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.

Reaching the steady state: 30 years of Anguillicola crassus infection of European eel, Anguilla anguilla L., in Northern Germany.

A 30 years long data series on the infection dynamics of European eel (Anguilla anguilla L.) with the non-native invasive nematode Anguillicola crassus Kuwahara, Niimi & Hagaki, 1974 is presented. Parasite burden was evaluated for 30 years in inland and coastal waters in Mecklenburg-Western Pomerania from 1991 to 2020. The total prevalence, mean intensity and damage status of the swim bladders were very high during the first decade (1991­2000), and significantly decreased in both marine and freshwater eel populations in the following decades (2001­2010, 2011­2020). The parasite intensity of eels in coastal waters was significantly lower compared with the freshwater systems (61.3% vs 79.5% in the first decade), indicating the vulnerability of the parasites to brackish water conditions and the fact that the life cycle of A. crassus cannot be completed under high saline conditions. Eel caught in the western part of the Baltic Sea (west of Darss sill) had the lowest mean infection (51.8% in first decade) compared to the eastern part with 63.8%. Thus, besides different infection patterns caused by the environmental conditions, a temporal trend towards a reduced parasite intensity and a more balanced parasite­host relationship developed in the 30 years of interaction after the first invasion. Possible reasons and mechanisms for the observed trends in parasite­host interactions are discussed.

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.

Infection with swim bladder nematode Anguillicola crassus in relation to European eel growth, age, and habitat along the German Baltic coast.

One possible reason for the European eel (Anguilla anguilla) population decline is the neozoan eel swim bladder nematode Anguillicola crassus. To investigate whether the prevalence of A. crassus and the associated swim bladder pathology is related to eel habitat, growth rate, and age, 728 yellow eels from 6 habitats differing in salinity and located along the German Baltic coast were examined between 2005 and 2009. The prevalence of A. crassus varied between habitats, ranging from 9 to 57%. Infection prevalence and the percentage of eels with a damaged swim bladder were significantly higher in inner coastal waters compared to more saline open coastal water. In infected eels, 1 to 32 adult and preadult individuals of A. crassus were observed. The mean infection intensity varied between habitats from 2 to 7 nematodes per eel but did not significantly differ between inner and open coastal waters. Infection prevalence and intensity decreased significantly with age when all open coastal waters and all habitats were combined. Both the lower prevalence of A. crassus and the swim bladder damage of older eels and of eels originating from open coastal water habitats suggest that these eels have a higher fitness for spawning migrations than eels from inner coastal waters. The present study underlines the importance of eel screening on a sufficiently small geographical scale for the accurate estimation of eel recruitment and the identification of priority areas that are likely to produce healthy silver eels.

Effects of the invasive swim bladder parasite Anguillicola crassus on health and condition indicators in the European eel.

Parasites negatively affect biological processes within their hosts, which may alter for example health, growth, and reproductive ability. Non-native invasive parasites, in particular, may have large effects on the endemic hosts, given that the hosts lack evolved specific defences against such parasites. The swim bladder nematode Anguillicola crassus, an invasive parasite originating from Asia, is found in the European eel (Anguilla anguilla, L. 1758), since the 1980s. We investigated whether A. crassus affected several indicators related to health of the European eel (spleen- and liver size, body fat content and relative condition). Our results indicate that during the continental residency of the eels, infection by A. crassus had no major negative impacts on the investigated health indicators at the generally low infection intensities present in this study (median 2-3 visible parasites). Given that many of the adult eels were found to have swim bladder damage, concerns about their spawning migration through deeper oceanic environments can still be raised. To allow further investigations, we suggest that quantification of swim bladder damage should be implemented in eel-monitoring programs. Compared to other parasite pressure parameters, swim bladder damage provides additional information about past infections and future problems.

Two new and one newly recorded gonad-infecting species of Philometra Costa, 1845 (Nematoda: Philometridae) parasitising marine fishes in Iraq.

