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Northeast Arctic cod, saithe and haddock are among the most important fisheries resources in Europe, largely shipped to various continental markets. The present study aimed to map the presence and distribution of larvae of parasitic nematodes in the Anisakidae family which are of socioeconomic and public health concern. Fishes were sourced from commercial catches during winter or spring in the southern Barents Sea. Samples of fish were inspected for nematodes using the UV-press method while anisakid species identification relied on sequencing of the mtDNA cox2 gene. Anisakis simplex (s.s.) was the most prevalent and abundant anisakid recorded, occurring at high infection levels in the viscera and flesh of cod and saithe, while being less abundant in haddock. Contracaecum osculatum (s.l.) larvae, not found in the fish flesh, showed moderate-to-high prevalence in saithe, haddock and cod, respectively. Most Pseudoterranova spp. larvae occurred at low-to-moderate prevalence, and low abundance, in the viscera (Pseudoterranova bulbosa) and flesh (Pseudoterranova decipiens (s.s.) and Pseudoterranova krabbei) of cod, only 2 P. decipiens (s.s.) appeared in the flesh of saithe. Body length was the single most important host-related factor to predict overall abundance of anisakid larvae in the fish species. The spatial distribution of Anisakis larvae in the fish flesh showed much higher abundances in the belly flaps than in the dorsal fillet parts. Trimming of the flesh by removing the belly flaps would reduce larval presence in the fillets of these gadid fish species by 86–91%.

Nematode parasites of the genus

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Northeast Atlantic (NEA) mackerel (Scomber scombrus, Scombridae) represents an economically important target for the Norwegian pelagic fishing industry. Despite the commercial significance of NEA mackerel, little is known about the infections with the myxosporean parasite Kudoa thyrsites (Kudoidae). The parasite may cause post-mortem myoliquefaction of the fish skeletal muscle and therefore reduce the quality of the fish product. In this study, we examined ‘soft flesh’ occurrence in commercial size groups of NEA ‘autumn mackerel’ caught between 2007 and 2020, and investigated the prevalence and density of K. thyrsites (qPCR) and how they related to the occurrence of ‘soft flesh’. The present study is the first long-term investigation of the occurrence of K. thyrsites-induced ‘soft flesh’ in NEA mackerel. After appearing stable for over a decade, the ‘soft flesh’ occurrence increased three- to six-fold in 2019 and 2020. This increase, together with the findings that ‘soft flesh’ seems primarily to affect the commercially most valuable mackerel size group (>400 g), may have important implications for the fishing industry and the fishery management. Molecular analysis (qPCR) suggests that the prevalence of K. thyrsites is substantially higher than ‘soft flesh’ occurrence. The majority (87.4%, n = 76/87) of infected mackerel did not develop ‘soft flesh’ and only individuals with high parasite density in the musculature (12.6%, n = 11/87) showed the condition. Therefore, qPCR analyses should be used for estimating the prevalence of K. thyrsites in fish. The method may also be used to assess the risk of NEA mackerel to develop post-mortem ‘soft flesh’. publishedVersion

The parasitic nematode Hysterothylacium aduncum commonly occurs in many fish species in the Northeast (NE) Atlantic. The parasite is considered non-pathogenic to humans. During spring and summer of 2018, lots of head-on eviscerated fresh NE Arctic cod (Gadus morhua) were shipped from Norway to Spain for commercialization. At arrival, the presence of lively roundworms (i.e. H. aduncum) in the transporting boxes was noticed. Consequently, fish lots were rejected causing substantial monetary losses to all involved parties. As part of the hazard assessment process, the epidemiology of H. aduncum in cod, NE Arctic saithe (Pollachius virens) and NE Arctic haddock (Melanogrammus aeglefinus) fished off West-Finnmark, Norway, was studied. Parasites were morphologically and molecularly identified to species level. Additionally, the viability of H. aduncum was assessed by simulating the conditions that prevail during transport of fresh cod to European market. The infection values of L4 larval stage or adult H. aduncum in the digestive tract of fish were highly variable, ranging from 100% prevalence with mean abundance (range) 238 (10–1092) in cod to 27% prevalence with mean abundance (range) 1 (0–22) in haddock. Fishing season was identified as most important explanatory factor for parasite abundance. Infection levels were higher during winter and early spring, and lower during late spring. Infection peaks of H. aduncum in the three fish species seemed to coincide with heavy predation on spawning capelin (Mallotus villosus) during winter and early spring. Thorough evisceration seems to remove most of the nematodes from the fish. However, parasites may remain hidden within the head cavities where they can stay alive and active under regular transport conditions for at least 14 days. Hysterothylacium aduncum can be completely removed from the product by evisceration, beheading and rinsing the fish prior to shipping. Alternatively, thorough cleaning or completely removal of the gills and pharynx may be considered.

Trypanorhynch tapeworms are marine heteroxenous parasites, involving sharks and rays as definitive hosts, invertebrates (i.e. crustaceans) as first intermediate hosts, and various teleost fishes as intermediate/paratenic ones. The massive presence of Trypanorhyncha larval forms in the flesh or body cavity of the fish hosts reduces their market value, making them unappealing to consumers, or causing discards of fish products. The identification of merocercoids (N = 100) of Molicola uncinatus and plerocercoids (N = 46) of Hepatoxylon trichiuri parasitizing the silver scabbardfish, Lepidopus caudatus, from the Central Mediterranean Sea (off Malta coast), was obtained, for the first time, by using sequences analysis of the complete small subunit (ssrDNA) and the partial large subunit (lsrDNA) ribosomal RNA gene loci. The Bayesian Inference from the concatenated sequences obtained at the two gene loci showed that the individuals of M. uncinatus and H. trichiuri clustered, respectively, in two well distinct and supported phylogenetic lineages, corresponding to the two cestode species. High prevalence (P) and mean abundance (MA) values were observed in the infection with merocercoids of M. uncinatus (P = 100%, A = 28.81), with the ventral musculature of the silver scabbardfish as the most parasitized site. Plerocercoids of H. trichiuri were found to infect only the mesenteries, attached to various fish tissues, with a mean abundance rate of 1.28. Even if harmless to humans, a heavy parasitic load with larval stages of Trypanorhyncha, particularly in the edible part of the silver scabbardfish (as here reported for merocercoids of M. uncinatus), can compromise the appearance of the fish-food, making it repugnant and unappealing for the final consumer. It has been also discussed that when managing the risk related to parasites affecting the fish quality and safety of fisheries products, the fishing ground where the life cycle of those parasites takes place should be also taken into account, as it would include the ecological drivers of the infection with those parasites. This wider ecological approach would be of help to the Food Business Operators (FBOs), gathering knowledge useful to manage fisheries in a wide “One-Health” perspective, aware of sustainability, quality and consumer safety aspects of sea-food production.

