A new species of philometrid nematode, Philometroides africanus sp. n., is described from female specimens found encapsulated in gill arches and inner surface of gill covers of the African pike, Hepsetus odoe (Bloch), an endemic freshwater fish in Africa, from the Okavango River and Delta in Botswana. This new nematode is characterised mainly by a markedly small and plump body of gravid females (body length 6-9 mm), a separate anterior oesophageal bulb, a conspicuously small oesophageal gland, presence of four pairs of very small submedian cephalic papillae, and absence of any caudal processes. The prevalence of P. africanus in African pike of the Okavango Delta was 29%, with the intensity 1-8 (mean 3) encapsulated nematodes per fish. The genus Margolisianum Blaylock et Overstreet, 1999 is considered a junior synonym of Philometroides Yamaguti, 1935 and, consequently, its type species is transferred to the latter as Philometroides bulbosus (Blaylock et Overstreet, 1999) comb. n.
A new nematode, Rhabdochona mexicana sp. n., is described based on specimens recovered from the intestine of two species of fishes, Astyanax mexicanus (De Filippi) (type host) and Astyanax J'asciatus (Cuvier) (Characidae: Characiformes) in central Mexico. This species is characterised by the following characters: 10 anteriorly directed teeth in the prostom, a larger (left) spicule which is slender in form with a small bifurcation at its distal tip covered by a culicular membrane, a smaller (right) spicule without a barb at its distal tip, eggs bearing an irregular flock-like coaling, and a conical tail without a cuticular spike (in both sexes).
Based on light and scanning electron microscopical studies, three new, one already known and one not identified species of the nematode genus Rhabdochona Railliet, 1916 are reported from the intestine of freshwater fishes in Dzanga-Sangha Protected Areas (Congo River basin), the Central African Republic: Rhabdochona (Rhabdochona) centroafricana sp. n. from Barbus miolepis Boulenger, R. (R.) marcusenii sp. n. from Marcusenius greshoffii (Schilthuis), R. (Globochona) paski Baylis, 1928 from Phenacogrammus aurantiacus (Pellegrin) (new host record), R. (G.) tricuspidata sp. n. from Raiamas christyi (Boulenger) and Rhabdochona (G.) sp. (only females) from Epiplatys multifasciatus (Boulenger). Rhabdochona centroafricana is mainly characterised by the length of the left spicule (333 µm) and the presence of the operculum bearing a conspicuous gelatinous formation on one of egg poles, R. marcusenii by the length of the left spicule (453-486 µm) and the presence of a single broad filament on one egg pole only and R. tricuspidata by the body with marked cuticular ornamentations and deirids branching into three prongs. A key to valid species of Rhabdochona parasitic in fishes of Africa is provided.
Two new nematode species, Paragendria papuanensis sp. n. (Quimperiidae) and Rhabdochona papuanensis sp. n. (Rhabdochonidae), are described from the intestine of freshwater fishes Glossamia gjellerupi (Weber et Beaufort) (Apogonidae) and Melanotaenia affinis (Weber) (Melanotaeniidae), respectively, from the Sogeram River (Ramu River basin), Madang Province, northern Papua New Guinea. The former species is characterized mainly by the absence of oesophageal teeth, the presence of conspicuously inflated papillae of the last two subventral pairs, a gubernaculum, spicules 69-75 µm long, eggs measuring 57-66 × 39-45 µm, and by a small body (male and female 3.2-3.7 and 5.8 mm long, respectively). Paragendria is considered a valid genus, to which P. aori (Khan et Yaseen, 1969) comb. n., P. guptai (Gupta et Masoodi, 2000) comb. n., P. hanumanthai (Gupta et Jaiswal, 1988) comb. n. and P. vermae (Gupta et Masoodi, 2000) comb. n. are newly transferred. Rhabdochona papuanensis differs from all congeners mainly in having hammer-shaped deirids and from individual species also in other characters. Both findings represent the first records of species of Paragendria and Rhabdochona from the Australian zoogeographical region and the first records of the representatives of these genera from fishes of the families Apogonidae and Melanotaeniidae, respectively.
Two new species of rhabdochonid nematodes are described from the intestine of freshwater fishes in Chiang Mai Province, northern Thailand: Rhabdochona (Rhabdochona) pseudomysti sp. n. from the catfish Pseudomystus siamensis (Regan) (Bagridae, Siluriformes) in the Fang Brook, a tributary of the Kok River (the Mekong River basin), Fang District and Rhabdochona (Globochona) thaiensis sp. n. from the cyprinid Mystacoleucus marginatus (Valenciennes) (Cyprinidae, Cypriniformes) in the Ping River (the Chao Phraya River basin), Muang District. Rhabdochona pseudomysti is mainly characterized by simple, leaf-like oval deirids (a unique feature among Rhabdochona spp.), a prostom with 14 anterior teeth, the presence of basal prostomal teeth, the length ratio of the muscular and glandular portions of oesophagus (1:2.1-2.6), an unusually long left spicule (1.10-1.22 mm), length ratio of spicules (1:11.5-14.7), arrangement of genital papillae, and conspicuously elevated vulval lips. Rhabdochona thaiensis differs from other representatives of the subgenus Globochona Moravec, 1972 possessing caudal projections on the tail tip in that it has only 2 claw-shaped projections located ventrally on the tail tip of both males and females; the species is mainly characterized by the presence of distinct pseudolabia, 8 anterior prostomal teeth, absence of basal teeth, bifurcated deirids, length ratio of the muscular and glandular portions of oesophagus (1:11.3-11.9), conspicuously short (135-141 µm) left spicule, arrangement of genital papillae, and somewhat elevated vulval lips. Fully developed eggs of R. pseudomysti and R. thaiensis remain unknown. These are the first nominal species of Rhabdochona reported from Thailand.
A new nematode species, Rhabdochona (Globochona) kurdistanensis sp. n. (Rhabdochonidae), is decribed based on specimens collected from the intestine of the barbel Luciobarbus kersin (Heckel) (Cyprinidae) in the Greater Zab (type locality) and the Lesser Zab Rivers, Tigris River basin, Kurdistan Region, northern Iraq. It is mainly characterized by a prostom with 8 anterior teeth, the presence of basal prostomal teeth, bifurcated deirids, length ratio of the muscular and glandular portions of oesophagus (1:14.4-17.8), conspicuously short left spicule (180-204 µm), arrangement of genital papillae, nonfilamented eggs, and by having cuticular ornamentations on the tail tip (2 lateral denticular outgrowths in female and numerous fine spines in male). Description of a gravid female of Rhabdochona (Rhabdochona) sp. with 14 anterior prostomal teeth and filamented eggs, recorded from L. kersin of the Greater Zab River, is also provided. R. kurdistanensis sp. n. is the fifth valid species of Rhabdochona Railliet, 1916 and the only representative of the subgenus Globochona Moravec, 1972 recorded from Iraq.