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This study determines the occurrence and molecular characterisation of Monogenea from three commercially important Australian fish: Australian sardine Sardinops sagax (Jenyns), Australian anchovy Engraulis australis (White), and eastern school whiting Sillago flindersi McKay. Earlier studies have provided only morphological species identification, whereas this study combines both morphological and molecular methods. A total of 247 fish across 3 species, sourced from the New South Wales and Victorian coasts, were examined for Monogenea. A total of 187 monogenean parasites were recovered from the gills. The overall prevalence, mean intensity, and mean abundance were 34%, 2.23, and 0.78, respectively. The parasites were initially classified morphologically as three species across two families. Family Mazocraeidae was represented by Mazocraes australis Timi et al. J Parasitol 85:28–32, 1999, and family Microcotylidae by Polylabris sillaginae (Woolcock, Parasitology 28:79–91, 1936) Dillon, Hargis, and Harrises, 1983 and P. australiensis Hayward, 1996. Molecular identification of parasites was conducted through sequencing of the mitochondrial cytochrome c oxidase subunit 1 (cox1) gene. The fish hosts in the present study were also barcoded (mitochondrial cox1 gene) to confirm specific identities. There was no comparable cox1 sequence available in GenBank for the parasites found in the present study. However, the phylogenetic tree clustered the monogenean species identified in this study according to their familial groups of Mazocraeidae and Microcotylidae. The presence of M. australis on E. australis and S. sagax was confirmed in this study. Polylabris australiensis was only found on S. sagax but Si. flindersi was found to be a host for both Polylabris species. This study is the first to explore the mitochondrial cox1 genes of these three-monogenean species. These findings will serve as a foundation for future monogenean research in Australian waters and elsewhere.

A review was conducted to identify the most common causative agents of anisakidosis, the methods used for identification of the causative agents, and to summarize the sources of infection, and patients’ demographics. A total of 762 cases (409 articles, inclusive of all languages) were found between 1965 and 2022. The age range was 7 months to 85 years old. Out of the 34 countries, Japan, Spain, and South Korea stood out with the highest number of published human cases of anisakidosis, respectively. This raises the question: Why are there few to no reports of anisakidosis cases in other countries, such as Indonesia and Vietnam, where seafood consumption is notably high? Other than the gastrointestinal tract, parasites were frequently found in internal organs such as liver, spleen, pancreas, lung, hiatal and epigastric hernia, and tonsils. There are also reports of the worm being excreted through the nose, rectum, and mouth. Symptoms included sore throat, tumor, bleeding, gastric/epigastric/abdominal/substernal/lower back/testicular pain, nausea, anorexia, vomiting, diarrhea, constipation, intestinal obstruction, intussusception, blood in feces, hematochezia, anemia, and respiratory arrest. These appeared either immediately or up to 2 months after consuming raw/undercooked seafood and lasting up to 10 years. Anisakidosis commonly mimicked symptoms of cancer, pancreatitis, type I/II Kounis syndrome, intussusception, Crohn’s disease, ovarian cysts, intestinal endometriosis, epigastralgia, gastritis, gastroesophageal reflux disease, hernia, intestinal obstruction, peritonitis, and appendicitis. In these cases, it was only after surgery that it was found these symptoms/conditions were caused by anisakids. A range of not only mainly marine but also freshwater fish/shellfish were reported as source of infection. There were several reports of infection with >1 nematode (up to >200), more than one species of anisakids in the same patient, and the presence of L4/adult nematodes. The severity of symptoms did not relate to the number of parasites. The number of anisakidosis cases is grossly underestimated globally. Using erroneous taxonomic terms, assumptions, and identifying the parasite as Anisakis (based solely on the Y-shaped lateral cord in crossed section of the parasite) are still common. The Y-shaped lateral cord is not unique to Anisakis spp. Acquiring a history of ingesting raw/undercooked fish/seafood can be a clue to the diagnosis of the condition. This review emphasizes the following key points: insufficient awareness of fish parasites among medical professionals, seafood handlers, and policy makers; limited availability of effective diagnostic methodologies; and inadequate clinical information for optimizing the management of anisakidosis in numerous regions worldwide.

Specimens of Dolichoperoides macalpini (Nicoll, 1914) (Digenea: Dolichoperoididae) were collected from Australian venomous snakes (Elapidae): Notechis scutatus Peters, 1861 and Austrelaps superbus (Günther, 1858) from Tasmania and surrounding islands and N. s. occidentalis Glauert, 1948 from wetlands near Perth, Western Australia. Despite variation in morphological measurements, genetic analysis showed that the one species of digeneans infected the snakes from all locations. This study presents the first DNA sequences for D. macalpini (internal transcribed spacer, 18S, 28S), confirming its placement in a family separate from the Reniferidae and Telorchiidae. Analysis of the infection dynamics of infection in Western Australian snakes showed significant differences in levels of infection between wetland locations, season and year of collection. Infection of D. macalpini was reported in the gastrointestinal tract, including the mouth, in freshly euthanised snakes in Western Australia, and in the lung in Tasmanian snakes, consistent with earlier reports. Differences in morphology and site of infection are suggested to be due to a combination of season and maturity of the digenean, with infection potentially occurring early in the season, as the snakes emerge from torpor. The need for research on the seasonal dynamics of infection with this parasite is discussed.

Identification of specimens belonging to the genus Linguatula (Pentastomida) is relatively easy due to their unique morphology. However, differentiation between species of Linguatula can be challenging for several reasons, including considerable differences between different developmental stages of the parasite within and between species. Currently, 18S rRNA and Cox1 sequences are the only available comparable sequences in GenBank, but recent research has discussed the utility of 28S rRNA for pentastomid phylogenetics. This study presents 28S rRNA gene sequences for two members of the genus Linguatula. Sequences of 28S rRNA were successfully obtained from well-identified samples of L.serrata (collected in Australia) and L.nuttalli (collected in South Africa), with voucher specimens. Phylogenetic analysis of the 28S rRNA region showed 6% difference between L.serrata and L.nuttalli, with low levels of intraspecific variation. In comparison, 18S rRNA and Cox1 sequences from the same specimens showed 0.23% and 13% interspecific differences, respectively. The results of this study show that 28S rRNA has greater genetic diversity to allow for improved differentiation between species of Linguatula than 18S rRNA but is on par with Cox1. Records that do not provide adequate morphological or molecular data to justify independent specific diagnoses must be regarded cautiously, and the need for continued research on species of Linguatula, using a combined morphological and molecular analysis, across a number of different hosts, development stages, geographical regions and molecular markers is highlighted.