The southern Pacific Ocean, off the New Zealand coast, has been reported as one sympatric area of the two parasite species Anisakis pegreffii and A. berlandi. Here, a multilocus genotyping approach, based on a panel of eleven DNA microsatellite (SSR) loci plus the sequences analysis of the nuclear nas10 nDNA and the mitochondrial mtDNA cox2 gene loci, was applied to a total of N = 344 adults and larvae of Anisakis spp. from cetacean and fish species, respectively. Out of the newly scored SSR loci, Anisl 15 and Anisl 2 showed fixed alternative alleles between A. pegreffii and A. berlandi resulting as 100% diagnostic loci. Out of SSRs Anisl 00314 and Anisl 7 previously disclosed, two additional loci, i.e., Anisl 4 and Anisl 22, were found to be sex-linked. The Bayesian genotypes clustering approach (STRUCTURE) allowed identification, with a 100% of probability value, N = 208 specimens to the “pure parental” A. pegreffii, N = 133 to the “pure parental” A. berlandi, while one adult and two larval stages showed mixed ancestry between the two groups having, in all cases, a Q-value = 0.50. NEWHYBRIDS analysis assigned (100% of probability) those specimens to their F1 hybrid category. This represents the first evidence of contemporary hybridization between the two parasite species in a sympatric area. The pairwise FST values estimated at intraspecific and interspecific level, inferred from both SSR loci and mitochondrial mtDNA cox2 sequences, have also demonstrated the existence of two distinct panmictic units in this study area, corresponding respectively to A. pegreffii and A. berlandi. The results obtained support the useful application of a multilocus approach in the identification of sibling species and their hybrid categories in sympatric areas. The possible use of sex-linked SSR loci of the two species of the A. simplex (s. l.), for sex determination of their larval stages, is also suggested.

A survey on Anisakis simplex (sensu stricto (s.s.)) from blue whiting, Micromesistius poutassou, in the north-eastern Atlantic Ocean revealed the occurrence of high infection levels of third larval stages in visceral organs and flesh. Larvae were genetically identified with a multilocus approach as A. simplex (s.s.). Histochemical, immunohistochemical and ultrastructural observations were conducted on 30 M. poutassou specimens. Gonads, pyloric caeca and flesh harboured encapsulated larvae of A. simplex (s.s.) but no intense host reaction was encountered around the parasite in the above organs. In the liver, the most infected organ, the larvae co-occurred with the coccidian Goussia sp. Within the granuloma around the A. simplex (s.s.) larvae, two concentric layers were recognized, an inner mostly comprising electron-dense epithelioid cells and an outer layer made of less electron-dense epithelioid cells. Macrophages and macrophage aggregates (MAs) were abundant out of the granulomas, scattered in parenchyma, and inside the MAs, the presence of engulfed Goussia sp. was frequent. In liver tissue co-infected with Goussia sp. and A. simplex (s.s.), hepatocytes showed cytoplasmic rarefaction and acute cell swelling. Results suggest that the host-induced encapsulation of A. simplex (s.s.) larvae is a strategic compromise to minimize collateral tissue damage around the larval infection sites, to facilitate the survival of both parasite and host.

Few reports exist upon the occurrence and localization of zoonotic anisakid nematodes in T. sagittatus, especially in the mantle of the squid. The occurrence and site of infection of larval anisakids in 98 T. sagittatus caught West off St. Kilda, NE Atlantic Ocean, were investigated. Squids were examined for anisakids using the UV-Press method. In total, 689 nematodes were detected in the viscera and mantle. According to morphology, all the larvae (L3) were assigned to genus Anisakis. Diagnostic allozymes and mtDNA cox2 sequence analysis permitted to genetically identify all larvae as Anisakis simplex (s.s.) (N = 100). Overall prevalence (P = 81%) and mean intensity (mI = 8.6) of infection with A. simplex are provided. Most of the larvae present in the mantle cavity were embedded in the stomach wall or attached in the outer layer of the stomach and caecum (49%). Over a third of squids (37%) hosted A. simplex (s.s.) larvae in the mantle. A novel schematized representation of larvae distribution in the mantle is provided, showing where they were mostly located. According to the results obtained, the risk of anisakiasis associated with consumption of raw or undercooked T. sagittatus should be considered.

The third-stage larvae of the parasitic nematode genus Anisakis tend to encapsulate in different tissues including the musculature of fish. Host tissue penetration and degradation involve both mechanic processes and the production of proteins encoded by an array of genes. Investigating larval gene profiles during the fish infection has relevance in understanding biological traits in the parasite&rsquo, s adaptive ability to cope with the fish hosts&rsquo, defense responses. The present study aimed to investigate the gene expression levels of some proteins in L3 of A. simplex (s.s.) infecting different tissues of blue whiting Micromesistius poutassou, a common fish host of the parasite in the NE Atlantic. The following genes encoding for Anisakis spp. proteins were studied: Kunitz-type trypsin inhibitor (TI), hemoglobin (hb), glycoprotein (GP), trehalase (treh), zinc metallopeptidase 13 (nas 13), ubiquitin-protein ligase (hyd) and sideroflexin 2 (sfxn 2). Significant differences in gene transcripts (by quantitative real-time PCR, qPCR) were observed in larvae located in various tissues of the fish host, with respect to the control. ANOVA analysis showed that relative gene expression levels of the seven target genes in the larvae are linked to the infection site in the fish host. Genes encoding some of the target proteins seem to be involved in the host tissue migration and survival of the parasite in the hostile target tissues of the fish host.

The European hake Merluccius merluccius is one of the most commercially important and widely distributed fish species, occurring both in European and Mediterranean Sea fisheries. We analyzed the distribution and infection rates of different species of Anisakis in M. merluccius (N = 1130 hakes), by site of infection in the fish host (viscera, dorsal and ventral fillets) from 13 different fishing grounds of the Mediterranean Sea (FAO area 37). The fillets were examined using the UV-Press method. A large number of Anisakis specimens (N = 877) were identified by diagnostic allozymes, sequence analysis of the partial EF1 α-1 region of nDNA and mtDNA cox2 gene. Among these, 813 larvae corresponded to A. pegreffii, 62 to A. physeteris, 1 to A. simplex (s. s.), whereas one resulted as a F1 hybrid between A. pegreffii and A. simplex (s. s.). Remarkably high levels of infection with A. pegreffii were recorded in hakes from the Adriatic/Ionian Sea compared to the fish of similar length obtained from the western Mediterranean fishing grounds. A positive correlation between fish length and abundance of A. pegreffii was observed. Concerning the localization of A. pegreffii larvae in the fish, 28.3% were detected in the liver, 62.9% in the rest of the viscera, 6.6% in the ventral part of the flesh, whereas 2.1% in the dorsal flesh.

This review provides an inventory of the biodiversity of the anisakid species identified so far from fish and marine mammals of the NE Atlantic Ocean. The paper reviews and discusses various taxonomical and epidemiological aspects related to biodiversity assessment, with emphasis on: (1) taxa recognized as ‘biological species’ based on molecular/genetic markers; (2) current molecular/genetic approaches to identify the species at different developmental stages; (3) ecological data related to the actual geographical distribution and definitive host preferences of the species; (4) their distribution in various, commercially important fish species in northern European waters; (5) their possible occurrence in farmed fish; and, finally, (6) an update of their zoonotic potential as causative agents of anisakidosis in humans.