Specimens of two undescribed and one known gonad-infecting species of Philometra Costa, 1845 (Nematoda: Philometridae) were collected in some marine fishes from off the southern coast of Iraq. Based on light and scanning electron microscopy, the following new species are described: Philometra tayeni n. sp. (males and nongravid females) from ovaries of the purple-spotted bigeye Priacanthus tayenus Richardson (Priacanthidae, Acanthuriformes), and Philometra nibeae n. sp. (males and gravid female) from the ovary of the blotched croaker Nibea maculata (Bloch et Schneider) (Sciaenidae, Acanthuriformes). Philometra tayeni is mainly characterised by a pair of postanal papillae and a V-shaped caudal mound in males and by their body lengths (2.42-2.99 mm), whereas P. nibeae differs from its gonad-infecting congeners parasitising scienids mainly based on the body length of males (2.29-2.49 mm) and their spicules (96-117 µm), absence of a pair of postanal papillae and shape of caudal mound consisting of two parts. Philometra piscaria Moravec & Justine, 2014 (males and nongravid females), a parasite of the orange-spotted grouper Epinephelus coioides (Hamilton) (Epinephelidae, Perciformes), is recorded from the Arabian (= Persian) Gulf for the first time; previously unknown females of this species are described.

A qPCR-based method to detect the eel parasitic nematode Anguillicola crassus in intermediate and final hosts.

Being able to systematically detect parasitic infection, even when no visual signs of infection are present, is crucial to the establishment of accurate conservation policies. The nematode Anguillicola crassus infects the swimbladder of anguillid species and is a potential threat for eel populations. In North America, naïve hosts such as the American eel Anguilla rostrata are affected by this infection. The accidental introduction of A. crassus following restocking programs may contribute to the actual decline of the American eel in Canada. We present a quantitative real time PCR-based method to detect A. crassus infection in final and intermediate hosts. We tested two protocols on samples from different geographical origins in Canada: 1) a general detection of A. crassus DNA in pools of young final hosts (glass eels) or crustacean intermediate hosts 2) a detection at the individual scale by analyzing swim bladders from elvers, or from adult yellow and silver eels. The DNA of A. crassus was detected in one pool of zooplankton (intermediate host) from the Richelieu River (Montérégie-Québec), as well as in individual swim bladders of 13 elvers from Grande and Petite Trinité rivers (Côte-Nord-Québec). We suggest that our qPCR approach could be used in a quantitative way to estimate the parasitic burden in individual swim bladders of elvers. Our method, which goes beyond most of previous developed protocols that restricted the diagnosis of A. crassus to the moment when it was fully established in its final host, should help to detect early A. crassus infection in nature.

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.

Monitoring for Anguillicoloides crassus, Anguillid herpesvirus 1, aquabirnavirus EVE and rhabdovirus EVEX in the European eel population of southern Spain.

European eel is critically endangered in Europe. Among other stressors, pathogens are well-known to harm eels' fitness. One hundred and eighty-two eels were captured in three Eel Management Units in Andalucía (SE Spain) and analysed for Anguillicoloides crassus, Anguillid herpesvirus 1 (AngHV1), the rhabdovirus Eel Virus European X (EVEX) and the aquabirnavirus Eel Virus European (EVE). A. crassus adults and preadults were isolated and morphometrically identified, and the eel swimbladders were artificially digested to count A. crassus larvae. Also, eel tissues were examined by PCRs for the presence of viruses. EVEX and EVE were not detected in any of the eels. The estimated prevalence (95% confidence limits) was 71 (64-78)% for A. crassus and 35 (28-42)% for AngHV-1, varying these prevalences significantly between and within EMUs. Moreover, A. crassus prevalence was highest in smaller eels, in sites closest to the sea and eels sampled in the autumn. By contrast, AngHV-1 prevalence was highest in biggest eels, in sites far from the sea and sampled in the summer or winter. However, in mixed effects logistic models including site as a random variable, the risk of infection was associated with distance to the sea in both A. crassus and AngHV-1 infections and also to winter sampling in the case of AngHV-1 and not to other variables. These results are evidence that both pathogens are highly endemic in eels from Andalusian habitats. Further studies are needed to better understand the risk factors associated with these pathogens on eel populations.

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.

Description of Ichthyascaris grandis sp. n., redescription of Raphidascaroides halieutaeae Yin, 1983 and new records of some other raphidascaridid and philometrid nematodes from marine fishes off Java, Indonesia.