This study describes the occurrence and molecular identification of Monogenea from blue-spotted flathead Platycephalus caeruleopunctatus (McCulloch) (Scorpaeniformes: Platycephalidae) from waters off the NSW coast, Australia. Platycephalus spp. are favoured by consumers for delicate, white, mild flavoured flesh and therefore are commercially important species within Australia. Platycephalus spp. are also extensively targeted by Australian recreational fishers. There has been no previous study that has exclusively focused on Pl. caeruleopunctatus in Australia or globally. Although a single study by Dillon (1985), of monogeneans infecting Platycephalus spp. from Australian waters, identified Microcotyle bassensis Murray, 1931 in Pl. caeruleopunctatus. The present study combines both morphological and molecular methods to identify both host and parasites. A total of 116 fish, sourced from the waters off the coast of New South Wales, Australia, were examined. A total of 1498 Monogenea were recovered from the gills. The overall prevalence, mean intensity, and mean abundance were 72%, 18.05, and 12.91, respectively. Monogenea were initially classified morphologically as two different species M. bassensis (family: Microcotylidae) and Platycephalotrema bassense (Hughes, 1928) KritskyNitta, 2019 (family: Ancyrocephalidae). Molecular identification of Monogenea was conducted through sequencing of their mitochondrial cytochrome c oxidase subunit 1 (cox1) and nuclear 28S genes. The specific identification of host Pl. caeruleopunctatus was confirmed through sequencing the cox1 gene. There was no comparable sequence for cox1 and 28S genes available in GenBank for the monogenean species found in the present study. Only a single sequence (obtained from the nuclear ITS2-rDNA) was deposited in GenBank for M. bassensis. However, the phylogenetic analyses of mitochondrial and nuclear sequences revealed that the identified Monogenea clustered according to their familial groups. Platycephalotrema bassense was identified for the first time in Pl. caeruleopunctatus in the present study. This study has provided the first evidence for the exploration of both cox1 and 28S sequences of all Monogenea. The findings of this study serve as a foundation for future monogenean research on other Platycephalus spp. from Australian waters.

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.

Anoplotaenia dasyuriBeddard, 1911 (Cestoda), from the Tasmanian devil,Sarcophilus harrisii(Boitard, 1842), is a taxonomic enigma, where a combination of morphological features, host type and geographical location have prevented it from being placed within a family and it is consideredincertae sedis, despite its accepted validity. We performed a phylogenetic analysis of threeA. dasyurispecimens collected from three Tasmanian devils using 18S and 28S rRNA sequences.Anoplotaenia dasyuriwas found to have closest affinity with the family Paruterinidae, especially the genusCladotaeniaCohn, 1901. The postulated theory of transfer of an ancestor ofAnoplotaeniaBeddard, 1911 transferring to the Tasmanian devil from an unrelated carnivorous host, such as an accipitriform or other carnivorous bird, is discussed and supported.

As one of the world's megadiverse countries, Australian biodiversity is vital for global biodiversity. Nematodes belonging to the genus Anisakis (family Anisakidae) are an important part of this biodiversity due to their ability to be repeatedly transmitted among their intermediate hosts before reaching the top of the food pyramid. Therefore, they have a significant impact on the community structures of various ecosystems. In addition, globally, they are known to be of medical and veterinary significance. The aim of this article is to provide an update on the current knowledge about these important parasites in Australia. Since 1916, a total of 234 records of Anisakis spp. from various hosts and localities have been found in Australia. It is estimated that the occurrence of Anisakis spp. and their health impacts in at least 84, 98.5, and 95% of Australian marine mammals, fish, and water birds, respectively, have not been documented yet. The results of this study suggest Australia is perhaps home to the most diverse Anisakis fauna. Available information is dominated by reports of these parasites in fish hosts, many of them among edible fish. Given the popularity of seafood in Australia and the occurrence of infectious stages of Anisakis spp. in edible fish, all stakeholders should be made aware of the occurrence, prevalence, and survival of Anisakis spp. in seafood. Also, as more pet owners feed their pets with a variety of fish and seafood products, it is important for veterinarians to be aware of seafood transmitted Anisakis spp. in pet animals. This study also highlights several important knowledge gaps: (i) The detailed life cycle of Anisakis spp. in Australia is not known. Detecting their first intermediate hosts is important for better management of crustacean zooplankton populations in our waters. (ii) Research on Anisakis spp. in Australia has been restricted to limited taxonomical studies and should extend to other aspects of these important parasites. (iii) The capacity to identify parasite taxa to species is especially important for resolving biological diversity around Australia; however, opportunities to formally train in parasite taxonomy are rare and diminishing. There is a need to train researchers with taxonomy skills. (iv) Given the vast range of biodiversity in Australia and the broad host-specificity of Anisakis spp., particularly in the larval stages, the full range of their intermediate hosts remains unknown. (v) The health impacts of the infection of the intermediate/definitive hosts with Anisakis spp. are not fully understood. Thus, one of the important areas for future studies is investigating the pathogenicity of Anisakis spp. in affected animals. This is a crucial yet unknown factor for the conservation of some endangered species in Australia.

Clinostomum Leidy, 1856 (Trematoda: Clinostomidae) is a cosmopolitan, zoonotic genus of fluke that has been poorly studied in an Australian setting. Following previous reports of reservoir fish in Australian fish ponds being heavily infected with Clinostomum metacercaria, the current study was conducted to determine the specific identity of Clinostomum sp. in inland Australia, by examining and characterizing parasites collected from a potential definitive host, cormorants. A total of 33 parasite specimens belonging to the genus Clinostomum were collected from two cormorants (little black cormorants, Phalacrocorax sulcirostris) that were collected from the Narrandera Fisheries Research Centre, New South Wales, at the same locality where metacercaria of Clinostomum sp. have been reported in fish. All specimens in our study were immature adults. Clinostomum specimens with similar morphology have been identified as C. complanatum in the past, based on their morphological characteristics. However, phylogenetic analyses based on the ITS sequence data in the present study suggest they are the same as the Clinostomum sp. previously reported from carp gudgeons (Hypseleotris spp.) from the same farm, and distinct from C. complanatum. The ITS sequences obtained from the specimens in the present study were most similar to those belonging to C. phalacrocoracis (never reported in Australia). Our specimens formed a distinct clade on the phylogenetic tree and their specific identity awaits until fully mature specimens are described in future studies.