Contracaecum rudolphii (s. l.) is a complex of sibling species of anisakid nematodes having the fish-eating birds belonging to the Family Phalacrocoracidae as final hosts. The great cormorant Phalacrocorax carbo sinensis is parasitized by C. rudolphii A and C. rudolphii B. Adults and L4 specimens of C. rudolphii (s. l.) (N = 3282) were collected in cormorants from brackish and freshwater ecosystems of Central Italy. Third-stage larvae of Contracaecum (N = 882) were obtained from the fish species Dicentrarchus labrax, Anguilla anguilla, Aphanius fasciatus, Atherina boyeri, Leuciscus cephalus, Barbus barbus, and Carassius carassius captured in the same geographical areas of cormorants’ standings. Contracaecum rudolphii A and C. rudolphii B were identified by a multilocus genetic approach: allozymes, sequences analysis of the mtDNA cox2, and ITS region of rDNA gene loci. Differential distribution of the two parasite species was observed in different aquatic environments. Contracaecum rudolphii B outnumbered C. rudolphii A in wintering cormorants from freshwater ecosystems; the opposite trend was found in cormorants from brackish water. Analogously, C. rudolphii A larvae were more prevalent in brackish water fish, while C. rudolphii B larvae were found infecting only freshwater fish. The findings seem to confirm that C. rudolphii A and C. rudolphii B would have a life-cycle adapted to brackish and freshwater environments, respectively. A differential feeding behavior of wintering cormorants, the ecology of the infected fish species, and abiotic factors related to early stages of the parasites are supposed to maintain the distinctiveness of the two parasite species’ life cycles in the two different aquatic ecosystems.

Myxosporean parasites of the genus Kudoa are fish parasites of great economic importance, as some species can affect the fish fillet quality by producing macroscopic cysts or generating post mortem myoliquefaction, commonly referred to as &lsquo, soft flesh&rsquo, Kudoa mirabilis is a &lsquo, inducing species originally described based on morphology in the musculature of Trichiurus lepturus from the Indian Ocean. An integrative morphological and genetic characterization of K. mirabilis from the type host caught off the coast of Tanzania is here provided. The spores were stellate with four unequal polar capsules, showing similarities to Kudoa thyrsites. For comparative and validation purpose, K. mirabilis was compared morphologically and genetically with K. thyrsites reference isolates, including new obtained samples from the type host Thyrsites atun caught in the SE Atlantic Ocean. Morphological analyses of spores revealed key diagnostic characters clearly distinguishing the two Kudoa species. Phylogenetic analyses based on SSU and LSU rRNA genes demonstrated that K. mirabilis is a distinct and valid species, representing a sister group to a K. thyrsites subclade that comprises several isolates from Japan and one single isolate from South Africa. This finding raises questions about the true diversity likely hidden in the K. thyrsites complex.

A total of 80 stockfish fillets of Northeast Arctic cod (Gadus morhua), traditionally open-air-dried in northern Norway, was examined for the presence and viability of larval parasitic nematodes of the family Anisakidae. Anisakids (particularly those belonging to genera Anisakis and Pseudoterranova) are of public health and economic concern globally, since they are responsible for an underestimated fish-borne zoonotic disease called anisakidosis (anisakiasis when caused by members of the Anisakis genus). Stockfish fillets were inspected for anisakids by candling and artificial (pepsin) digestion methodologies. The recovered nematodes (n = 342) were morphologically identified to genus level and their viability assessed. Subsamples of anisakid larvae (n = 31) were identified by molecular/genetic markers inferred from sequences analyses and real time polymerase chain reaction (RT-PCR) of the mtDNA cox2 gene, as Anisakis simplex sensu stricto (s.s.) (n = 29) and as Pseudoterranova decipiens (s.s.) (n = 2). This is the first time a RT-PCR primer/probe system was used to identify anisakids in a processed fishery product. Anisakis simplex (s.s.) larvae were found in 81% of the fillets, with average (range) 4 (0–35). In total, 338 A. simplex (s.s.) and 4 P. decipiens (s.s.) larvae, all dead, were recovered from the fillets. Anisakids were devitalised by the air-dried stockfish production process in 7.5 months (common stockfish production time from sea to plate). The results suggest that there is a negligible risk of acquiring anisakidosis from consumption of air-dried stockfish. Further research is recommended to evaluate if anisakids can be devitalised in five months (i.e. minimum stockfish production time). The health risk for sensitized consumers posed by the potential presence of anisakid allergens in stockfish needs to be assessed. This is the first report on the viability of anisakid larvae in an unsalted, naturally dried fishery product. Drying could represent an alternative and efficient treatment for the inactivation of anisakids in fishery products. Trimming of the belly flaps of highly parasitized cod may reduce the number of anisakids in stockfish by 74%.

The species of Anisakis constitute one of the most widespread groups of ascaridoid nematodes in the marine ecosystem. Three closely related taxa are recognised in the A. simplex (s. l.) complex, i.e. A. pegreffii, A. simplex (s. s.) and A. berlandi. They are distributed in populations of their intermediate/paratenic (fish and squids) and definitive (cetaceans) hosts. A panel of seven microsatellite loci (Anisl 05784, Anisl 08059, Anisl 00875, Anisl 07132, Anisl 00314, Anisl 10535 and Anisl 00185), were developed and validated on a total of N = 943 specimens of A. pegreffii and A. simplex (s. s.), collected in fish and cetacean hosts from allopatric areas within the range of distribution of these parasite species. In addition, the locus Anisl 7, previously detected in those Anisakis spp., was investigated. The parasites were first identified by sequence analysis of the EF1 α-1 nDNA. The panel of the microsatellites loci here developed have allowed to: (i) detect diagnostic microsatellite loci between the two species; (ii) identify specimens of the two species A. pegreffii, A. simplex (s. s.) in a multi-marker nuclear genotyping approach; (iii) discover two sex-linked loci in both Anisakis species and (iv) estimate levels of genetic differentiation at both the inter- and intra-specific level.

Capelin (Mallotus villosus) is among the most abundant fish species in the Barents Sea, and represents a critical food source for many predators in the area including Atlantic cod and harp seal. In Norway, the fish is of economic importance since whole capelin and roe are valuable export products. Despite its economic and ecological importance, the parasites of Barents Sea capelin are poorly known. However, the presence of parasites in the edible parts may adversely affect product quality and consumer safety. During the main annual catching seasons of 2009-2012, we investigated the diversity and infection dynamics of ascaridoid nematodes in capelin (n = 620) from the southern Barents Sea. Three anisakid species were identified by genetic or molecular methods; Anisakis simplex (s.s.), Contracaecum osculatum sp. B, and Hysterothylacium aduncum, with C. osculatum sp. B as the most prevalent and abundant species. The present findings suggest that the ascaridoid species composition in capelin reflects its trophic position in the Barents Sea ecosystem. There appears to be a link between infection level of the nematode species and the preferred prey organisms of the different developmental phases of capelin. Thus, the higher abundance of C. osculatum sp. B compared to A. simplex (s.s.) and H. aduncum may be related to more extensive feeding on calanoid copepods over a wider ontogenetic size range including adolescence, while the main intermediate hosts of the latter nematode species, i.e. euphausiids and amphipods, appear to be the preferred prey of larger capelin.