Examinations of nematodes collected from some marine fishes off the southwestern coast of Java, Indonesia in 2000 and 2001 revealed the presence of the following six species: ascaridoids Ichthyascaris grandis sp. n. from the intestine of Lophiomus setigerus (Vahl), I. cf. longispicula Li, Liu, Liu et Zhang, 2012 from the intestine of Conger cinereus Rüppel, Ichthyascaris sp. from the body cavity of Lobotes surinamensis (Bloch), and Raphidascaroides halieutaeae Yin, 1983 from the intestine of Halieutaea stellata (Vahl), and philometrids Philometra ivaschkini Parukhin, 1976 from the stomach wall of Trichiurus lepturus Linnaeus and P. psettoditis Moravec, Walter et Yuniar, 2012 from the body cavity (liver) of Psettodes erumei (Bloch et Schneider). Descriptions of these nematodes based on light and scanning electron microscopical studies are provided. The new species I. grandis sp. n. is mainly characterised by large body measurements (males and females up to 41.8 mm and 73.6 mm long, respectively), the length of spicules (0.99-1.05 mm), the tail tip usually without rudimentary spines and by the presence of 44-53 pairs of caudal papillae, eight to twelve of which being postanals. In addition to new data on the morphology of R. halieutaeae and other nematodes recorded, the 11 species of Raphidascaroides Yamaguti, 1941 poorly described from marine fishes in South Asia and reviewed in the monograph of Sood (2017) are considered species inquirendae and incertae sedis.

Hybridization between Anguillicola crassus and A. novaezelandiae, and viability of the F1 generation.

For decades, it has remained unclear how the Asian swim bladder nematode Anguillicola crassus was able to supplant the previously stable population of its relative from New Zealand Anguillicola novaezelandiae in the Lake Bracciano, Italy. Previously, researchers have hypothesized that A. crassus possesses an ecological advantage due to a more efficient life cycle in combination with a pattern of unidirectional hybridization between A. novaezelandiae females and A. crassus males. The present study focuses on the viability of hybrid offspring and their allelic pattern, particularly in developed adult stages of the hybrid F1 generation. While the percentages of hybrid individuals from A. novaezelandiae mothers and A. crassus fathers increased from egg to adult stages, it was more distinct in egg stages of A. crassus females and A. novaezelandiae males, but did not occur in adult F1 individuals at all. Therefore, we corroborate the hypothesis of unidirectional hybridization by differentiating between egg and adult stages, and suggest this as another explanatory factor for the extinction of A. novaezelandiae in Lake Bracciano in Italy and the predominance of A. crassus.

Towards an in situ non-lethal rapid test to accurately detect the presence of the nematode parasite, Anguillicoloides crassus, in European eel, Anguilla anguilla.

Anguillicoloides crassus is an invasive nematode parasite of the critically endangered European eel, Anguilla anguilla, and possibly one of the primary drivers of eel population collapse, impacting many features of eel physiology and life history. Early detection of the parasite is vital to limit the spread of A. crassus, to assess its potential impact on spawning biomass. However accurate diagnosis of infection could only be achieved via necropsy. To support eel fisheries management we developed a rapid, non-lethal, minimally invasive and in situ DNA-based method to infer the presence of the parasite in the swim bladder. Screening of 131 wild eels was undertaken between 2017 and 2019 in Ireland and UK to validate the procedure. DNA extractions and PCR were conducted using both a Qiagen Stool kit and in situ using Whatman qualitative filter paper No1 and a miniPCR DNA Discovery-System™. Primers were specifically designed to target the cytochrome oxidase mtDNA gene region and in situ extraction and amplification takes approximately 3 h for up to 16 individuals. Our in-situ diagnostic procedure demonstrated positive predictive values at 96% and negative predictive values at 87% by comparison to necropsy data. Our method could be a valuable tool in the hands of fisheries managers to enable infection control and help protect this iconic but critically endangered species.

Five species of Philometra Costa, 1845 (Nematoda: Philometridae) newly recorded from marine fishes in Iraq, including the description of P. arabiensis sp. n. from the ovary of the shrimp scad Alepes djedaba (Carangidae).

