New record of Philometra species from the marine edible fish Terapon jarbua collected from the Sindh, Arabian Sea, Pakistan.

Diseases in fish due to helminth parasites, especially Philometra species, are the primary worry in aquaculture. Philometra are responsible for health problem in fishes they directly affect fish growth and population parameters. A comprehensive survey was conducted involving the examination of the marine fish species Terapon jarbua, gathered from the coastal waters of Sindh, Pakistan In this research different Philometra species from marine fish Terapon jarbua during 2021 and 2022. Philometra nematodes, belonging to the family Philometridae, are common parasitic organisms inhabiting both marine and freshwater environments. Their prevalence, particularly when existing in high numbers within host organisms, can lead to severe and potentially lethal consequences. Employing light microscopy techniques, diverse species of Philometra were identified, including Philometra teraponi, P. jarbuai, P. arabiai, P. karachii, and P. awarii, localized primarily within the ovaries of the host fish. A total of 140 fish samples were examined and 76 were infected. The intensity of infected fish was 54.28%. The identification process encompassed meticulous analysis of crucial parameters, such as body size, esophagus length, positioning of the nerve ring, dimensions of the ventriculus, and ligament size. Intriguingly, the parasites were found in varying contexts; while some were free within the ovaries, others were embedded within tissues, inducing severe muscular dystrophy. This research presents novel findings of Philometra nematodes in the marine waters of Pakistan, extending their host and geographical distribution records. Future studies are needed to better evaluate and describe the dynamics and the epidemiology of Philometra infection in wild and cultured fish species.

The jaguar (Panthera onca) as a potential new host of Dracunculus sp.

Nematode species of the genus Dracunculus (Spirurida: Dracunculoidea) infect tissues and body cavities of reptiles, domestic and wild carnivores, and humans. The definitive hosts acquire the infection by ingesting intermediate (i.e., cyclopoid copepod) or paratenic (i.e., amphibians and fishes) hosts. Here we report the jaguar (Panthera onca) as a potential new host for Dracunculus sp. The nematode was collected from an ulcerated cutaneous nodule on the left anterior limb of a female jaguar in the municipality of Miranda, Mato Grosso do Sul state, Brazil. Based on the morphology of first stage larvae collected from a small fragment of the uterus of the adult nematode, the species was identified as Dracunculus sp. Reichard, 1759. Additionally, the morphological identification was molecularly confirmed by sequencing the cox1 gene. This report advocates for further investigations into the transmission cycle of this parasite in the Brazilian Pantanal wetland, considering the role of wildlife hosts and the zoonotic potential of Dracunculus species in that area.

Occurrence of new Philometra sp. in mangrove red snapper Lutjanus argentimaculatus from the Karachi coast, Pakistan.

A recent examination of Philometra nematodes from mangrove red snapper Lutjanus argentimaculatus (Forsskal, 1775) from the Karachi coast, Kemari was done in the years 2021-2022. The present study reported three new species of genus Philometra (Costa, 1845) (Nematoda: Philometridae) Philometra kolachii, Philometra lutjani and Philometra kemarii. A total of 140 fish samples were examined, and 76 were infected. The intensity of infected fish was 54.28%. In Pakistan, literature on Philometrid nematodes is limited, therefore, this research would be helpful for the documentation and enhancement of nematods in Pakistan.

Molecular phylogenetic relationship between Philometroides tahieli (Nematoda, Philometridae) and other philometrids from South America.

In South America, the family Philometridae is represented by several genera and species. In particular, Philometra and Philometroides are the most speciose genera. In Argentina, only Philometroides tahieli has been reported so far. The main objective of this study was to analyze the phylogenetic relationship between Ps. tahieli and other South American philometrids using molecular data. The molecular analysis was performed using a female specimen of Ps. tahieli found on the opercular muscle of a juvenile Micropogonias furnieri from brackish waters in Argentina. Phylogenetic relationships were studied based on partial sequences of the 18S rDNA and 28S rDNA genes. In the 18S rDNA tree, Ps. tahieli was mainly grouped with other Philometroides from freshwater hosts from China, sharing the site of infection (head tissues or muscles). In the 28S rDNA tree, obtained with fewer sequences, Ps. tahieli is related species from subcutaneous tissues of head. This study contributes with information on philometrids and confirms the presence of different lineages among South American species, with Ps. tahieli representing a new one. Further studies on South American species using more molecular markers and new morphological characters will improve our knowledge of philometrid biodiversity and phylogeny.

Review of the parasitic nematodes of marine fishes from off the American continent.

