (Mochokidae), whereas G. longispiculata by very long (1.2 mm) spicules, the shape of the oesophagus and cephalic vesicle, distribution of postanal papillae and the host family (Schilbeidae). Main characteristic features of G. sanghaensis are the presence of a hexagonal oral aperture surrounded by lip-like structures, the posterior portion of the oesophagus moderately expanded, spicules and the gubernaculum 414-438 µm and 54-57 µm long, respectively, deirids located at the level of the posterior end of the oesophagus and the absence of cervical alae. Cucullanus congolensis differs from congeneric species parasitising African freshwater and brackish-water fishes mainly in the absence of a ventral precloacal sucker and lateral preanal papillae, the presence of a large median precloacal papilla-like formation, spicules 480-489 µm long and the location of the excretory pore in the region of the oesophago-intestinal junction. Chabaudus Inglis et Ogden, 1965 is considered a junior synonym of Gendria Baylis, 1930 and, consequently, species listed in the former genus are transferred to the latter as G. alaini (Alfonso-Roque, 1981) comb. n., G. chabaudi (Inglis et Ogden, 1965) comb. n., G. dehradunensis (Rizvi, Bursey et Maity, 2016) comb. n., G. thysi (Puylaert, 1970) comb. n. and G. williamsi (Puylaert, 1970) comb. n. The findings represent many new host and geographical records.

Some nematodes, including two new species, from freshwater fishes in the Sudan and Ethiopia

Fourteen species (twelve adult and two larval) of nematodes belonging to the Ascaridoidea, Camallanoidea, Cosmocercoidea, Habronematoidea, Oxyuroidea, Seuratoidea and Trichinelloidea were collected from fishes in the Sudan (River Nile and Atbara Dam Lake), whereas only four species (one adult and three larval) of the Ascaridoidea, Camallanoidea, Dioctophymatoidea and Trichinelloideafrom fishes in Ethiopia (Lake Tana). The Sudanese material also contained two previously unknown species, Cucullanus mormyri sp. n. from Mormyrus caschive Linnaeus (type host), Mormyrus sp. and Marcusenius cyprinoides (Linnaeus) (all Mormyridae), and Procamallanus (Spirocamallanus) pseudospiralis sp. n. from Synodontis schall (Bloch et Schneider) (type host), S. frontosus Vaillant and S. nigrita Valenciennes (all Mochokidae), which are described based on light and scanning electron microscopical studies. Cucullanus baylisi Campana-Rouget, 1961, a little-known parasite of Synodontis spp., is redescribed in detail. A key to Procamallanus (Spirocamallanus) spp. from African inland fishes is provided. Falcaustra guiersi Vassiliadès, 1973 is considered a junior synonym of F. hexapapillata (Khalil, 1962). The findings represent several new host and geographical records. Cucullanus baylisi Lakshmi, 2000 (= a homonym to C. baylisi Campana-Rouget, 1961) is re-named as C. dubius nom. n. and is considered a species inquirenda.

Orientatractis moraveci n. sp. and Rondonia rondoni Travassos, 1920 (Nematoda: Atractidae), parasites of Pimelodus blochii (Osteichthyes, Pimelodidae) from the Acre and Xapuri Rivers, Western Amazon, Brazil

The fish fauna in the State of Acre represents 10·7% of all fish species recorded from Brazil, but, despite this, there are few fish parasite studies in this area. The recent expansion of fish farming in Acre prompted a need for helminthological studies of the most commonly consumed fish species in the area, Pimelodus blochii (Pimelodidae). The aim of this study was to analyse the helminth fauna of P. blochii from the Acre and Xapuri Rivers in Northwestern Brazil. Numerous nematodes were collected from the intestine and two species of the family Atractidae were identified: Rondonia rondoni Travassos, 1920 and Orientatractis moraveci n. sp. The new species is distinguished from its congeners mainly by having: 10 pairs of caudal papillae (3 pairs pre-cloacal, 2 pairs ad-cloacal and 5 pairs post-cloacal); unequal spicules of 161-198 and 69-100 µ m long; and a gubernaculum 38-58 µ m long with an antero-lateral process. Morphological and ultrastructural data on O. moraveci n. sp. and R. rondoni are presented, in addition to new genetic data based on partial 18S rDNA and 28S rDNA. The taxonomic status of Labeonema synodontisi (Vassiliadès, 1973) is discussed, suggesting that it should be returned to the genus Raillietnema.

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

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.

Studies on ascaridid, oxyurid and enoplid nematodes (Nematoda) from fishes of the Okavango River, Botswana

Based on light and scanning electron microscopical studies, eight species (five adult and three larval) of nematodes belonging to the Ascaridida, Oxyurida and Enoplida were collected from fishes of the Okavango River, Botswana, namely Falcaustra similis Moravec et Van As, 2004, Atractidae gen. sp. (only female) (both Cosmocercoidea), Cucullanus sp. (only female) (Seuratoidea), Cithariniella longicaudata sp. n., Synodontisia annulata sp. n. (both Oxyuroidea), Contracaecum sp. third-stage larvae, third-stage larvae of Galeiceps sp. (both Ascaridoidea) and Eustrongylides sp. fourth-stage larvae (Dioctophymatoidea). The new species Citharinella longicaudata (type host Schilbe intermedius Rüppel) is mainly characterised by the shape and size of cephalic papillae and the spicule 108 µm long, and Synodontisia annulata (type host S. intermedius) by the shape of cephalic papillae, body length of gravid females (4.88-5.33 mm) and a short spicule (66 µm long). The female specimen of Cucullanus sp. from Tilapia sparmanni Smith markedly differs from congeners parasitising inland fishes in Africa by the elongate pseudobuccal capsule and by the excretory pore far posterior to the oesophago-intestinal junction; apparently, it belongs to an undescribed species. Galeiceps larvae parasitising fishes are described for the first time. Cithariniella gonzalezi Van Waerebeke, Chabaud, Bain et Georges, 1988 is considered a junior synonym of C. khalili Petter, Vassiliadès et Troncy, 1972, and the previous records of Cithariniella citharini Khalil, 1964 from Synodontis spp. in Egypt concern, in fact, Cithariniella khalili Petter, Vassiliadès et Troncy, 1972. The specimens of Cithariniella reported by Koubková et al. (2010) from Paradistichodus dimidiatus (Pellegrin) in Senegal and misidentified as C. gonzalesi Van Waerebeke, Chabaud, Bain et Georges, 1988 are considered to represent a new species, C. koubkovae sp. n.; this is established by reference to the description and drawings provided by Koubková et al. (2010).