Recent examinations of some marine fishes from off the southern coast of Iraq revealed the presence of five species of Philometra Costa, 1845 (Nematoda: Philometridae): Philometra arabiensis sp. n. (males and females) from the ovary of the shrimp scad Alepes djedaba (Forsskål) (Carangidae, Carangiformes), Philometra psettoditis Moravec, Walter et Yuniar, 2012 (females) from the body cavity of the Indian halibut Psettodes erumei (Bloch et Schneider) (Psettodidae, Pleuronectiformes), Philometra terapontis Moravec, Gopalakrishnan, Rajkumar, Saravanakumar et Kaliyamoorthy, 2011 (female) from the ovary of the jarbua terapon Terapon jarbua (Forsskål) (Terapontidae, Centrarchiformes), Philometra sp. (females) from the ovary of the Arabian blackspot threadfin Polydactylus mullani (Hora) (Polynemidae, Carangariformes) and Philometra sp. 2 of Moravec et al. (2016a) (females) from the ovary and body cavity of the bartail flathead Platycephalus indicus (Linnaeus) (Platycephalidae, Perciformes). Philometra arabiensis sp. n. is mainly characterised by the length of spicules (198-243 µm) and gubernaculum (75-99 µm), the gubernaculum/spicule length ratio (1 : 2.33-2.79), the structure of the gubernaculum distal portion and the male caudal end, and the body length of males (1.86-2.73 mm). The present findings of P. psettoditis and P. terapontis in fishes of the Arabian Gulf represent new geographical records for these parasites.

Phylogenetic relationships of philometrid nematodes (Philometridae Baylis & Daubney, 1926) inferred from 18S rRNA, with molecular characterisation of recently described species.

Nematodes of the family Philometridae Baylis & Daubney, 1926 (Dracunculoidea Stiles, 1907) are generally poorly known, and there are many taxonomic issues within the family. Philometrids are parasites of fish and are found in various locations throughout the host, including within the subcutaneous tissues and musculature, the abdominal cavity and gonads; vast sexual dimorphism often means the males are not collected, leading to many species being described solely on female characteristics. Although there have been a number of studies utilising molecular data, the vast majority of species are yet to be sequenced. This study undertook genetic sequencing of 15 recently described species of philometrids across 4 genera, many of which were from specimens collected from waters off Australia. All of the sequences obtained were closely related with representatives of the family Philometridae. Species were found to be distributed in the phylogenetic trees within 4 clades based on a combination of site of infection within the host and host habitat. Family of host and geographical location was not as important for position within the trees. Clade A contained philometrids collected from the abdominal cavities and head tissues of South American freshwater fish. Clade B contained philometrids primarily from the abdominal cavities of freshwater European cyprinids. Clade C contained philometrids primarily from the ovaries of marine fish. Clade D contained philometrids from the body tissues of marine and freshwater fish. The potential co-evolutionary patterns between philometrids and their fish hosts are highlighted as an area of future research. This research also highlighted the importance of correct identification of any sequenced specimen.

Morphology and phylogeny of the parasitic nematode Mooleptus rabuka (Machida, Ogawa & Okiyama, 1982) (Rhabditida, Spirurina: Mooleptinae nom. nov.), with notes on taxonomy of the family Gnathostomatidae.

The nematode Mooleptus rabuka is recorded in the digestive tract of catshark Apristurus fedorovi caught at the Imperial Ridge (Pacific Ocean). Important morphological features such as the number of cephalic and caudal papillae, the position of amphids and the shape of the gubernaculum are detailed in this parasite species. According to the phylogenetic analyses based on the 18S ribosomal RNA gene sequences, M. rabuka forms a lineage, Mooleptinae nom. nov., which is close to the gnathostomatid genus Echinocephalus (maximum likelihood analysis), or else forms a polytomy with this genus and the lineages of Anguillicola + Spiroxys and Tanqua + 'Linstowinema' sp. (Bayesian inference analysis). Overall, our findings do not support the monophyly of the Gnathostomatidae. We elevate spiroxyines to the family status, Spiroxyidae stat. nov., and temporarily consider the Gnathostomatidae to include the following subfamilies: Ancyracanthinae Yorke & Maplestone, 1926, Gnathostomatinae Railliet, 1895 sensu lato and Mooleptinae nom. nov. The name Mooleptinae nom. nov. is suggested instead of the Metaleptinae Moravec & Nagasawa, 2000, which is based on a preoccupied generic name Metaleptus Machida, Ogawa & Okiyama, 1982.

Anguillicola (Anguillicoides) crassus: Morphometric characteristics and pathogenicity in eels (Anguilla anguilla) in Greece.