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 Gunther (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.

A new nematode species, Philometra longa n. sp. (Philometridae), is described from male and female specimens collected from the body cavity of the marine fish, Hyporhamphus australis (Steindachner) (Hemirhamphidae, Beloniformes) from off the south-eastern coast of Australia. Based on examination by light and scanning electron microscopy, the new species differs from those parasitising other beloniform hosts mainly in the body length (4.69 mm), the length of spicules (141 µm) and the structure of the caudal end and the distal tip of gubernaculum in the male, and in the conspicuously long body (455-560 mm) of the gravid female. Philometra longa n. sp. is the first species of philometrids described from fishes of the family Hemiramphidae. It is the 26th nominal species of philometrids and the 19th species of Philometra so far recorded from Australian marine and brackish waters. Re-examined museum specimens of Philometra sp. from Hyporhamphus melanochir (Valenciennes) off Tasmania, as well as those previously reported from the same host species off the Australian coast, were found to be identical with P. longa sp. n.

This study aimed to determine the integrative characterisation of nematodes from three species of edible flathead fishes (Scorpaeniformes: Platycephalidae) in New South Wales, Australia, and describe nematode communities within three species of flatheads. Tiger (Platycephalus richardsoni (Castelnau); n = 20) and sand flatheads (Platycephalus bassensis (Cuvier); n = 20), sourced from the Nelson Bay area, and dusky flathead (Platycephalus fuscus (Cuvier); n = 20) from the Manning River, Taree, were examined for the presence of nematodes. The nematodes were initially classified morphologically as 12 different morphotypes belonging to the families Anisakidae (Anisakis types I, II, and III, Contracaecum type II, Terranova types I and II), Raphidascarididae (Hysterothylacium types IV, VI, VIII, and H. zhoushanense larva), and Gnathostomatidae (Echinocephalus sp. larva), Capillariidae (Capillaria sp.), followed by genetic identification through sequencing of the internal transcribed spacer (ITS-1, 5.8S, ITS-2) regions. Phylogenetic analyses revealed the evolutionary relationship between the identified larval specimens in the present study with available GenBank larval and adult nematodes. Sand flathead was 90% infected with nematodes followed by tiger flathead at 85% and dusky flathead at 15%. Nematodes infecting estuarine dusky and oceanic sand and tiger flatheads contrasted markedly. The analysis of similarities (ANOSIM) showed significant differences (p

Choricotyle australiensis Roubal, Armitage & Rohde, 1983, a diclidophorid monogenean species, is redescribed and genetically characterised using the partial nuclear 28S ribosomal RNA gene (28S rRNA) and a fragment of mitochondrial cytochrome c oxidase subunit 1 (cox1) gene sequences for specimens collected from Chrysophrys auratus (Forster) off Australia and New Zealand. Previous studies have either provided morphological or genetic results, whereas this study combines morphological and advanced molecular methods. A total of 70 Ch. auratus were examined with 22 individuals of C. australiensis recovered from the gills (overall prevalence of 23%). This study has provided the first evidence for the exploration of mitochondrial cox1 region for C. australiensis. Comparison of the newly generated sequences with other available data supported the distinction of C. australiensis among diclidophorid Furhmann, 1928 species thus confirming its taxonomic status.

Platyhelminths belonging to the family Clinostomidae (Digenea) have a worldwide distribution and are known to infect piscivorous birds through their intermediate hosts, usually fish species. In the present study, clinostome metacercariae were collected from fish hosts, including Channa punctata (Bloch 1793) (n = 25) and Trichogaster fasciata Bloch and Schneider 1801 (n = 25), from a freshwater system in India. The experimental infection of cattle egrets, Ardea (Bubulcus) ibis Linnaeus 1758, with some of the live metacercariae found in the present study was successful. Live adult parasites were obtained from the buccal cavity of the birds. Both metacercaria and adult specimens were subjected to molecular studies to obtain the sequences of 28S, ITS1, and ITS2 (nuclear rDNA) regions. The parasites were found to belong to three species, Clinostomum giganticum Agarwal 1959; C. piscidium Southwell and Prashad 1918; and Euclinostomum heterostomum (Rudolphi 1809). Phylogenetic analyses of the sequences obtained from the adults and metacercariae established a link between the metacercariae in the fish hosts and adults in the avian host, which is essential to elucidate their partial life cycle and specify morphological characteristics in the metacercarial stage.

Macrobrachium australiense, is one of Australia’s most widespread freshwater invertebrates. Although a significant amount of research has been conducted to understand the diversity of crustacean species in Australia, there has been considerably less effort focused on their Temnocephalidae symbionts. The present study aims to identify Temnocephalidae species found in M. australiense, along with determining their impacts on the fitness of their hosts. A total of 54 M. australiense (common Australian river prawn) were examined for evidence of infection with Temnocephalidae species, of which 96.3% showed at least one sign of infection with Temnocephalidae. Due to damage and immaturity of the worms collected from, they have been referred to as Temnocephalidae sp. based on the presence of tentacles on the anterior margin of the body, and pedunculate sucker located dorsally on the ventral surface. Possible mechanical damage to gill lamellae resulting from either egg deposition or autolysis is evident. In the phylogenetic tree built based on sequences of the 28S rRNA gene, specimens in the present study grouped separately from other Temnocephalidae species reported from Australia.

International audience; A collection of nematodes from the Muséum National d’Histoire Naturelle (National Museum of Natural History), Paris, France, was studied. The nematodes had previously been collected from a range of marine fish hosts. The aim of this study was to investigate the identity of these nematodes. Detailed body measurements of the nematodes were taken via light microscopy and where possible first and second internal transcribed spacers (ITS-1 and ITS-2) of ribosomal DNA were subjected to PCR, purified and sequenced. Six species and three larval types were found from a range of fish species and included 13 new host records and two new geographical records. Of the taxa found, Hysterothylacium kajikiae is the only species which may have zoonotic potential. The majority of host fish in this study are edible species, commercially and recreationally fished and frequently incorporated into the cuisine of New Caledonia as raw fish dishes. This study will allow better understanding of the diversity, life cycles, distribution and host-parasite relationships in the New Caledonia area.

