Based on light and scanning electron microscopical studies, the following five gonad-infecting species of the Philometridae (Nematoda: Dracunculoidea) are described from marine perciform fishes off the eastern coast of India (Bay of Bengal): Philometra sphyraenae sp. n. (males and females) from the pickhandle barracuda Sphyraena jello Cuvier (Sphyraenidae), Philometra gerrei sp. n. (males and females) from the whipfin silver-biddy Gerres filamentosus Cuvier (Gerreidae), Philometra otolithi sp. n. (single female) from the tigertooth croaker Otolithes ruber (Bloch et Schneider) (Sciaenidae), Philometra sp. (females) from the Belanger's croaker Johnius belangerii (Cuvier) (Sciaenidae), and Philometroides eleutheronemae sp. n. (females) from the fourfinger threadfin Eleutheronema tetradactylum (Shaw) (Polynemidae). All new species are distinguished from their congeners parasitizing gonads of marine fishes by morphological (mainly the gubernaculum structure in males and the shape and structure of the cephalic and caudal ends and of the oesophagus in females) and biometrical features. Philometra rajani Mukherjee, 1963 is considered a species inquirenda.
Previously undescribed third-stage larvae of two species of Spirurida were found in the haemocoel of the stalk-eyed mud crab Macrophthalmus hirtipes (Heller) (Ocypodidae) in New Zealand. Examinations by light and scanning electron microscopy showed that the larger larvae (about 7 mm long) belonged to a species of Ascarophis van Beneden, 1871 (Cystidicolidae), the genus including parasites of fishes, whereas the smaller larvae (about 4-5 mm long) belonged to the Acuariidae, a family with species parasitic as adults mostly in aquatic birds. In a sample of 82 specimens of M. hirtipes collected in July 2002 from Papanui Inlet, on Otago Peninsula, South Island, 74 crabs (90.2%) were infected with larval nematodes with an intensity of 1-18 (mean 4.6) nematodes per crab; no distinction between nematode species was made in these estimates, although juvenile Acuariidae greatly outnumbered larval Ascarophis. Apparently, crabs play a role as intermediate hosts of these nematode species. This is the first record of larval representatives of Cystidicolidae and Acuariidae from invertebrates in the Australasian Region.
Two new species of philometrid nematodes (Philometridae) from needlefishes (Belonidae) in Florida are described based on morphological and genetic characteristics: Philometra aequispiculata sp. n. (males and females) collected from the ovary of Strongylura marina (Walbaum) (type host) and Strongylura notata (Poey), and Philometra notatae sp. n. (females) from the swimbladder of S. notata. Both species are described and illustrated based on light and scanning electron microscopical examinations. Morphologically, P. aequispiculata sp. n. differs from all congeners mainly in the unique structure of the distal tip of the gubernaculum, whereas P. notatae sp. n. is mainly characterised by the presence of eight markedly large cephalic papillae of the outer circle in gravid and subgravid females, the body length of the gravid female (54 mm) and by the absence of caudal projections. Molecular characterisation of the new species was assessed from phylogenetic analysis of mitochondrial cytochrome c oxidase I (COI) and SSU rRNA small-subunit ribosomal RNA (SSU) sequences among closely related philometrids by way of Bayesian inference. Phylogenetic reconstructions based on COI and SSU sequences show each of the new species comprise discrete ancestor-descendent lineages.
Recent examinations of newly obtained materials of dracunculoid nematodes (Dracunculoidea) parasitizing marine fishes off New Caledonia, South Pacific, revealed the presence of several nematodes of the genera Philometra Costa, 1845 (Philometridae) and Ichthyofilaria Yamaguti, 1935 (Guyanemidae), including the following four new species: Philometra priacanthi sp. n. (males) from the gonads of Priacanthus hamrur (Forsskål) (Priacanthidae), Philometra tenuicauda sp. n. (male and mature and gravid females) from the gonads of Lagocephalus sceleratus (Gmelin) (Tetraodontidae), Philometra dentigubernaculata sp. n. (males) from the oculo-orbit of Tylosurus crocodilus (Péron et Lesueur) (Belonidae), and Ichthyofilaria novaecaledoniensis sp. n. (subgravid female) from the musculature of Hoplichthys citrinus Gilbert (Hoplichthyidae). The new species are characterized mainly by the length and structure of spicules and the gubernaculum, body size, location in the host and by the type of hosts. In addition, the findings of Philometra lethrini Moravec et Justine, 2008 from the gonads of Lethrinus miniatus (Forster) and L. variegatus Valenciennes (both Lethrinidae) represent new host records for this parasite; for the first time, its subgravid females were found to be up to 350 mm long. The occurrence of Philometra ocularis Moravec, Ogawa, Suzuki, Miyazaki et Donai, 2002 in the oculo-orbit of Epinephelus areolatus (Forsskål) (Serranidae) off New Caledonia was confirmed.
