New data on the morphology of Ascarophis parupenei (Nematoda: Cystidicolidae), an intestinal parasite of the marine fish Parupeneus indicus in the Indian Ocean, revealed by SEM

Scanning electron microscopy studies of three paratype specimens (two males and one female) of Ascarophis parupenei Moravec, Orecchia & Paggi, 1988, an intestinal parasite of the marine fish Parupeneus indicus (Shaw) in the Indian Ocean, made it possible to redescribe in detail the cephalic structures of this nematode as well as the morphology of the male caudal end. The presence of non-bilobed sublabia, phasmids in both males and females, bifurcated deirids, well-developed precloacal cuticular ridges (area rugosa) and a ventral median caudal protuberance in the male are reported in this species for the first time. The general morphology and measurements of A. parupenei somewhat resemble those of Rasheedia novaecaledoniensis Moravec & Justine, 2018 described from the same host species (P. indicus) from off New Caledonia, but both species clearly differ from each other by the shape and structure of pseudolabia and the anterior portion of the digestive tract, belonging thus to different nematode families (Cystidicolidae and Physalopteridae, respectively).

Three new species of Ascarophis van Beneden, 1871 (Nematoda: Cystidicolidae) from deep-sea hydrothermal vent fishes of the Pacific Ocean

Examinations of some deep-sea hydrothermal vent fishes from the western and eastern regions of the Pacific Ocean revealed the presence of three new species of Ascarophis van Beneden, 1871 (Nematoda: Cystidicolidae), all gastrointestinal parasites, namely: A. justinei n. sp. from Thermarces cerberus Rosenblatt & Cohen (type host) and Thermichthys hollisi Cohen, Rosemblatt & Moser (both Zoarcidae, Perciformes) and A. globuligera n. sp. from T. cerberus from the Northern East Pacific Rise, and A. monofilamentosa n. sp. from Pyrolicus manusanus Machida & Hashimoto (Zoarcidae, Perciformes) from the Manus Basin near Papua New Guinea. Specimens are described and illustrated based on light and scanning electron microscopical examinations. In addition to other morphological differences, all the three new species differ from each other by the structure of eggs: eggs bearing a lateral superficial swelling (A. globuligera n. sp.), eggs with one conspicuously long filament on one pole (A. monofilamentosa n. sp.) and eggs smooth, without any filaments or swellings (A. justinei n. sp.). The egg morphology of the two first-named species is unique within all species of Ascarophis, which indicates that all the three newly described species of Ascarophis are probably endemic to the respective hydrothermal vents as their fish hosts.

Redescription and genetic characterization of Cystidicoloides vaucheri, including first description of male and current status on the phylogeny of Cystidicolidae (Nematoda: Habronematoidea)

Cystidicoloides vaucheri collected in the stomach of the redtail catfish Phractocephalus hemioliopterus from River Acre, State of Acre, Brazil is redescribed, including the first description of males and the first genetic characterization based upon 18S and 28S genes of the rRNA. Newly collected females were biometrically smaller than those reported in the original description, but similar morphology shared by the two samples revealed that they belong to the same species. Scanning electron micrographs showed the accurate structure of the cephalic region, described here in detail. Furthermore, the morphology of males completed the specific diagnosis, strengthening the validity of the species. The three other congeners differ from C. vaucheri mainly as follows: in C. dlouhyi the area rugosa is absent, the cephalic structures in C. fischeri are completely distinct, and in both species the spicules have membranous outgrowths, absent in C. vaucheri. Despite the dubious generic assignment of C. izecksohni, it differs from C. vaucheri in several biometrical and morphological features. Because of data availability, only sequences of the 18S were used for phylogenetic reconstructions. Results showed that the genus Ascarophis and the families Cystidicolidae and Physalopteridae are not monophyletic. Cystidicoloides vaucheri formed an independent branch clustering with representatives of Cystidicolidae, confirming its validity. The inclusion of Salmonema and Spinitectus within Cystidicolidae should be reviewed, since they formed an assemblage with species from Rhabdochonidae. In fact, current classification of some taxa belonging to Habronematoidea, Physalopteroidea and Thelazioidea need to be re-evaluated, mainly based on molecular data from different genes.