Being listed in the IUCN Red List of Threatened Species, knowledge on the biology, health and diseases of the scalloped hammerhead, Sphyrna lewini (Griffith & Smith) is limited; this is especially true for its parasites. In this paper, a new species, Pulchrascaris australis, is morphologically described followed by genetic characterisation based on the sequence of the ITS region. The new species can be easily differentiated from its congeners based on the morphology of the mouthpart, spicules, plectanes, eggs and vulva. Phylogenetic analyses clearly distinguish specimens in the present study from other parasitic nematodes found in the Australasian waters and elsewhere. The sequencing data also suggest that Terranova larval type I found previously in various fish from New Caledonian and Australian (Queensland) waters also belong to Pulchrascaris australis n. sp.

We describe adult males and females and a nymph belonging to Linguatula serrata in Australia, based on light and scanning electron microscopies. In addition, 18S and Cox1 sequence data have also been provided and were compared with similar sequences in GenBank. Our specimens had identical 18S sequences and limited genetic distance in Cox1 region which fell within the intra-specific range observed for Linguatula spp. suggesting that they all belong to one species. Phylogenetic analyses showed that Australian specimens were grouped with L. serrata in Europe where the species was first found and described. A number of L. serrata from Iran and Bangladesh formed a distinct group. The genetic distance between these Linguatula and Australian/European L. serrata ranged from 0.46% to 2.21% which is larger than the genetic distance observed between L. arctica and Australian/European L. serrata (0.12%) suggesting that they belong to a different species. As pointed out previously by several other authors, L. serrata comprises more than one species and those from the Palearctic region (including Iran and Bangladesh) should not be automatically named L. serrata unless there is enough evidence for the identification. To accurately address the complex taxonomy of Linguatula spp. a detailed morphological and genetic characterisation of numerous developmental stages of the parasite is necessary, to ensure morphological differences are not due to development. This however may not be achievable in the near future due to significant reduction in expertise as well as research funding awarded in this area of research to understand the basics of our planet. Keywords: Linguatula, Scanning electron microscopy, Sequence data, Taxonomy

We confirm the presence of nymphs of the introduced pentastomid, Linguatula serrata, in the introduced rabbit, Oryctolagus cuniculus, in Australia, based on morphological and molecular results. Two nymphs were collected from a single rabbit near the Kosciuszko National Park in New South Wales. Unlike reports of nymphs from domestic animals, these nymphs were not encapsulated, despite having the morphological features of infective nymphs. The possibility of different development pathways in lagomorphs is discussed. Examination of feral deer for L. serrata was unsuccessful and potential reasons for a lack of infection in these animals are postulated. Our results reiterate the need for a combined morphological and molecular approach to the identification of L. serrata. Further sampling of a range of feral and native animals is required to determine the true range of intermediate hosts and their relative importance in the transmission of L. serrata in Australia.

In Australia and New Zealand (NZ), snapper Chrysophrys auratus is known for delicate mild flavoured flesh and is a favoured species to serve raw as sashimi or in sushi. The diet of snapper includes a variety of intermediate hosts of larval nematodes, and as a result, snapper has potential to become highly infected with zoonotic/non-zoonotic nematodes. The aims of this study were to survey nematodes in snapper from Australia and New Zealand waters and to identify nematode species using combined morphological and molecular methods. The zoonotic potential of nematodes identified in this study are discussed. A total of 112 snapper were purchased from the Sydney fish market, New South Wales, Australia. Fish were dissected and only the visceral content and digestive tract were examined for nematode infection. Parasites were initially identified by the microscopic method as four different types belonging to the families Anisakidae (Anisakis types I & III, and Terranova type II) and Cucullanidae (Dichelyne spp.). All Anisakidae nematodes were at infective stages. Species-level identification was actualised through sequencing of the internal transcribed spacer (ITS–1, 5.8S, ITS–2) regions. The Anisakis types I & III were confirmed as Anisakis pegreffii and A. brevispiculata, respectively of which A. pegreffii is considered globally as a zoonotic nematode. The specific identification of Terranova type II and Dichelyne spp. was not possible as no comparable sequence data were available in GenBank. The phylogenetic tree clustered Anisakis types I & III with A. pegreffii and A. brevispiculata, respectively; Terranova type II sequences as a separate clade with previously identified larval and adult Terranova and Pseudoterranova species. Based on phylogenetic analyses the present Cucullanid specimens were assigned herein as Dichelyne cf. pleuronectidis, and an unknown species Dichelyne sp. 1. This study represents the first host record globally for zoonotic Anisakid nematodes in this popularly consumed table fish and a new region record for D. cf. pleuronectidis and Dichelyne sp. 1. Further investigation is required, using more comprehensive parasite detection and recovery methods, to assess the health risk these nematodes may pose to human and fish health in Australia/NZ.

Terranova pectinolabiata n. sp. is described from the great hammerhead, Sphyrna mokarran, from Australian waters. This represents the first report of a species of Terranova from the host species. The new species is characterised by the morphology of the caudal plates and labia. ITS sequences were obtained for 20 specimens which were identical, despite morphological variation that has traditionally been indicative of separation of species. Additionally, genetic analyses confirmed the identification of the larval Terranova Type II previously reported in Australian and New Caledonian waters as Terranova pectinolabiata n. sp.

Tongue worms utilise herbivorous mammals as intermediate hosts and reside in the nasopharynx of carnivores as their definitive hosts. A recent study in south eastern Australia showed an unexpectedly high infection (67%) of wild dogs with these parasites. The present study aimed at determining the pathogenicity of the parasite in both definitive (dog) and intermediate (cattle) hosts by histopathology. The definitive host showed multifocal haemorrhage of the interstitium of the nasal mucosa, multifocal mucosal erosion, congestion and haemorrhage, with haemosiderin laden macrophages present in those foci and distortion and destruction of the nasal mucosa. Histopathologic examination of lymph nodes from an infected cow showed diffuse eosinophilic granulomatous necrotising lymphadenitis and perinodal panniculitis with intralesional parasitic remnants and comparatively large numbers of eosinophils. A large, ~300-500 μm diameter, area of necrosis was also observed in one lymph node. This is the first time a study has been undertaken in Australia to determine the pathogenicity of tongue worms in both their definitive and intermediate hosts. This is a preliminary study and to properly estimate the health impact of infection with this pathogenic parasites on Australian production and companion animals more studies are necessary.