Myxozoans of the genus Kudoa (Myxosporea, Multivalvulida) infect marine and estuarine fish species worldwide. Some Kudoa species are of concern to the seafood industry since they may generate macroscopic cysts in the fish host's musculature, or cause post mortem myoliquefaction, commonly known as 'soft flesh'. One of the economically most important species is K. thyrsites, a myoliquefactive myxosporean parasite that occurs in many wild and cultured marine fish species worldwide. Here we identified a K. thyrsites isolate as the causative agent of myoliquefaction in silver scabbardfish Lepidopus caudatus from the Alboran Sea (western Mediterranean Sea). For comparative and validation purposes, the morphological and molecular characteristics of the isolate were compared with fresh spores of a K. thyrsites isolate infecting Atlantic mackerel Scomber scombrus from the Norwegian Sea. Myxospores of both isolates shared a stellate appearance and contained 4 unequal pyriform polar capsules (1 large, 1 small and 2 intermediate). These morphological traits were consistent with all other previously described K. thyrsites isolates. Moreover, the small subunit rDNA sequences of the Mediterranean and Norwegian Sea isolates revealed 100% similarity, and matched 100% with K. thyrsites isolates previously recorded in myoliquefactive Atlantic mackerel from the North Sea and off southern England. The findings suggest that K. thyrsites is the primary cause of myoliquefaction in silver scabbardfish from the Alboran Sea. This report represents the first morphological and molecular characterization of K. thyrsites in the Mediterranean Sea. A set of new allometric characters is proposed as additional descriptors for more accurate and specific description of kudoid myxospores.

The species ofAnisakisconstitute one of the most widespread groups of ascaridoid nematodes in the marine ecosystem. Three closely related taxa are recognised in theA. simplex(s. l.) complex, i.e.A. pegreffii,A. simplex(s. s.) andA. berlandi.They are distributed in populations of their intermediate/paratenic (fish and squids) and definitive (cetaceans) hosts. A panel of seven microsatellite loci (Anisl 05784,Anisl 08059,Anisl 00875,Anisl 07132, Anisl 00314, Anisl 10535andAnisl 00185), were developed and validated on a total ofN= 943 specimens ofA. pegreffiiandA. simplex(s. s.), collected in fish and cetacean hosts from allopatric areas within the range of distribution of these parasite species. In addition, the locusAnisl 7, previously detected in thoseAnisakisspp., was investigated. The parasites were first identified by sequence analysis of the EF1α-1 nDNA. The panel of the microsatellites loci here developed have allowed to: (i) detect diagnostic microsatellite loci between the two species; (ii) identify specimens of the two speciesA. pegreffii, A. simplex(s. s.) in a multi-marker nuclear genotyping approach; (iii) discover two sex-linked loci in bothAnisakisspecies and (iv) estimate levels of genetic differentiation at both the inter- and intra-specific level.

The Argentinean short-finned squid (Illex argentinus) is an oceanic, neritic species widely distributed off the east coast of South America, representing the most abundant commercially exploited squid species in these waters. Despite the great commercial importance of Argentinean short-finned squid as a food resource, and as frozen product exported to Europe, the presence of zoonotic anisakid nematodes, especially in the mantle of the squid, is poorly known. The occurrence and site of infection of larval ascaridoid nematodes in 70 I. argentinus caught off the Falkland Islands were investigated. Squids were examined using the UV-Press method. In total, 30 nematodes were detected in the viscera and mantle. According to morphology, 27 were third-stage larvae (L3) belonging to genus Anisakis, while three were L3 assigned to Hysterothylacium. Anisakis pegreffii (n = 27) were identified by sequence analysis of the mtDNA cox2 and the partial EF1 α-1 region of nDNA genes; Hysterothylacium aduncum (N = 3) were identified by sequence analysis of the ITS rDNA region. These findings represent the first molecular identification of A. pegreffii and H. aduncum in I. argentinus. Both prevalence (P = 15.7%) and abundance (A = 0.39) of infection with A. pegreffii were low, and even lower values of infection were recorded for H. aduncum (P = 2.1%, A = 0.04). Only 3 out of 70 (4.3%) squids hosted A. pegreffii larvae in the mantle. Larvae infecting viscera were coiled and mainly attached to outer surface of visceral organs. Mantle-infecting larvae were situated in the posterior half. Thus, these results suggest that – although low - the risk of acquiring anisakiasis from consumption of raw, marinated and/or undercooked short-finned squid products still exists.

Limited data exist on the occurrence of the dwarf sperm whale Kogia sima in the Mediterranean Sea and its parasite fauna. Here, the occurrence of the anisakid species Anisakis physeteris and A. pegreffii in the stomach chambers of an adult female dwarf sperm whale, stranded in southern Italy, is reported. In addition, the occurrence of Phyllobothrium delphini larvae infecting the blubber of the caudal peduncle region was recorded. A. physeteris and A. pegreffii represent the 2 parasite species of the genus, mostly distributed in the Mediterranean Sea in fish and squids. The finding of A. pegreffii and A. physeteris in the dwarf sperm whale represents a new record in this host species for the Mediterranean Sea. The study of gastrointestinal content also revealed a massive presence of cephalopod beaks identified as belonging to pelagic squids including the umbrella squid Histioteuthis bonnellii, the reverse jewel squid H. reversa, the long-armed squid Chiroteuthis veranii, and the comb-finned squid Ctenopteryx sicula. The feeding habits of the dwarf sperm whale, as well as the occurrence of these squid residuals in the cetacean host, suggest that these squid species play a major role in maintaining the life cycle of anisakid parasite species and P. delphini.

Anisakid nematodes belonging to the species Anisakis pegreffii are distributed in a wide variety of fishes from the Mediterranean Sea and they are known to cause the human zoonosis anisakiasis. The present study investigated, for the first time, the response of A. pegreffii larvae (identified to species level by allozymes and mtDNA cox2 sequence analysis) to the storage temperature of European anchovies, Engraulis encrasicolus . The larval motility of A. pegreffii was studied in 1300 fish specimens, captured from a highly infested area (FAO 37.2.1, 43°8′N, 14°16′E), maintained under different temperatures (2 °C, 5 °C, 7 °C), and examined at different time intervals (immediately after fishing, 24 h, 48 h and 72 h). Parasitological analysis was carried out with the UV-press method. The results showed that the increase of infection values with A. pegreffii in the fillets of anchovies was statistically positively related to the increase of the temperature (at 5 °C and 7 °C) and time of storage (after 24 h, 48 h, and 72 h). Accordingly, a significant statistical correlation between the increasing of the worm burden in the fillets and a decreasing of A. pegreffii in the viscera was observed. In contrast, those fish constantly maintained at 2 °C showed no statistically significant variation in infection either in the viscera or the fillets, after 24, 48 and 72 h. In the same batches of anchovies, larvae of the non-zoonotic nematode parasite Hysterothylacium aduncum (identified to the species level by ITS rDNA sequences analysis) were found, but they were never observed infecting the musculature of the anchovies. Our results suggest that temperature plays an important role in the post-mortem motility of A. pegreffii larvae in anchovies. In addition, the presence of A. pegreffii in the fillets inspected immediately after their capture indicates that intra-vitam migration may also occur. As a consequence, the importance of the adoption of rules to prevent human anisakiasis, as the deep freezing to −20 °C for 24 h, was underlined.

