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Recent examinations of camallanid nematodes (Camallanidae) from marine fishes off New Caledonia, collected in the years 2003-2011, revealed the presence of the following five new species of Procamallanus Baylis, 1923, all belonging to the subgenus Spirocamallanus Olsen, 1952: Procamallanus (Spirocamallanus) dispar n. sp. from the common ponyfish Leiognathus equulus (type host) and the striped ponyfish Aurigequula fasciata (both Leiognathidae, Perciformes); Procamallanus (Spirocamallanus) bothi n. sp. from the leopard flounder Bothus pantherinus (Bothidae, Pleuronectiformes); Procamallanus (Spirocamallanus) hexophtalmatis n. sp. from the speckled sandperch Parapercis hexophtalma (Pinguipedidae, Perciformes); Procamallanus (Spirocamallanus) synodi n. sp. from the sand lizardfish Synodus dermatogenys (Synodontidae, Aulopiformes); and Procamallanus (Spirocamallanus) thalassomatis n. sp. from the yellow-brown wrasse Thalassoma lutescens (Labridae, Perciformes). These are described based on light and scanning electron microscopical (SEM) studies. An additional three congeneric nematodes unidentifiable to species are reported from perciform fishes and a shark: Procamallanus (Spirocamallanus) sp. 3 of Moravec et al., 2006, Procamallanus (Spirocamallanus) sp. 1, and Procamallanus (Spirocamallanus) sp. 2. Ten fish species are recorded as new hosts for Camallanus carangis Olsen, 1954. Two camallanids, Procamallanus (Spirocamallanus) sp. 3 (subgravid female) and Camallanus carangis (fourth-stage larva) were also found in the digestive tract of the New Caledonian sea krait Laticauda saintgironsi, serving apparently as postcyclic and paratenic hosts, respectively, for these fish nematodes., (© F. Moravec & J.-L. Justine, published by EDP Sciences, 2019.)

Three species of nematodes from the Camallanidae that are known to infect Xenopus laevis Daudin (Anura: Pipidae) were collected from several localities across South Africa. New data on morphology, partial 28S and cox1 genes, infection levels and distribution are presented herein. The most common species, Batrachocamallanus slomei Southwell et Kirshner, 1937, from the stomach and less often oesophagus, was found in eight localities. Camallanus kaapstaadi Southwell et Kirshner, 1937, also from the oesophagus, was found in two localities and C. xenopodis Jackson et Tinsley, 1995, from the intestine, at a single locality. New localities for both C. kaapstaadi and C. xenopodis provide a geographical range extension. Males of C. xenopodis are described for the first time herein. The existence of a left spicule in the males of both the species of Camallanus Railliet and Henry, 1915 is confirmed and measurements are provided. Although C. xenopodis is distinguished from C. mazabukae Kung, 1948 in the present study, we suggest greater sampling effort in other African amphibians to confirm the species status of the latter taxon. Finally, the new molecular data showed distant relationships between collected species of Camallanus and species parasitising fish and freshwater turtles.

Procamallanus (Spirocamallanus) belenensis n. sp. is described using light and scanning electron microcopy, based on specimens taken from Ageneiosus ucayalensis, Castelnau, 1855 (Pisces: Siluriforme), a freshwater fish commonly called mandubé, in Pard State, Brazil; Procamallanus (Spirocamallanus) rarus is recorded from the same host. To our knowledge there are no previous reports of nematodes from this fish species. Procamallanus (S.) belenensis is characterized by the presence of 8-13 cuticular spiral thickenings coating 2/3 of posterior region of the buccal capsule of males and females (the anterior third is smooth); small sub-equal spicules; 3 and 4-5 pairs of pre- and post-cloacal papillae, respectively; the proportion of muscular and glandular esophagus is 1:1.5-2; males present 2 spike-like projections at the tail tip, which are absent in females by light microscopy. The most closely related species are Procamallanus (Spirocamallanus) inopinatus and Procamallanus (Spirocamallanus) pintoi. The new species differs from the most closely related species by the presence of 8-10 cuticular spiral thickenings in the buccal capsule of males and 9-13 in the females, 8 pairs of male clocal papillae (3 pre- and 5 post-cloacal, respectively), and only males bearing 2 minute, spike-like projections at the posterior end.