The nematode Ascarophis distorta Fusco et Overstreet, 1978 (Cystidicolidae), originally described from the butterflyfish Chaetodon paucifasciatus Ahl (Perciformes, Chaetodontidae) in the Red Sea, was established based solely on the light microscopical (LM) examination of specimens. However, the present taxonomy of cystidicolid nematodes is mostly based on details of the cephalic structures properly visible only with the use of scanning electron microscopy (SEM). Helminthological examinations of some marine fishes from coral reefs off New Caledonia, South Pacific, carried out in the years 2003–2007, revealed the presence of A. distorta in two Chaetodon spp. and thus enabled its redescription. The nematode specimens were studied with the use of both LM and SEM. The specimens of A. distorta were obtained from the stomach of the threadfin butterflyfish Chaetodon auriga Forsskal and the vagabond butterflyfish Chaetodon vagabundus Linnaeus. This is just the second record of this parasite since its description 43 years ago. SEM, used in this species for the first time, revealed some taxonomically important, previously unreported or insufficiently described morphological features, such as details in the cephalic structure, the shape of deirids, structure of the distal tip of the left spicule, or the exact number and distribution of male caudal papillae. The finding of A. distorta in C. auriga and C. vagabundus off New Caledonia represents new host and geographical records. The examination of 39 specimens of butterflyfishes from off New Caledonia, belonging to 14 Chaetodon spp. and 3 Heniochus spp., revealed that the nematode was only present in the 2 fish species listed above. This parasite seems to be host-specific to only certain species of butterflyfishes (Chaetodon spp.), and is probably widespread in the Indo-Pacific region, as well as its hosts.

This study determines the occurrence and molecular identification of nematodes from blue mackerel Scomber australasicus Cuvier (Perciformes: Scombridae), an edible fish from Australian waters. A total of 150 fish were sourced from the New South Wales and Victorian coasts. Nematodes were initially classified morphologically as 10 morphotypes belonging to the families Anisakidae (Anisakis morphotypes I and II, Contracaecum morphotype II, Terranova morphotypes I and II), Raphidascarididae (Hysterothylacium morphotypes IV, VI, VIII, and XIV), and Capillariidae (Capillaria sp.), followed by molecular identification through sequencing of their internal transcribed spacer (ITS-1, 5.8S, ITS-2) region. Anisakis morphotype I was confirmed as A. pegreffii Campana-RougetBiocca, 1955 and A. berlandi Mattiucci, Cipriani, Webb, Paoletti, Marcer, Bellisario, GibsonNascetti, 2014. Anisakis morphotype II and Contracaecum morphotype II were confirmed as A. physeteris Baylis, 1923 and C. ogmorhini JohnstonMawson, 1941, respectively. Terranova morphotypes I and II were identified as Pulchrascaris australis Shamsi, BartonZhu, 2020 and Euterranova pectinolabiata n. comb. (Shamsi, BartonZhu, 2019) MoravecJustine, 2020, respectively. The specific identification of Hysterothylacium morphotypes IV, VI, and VIII was not possible as no comparable adult Hysterothylacium species sequences were available in GenBank, with the exception of morphotype XIV which was confirmed as H. persicum Shamsi, Ghadam, Suthar, Mousavi, SoltaniMirzargar, 2016. Seven nematode morphotypes were identified for the first time in Australian blue mackerel. The outcomes of the study provide a basis for future research into the community structure, life cycles, and distribution of nematode species in Australian mackerel and to analyse and clarify their importance for public health.

The Tasmanian devil (Sarcophilus harrisii (Boitard)) is an endangered carnivorous marsupial, limited to the islands of Tasmania in southern Australia. The parasites of the Tasmanian devil are understudied. This study aimed to increase the knowledge of the nematode fauna of Tasmanian devils. Ten Tasmanian devils were examined for parasites from northern and southern Tasmania. Nematodes that were collected were morphologically characterized as two separate species. Molecular sequencing was undertaken to verify the identity of these species. A new genus and species of oxyurid nematode was collected from a single Tasmanian devil from the northern part of Tasmania. The nematode is differentiated from oxyurids described from other Australian amphibians, reptiles and marsupials by the characters of the male posterior end – that is, in having three pairs of caudal papillae, two pairs peri-cloacal, one large pair post-cloacal, a long tapering tail, a stout spicule and a gubernaculum and accessory piece, as well as its much larger overall size. Molecular sequencing was unsuccessful. The remaining nematodes collected from the Tasmanian devil in this study were all identified as Baylisascaris tasmaniensis Sprent, 1970, through morphology and molecular sequencing. This paper presents the first description of a new genus and species of oxyurid nematode from the Tasmanian devil, Sarcophiloxyuris longus n. gen., n. sp. The need to undertake more sampling of the parasites of endangered hosts, such as the Tasmanian devil, to assist with a better understanding of their conservation management, is discussed.

Specimens of a pentastomid, identified as a nymphal Linguatula serrata, have previously been reported from the nasal cavity of the endangered Australian marsupial, the spotted-tail quoll, Dasyurus maculatus. These specimens were made available for morphological and molecular characterisation to confirm their species identity. Specimens were examined by light microscopy. Molecular sequencing attempts were unsuccessful. Examination showed that the specimens were adult pentastomes of the genus Linguatula. Morphological differences are reported between these specimens and published measurements of specimens from other hosts collected from the same region. This is the first confirmed report of an adult Linguatula pentastome in a native Australian animal. Due to the small number of specimens and the lack of successful molecular characterisation, the pentastomes have been referred to Linguatula sp. until future work can confirm the species identity. The need for combined molecular and morphological analysis of pentastome specimens is reiterated.

Australia imports a significant amount of edible freshwater fish. The safety of the imported product is therefore of great importance. Previous research has shown that certain types of edible freshwater fish imported into Australia are not compliant with Australian importation guidelines and additionally are contaminated with many species of parasites, some of which may cause illness in humans if consumed. The present study, to the best of authors knowledge, is the first to publish the occurrence of zoonotic parasites in edible fish imported into Australia. Eustrongylides sp. Jägerskiöld, 1909 (P. 15.5%), family Dioctophymidae; Euclinostomum sp. Travassos, 1928 (P. 4.8%), family Clinostomidae, were recovered from imported edible and consumer ready Channidae fish and Isoparorchis sp. Southwell, 1913 (P. 11%), family Isoparorchiidae, from imported edible Bagridae fish. Euclinostomum sp. and Isoparorchis sp. were identified using morphological method. Molecular identification of Eustrongylides sp. was achieved through sequencing of the 18S ribosomal RNA gene sequence. Eustrongylides sp. and Isoparorchis sp. have been identified as the causative agent in cases of human infection and are a recognised zoonosis. Euclinostomum sp. is considered to have zoonotic potential and for this reason this species has been included in the importation risk assessments for freshwater fish from certain countries. This study confirmed the presence of zoonotic parasite species in edible imported fish. Whilst this fish product was frozen and parasites therefore inactivated, both fish species according to importation commodity codes, at the time this manuscript was written, are permitted entry into Australia chilled. Further study using a greater sample size is required to understand the human health risks., Graphical abstract Unlabelled Image, Highlights • Zoonotic parasites identified in edible freshwater fish imported into Australia. • Identified zoonotic parasites were at the developmental stage infective to humans. • Importation of infected fresh/chilled fish may be an unacceptable human health risk.