Aporocotyle michaudi n. sp. is described from the gill blood vessels of the emerald rock cod Trematomus bernacchii in the Ross Sea, Antarctica. It is distinguished from all other species of Aporocotyle by its body tegument showing single conical spines, spinous buccal capsule, and genital atrium positioned medially; all congeners described to date are characterized by clusters of tegumental spines, unspined buccal capsule and genital atrium located in the lateral part of the body. Aporocotyle michaudi n. sp. clearly differs from A. notothenia (the only other species of Aporocotyle found in a perciform fish) in its shape and arrangement of tegumental spines, buccal capsule features, location of genital atrium, body size, ratio of esophagus/body length, anterior caeca/posterior caeca ratio, number of testes, cirrus sac and ovary size and shape, and host. The new species is easily distinguished from A. argentinensis (the species that most closely resembles A. michaudi) by the shape and arrangement of tegumental spines, buccal capsule features, genital atrium location, left anterior caecum longer than right, esophagus/body length ratio, number of testes, cirrus sac size and shape, host and molecular analyses. Phylogenetic analyses of partial 28S rDNA genetic data showed that sequences representing the new species form a distinct clade with all other sequences for species of Aporocotyle and appear basal within the genus. Aporocotyle michaudi n. sp. represents the only species of genus described in Antarctica.

Mass strandings of sperm whales (Physeter macrocephalus) are rare in the Mediterranean Sea. Nevertheless, in 2014 a pod of 7 specimens stranded alive along the Italian coast of the Central Adriatic Sea: 3 individuals died on the beach after a few hours due to internal damages induced by prolonged recumbency; the remaining 4 whales were refloated after great efforts. All the dead animals were genetically related females; one was pregnant. All the animals were infected by dolphin morbillivirus (DMV) and the pregnant whale was also affected by a severe nephropathy due to a large kidney stone. Other analyses ruled out other possible relevant factors related to weather conditions or human activities. The results of multidisciplinary post-mortem analyses revealed that the 7 sperm whales entered the Adriatic Sea encountering adverse weather conditions and then kept heading northward following the pregnant but sick leader of the pod, thereby reaching the stranding site. DMV infection most likely played a crucial role in impairing the health condition and orientation abilities of the whales. They did not steer back towards deeper waters, but eventually stranded along the Central Adriatic Sea coastline, a real trap for sperm whales.

10 pages, 4 figures, 2 tables, Atlantic mackerel (Scomber scombrus) ranks among the most valuable fish species in Europe. The NE Atlantic mackerel population is considered to comprise three main stocks (southern, western and North Sea), with variable proportions of these three intermixing at the northerly feeding grounds. The southern and western mackerel stocks have moved over the past 4–5 years further north- and westward. Consequently, large-scale mackerel fishing and processing have become thriving industries in Iceland and the Faroe Islands in just a few years. The mackerel population structure in the Mediterranean Sea is less well known but seems to comprise at least one, more or less isolated, spawning component. Although mackerel is an important food resource, systematic and concerted epidemiological surveys of Anisakis species in Atlantic mackerel from European fishing grounds have been lacking. As part of the EU FP7 PARASITE project (GA no. 312068), occurrence and specific identity of Anisakis spp. from 1801 mackerel from Northeast Atlantic and Mediterranean waters was investigated. In general, mackerel caught at the Atlantic fishing grounds exhibited markedly higher Anisakis spp. infection levels than fish from the Mediterranean localities. Mackerel caught off NW Spain and Portugal (ICES VIIIc, IXa) showed highest overall and muscular prevalence, reaching 87% and 52%, respectively, which differed significantly from all other Atlantic samples. Lowest overall Anisakis spp. prevalence and abundance was recorded in mackerel from Faroe Isles waters, while lowest muscular infection levels were found in the samples from the North Sea. Genetic nematode species identification showed that A. simplex (sensu stricto) is the dominating species in mackerel from the Atlantic areas, while A. pegreffii dominated in the samples from the Mediterranean Sea. The latter species showed generally low prevalence and intensity in the flesh, not exceeding 6% and one larva, respectively. While A. simplex (s. s.) and A. pegreffii seem to co-occur in mackerel from off NW Spain and Portugal, several A. pegreffii were also recorded in mackerel from the North- and Norwegian Seas. These findings imply that the actual mackerel started their feeding migration in waters south to the British Isles, which include parts of the sympatric area of the two sibling species. Thus, A. pegreffii could prove a useful supplementary marker to track migration routes of the different mackerel stock components in NE Atlantic waters., The present survey was financially supported by the European Union's 7th Framework Program for Research, Technological Development and Demonstration, project Parasite risk assessment with integrated tools in EU fish production value chains (PARASITE), Grant agreement (GA) no. 312068

This review addresses the biodiversity, biology, distribution, ecology, epidemiology, and consumer health significance of the so far known species of Anisakis, both in their natural hosts and in human accidental host populations, worldwide. These key aspects of the Anisakis species' biology are highlighted, since we consider them as main driving forces behind which most of the research in this field has been carried out over the past decade. From a public health perspective, the human disease caused by Anisakis species (anisakiasis) appears to be considerably underreported and underestimated in many countries or regions around the globe. Indeed, when considering the importance of marine fish species as part of the everyday diet in many coastal communities around the globe, there still exist significant knowledge gaps as to local epidemiological and ecological drivers of the transmission of Anisakis spp. to humans. We further identify some key knowledge gaps related to Anisakis species epidemiology in both natural and accidental hosts, to be filled in light of new 'omic' technologies yet to be fully developed. Moreover, we suggest that future Anisakis research takes a 'holistic' approach by integrating genetic, ecological, immunobiological, and environmental factors, thus allowing proper assessment of the epidemiology of Anisakis spp. in their natural hosts, in human populations, and in the marine ecosystem, in both space and time.