In the paper, we explored the intra- and interspecific evolutionary variation among species of Camallanus collected from different fish species in various regions of China. We determined the internal transcribed spacers of ribosomal DNA (ITS rDNA) sequences of these nematodes. The divergence (uncorrected p-distance) of ITS1, ITS2, and ITS rDNA data sets confirmed 2 valid species of Camallanus in China, i.e., C. cotti and C. hypophthalmichthys. The 2 species were distinguished not only by their different morphologies and host ranges but also by a tetranucleotide microsatellite (TTGC)n present in the ITS1 region of C. cotti. Phylogenetic analyses of the nematodes disclosed 2 main clades, corresponding to different individuals of C. cotti and C. hypophthalmichthys from different fish species in various geographical locations, although the interior nodes of each clade received poor support.

Habitat fragmentation may have some significant effects on population genetic structure because geographic distance and physical barriers may impede gene flow between populations. In this study, we investigated whether recent habitat fragmentation affected genetic structure and diversity of populations of the nematode Procamallanus fulvidraconis in the yellowhead catfish, Pelteobagrus fulvidraco. The nematode was collected from 12 localities in 7 floodplain lakes of the Yangtze River. Using 11 intersimple sequence repeat markers, analysis of molecular variance showed that genetic diversity occurred mainly within populations (70.26%). Expected heterozygosity (He) of P. fulvidraconis was barely different between connected (0.2105) and unconnected lakes (0.2083). Population subdivision (Fst) between connected lakes (0.2177) was higher than in unconnected lakes (0.1676). However, the connected and unconnected lakes did not cluster into 2 clades. A Mantel test revealed significant positive correlation between genetic and geographic distances (R = 0.5335, P < 0.01). These results suggest that habitat fragmentation did not cause genetic differentiation among populations or a reduction of diversity in isolated populations of P. fulvidraconis. At least 2 factors may increase the dispersal range of the nematode, i.e., flash flooding in summer and other species of fish that may serve as the definitive hosts. Moreover, lake fragmentation is probably a recent process; population size of the nematode in these lakes is large enough to maintain population structure.

A new species of parasitic nematode, Procamallanus (Spirocamallanus) anguillae sp. n. (family Camallanidae), is described based on specimens recovered from the intestine of the Indonesian eel Anguilla bicolor McClelland (type host) from southern Thailand (type locality Phuket Island). It is characterized mainly by the presence of 10-13 spiral ridges in the buccal capsule, length of spicules (366-372 microm and 198-216 microm), presence of a gubernaculum, arrangement of caudal papillae, and by the broad female tail with a digit-like projection bearing two cuticular spikes. In addition, two species of larval nematodes, Physalopteridae gen. sp. and Anisakis cf. simplex (Rudolphi 1809), were recorded from A. bicolor. All species are briefly described and illustrated.

The nematode Camallanus hypophthalmichthys Dogel and Akhmerov, 1959 is redescribed from specimens collected from the intestine of the bighead carp Aristichthys nobilis, from Liangzihu Lake (Yangtze River basin), Hubei Province, central China. The light and scanning electron microscopical examination made it possible to study in detail the morphology of this so far little-known species and to confirm its validity. The main specific features of C. hypophthalmichthys distinguishing it from the most similar Camallanus spp. is the presence of 3 small caudal processes on the male tail tip, 13-16 longitudinal ridges on the inner surface of the valve of the buccal capsule, and the arrangement of preanal and postanal genital papillae in the male. This finding represents a new host record, the first record of this parasite in the Yangtze River basin, and the first documented record of C. hypophthalmichthys from China. Camallanus hypophthalmichthys is considered a specific intestinal parasite of fishes of the cyprinid Hypophthalmichthyinae.

The marine fish parasite Camallanus carangis Olsen, 1954 (Nematoda: Camallanidae) is redescribed from the honeycomb grouper Epinephelus merra (Serranidae) in the Tuamotu Islands of French Polynesia and the glasseye Heteropriacanthus cruentatus (Priacanthidae) in Hawai'i, both coral reef fishes. Camallanus carangis is reported for the first time from French Polynesia and Hawai'i. Camallanus marinus Schmidt and Kuntz, 1969 is designated a synonym of C. carangis and Camallanus paracarangis Velasquez, 1980 is regarded as a species inquirenda. Additionally, the genus Oncophora may need to be redefined to accommodate Camallanus aotea Slankis and Korotaeva, 1974, which bears more resemblance to Oncophora than Camallanus.