The ichthyofauna of the Atlantic and Pacific coasts off the American continent is very rich. Consequently, a high biodiversity of nematodes parasitizing these vertebrates is also expected. Currently, data on nematode parasites of marine fish off the Americas are fragmented. A review of all adult nematode species reported parasitizing marine fish from off the American continent is herein presented, as well as comments on their patterns of diversity, life cycles and advances in the taxonomic and phylogenetic knowledge. A total of 209 valid species, 19 species inquirendae and 6 dubious records have been recorded, the majority from the fish taxa Eupercaria and Perciformes. The families Sciaenidae, Serranidae and Lutjanidae, as well as the tropical and temperate Atlantic waters, exhibited the highest records of parasitic nematodes. The Cucullanidae, Philometridae and Cystidicolidae were the most speciose families of nematodes, which may be related to technological advances and relatively recent efforts of taxonomists, resulting in description of new taxa and the resolution of taxonomic problems. Numerous taxonomic questions still need resolution and, even though genetic data have been important for this process, the database is very scarce. This is the first review on all currently known nematode species parasitizing marine fish off the Americas and may serve as an important basis of reference for future approaches on these organisms.

Helminth diversity in Pimelodus blochii Valenciennes, 1840 (Osteichthyes: Pimelodidae) in two Amazon Rivers.

Structure of the helminth community and analyses of helminth population parameters of Pimelodus blochii collected in the Xapuri River in comparison with those in the Acre River were evaluated. Eight adult helminth species were found parasitizing P. blochii in the Acre River: the nematodes Orientatractis moraveci, Rondonia rondoni, Philometroides acreanensis, Cucullanus (Cucculanus) pinai pinai, Procamallanus (Spirocamallanus) pimelodus, Rhadochona acuminata, and Brasilnema sp., and the trematode Dadaytrema oxycephala. For Xapuri's fishes, nine helminth species were found: the nematodes O. moraveci, R. rondoni, C. (C.) pinai pinai, Procamallanus (Spirocamallanus) rarus, P. (S.) pimelodus, R. acuminata, Brasilnema sp., and Cystidicolidae gen. sp., and the trematode D. oxycephala. Nematode and Acanthocephala larvae were also reported. Helminth abundance, prevalence, and diversity were influenced by seasonality and locality (river). The helminth parasites from Acre's fishes formed a subset of the helminth community of the Xapuri's. The results indicate an influence of the environmental characteristics of the rivers on the helminth community structure and diversity. This is the first study of the parasite community of P. blochii in the Xapuri River. The paretheses of (Spirocamallanus) and (S.) should not be in italics all along the text and tables.

Molecular evidence linking the larval and adult stages of Mexiconema cichlasomae (Dracunculoidea: Daniconematidae) from Mexico, with notes on its phylogenetic position among Dracunculoidea.

We describe the larval developmental stages and life cycle of the dracunculid nematode Mexiconema cichlasomae in both the intermediate, Argulus yucatanus (Crustacea: Branchiura), and definitive hosts, Cichlasoma urophthalmus (Perciformes: Cichlidae), from the Celestun tropical coastal lagoon, Yucatan, Mexico. The morphological analyses showed significant differences between the total length of L1 found in M. cichlasomae gravid female and L2-L3 in A. yucatanus. This result indicates that the M. cichlasomae larval development occurs in the intermediate host. We obtained sequences from the small subunit (SSU) ribosomal marker from larval stages of M. cichlasomae in A. yucatanus and adult nematodes in C. urophthalmus. Our morphological and molecular results support conspecificity between M. cichlasomae larvae in A. yucatanus and the adult stages in C. urophthalmus. We briefly discuss the phylogenetic position of M. cichlasomae among the Daniconematidae, and provide evidence of the monophyly of the daniconematids associated with branchiurid intermediate hosts. Based on the phylogenetic results, we support the transfer of the Mexiconema genus to the family Skrjabillanidae and do not support the lowering of family Daniconematidae to subfamily.

First description of the male of Philometroides acreanensis and phylogenetic assessment of Philometridae (Nematoda: Dracunculoidea) suggest instability of some taxa.