18 pages, 10 figures, 6 tables.-- Arne Levsen ... et al., Harvesting and exploiting limited fisheries resources in a sustainable manner also implies achieving maximum added value from the raw material. However, the presence of parasites in the products may adversely affect consumer perception and/or pose a direct health hazard. As a major stepping-stone of the PARASITE project, an epidemiological survey was carried out to provide the basis for analysis and prediction of consumer exposure risk due to the presence of anisakid nematodes in fish from European wild-catch fisheries. The project consisted of nine separate workpackages (WP) where the exposure risk assessment survey was organized within WP2. The surveillance task also provided the data or samples needed for data management and sample storage (WP3, Biobank), molecular and genetic parasite species identification (WP4), and statistical modelling and inference (WP8). In total 17,760 fish belonging to 16 teleost species were examined for anisakids, with special emphasis on economically and ecologically important species such as Atlantic mackerel, herring, European hake, Atlantic cod and anchovy. The target fish species were sampled at four major European fishing areas including the Barents Sea, North Sea, Baltic Sea, Grand Sole Bank, waters off NW Spain and Portugal, central and western parts of the Mediterranean Sea, and the Adriatic Sea. Thus, the survey represents the largest and most comprehensive epidemiological data compilation of anisakids ever generated in terms of geographical range as well as number of fish host species and sample size. An important requirement of the survey was the use of commonly accepted nematode detection methods, i.e. the UV-press method or artificial digestion, to quantify infection level and spatial distribution of anisakid larvae in the target fish species. The basic layout, set-up and principles of the method, along with a discussion of possible source of errors are described. Additionally, the molecular and genetic markers which were used to identify and characterize different species and populations of anisakids from the targeted fish host species and geographical areas, are reviewed as well. Some basic parasite infection characteristics of each fish host species, and any relationships with the presumably most important infection predictors, i.e. fish host body size and fishing locality, are presented and discussed. Emphasis is put on anisakid occurrence in the flesh of the fish. Based on the findings, a graphical exposure risk profile is introduced, including fish species or products thereof, which due to common processing or preparation practices, are at highest risk to act as source of anisakiasis in Europe, The present work was financially supported by the European Union’s 7th Framework Programme for Research, Technological Development and Demonstration, project Parasite risk assessment with integrated tools in EU fish production value chains (PARASITE), Grant Agreement (GA) no. 312068

11 pages, 5 figures, 3 tables, Haddock and whiting are two species of the family Gadidae that are exploited by fisheries mainly in European waters, the former being one of the most important seafood resources in Scotland (UK). The present study aimed to quantify prevalence, abundance and intensity of infection of the zoonotic parasite Anisakis spp. and other ascaridoid nematodes in these fish as part of a study on the risk to consumers. Fish were sourced from research trawling surveys during 2013–2015, aiming to cover a range of size-classes and different times of year. Samples were obtained from the North Sea, west coast of Scotland and the Barents Sea. Fish were stored frozen prior to separation of viscera and fillets and the use of pressing and UV visualisation to locate, identify and count Anisakis spp. and other ascaridoids in fillets (divided into 8 parts), liver and other viscera. A subsample of Anisakis spp. collected from haddock were identified genetically by means of two diagnostic markers (mtDNA cox2 and EF1 α-1 nuclear DNA), and all were identified as A. simplex (s. s.). Both fish species showed moderate to high infection levels with Anisakis spp. (likely A. simplex (s. s.)) in the visceral organs and cavity, and rather low infection in the musculature. Those A. simplex (s. s.) larvae present in the musculature were mostly found in the anterior ventral area. In both fish species, the infection rate increased with fish length and in haddock a negative relationship was observed between Anisakis spp. numbers in muscle and body condition. From our sampling of Anisakis spp. in fish muscle, in Scotland, whiting presents a greater human health risk than haddock in Scotland. The risk arising from consumption of haddock from the Barents Sea (with 72% prevalence of Anisakis) is markedly higher, although in all cases the risk of infection in humans can be minimised if fish are frozen or adequately cooked prior to consumption. We present previously unpublished information on reported cases of anisakiasis in the United Kingdom during 2000–2013, which included 4 cases from Scotland among 22 overall. While these findings suggest that anisakiasis is relatively rare in the UK, underreporting is likely and further investigation of the incidence of anisakiasis is needed, The present work was supported by the European Union's 7th Framework Programme for Research, Technological Development and Demonstration, project Parasite risk assessment with integrated tools in EU fish production value chains (PARASITE), Grant Agreement (GA) no. 312068. GJP acknowledges additional support from the University of Aveiro and Caixa Geral de Depósitos (Portugal)

9 pages, 3 figures, 5 tables.-- Simonetta Mattiucci ... et al., The Atlantic herring is a schooling, pelagic species that inhabits both sides of the North Atlantic Ocean. Herring stock identification is usually based on several approaches, including fish meristic characters, population genetic analysis and the use of parasite species composition. A total of 654 Anisakis spp. larvae collected from herring of four fishing grounds in the Norwegian Sea, Baltic Sea, North Sea, and the English Channel off the French coast, was identified to species level using diagnostic allozymes and sequence analysis of EF1 α−1 nDNA and the mtDNA cox2 genes. Population genetic differentiation of Anisakis simplex (s. s.) among the different fishing areas was estimated, at the intraspecific level, on the basis of mtDNA cox2 sequences analysis. Spatial comparison based on molecular variance analysis and Fst values was performed for the collected specimens (among regions). Haplotype network construction showed relevant differences in haplotype frequencies between samples of A. simplex (s. s.) from the different geographical areas. Results indicate a genetic sub-structuring of A. simplex (s. s.) obtained from herring in different areas, with the population from the Norwegian Sea being the most differentiated one, and with North Sea and Baltic Sea populations being most similar. The population genetic structure of A. simplex (s. s.) was in accordance with the herring population genetic structure throughout the host’s geographical range in the NE Atlantic. Results suggest that mtDNA cox2 is a suitable genetic marker for A. simplex (s. s.) population genetic structure analysis and a valuable tool to elucidate the herring stock structure in the NE Atlantic Ocean, The research was carried out with funding received from the European Union’s Seventh Framework Programme for research, technological development and demonstration, under the grant agreement no. 312068 “PARASITE”

European pilchards are traditionally eaten marinated or salted in the Mediterranean countries often without thermal processing or gutting due to small size. Since ingestion of live third stage Anisakis larvae represents a causing agent in the onset of anisakiasis, the aim of our study was to assess prevalence and intensity of Anisakis infection in European pilchards originating from different Mediterranean regions in a three-year sampling period (2013–2015). A total of 1564 specimens of European pilchard collected from two geographically distinct sampling regions (western Mediterranean and Adriatic Sea) were examined using the UV-Press method, which utilises the fluorescence of frozen anisakids in flattened and subsequently frozen fillets and viscera. A subsample of 67 isolated larvae was identified as A. pegreffii by diagnostic allozyme markers and sequence analyses of the mtDNA cox2 locus. The overall prevalence in pilchards was 12.2% (range 0–44.9% for different sampling points) and mean intensity 1.8. More importantly, we have observed an overall larval prevalence of 1.5% in fillets. The highest prevalence (44.9%) was recorded in pilchards caught in western parts of the Mediterranean. As fish host size was a significant predictor of parasite abundance, it should be highlighted that these pilchards were also the largest (mean total length 173.2 mm) ; on average > 2 cm larger than the rest of the samples. Other isolated nematode species included Hysterothylacium sp. in viscera, showing almost a double of A. pegreffii prevalence, 20.1%. In summary, our study demonstrates that the presence of A. pegreffii in European pilchards from the Mediterranean Sea is highly influenced by both geographic and host size variation. This implies that, before future risk management measures are developed, these variables should be assessed in order to minimize public health concerns.