Studies on some spirurids (Nematoda: Spirurida) from fishes of the Okavango River, Botswana

Based on light and scanning electron microscopical studies, three adult spirurid nematode species, Camallanus (Zeylanema) ctenopomae Vassiliadès & Petter, 1972, Paracamallanus cyathopharynx (Baylis, 1923) (both Camallanidae) and Spinitectus polli Campana-Rouget, 1961 (Cystidicolidae), are redescribed from specimens collected in fishes of the Okavango River, Botswana: C. (Z.) ctenopomae from Ctenopoma sp. (Anabantidae), P. cyathopharynx from Clarias stappersi Boulenger, C. theodorae Weber (both new hosts, Clariidae) and C. gariepinus (Burchell), as well as S. polli from Synodontis nigromaculatus Boulenger (new host, Mochokidae). Moreover, spirurid larvae of an additional three species were found in fishes from the same locality: Rhabdochona paski Baylis, 1928 fourth-stage larva (Rhabdochonidae) in S. nigromaculatus (Mochokidae), Physalopteridae gen. sp. 1 third-stage larva in C. gariepinus (Clariidae) and Physalopteridae gen. sp. 2 third-stage larva in Serranochromis angusticeps (Boulenger) (Cichlidae), all representing new host and geographical records. Spinitectus zambezensis Boomker, 1993 is considered a junior synonym of S. polli.

Procamallanus (Procamallanus) spp. (Nematoda: Camallanidae) in fishes of the Okavango River, Botswana, including the description of P. (P.) pseudolaeviconchus n. sp. parasitic in Clarias spp. (Clariidae) from Botswana and Egypt

Parasitological dissections of fishes from the Okavango River, Botswana, revealed the presence of nematodes of the subgenus Procamallanus (Procamallanus) Baylis, 1923 in five fish species belonging to three different families. Based on light and scanning electron microscopical examinations, they proved to represent one previously known and one new species, i.e. P. (P.) laeviconchus (Wedl, 1861) from Synodontis nigromaculatus Boulenger, S. thamalakanensis Fowler (new host) (both Mochokidae) and Schilbe intermedius Rüppel (new host) (Schilbeidae), and P. (P.) pseudolaeviconchus n. sp. from Clarias stappersi Boulenger and C. theodorae Weber (both Clariidae). Specimens of the new species previously collected from Clarias gariepinus (Burchell) (type-host) in Egypt were also examined. Both of these nematode species are very similar, differing from each other mainly in the shape of the circumoral flange, which is conspicuously lobed in P. laeviconchus and unlobed in P. pseudolaeviconchus. Previously, these two species have been confused in the literature under the name P. laeviconchus. A key to Procamallanus (Procamallanus) spp. parasitising freshwater fishes in Africa, including Madagascar, is provided.

New morphological data on the first-stage larvae of two Procamallanus species (Nematoda: Camallanidae) based on SEM studies

First-stage larvae of camallanid nematodes Procamallanus (Procamallanus) laeviconchus (Wedl, 1862) and Procamallanus (Procamallanus) sp. from naturally infected Distichodus niloticus (Hasselquist) and Clarias gariepinus (Burchell), respectively, from Lake Turkana, Kenya (new geographical records) are described, being for the first time studied by scanning electron microscopy. Larvae of both species are characterised by the presence of a dorsal cephalic tooth, four submedian cephalic papillae and a pair of amphids, and by the elongate tail with several terminal digit-like processes. The latter formations probably serve for the attachment of larvae to the substrate in water when the larvae attract copepod intermediate hosts by their movements; these structures, especially their numbers, may be of taxonomic importance in camallanid nematodes.

Morphometric and molecular characteristics of Labeonema synodontisi n. comb. (Nematoda: Atractidae) from the West African fishes

Numerous nematodes were found in the rectum of three fish species Synodontis ocellifer, S. nigrita, and S. schall (Mochokidae, Siluriformes) from the Gambia River and Mare Simenti, National Park Niokolo Koba, Senegal. A nematode species Raillietnema synodontisi Vassiliadès, 1973 (host S. ocellifer), is redescribed using morphometric (including scanning electron microscopy) and molecular characteristics and transferred into the genus Labeonema Puylaert, 1970. It is morphologically and metrically similar to Labeonema intermedium Puylaert, 1970, the other congeneric species (L. bainae Baker, 1982; L. bakeri Van Waerebeke, Chabaud, Bain et Georges, 1988; and L. africanum Moravec et Van As, 2004) differ from them either by the spicule and gubernaculum lengths, distribution and number of pre-cloacal papillae, position of the vulva, as well as hosts and geographical distribution. The partial sequences of small ribosomal subunit rDNA of L. synodontisi were analyzed and compared with other nematode sequences. Molecular analyses seem to support the position of this nematode species based on the morphological observation.