The male of Philometroides acreanensis, parasitic in the anterior intestine external wall of the freshwater catfish Pimelodus blochii, from the Brazilian Amazon, is described for the first time. Additional data on the morphology of females is given. The new morphological data strengthened the validity of the species as well as its first genetic characterization, using three nuclear genetic markers (18S and 28S of the rDNA and ITS1-58S-ITS2), confirmed the high genetic resemblance of male and female specimens. Philometroides acreanensis shows morphological features of the generic diagnosis of Neophilometroides, Alinema, Philometra and Philometroides. Phylogenetic analyses using sequences of the18S rDNA from representatives of Dracunculoidea confirmed the validity of P. acreanensis and its close relatedness with Alinema rather than with other genera. The validity of Philonemidae was confirmed, as was the monophyly of Philometridae and Clavinema. However, Dentiphilometra, Philometra and Philometroides appear not to be monophyletic. Host taxa, habitat and geographic occurrence seem to have some relationship with the evolutionary traits of certain phylogenetic assemblages of philometrids, which were highly supported in the phylogentic reconstructions. Even though interesting aspects of the phylogeny and taxonomy of Philometridae came to light, further integrative approaches should be used that include additional genetic markers, due to the loose boundaries between some genera as observed here.

Pseudodelphis eleginopsis n. sp. (Nematoda: Guyanemidae), a new tissue-dwelling parasite of the Patagonian blennie Eleginops maclovinus (Cuvier) (Perciformes: Eleginopsidae) in Argentina, with notes on related forms.

Based on light and scanning electron microscopical studies, a new nematode parasite, Pseudodelphis eleginopsis n. sp. (Dracunculoidea: Guyanemidae), is described from tissues behind the gills of the Patagonian blennie Eleginops maclovinus (Cuvier) (Perciformes: Eleginopsidae) off the Atlantic coast (San Matías and San José Gulfs) of Patagonia, Argentina. The new species is mainly characterised by the length of the body (males 10-13 mm, larvigerous females 31-59 mm), the number (14) and arrangement of cephalic papillae, the absence of a buccal capsule, the muscular to glandular oesophagus length ratio (1:3-4) of larvigerous females, the length of the spicules (48-63 µm) and the number (7 pairs) and arrangement of the caudal papillae in the male. Pseudodelphis eleginopsis n. sp. is the first species of this genus described from a marine fish in the Atlantic Ocean and the first known dracunculoid parasitising the fish host belonging to the family Eleginopsidae. As revealed by the examination of very young females of the new species, the female genital tract of Pseudodelphis spp. is monodelphic. The genus Syngnathinema Moravec, Spangenberg & Frasca, 2001 is considered a junior synonym of Pseudodelphis Adamson & Roth, 1990 and, consequently, S. californiense and S. chitwoodi are transferred to Pseudodelphis as P. californiensis (Moravec, Spangenberg & Frasca, 2001) n. comb. and P. chitwoodi (Moravec & Kuchta, 2013) n. comb., respectively. Two dracunculoid species, Pseudodelphis limnicola Brugni & Viozzi, 2006 and the previously established Philonema percichthydis Moravec, Urawa & Coria, 1997, both described from the same freshwater host species, Percichthys trucha (Valenciennes), in the same region (Patagonia), are considered to be identical; therefore, the valid name of this species is Pseudodelphis percichthydis n. comb. and P. limnicola becomes its junior synonym. A key to the species of Pseudodelphis is provided.

The philometrid nematode Philometroides acreanensis n. sp. from the stomach wall of the catfish Pimelodus blochii in north-western Brazil.

A new nematode species, Philometroides acreanensis n. sp. (Philometridae), is described from female specimens recovered from the stomach wall of the freshwater catfish Pimelodus blochii Valenciennes (Pimelodidae) collected in the Acre River (Amazon River basin), Acre State, Brazil. Based on examination by light and scanning electron microscopy, the new species differs from the two other South American congeneric species mainly in the body length of the gravid female (240-280 mm), the length of the oesophagus (1.25 mm in holotype) representing 0.5% of the entire body length, the range of cuticular embossment, as well as the location in the host (stomach), order of the fish host (Siluriformes) and the geographical distribution (Amazon River drainage system). This is the third known species of Philometroides Yamaguti, 1935 reported from South America. A key to species of Philometroides occurring in the fish of America is provided.

A new species of philometrid parasite (Nematoda, Philometridae) and histopathological lesions in juvenile whitemouth croakers, Micropogonias furnieri (Desmarest).

A new species of nematode parasite, Philometroides tahieli sp. nov. is described. The juvenile whitemouth croaker, Micropogonias furnieri Desmarest, was collected during the spring and summer of the years 2008-2010 from estuarial environments of Argentina. During investigations of the parasite fauna a nematode encapsulated in the musculature of the operculum was found. The nematodes were removed from the host's muscle tissue and slide-mounted in lactophenol solution to clarify the specimens. Opercular muscle with the parasite was processed for histopathological examination. Philometroides tahieli sp. nov. can be identified by the location of gravid females in the host, presence of anterior oesophageal bulb, bosses on the surface of the body, presence of transversal mounds and 14 cephalic papillae in two circular rows. The pathogenicity of the parasite is low in the natural environment, but lesions are consistent with a chronic process. The appearance of caseous necrosis suggests the presence of a locally acting substance. Philometroides tahieli sp. nov. is the second species of this genera described from brackish waters, and since the discovery of Philometroides maplestoni in 1928, is the first species of this genus recorded for South America.