European anchovy Engraulis encrasicolus represents one of the principal target species for commercial fishing in Europe. This fish is mostly consumed in different raw dish preparations, which represents a major risk for the fish-borne zoonosis anisakiasis. The present study provides a detailed epidemiological report on ascaridoid larvae in E. encrasicolus from several fishing areas in the Mediterranean basin. Between June 2013 and June 2016, a total of 4152 specimens of E. encrasicolus were obtained from 13 sampling areas. Parasitological analysis was carried out using the UV-press detection method. Anisakis larvae (N = 547), identified by diagnostic allozymes and analyses of partial sequences of the EF1 α-1 region of nDNA and mtDNA cox2 gene, corresponded to Anisakis pegreffii. Additionally, sequence analyses of the ITS region of rDNA revealed the presence of Hysterothylacium aduncum larvae. The levels of infection with A. pegreffii significantly varied between the selected fishing areas. Fish from the Central and South Adriatic Sea showed the highest levels of infection. In contrast, anchovies from Southern Sicily, Ionian and Alboran Seas, were uninfected. A great majority of A. pegreffii larvae (95.8%) were located in the body cavity, whereas only a small percentage of them (4.2%) were detected in the flesh of the fish. A significant positive correlation between fish length and abundance of A. pegreffii was observed. The fish body condition index and infection levels observed in different sampling areas did not correlate significantly. The infection levels by H. aduncum also showed a significantly uneven distribution between different fishing areas of the Mediterranean Sea, and no larval specimens of H. aduncum were detected in examined fish flesh. This study is the first Mediterranean-wide epidemiological assessment of infection in the viscera and flesh of E. encrasicolus by A. pegreffii, an important causative agent of human anisakiasis.

17 páginas, 7 tablas, 4 figuras.-- This work is licensed under a Creative Commons Attribution 4.0 International License, Anisakiasis is an emerging zoonosis caused by the fish parasitic nematode Anisakis. Spain appears to have the highest reported incidence in Europe and marinated anchovies are recognised as the main food vehicle. Using data on fishery landings, fish infection rates and consumption habits of the Spanish population from questionnaires, we developed a quantitative risk assessment (QRA) model for the anchovy value chain. Spaniards were estimated to consume on average 0.66 Anisakis per untreated (non-frozen) raw or marinated anchovy meal. A dose-response relationship was generated and the probability of anisakiasis was calculated to be 9.56 × 10−5 per meal, and the number of annual anisakiasis cases requiring medical attention was predicted between 7,700 and 8,320. Monte Carlo simulations estimated post-mortem migration of Anisakis from viscera to flesh increases the disease burden by >1000% whilst an education campaign to freeze anchovy before consumption may reduce cases by 80%. However, most of the questionnaire respondents who ate untreated meals knew how to prevent Anisakis infection. The QRA suggests that previously reported figures of 500 anisakiasis per year in Europe is a considerable underestimate. The QRA tool can be used by policy makers and informs industry, health professionals and consumers about this underdiagnosed zoonosis, M. Bao is supported by a PhD grant from the University of Aberdeen and also by financial support of the contract from the EU Project PARASITE (grant number 312068).

Inventorying of anisakid nematode biodiversity is the discovering, surveying, quantifying and mapping of species, populations and their genetic diversity and variability. This aim, however, is compromised if discrimination of anisakid taxa relies solely on morphological features. Therefore, the accurate detection and delimitation of cryptic anisakid species requires molecular-based assessments. This, in turn, permits elucidation of patterns and process in their evolution and ecology, including biogeography, host-parasite association and co-evolution. In addition, a true picture of anisakids and their genetic diversity facilitates understanding of their temporal and spatial distribution also related to their hosts demographic changes and marine ecosystem food webs. This review represents an inventorying of the biodiversity, at species and gene level, of those anisakid species so far discovered belonging to the genera Anisakis, Pseudoterranova and Contracaecum, from the Austral Region, including: (1) taxa recognized as “biological species” based on the application of different molecular genetic markers; (2) current molecular/genetic approaches to identify them at any life-history stage; (3) ecological data relating to the geographical distribution, definitive host-association and host-preferences; (4) estimates of genetic variability values inferred from nuclear and mitochondrial genes, as a possible indicator of the integrity of marine food webs; (5) data so far known concerning the possible zoonotic role of those anisakid species to humans. Fil: Mattiucci, Simonetta. Università degli studi di Roma "La Sapienza"; Italia Fil: Paoletti, Michela. Universita Di Tuscia; Italia Fil: Cipriani, Paolo. Università degli studi di Roma "La Sapienza"; Italia. Universita Di Tuscia; Italia Fil: Webb, Stephen C.. Cawthron Institute; Nueva Zelanda Fil: Timi, Juan Tomas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Nascetti, Giuseppe. Universita Di Tuscia; Italia

A new taxon, Rhabdias esculentarum n. sp., is described based on DNA sequence analysis at multiple loci (i.e. mtDNA cox-1, 12S rRNA, ITS-1 and partial ITS-2 regions of the nuclear rDNA) and morphometric analysis carried out on specimens collected from the green frogs of the Rana esculenta species complex in Italy (i.e. R. lessonae Camerano and R. esculenta Linnaeus, identified genetically by diagnostic allozyme loci). Rhabdias esculentarum n. sp. was differentiated genetically, at both mitochondrial and nuclear levels, from Rh. bufonis (Schrank, 1788) (sensu Hartwich, 1972) and Rh. sphaerocephala Goodey, 1924 recovered from the toad Bufo bufo Linnaeus collected sympatrically with the specimens of Rana lessonae and R. esculenta examined in the present study. Moreover, the new taxon proved to be different from the other species of Rhabdias from anurans, which had previously been sequenced using the same genes and deposited in GeneBank. Phylogenetic analyses (MP and ML) inferred from mitochondrial (mtDNA cox-1 and 12S ribosomal RNA) and nuclear (ITS-1 and ITS-2 of the rDNA regions) sequences datasets were congruent in depicting Rh. esculentarum n. sp. as forming a highly supported clade distinct from the sympatric species Rh. bufonis, as well as from Rh. sphaerocephala, characterised on the basis of the same loci. Morphometric analysis and the differential diagnosis of genetically characterised specimens of the new species have revealed differences in several features in comparison with the type-species, Rh. bufonis. Material of the latter species included voucher specimens from Germany deposited by Hartwich (1972) and other specimens collected from B. bufo in Italy. Among the diagnostic characters, the particular cup-shaped buccal capsule characterising Rh. esculentarum is clearly different from the tear-shaped buccal capsule observed in material of R. bufonis obtained from Berlin Museum and collected in the same geographical area as the green frogs under study. Rh. esculentarum was also found to differ in some measurements and allometric characters from Rh. bufonis (sensu Moravec et al., 1997). The data so far collected appear to indicate a host-preference of Rh. esculentarum for Rana lessonae and R. esculenta, which belong to the R. esculenta hybridogenetic species complex in Italy.