Anguillicola (Anguillicoides) crassus is a swimbladder nematode parasite of Anguilla anguilla (Linnaeus, 1758). The present study investigates the morphology and pathogenicity of A. crassus in European eel, as well as, the effects of different aquatic environments on the infection of A. crassus, in Greece. A total of 268 nematodes were collected from four estuarine systems in Greece. In all collected parasites, measurements carried out to define the morphological characteristics of parasites: parasite length and width, oesophagus max length and max width. Τhe mean parasite length was 23.50 mm (95% CI: 22.42-24.58) for females, 12.95 mm (95% CI: 12.25-13.64) for the males and 6.39 mm (95% CI: 5.27-7.50) for the juveniles. The mean parasite width was 1.99 mm (95% CI: 1.88-2.10) for females, 0.93 mm (95% CI: 0.86-1.00) for males and 0.51 mm (95% CI: 0.39-0.64) for juveniles. In total, the mean intensity was found 3.15 (95% CI: 2.53-3.78), while the highest mean intensity per eel was 8.00 (95% CI: 0.00-29.51) in Tholi Lagoon and the lowest was 2.20 (95% CI: 0.36-4.04) in Amvrakikos Gulf. Longitudinal and transverse histological sections of two adults A. crassus and two swimbladders were carried out. Multiple granules were observed, as a tissue reaction of the organism to swath around the 4th stage larvae (L4) that have entered the swimbladder. Molecular analysis was performed on three female adults A. crassus derived from eel specimens coming from the Vistonis estuarine system. The high reproductive capacity of the parasite reveals that A. anguilla has low effective defense mechanisms against the parasite. Also, the morphometric variations of the A. crassus seems to have a plastic feature which is being differently expressed when exposed to various environments.

Records of two gonad-infecting species of Philometra (Nematoda: Philometridae) from marine fishes off Iraq, including the description of Philometra parabrevicollis n. sp. from the bigeye snapper Lutjanus lutjanus Bloch (Pisces, Lutjanidae).

Recent examinations of some marine fishes from off the southern coast of Iraq revealed the presence of two species of Philometra Costa, 1845 (Nematoda: Philometridae): P. parabrevicollis n. sp. (males and subgravid and nongravid females) from the ovary of the bigeye snapper Lutjanus lutjanus Bloch (Perciformes, Lutjanidae) and Philometra sp. (subgravid females) from the ovary of the bartail flathead Platycephalus indicus (Linnaeus) (Perciformes, Platycephalidae). Specimens of species are described and illustrated based on light and scanning electron microscopical examinations. Philometra parabrevicollis n. sp. is mainly characterised by the length of spicules (267-285 µm) and gubernaculum (159-168 µm), the gubernaculum/spicule length ratio (1:1.64-1.76), the structure of the gubernaculum distal tip and of the male caudal end, and the body length of males (4.03-4.90 mm). The description of this new species again confirms a high degree of host specificity of gonad-infecting species of Philometra in congeneric lutjanid hosts. Although Philometra sp. parasitising P. indicus in Iraqi waters was previously recorded, its subgravid females are described for the first time. A key to gonad-infecting species of Philometra parasitic in fishes of the family Lutjanidae is provided.

Two species of philometrid nematodes (Philometridae) newly recorded from marine fishes off South Australia, including Philometra inconveniens n. sp. from Hyporhamphus melanochir (Valenciennes) (Hemiramphidae).

Recent examinations of some marine fishes from off the coast of South Australia revealed the presence of two species of Philometra Costa, 1845 (Nematoda: Philometridae): P. inconveniens n. sp. from the ovary (males) and body cavity (subgravid female) of the southern garfish Hyporhamphus melanochir (Valenciennes) (Beloniformes, Hemiramphidae) and Philometra sp. (gravid and subgravid females) from the body cavity of the Australian barracuda Sphyraena novaehollandiae Günther (Perciformes, Sphyraenidae) (new host and geographical records). Specimens of species are described and illustrated based on light and scanning electron microscopical examinations. Philometra inconveniens n. sp. differs from the most similar species P. longa Moravec, Barton & Shamsi, 2021, a parasite of the body cavity of the congeneric host off eastern Australia, mainly by a different structure of the gubernaculum (absence of dorsal barbs and presence of lateral extensions on its distal portion). This indicates a high degree of host specificity of these nematodes in co-occuring congeneric hosts.