Three-spined stickleback Gasterosteus aculeatus, as a possible paratenic host for salmonid nematodes in a subarctic lake.

In Takvatn, a subarctic lake in northern Norway, 35 of 162 three-spined sticklebacks examined were infected with 106 specimens of third-stage larvae of Philonema oncorhynchi. The prevalence and mean intensity of P. oncorhynchi were 10 % and 2.0 in 2013 and 24 % and 3.0 in 2014, respectively. A single specimen of Cystidicola farionis was found in an additional sample. While the latter is considered an accidental infection, three-spined sticklebacks may function as paratenic hosts of P. oncorhynchi, potentially enhancing its transmission to salmonids due to their central role in the lacustrine food web of this subarctic lake.

Two new gonad-infecting philometrids (Nematoda: Philometridae) from the yellowedge grouper Hyporthodus flavolimbatus (Serranidae) and the great northern tilefish Lopholatilus chamaeleonticeps (Malacanthidae) in the northern Gulf of Mexico.

Based on light and scanning electron microscopical studies, two new gonad-infecting species of Philometra Costa, 1845 (Nematoda: Philometridae) are described from marine perciform fishes in the northern Gulf of Mexico: P. hyporthodi n. sp. from the ovary of the yellowedge grouper Hyporthodus flavolimbatus (Poey) (Serranidae) and P. lopholatili n. sp. from the ovary of the great northern tilefish Lopholatilus chamaeleonticeps Goode & Bean (Malacanthidae). Philometra hyporthodi is mainly characterised by the body length of both the males (3.62-4.07 mm) and gravid female (105 mm), the length of the spicules (135-138 µm) and the presence of dorsal transverse lamella-like structures on the distal portion of the gubernaculum. Philometra lopholatili is distinguished by the presence of a distinct dorsal protuberance consisting of two dorsolateral lamellated parts separated from each other by a smooth median field, an uninterrupted mound on the male caudal extremity, the length of the spicules (165-189 µm) and the body length of the males (2.19-2.34 mm) and gravid female (280 mm). Philometra lopholatili is the first representative of the genus and the second philometrid species reported from fishes of the family Malacanthidae.

Temporal variation of Mexiconema cichlasomae (Nematoda: Daniconematidae) in the Mayan cichlid fish Cichlasoma urophthalmus and its intermediate host Argulus yucatanus from a tropical coastal lagoon.

The aim of the present investigation was to determine whether temporal variation in environmental factors such as rainfall or temperature influence long-term fluctuations in the prevalence and mean abundance of the nematode Mexiconema cichlasomae in the cichlid fish Cichlasoma uropthalmus and its crustacean intermediate host, Argulus yucatanus. The study was undertaken in a tropical coastal lagoon in the Yucatan Peninsula (south-eastern Mexico) over an 8-year period. Variations in temperature, rainfall and monthly infection levels for both hosts were analysed using time series and cross-correlations to detect possible recurrent patterns. Infections of M. cichlasomae in A. yucatanus showed annual peaks, while in C. urophthalmus peaks were bi-annual. The latter appear to be related to the accumulation of several generations of this nematode in C. urophthalmus. Rainfall and temperature appear to be key environmental factors in influencing temporal variation in the infection of M. cichlasomae over periods longer than a year together with the accumulation of larval stages throughout time.

A new species of Philometra Costa, 1845 (Nematoda: Philometridae) from the freshwater fish (red piranha) Pygocentrus nattereri Kner (Characidae) in Amazonia, Brazil.

A new nematode species, Philometra nattereri n. sp. (Philometridae), is described from female specimens found in the oculo-orbits and nasal cavity of the red piranha Pygocentrus nattereri Kner (Characiformes: Characidae) from five lakes in Central Amazonia, Brazil, collected in 2008 and 2009 (overall prevalence 12%, intensity 1-3 nematodes per fish). Based on light and scanning electron microscopical examination, the new species differs from most other congeners parasitising freshwater fishes in that its oesophageal gland extends anteriorly far anterior to the level of the nerve-ring, in the presence of 14 small cephalic papillae arranged in two circles and in having two minute caudal projections. This is the first species of Philometra Costa, 1845 reported from fishes of the family Characidae and the second valid species of this genus parasitic in freshwater fishes of Brazil and South America.