Two little-known nematode species of the genus Spinitectus Fourment, 1883, S. petrowi Belous, 1965 (prevalence 25%, intensity 1-8) and S. gigi Fujita, 1927 (prevalence 10%, intensity 2-3), were collected from the gastrointestinal tract of the yellow catfish, Pelteobagrus fulvidraco (Richardson), from Liangzihu Lake, Hubei Province, central China, in September of 2002. The light and scanning electron microscopical examination of this material, supplemented by a few museum specimens of S. gigi collected from the catfish Clarias fuscus (Lacépède) in southern China, made it possible to study in detail the morphology of these parasite species and to redescribe them. The first species, whose correct name is S. petrowi Belous, 1965, exhibits some morphological features (e.g., unusually short vestibule, shape of pseudolabia and of the left spicule) not found in most other congeners; a unique feature is the presence of peculiar pairs of transversely oriented peg-like cuticular spines with rounded ends on the ventral surface of the female tail. Spinitectus gigi was found to have 28-31 cuticular spines in the first ring, relatively long distances between the 2nd-7th rings of spines, and anterior rings divided into 2 sectors; the excretory pore is located at the level of the 4th ring of cuticular spines; males posses 4 pairs of preanal- and 6 pairs of postanal caudal papillae and a pair of small phasmids. Spinitectus bagri Wang, Wu et Yu, 1993 and S. wulingensis Yu et Wang, 1997 are considered junior synonyms of S. petrowi, whereas S. clariasi Ky, 1971, S. ophicephali Ky, 1971 and S. yuanjiangensis Wang, Wu et Yu, 1997 are regarded to be junior synonyms of S. gigi. Spinitectus petrowi was not previously reported from China.
Adult specimens of five little-known species of spiruridan nematodes (Spirurida) were collected during occasional examinations of some fishes from the Poonch River in Jammu and Kashmir, India: Procamallanus (Spirocamallanus) bilaspurensis Gupta et Duggal, 1973 in Mastacembelus armatus (Lacépède) (Mastacembelidae, Synbranchiformes), Rhabdochona (Rhabdochona) indica Moravec, Scholz, Ash et Kar, 2010 in Crossocheilus latius (Hamilton) (Cyprinidae, Cypriniformes), Rhabdochona (Rhabdochona) turkestanica (Skryabin, 1917) in Schizothorax richardsonii (Gray) (Cyprinidae, Cypriniformes) and both Rhabdochona (Rhabdochona) hospeti Thapar, 1950 and Rhabdochona (Globochona) cf. chodukini Osmanov, 1957 in Tor putitora (Hamilton) (Cyprinidae, Cypriniformes); besides these, unidentifiable physalopterid larvae were recorded from M. armatus and T. putitora. Their detailed light and electron microscopical studies revealed some taxonomically important, previously not observed features and made possible their redescription. Fourth-stage larvae of P. (S.) bilaspurensis and R. (R.) turkestanica are described for the first time. The latter is resurrected as an independent species. The following are considered to be species inquirendae: a total of nine poorly described species of Rhabdochona Railliet, 1916 from T. putitora in Balochistan, Pakistan, all listed in the monograph of Kakar et al. (2011), plus an additional 15 species of the genus reported from cyprinids and a catfish in the same region (Balochistan) by the same authors. Also three congeneric species from India (R. nemacheili Rautela et Malhotra, 1982, R. putitora Kaur et Khera, 1991 and R. tori Gupta et Srivastava, 1982) and one from Pakistan (R. charsaddiensis Siddiqi et Khattak, 1984) should be considered as species inquirendae due to their poor descriptions. The names of Rhabdochona putitori Anjum, 2013, R. indusi Soofi, Birmani et Dharejo, 2017 and R. sindhicus Soofi, Birmani, Dharejo, Abbasi et Ghachal, 2020 are invalid according to the International Code of Zoological Nomenclature.
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.