Cases of gnathostomiasis, an infection caused by consuming infected seafood, have been reported in Australia. However, doubt exists over the validity of these diagnoses as there are no reports of Gnathostoma spp. in Australian teleost fish. Also, the diagnoses in human cases were based on a serological test developed in Thailand. The specificity and sensitivity of this test in non-endemic areas are uncertain. Interestingly, parasites belonging to the genus Echinocephalus, which morphologically are very similar to Gnathostomum, are commonly found in Australian fish and shellfish and can potentially infect humans. The aim of this study was to determine the occurrence of these zoonotic nematodes within commercial fish and to characterise nematode larvae in order to provide insights into the specific identity of the potential causative agents of gnathostomiasis in Australia. Six edible fish species (n = 163) were examined. Gnathostomid-type larvae were found only in Acanthopagrus australis and Rhabdosargus sarba. Detailed examination and sequence data suggested parasite larvae belonged to the genus Echinocephalus. Further investigation of the occurrence of zoonotic nematodes within marine environments and observation of their spatial and temporal patterns will help raise awareness of the significance of this food safety issue within global fishing industries and health sectors. The accurate identification of zoonotic nematodes is a key component of disease surveillance and control. This information can also be used to develop specific and sensitive diagnostic test.

This study aimed to investigate the links between parasites and behavioural traits of juvenile Murray cod (Maccullochella peelii). The Murray cod is an endangered Australian freshwater fish for which restocking programs are in place and there is a growing human consumption market. However, little is known about the parasites of these fish and how these parasites influence their behaviour and survival. Fingerlings and yearling fish were sourced from a hatchery and the wild, and after acclimatisation in the laboratory, variation in behavioural traits was examined using emergence, exploration and predator inspection tests. The fish were then euthanised to determine their age and examined for infection with parasites. Wild fish had more camallanid nematodes and lernaeid copepods than hatchery fish. An information theoretic approach using Akaike's Information Criterion (AIC) indicated that infection with protozoan cysts was an important factor for predicting the latency to emerge and explore a new environment, which was interpreted as reduced "boldness". In contrast, the presence of lernaeid copepods was included in two of the four best models predicting predator inspection, indicating that infected fish were less likely to inspect a predator. Source of fish (wild or hatchery) was found to be a strong influence on behavioural responses in all our tests. All parasites found in the present study are known to result in clinical signs of diseases in their fish hosts, raising the possibility that responses in tests of behavioural traits reflect side effects of infection. Additionally, the effect of host adaptation to not show signs of parasite infection, or more simply that the effects on behaviour are subtle and difficult to reveal with small sample sizes, is discussed. Nonetheless, we propose that it is important that infection with parasites is considered in fish behavioural studies both to assess survival behaviour and to avoid misinterpretation of behavioural tests of animal personality.

The infective stage of Anisakidae nematodes responsible for allergic reactions in humans is found in a variety of edible fish and cephalopods. The identification of geographical regions that are high risk for infected seafood may help prevent allergic reactions in humans. Despite an abundance of published literature which has identified anisakid larvae in an array of edible seafood as well as scattered reports of human allergic anisakiasis, the relationship between the two has not been fully explored. Therefore, a systematic spatio-temporal study was conducted to determine the prevalence of Anisakis spp. in fish from January 2000 to August 2020 firstly to explore the relationship between fish infection and cases of allergic anisakiasis and secondly to use fish infection data to map potential allergic anisakiasis 'hot spots'. A systematic literature search for original English text articles was conducted through search engines, Web of Science, Scopus, PubMed, Science Direct and Google Scholar. Out of 3228 articles which describe anisakid infection in fish, 264 were used for data extraction. Of 904 articles describing allergic anisakiasis, 37 were used for data extraction. A qualitative summary of the extracted data was performed using equal interval method (ArcMap software) in order to compare the global distribution of Anisakis-infected fish. Of the 152-identified fish hosts, five families were most commonly infected with Anisakis spp. These included Lophiidae (86.9%), Trichiuridae (77.05%), Zeidae (70.9%), Merlucciidae (67.8%) and Gadidae (56.8%). The hot spot areas for allergic anisakiasis were North and northeast of Atlantic Ocean, southwest of USA, west of Mexico, south of Chile, east of Argentina, Norway, UK and west of Iceland (confidence 99%). The highest rate of allergic anisakiasis was in Portugal and Norway with the prevalence rate of 18.45-22.50%. Allergologists should consider allergic anisakiasis as a public health issue particularly in high-risk countries where high prevalences in fish have been demonstrated.

Here we report on the infection of captive crested geckosCorrelophus ciliatusGuichenot (Reptilia: Diplodactylidae), with adults of the ascaridoid nematode,Hexametra angusticaecoidesChabaud & Brygoo, 1960 (Ascarididae). A population of captive crested geckoes became ill and died within a short period of time. Nematodes were recovered from the crested geckoes examined from within the coelomic cavity, penetrating various organs and migrating through subcutaneous tissues, as well as emerging through the geckos' skin. One gecko was treated with levamisole following surgical excision of nematodes from under the skin; this gecko survived. The potential source of the nematode infection in the captive geckoes is discussed. It is most likely that wild-caught Madagascan mossy geckoes,Uroplatus sikoraeBoettger (Reptilia: Gekkonidae), introduced the infection to the colony. Molecular sequences of the nematodes are the first produced for the members of this genus. A redescription of the species and its genetic characterization based on the internal transcribed spacer sequence data is provided, suggesting some of the morphological criteria that have been used in the past to distinguish betweenHexametraspp. may have been intraspecific morphological variations.