New observations on philometrid nematodes (Philometridae) in marine fishes from the Northern Gulf of Mexico and the Indian River Lagoon of Florida (Usa), with first description of the male of Caranginema americanum.

The following 3 species of Philometra Costa, 1845 (Nematoda: Philometridae) were recorded from marine fishes off Florida: Caranginema americanum Moravec, Montoya-Mendoza and Salgado-Maldonado, 2008 from the subcutaneous tissue of the crevalle jack Caranx hippos (Linnaeus) (Carangidae); Philometra charlestonensis Moravec, de Buron, Baker and González-Solís, 2008 from the gonads (ovaries) of the scamp Mycteroperca phenax Jordan and Swain (Serranidae); and Philometra sp. (only subgravid females) from the gonads (ovaries) of the Atlantic needlefish Strongylura marina (Walbaum) (Belonidae). The male of C. americanum , the type species of Caranginema Moravec, Montoya-Mendoza, and Salgado-Maldonado, 2008 , is described for the first time. Its general morphology is similar to that of males of Philometra and Philometroides species. The males of C. americanum are mainly characterized by an elongate body, 3.13-3.28 mm long, a markedly elongate esophagus, and spicules and a gubernaculum 69-75 µm and 48-51 µm long, respectively. The present findings of C. americanum and P. charlestonensis represent new geographical records. The gonad-infecting Philometra sp. from S. marina probably belongs to an undescribed species.

Systematics of Mexiconema cichlasomae (Nematoda: Daniconematidae) based on sequences of SSU rDNA.

The molecular characterization of the daniconematid dracunculoid Mexiconema cichlasomae Moravec, Vidal, and Salgado-Maldonado, 1992 through the sequencing of SSU rDNA from adult individuals is presented herein. Additionally, preliminary genetic relationships of this nematode are inferred from alignment of sequences generated previously for other dracunculoids. Maximum parsimony and maximum likelihood analyses recovered identical trees. As anticipated by previous taxonomic work, M. cichlasomae is putatively closely related to skrjabillanid dracunculoids represented by Molnaria intestinalis (Dogiel and Bychovsky, 1934) and Skrjabillanus scardinii Molnár, 1966 SSU rDNA sequences, but the relationships of this newly discovered clade to other dracunculoid clades remain unresolved.

A new gonad-infecting species of Philometra (Nematoda: Philometridae) from the red cusk-eel Genypterus chilensis (Osteichthyes: Ophidiidae) off Chile.

A new nematode species, Philometra genypteri sp. n. (Philometridae), is described from male and female specimens found in the ovary of red cusk-eel, Genypterus chilensis (Guichenot) (Ophidiidae, Ophidiiformes), from the eastern South Pacific Ocean off the coast of northern Chile. Based on light and scanning electron microscopy examination, the new species differs from most other gonad-infecting Philometra spp. in the length of spicules (126-135 µm), a gubernaculum with dorsal lamella-like structures on its distal end, and the number and arrangement of genital papillae in the male. From a few congeneric, gonad-infecting species with unknown males, it can be distinguished by some morphological and biometrical features found in gravid female (absence of caudal projections, length of first-stage larvae or oesophagus, moderately developed anterior oesophageal inflation) and by the host type (fish family) and geographical distribution. P. genypteri is the first philometrid species reported from a fish belonging to the order Ophidiiformes and the second nominal species of Philometra recorded from marine fishes of the eastern South Pacific.

A new species of Philometra (Nematoda: Philometridae) from the sand perch Diplectrum formosum (Serranidae) off Florida, northern Gulf of Mexico.

A new nematode species, Philometra diplectri n. sp. (Philometridae), is described from male and female specimens found in unidentified tissues of head and anterior trunk (males) and subcutaneously in the mouth and under the operculum (females) of sand perch, Diplectrum formosum (Linnaeus) (Serranidae, Perciformes), from the northern Gulf of Mexico off Florida (Florida Middle Grounds). Based on light and scanning electron microscopy examination, the new species differs from other congeners parasitizing the subcutaneous tissues, fins, tissues of the buccal cavity, and gill covers or gill arches of marine and brackish-water fishes, mainly in having 8 conspicuously large cephalic papillae of the external circle, the absence of caudal projections, and the shape and small size of the anterior inflation of the esophagus in gravid females, and in possessing 5 pairs of caudal papillae and spicules 66-78 µm long in males. Philometra diplectri is the first known species of this genus whose gravid females are parasitic in the head tissues of serranid fishes.