Pseudascarophis brasiliensis sp. nov. (Nematoda: Cystidicolidae) parasitic in the Bermuda chub Kyphosus sectatrix (Perciformes: Kyphosidae) from southeastern Brazil

A new species of Pseudascarophis (Nematoda: Cystidicolidae) found in the stomach of Kyphosus sectatrix (Linnaeus) (Kyphosidae), off Rio de Janeiro, Brazil, is described. The new species can be differentiated from the other congeners by the presence of lateral alae, distinct but inconspicuous cephalic papillae at the anterior end, three pairs of precloacal and one pair of adcloacal papillae in males, egg morphology and morphometry of glandular oesophagus and spicules. Pseudascarophis tropica is transferred to Ascarophis as Ascarophis tropica (Solov'eva) comb. n. due to its ambiguous diagnosis.

Two new genera and species of cystidicolids (Nematoda, Cystidicolidae) from marine fishes off New Caledonia

Two new nematode species of the family Cystidicolidae, each representing a new genus, were recovered from marine perciform fishes off New Caledonia, South Pacific: Ascarophisnema tridentatum n. gen., n. sp. from the stomach of the Japanese large-eye bream, Gymnocranius euanus (Günther) (Lethrinidae) and Metabronemoides mirabilis n. gen., n. sp. from the stomach of the painted sweetlip, Diagramma pictum (Thunberg) (Haemulidae). Ascarophisnema is characterized mainly by its cephalic structures (presence of two tooth-like projections on either side of the base of each pseudolabium, dorsal and ventral inner extensions of each pseudolabium recurved laterally in apical view, and submedian sublabia fused together dorsally and ventrally) and the presence of trident-like deirids, and Metabronemoides by its unique cephalic structures (presence of one dorsal and one ventral labium and four large dorsolateral and ventrolateral labia, and absence of sublabia). Rhabdochona gymnocranius (considered a species inquirenda) is provisionally transferred to the former genus as Ascarophisnema gymnocranius (Yamaguti, 1935) n. comb. To date, a total of seven species of cystidicolids are reported from marine fishes off New Caledonia.

New data on the morphology of Comephoronema oschmarini (Nematoda, Cystidicolidae), a little-known gastrointestinal parasite of Lota lota (Teleostei) in Palaearctic Eurasia

The nematode Comephoronema oschmarini Trofimenko, 1974 (Cystidicolidae) was found in the stomach of the burbot Lota lota (Linnaeus) of Lake Geneva, Savoy, France, collected on 23 March 2000 [prevalence 60% (3/5); intensity of infection 2–66 (mean 35)]. This material made it possible to study in detail the morphology of this so far little-known parasite, using both light and scanning electron microscopy (the latter not previously used for this species). The SEM examination showed taxonomically important morphological features, not previously reported, including the presence of distinct terminal pseudolabial projections (protuberances), four submedian labia, four bilobed submedian sublabia, and only four cephalic papillae. Deirids were found to be bifurcated. A description of the true arrangement of the two last pairs of minute caudal papillae and phasmids in the male is given. Species of Compehoronema Layman, 1933 are considered to be closely related to those of Ascarophis van Beneden, 1871. A key to valid species of Comephoronema is provided.

A new species of Ascarophis (Nematoda, Cystidicolidae) from the stomach of the marine scorpaeniform fish Hoplichthys citrinus from a seamount off the Chesterfield Islands, New Caledonia

A new species of parasitic nematode, Ascarophis (Similascarophis) richeri sp. nov. (Cystidicolidae), is described from the stomach of the marine scorpaeniform fish Hoplichthys citrinus Gilbert (Hoplichthyidae) (prevalence 19%, intensity 1–8 nematodes per fish) collected in the region of the Chesterfield Islands (Coral Sea, west of New Caledonia) in October 2005. The new species, studied using both light and scanning electron microscopy, is characterized mainly by the structure of the mouth (highly reduced pseudolabia, high pseudolabial terminal projections, no submedian labia, well-developed, bilobed sublabia), bifurcate deirids, the length of the spicules (663–729 μm and 105–108 μm) and the presence of filaments on both egg poles (2–5 on each). Similascarophis Muñoz, González et George-Nascimento, 2004 is considered a subgenus of Ascarophis van Beneden, 1871 to accommodate the species characterized by highly reduced pseudolabia. Presence of the new species in fish from Seamount Nova (Lord Howe Rise) but not from the Chesterfield plateau suggests that it is endemic to this seamount, a case already encountered for many benthic invertebrates.