SUMMARYA multi-marker nuclear genotyping approach was performed on larval and adult specimens ofAnisakisspp. (N= 689) collected from fish and cetaceans in allopatric and sympatric areas of the two speciesAnisakis pegreffiiandAnisakis simplex(s. s.), in order to: (1) identify specimens belonging to the parental taxa by using nuclear markers (allozymes loci) and sequence analysis of a new diagnostic nuclear DNA locus (i.e. partial sequence of the EF1α−1nDNA region) and (2) recognize hybrid categories. According to the Bayesian clustering algorithms, based on those markers, most of the individuals (N= 678) were identified as the parental species [i.e.A. pegreffiiorA. simplex(s. s.)], whereas a smaller portion (N= 11) were recognized as F1hybrids. Discordant results were obtained when using the polymerase chain reaction–restriction fragment length polymorphisms (PCR–RFLPs) of the internal transcribed spacer (ITS) ribosomal DNA (rDNA) on the same specimens, which indicated the occurrence of a large number of ‘hybrids’ both in sympatry and allopatry. These findings raise the question of possible misidentification of specimens belonging to the two parentalAnisakisand their hybrid categories derived from the application of that single marker (i.e. PCR–RFLPs analysis of the ITS of rDNA). Finally, Bayesian clustering, using allozymes and EF1α−1nDNA markers, has demonstrated that hybridization betweenA. pegreffiiandA. simplex(s. s.) is a contemporary phenomenon in sympatric areas, while no introgressive hybridization takes place between the two species.

Biology of foodborne parasites , Biology of foodborne parasites , کتابخانه مرکزی دانشگاه علوم پزشکی تهران

The consumption of the hake Merluccius merluccius is widespread in European countries, where this fish has a high commercial value. To date, different larval species of Anisakis have been identified as parasites in M. merluccius from European waters, Anisakis pegreffii and Anisakis simplex (s. s.) being the two most common. The aim of the study is to present data on the occurrence of Anisakis spp. larvae in the viscera and flesh of M. merluccius. Consequently, the distribution and infection rates of different species of Anisakis in different sites (viscera, and dorsal and ventral fillets) were investigated in hake caught in the central Tyrrhenian Sea (FAO 37.1.3) and the NE Atlantic Ocean (FAO 27 IXa). A sample of N=65 fish individuals (length>26 cm) was examined parasitologically from each fishing ground. The fillets were examined using the pepsin digestion method. A large number (1310) of Anisakis specimens were identified by multilocus allozyme electrophoresis (MAE) and mtDNA cox2 sequence analysis; among these, 814 larvae corresponded to A. simplex (s. s.) and 476 to A. pegreffii. They were found to infect both the flesh and the viscera. The two species co-infected the same individual fish (both in the viscera and in the flesh) from the FAO 27 area, whereas only A. pegreffii was found in hake from the Tyrrhenian Sea. The average parasite burden of A. pegreffii in hake from the Tyrrhenian Sea was significantly lower to that observed from hake off the Atlantic coast of Spain, both in prevalence and in abundance. In addition, whereas no significant difference in overall prevalence values was recorded between the two Anisakis species in the viscera of the FAO 27 sample, significant differences were found in the abundance levels observed between these species in the flesh, with A. simplex (s. s.) exhibiting significantly higher levels than that observed for A. pegreffii (p

SUMMARYThe unique environment of the Mediterranean Sea makes fish stock assessment a major challenge. Stock identification of Mediterranean fisheries has been based mostly from data on biology, morphometrics, artificial tags, otolith shape and fish genetics, with less effort on the use of parasites as biomarkers. Here we use some case studies comparing Mediterranean vs Atlantic fish stocks in a multidisciplinary framework. The generalized Procrustes Rotation (PR) was used to assess the association between host genetics and larval Anisakis spp. datasets on demersal (hake) and pelagic (horse mackerel, swordfish) species. When discordant results emerged, they were due to the different features of the data. While fish population genetics can detect changes over an evolutionary timescale, providing indications on the cohesive action of gene flow, parasites are more suitable biomarkers when considering fish stocks over smaller temporal and spatial scales, hence giving information of fish movements over their lifespan. Future studies on the phylogeographic analysis of parasites suitable as biomarkers, and that of their fish host, performed on the same genes, will represent a further tool to be included in multidisciplinary studies on fish stock structure.

Thirteen parasite taxa were identified in the Mediterranean swordfish by morphological and genetic/molecular methods. The comparison of the identified parasite taxa and parasitic infection values observed in the Mediterranean swordfish showed statistically significant differences with respect to those reported for its Atlantic populations. A stepwise Linear Discriminant Analysis of the individual fish examined showed a separation among three groups: one including fish from the Mediterranean Sea (CTS, STS, and IOS); one consisting of fish from the Central South (CS), Eastern Tropical (ET), and Equatorial (TEQ) Atlantic; and a third comprising the fish sampled from the North-West Atlantic (NW); the CN Atlantic sample was more similar to the first group rather than to the other Atlantic ones. The nematodes Hysterothylacium petteri and Anisakis pegreffii were the species that contributed most to the characterization of the Mediterranean swordfish samples with respect to these Atlantic ones. Anisakis brevispiculata , A. physeteris , A. paggiae , Anisakis sp. 2, Hysterothylacium incurvum , Hepatoxylon trichiuri , Sphyriocephalus viridis , and their high infection levels were associated with the swordfish from the Central and the Southern Atlantic areas. Finally, H. corrugatum , A. simplex (s.s.), Rhadinorhynchus pristis , and Bolbosoma vasculosum were related to the fish from the North-West (NW) Atlantic area. These results indicate that some parasites, particularly Anisakis spp. larvae identified by genetic markers, could be used as “biological tags” and support the existence of a Mediterranean swordfish stock.

Parasite communities of Chionodraco hamatus were investigated from Terra Nova Bay (Ross Sea, Antarctica) during host spawning time. Special attention was given to helminth infracommunities and effect of host sex on its structure. A total of 21 taxa including 5 ecto-parasites and 16 endo-parasites were identified. The number of ecto and endo-parasite species per individual host ranged from 1 to 3 and 3 to 10, respectively, while the mean numbers of parasite specimens per individual host were 4.7 and 1309.7, respectively. The rich abundance of infection suggests a rich concentration of helminth intermediate/paratenic hosts in the coastal waters of Terra Nova Bay. Chionodraco hamatus serves as a definitive host for 10 helminth taxa, while it acts as an intermediate/paratenic host for 6 helminth taxa. Larvae of 6 helminth taxa for which C. hamatus serves as intermediate/paratenic host represented 98.7% of all specimens found. Of these, the tetraphyllidean and diphyllobothridean cestodes and the nematode Contracaecum osculatum s.l. were the most prevalent and abundant. 'Larval' infracommunities had significantly higher species richness, total abundance and diversity than 'adult' infracommunities, suggesting the important role of C. hamatus in supporting the life cycles of those parasites in the study area as a paratenic/intermediate host. Significant differences in the pattern of helminth infracommunities of larval forms between male and female fish were found. These differences could be caused by physiological, and most probably by behavioral differences between sexes suggesting that sex is an important factor influencing parasite burden in C. hamatus during reproductive season.