A total of 509 mammalian vertebrates, belonging to 76 species, were examined for infection with pentastomid parasites. These animals were from 8 of the 9 provinces in South Africa. Linguatulid pentastomes were found only in 7 animals, specifically the African Lion (n = 3) and African Buffalo (n = 4). Adult parasites were found in the lion but nymphs, of various stages, were found in the buffalo. A detailed morphological examination of adult parasites using both light and scanning electron microscopy techniques suggested the specimens were Linguatula nuttalli Sambon1922. Sequences of 18S ribosomal DNA and Cox1 regions obtained from both adult and nymph stages suggested they belong to the one species. Phylogenetic analyses of Linguatula spp. based on the 18S and Cox1 sequences available in GenBank and obtained in the present study showed a clear distinction between L. nuttalli, L. arctica and L. serrata (from Europe and Australia). Several specimens from the Palearctic region which were previously assumed to be L. serrata formed a distinct group in the phylogenetic tree suggesting they probably belong to a different, and as of yet, unknown species., Graphical abstract Image 1, Highlights • Genetic and morphological characterisation of Linguatula nuttalli in South Africa. • Occurrence of Linguatula nuttalli in 509 mammalian vertebrates, belonging to 76 species. • Phylogenetic analyses of Linguatula spp. from different continents.

There is a paucity of information on the diversity and occurrence of freshwater fish parasites in Australia. This study investigates the distribution and occurrence of a parasitic nematode of the genusContracaecumin freshwater fish from south-eastern Australia. Fish (n= 508) belonging to nine species and eight families were collected from eight wetlands associated with the Murrumbidgee River floodplain in the southern Murray–Darling Basin and subjected to laboratory examination. Third-stage nematode larvae were found in eight of the nine fish species. The exception was the fly-specked hardeyhead (Craterocephalus stercusmuscarum), although only one specimen of this species was examined. Nematode larvae were identified asContracaecum bancroftiusing a combined morphological and molecular approach. The parasite was most prevalent in weather loach (Misgurnus anguillicaudatus; 34.8%) and Australian smelt (Retropinna semoni; 21.4%), followed by carp (Cyprinus carpio; 9.5%), of which the former and latter are non-native species.Contracaecumprevalence differed between locations, with Two Bridges having the highest number of infected fish. This may be due to the higher number of suitable host species collected at these localities.Contracaecumspp. are parasites with low host specificity that have also been reported in Australian marine fish, humans and piscivorous birds. The high parasite prevalence in the two abundant non-native fish species in the region suggests that they act as a suitable host for this endemic parasite, resulting in the increase in the parasite population. It would be interesting to study host–parasite interactions in this area, especially if introduced fish populations declined dramatically in the attempt to eradicate them or control their population.

Controlling pathogens within the aquaculture systems is important to prevent their impact on both human health and wild native populations. It is not uncommon for aquaculture ponds to contain undesirable species of fish which can compete for food or space with the farmed fish or play a role as a reservoir of diseases. The aims of this study were to determine the occurrence of parasites in undesirable species of fish commonly found in Australian Murray cod farms in New South Wales to determine if they can act as a reservoir for important parasites. In the present study, a total of 106 Australian smelt (Retropinna semoni), and 144 gudgeons (Hypseleotris spp.) were sampled from Murray cod ponds for parasitic infections. These fish are among the most common undesirable fish found on Murray cod farms in the region. No metazoan parasites were found in Australian smelt. One hundred and nine gudgeons were used for parasitology and 35 for histology. Parasites were examined morphologically followed by analyses of their DNA sequence data. Seven percent of infected gudgeons (out of total 109 examined) had externally visible signs of parasitic infection. The gudgeons had high parasitic burdens with 89.9% containing encysted metacercaria, identified as Apatemon hypseleotris, belonging to the family Strigeidae, 41.3% non-encysted metacercaria identified as Clinostomum sp., belonging to the family Clinostomidae, 6.4% (larval) cestodes identified as the metacestode of the genus Parvitaenia, belonging to the family Gryporhynchidae and a single Camallanus larval nematode (0.9%), all known to be of low host specificity and potentially transmissible to Murray cod. Histopathology results showed the presence of an additional parasite, a monogenean parasite in the gill. Some of the parasites found in the present study can be pathogenic for infected fish. This study provides critical baseline information on the occurrence of parasites in wild reservoir fish on Murray cod farms. Further research is needed to understand the potential risks to Murray cod populations in farm systems as well as to other fish in natural water resources where Murray cod are released.

SUMMARYThe acanthocephalan fauna of Australian freshwater fishes was documented from field surveys, a literature survey and examination of specimens registered in Australian museums. From the 4030 fishes, representing 78 of the 354 Australian freshwater fish species (22%), examined for infection seven species of acanthocephalan were recovered. These species comprised five endemic species, three in endemic genera, two species in cosmopolitan genera, one species not fully identified and 1 putative exotic species recovered from eight species of fish. Of theseEdmonsacanthus blairifromMelanotaenia splendida,was the only acanthocephalan found at a relatively high prevalence of 38·6%. These findings are indicative of a highly endemic and possibly depauperate acanthocephalan fauna. Species richness was higher in the tropical regions than the temperate regions of the country. Exotic acanthocephalan species have either not been introduced with their exotic hosts or have been unable to establish their life cycles in Australian conditions. Consequently, acanthocephalans have not yet invaded endemic Australian fish hosts.

We describe the first case of angiostrongyliasis in a water rat, Hydromys chrysogaster, a large rodent adapted to aquatic life, which is endemic to Australia, New Guinea and adjacent islands.

In this study, we genetically characterised Monogenea found on common carp in Iran. In total, 5603 parasites were recovered from 112 fish. The parasites were first identified morphologically as Dactylogyrus extensus, D. anchoratus, D. vastator, D. minutus, D. achmerowi and Gyrodactylus sprostonae. Representative samples were then subjected to sequencing. This is one of the first studies which has provided both morphological and sequence data for Dactylogyrus spp. and G. sprostonae. Our findings provide a foundation for future research into the genetic make-up of these economically significant parasites and the establishment of effective strategies for their control and prevention in aquaculture systems.

Three new species of Hysterothylacium Ward & Magath, 1917, including H. australe, H. kajikiae and H. brucei, from Australian marine fish are described and illustrated by light microscopy followed by genetic characterization of their first and second internal transcribed spacers (ITS-1 and ITS-2, respectively). This is the first study reporting ITS sequence data for adult Hysterothylacium spp. in Australia, which provides an insight into the identification of some of the Hysterothylacium larval types. Alignment of ITS sequences of these species with Hysterothylacium larval types previously reported in Australia showed that fourth-stage Hysterothylacium larval type XI from Seriola lalandi and third-stage Hysterothylacium larval type X from Sphyraene novae-hollandiae are identical with ITS sequences of H. australe, suggesting that these fish are natural intermediate/paratenic hosts of H. australe.

Anisakid nematodes are the most infamous parasites occurring in seafood with ability to infect humans. In the present study, the infective stages of five anisakid larval types, including Anisakis types I and III, Terranova types I and II and Contracaecum larval type, as well as adult Anisakis paggiae are reported from 16 host species from New Caledonian waters. The specific identity of the larval types was investigated using ITS sequence data. Anisakis larval types I and III were identified as Anisakis typica and Anisakis brevispiculata, respectively, based on identical ITS sequences. However, the specific identity of the Terranova larval types and Contracaecum larval type remains unknown until a matching ITS sequence from a well-identified adult is available. Several fish host species are reported for the first time for anisakid larval types found in this study. Considering that third-stage larvae of anisakids are known to be the infective stage of the parasite for humans and the popularity of seafood in New Caledonia, presence of these parasites in New Caledonian fish is of high importance in terms of public health and raising awareness among various stakeholders. Although adult nematodes in the present study were identified as Anisakis paggiae, the spicule length is shorter in our specimens and falls within the range reported for Anisakis oceanicus previously reported in Pacific waters from black fish (genus Globicephala) and later synonymised with Anisakis physeteris. However, our specimens are different from A. physeteris in morphology of ventriculus. Anisakis paggiae has been reported from whales in southern hemisphere and this is the first report from the Pacific regions.

Nematodes belonging to the genus Anisakis are important parasites due to their abundance in seafood and health impacts on humans. In the present study Anisakis larvae were found in a number of uncommon hosts including the Grey petrel, Procellaria cinerea, the Little penguin, Eudyptula minor, Blue-lipped sea krait, Laticauda laticaudata and Spinner shark, Carcharhinus brevipinna. Morphological examination showed nematodes in these animals are Anisakis larval type I. Genetic characterisation suggested that the larva from one Grey petrel was Anisakis berlandi, whereas the other larvae from the second Grey petrel and from the little penguin were Anisakis pegreffii. A number of larvae found in Blue-lipped sea krait and Spinner shark were identified as Anisakis typica. This is the first report of infective stage of Anisakis larvae parasitising hosts other than teleost fish. Understanding of the extent of infection and the pathogenicity of anisakid nematodes in hosts found in the present study is important in the conservation studies and management plans of these hosts.

In recent years, there has been a steady decline in the populations of clupeid fish in the Caspian Sea which has been attributed to factors such as overfishing and introduced invasive species of jellyfish. Very little is known about the diseases and possible health impacts of infectious agents such as parasites on the population of these important fish in the Caspian Sea. The aim of this study was to determine if infection with parasites can have adverse impacts on fish health and population. Sixty fish were collected, measured for weight and length, aged, and then examined for presence of Acanthocephala. Ages were recorded, as well as length and weight data for each age category and the number of acanthocephalan parasites. The internal organs, including the liver, ovary, and testis, were subjected to histopathological examination. Ninety percent of fish were found to be infected with acanthocephalan parasites, identified as Corynosoma strumosum. Fish data including the number of parasites, age, length, and weight showed that there was no significant difference in length and weight between different age groups, e.g., between 2 and 6 years old, suggesting that those fish may not grow fully as they age. There were several granuloma of different sizes in the liver and gonads, indicating the occurrence of a chronic inflammation. It is known that large numbers of granuloma may disturb the normal function of the liver and gonads and if associated with long term infection this may cause sterility, affecting the population numbers. Further research, with targeted aims, is needed to understand the impact of infection with acanthocephala on this fish and to determine the causative agents of the histopathological changes observed in the present study.

Based on light and scanning electron microscopical studies, a new nematode parasite, Barracudia australiensis n. sp. (Philometridae), is described from the gall-bladder of the marine fish (obtuse barracuda) Sphyraena obtusata Cuvier (Sphyraenidae, Perciformes) from off the eastern Pacific coast of Australia, for which a new genus Barracudia n. g. is established. This new genus is mainly characterised by features found in the male: sickle-shaped, ventrally curved spicules, a gubernacum with a broad, dorsally bent distal portion and a markedly dorsoventrally elongated cloacal aperture. Based on these features, Barracudia spp. conspicuously differ from representatives of all other philometrid genera with known males. Philometra philippinensis Quiazon & Yoshinaga, 2013 is transferred to Barracudia as B. philippinensis (Quiazon & Yoshinaga, 2013) n. comb. Barracudia australiensis is the third nominal species of philometrids described from the Sphyraenidae and the 19th species of the Philometridae recorded from fishes in Australian waters.

Hysterothylacium species are perhaps the most abundant and diverse group of marine ascaridoids; however, their life cycle and specific identification in larval stages in many parts of the world, particularly in Iraqi marine waters, have not been completely understood. In this study three members of the genus Hysterothylacium collected from Khor Abdulla in Iraq are morphologically described, genetically characterized and their relationship with other closely related taxa are compared and discussed. A new Hysterothylacium larval type in the fourth stage of development is described, and morphological and molecular evidence (based on the sequences of internal transcribed spacers) are provided for its distinction from previously known fourth-stage Hysterothylacium larval types. Based on the sequence data it is suggested that the new larval type, which herein was assigned as Hysterothylacium larval type XVI, is H. persicum which was previously reported from the close proximity in Bandar Abbas, Iran. In addition, two other taxa, including Hysterothylacium larval type XV and H. reliquens, have been found in the present study, for which new hosts are reported. This study provides some insights into the taxonomy and systematics of these parasites, not only in this region but also for similar studies elsewhere.

Contracaecum spp. are parasitic nematodes belonging to the family Anisakidae. They are known to be able to have highly pathogenic impacts on both wildlife (fish, birds, marine mammals) and humans. Despite having the most numerous species of any genus of Anisakidae, and despite a wide range of publications on various aspects of their pathogenicity, biology and ecology, there are no recent comprehensive reviews of these important parasites, particularly in the Southern Hemisphere. In this article, the diversity of Contracaecum parasites in Australian waters is reviewed and possible anthropological impacts on their populations are discussed. The abundance and diversity of these parasites may have been under-reported due to the inadequacy of common methods used to find them. Populations of Contracaecum parasites may be increasing due to anthropogenic factors. To minimise the risk these parasites pose to public health, preventive education of stakeholders is essential. There are still many unknown aspects of the parasites, such as detailed information on life cycles and host switching, that will be interesting directions for future studies.