Ecology and Genetic Structure of Zoonotic Anisakis spp. from Adriatic Commercial Fish Species

Consumption of raw or thermally inadequately treated fishery products represents a public health risk, with the possibility of propagation of live Anisakis larvae, the causative agent of the zoonotic disease anisakidosis, or anisakiasis. We investigated the population dynamics of Anisakis spp. in commercially important fish—anchovies (Anisakis), sardines (Sardina pilchardus), European hake (Merluccius merluccius), whiting (Merlangius merlangus), chub mackerel (Scomber japonicus), and Atlantic bluefin tuna (Thunnus thynnus)—captured in the main Adriatic Sea fishing ground. We observed a significant difference in the numbers of parasite larvae (1 to 32) in individual hosts and between species, with most fish showing high or very high Anisakis population indices. Phylogenetic analysis confirmed that commercial fish in the Adriatic Sea are parasitized by Anisakis pegreffii (95.95%) and Anisakis simplex sensu stricto (4.05%). The genetic structure of A. pegreffii in demersal, pelagic, and top predator hosts was unstructured, and the highest frequency of haplotype sharing (n = 10) was between demersal and pelagic fish.     

Adaptive radiation within marine anisakid nematodes: a zoogeographical modeling of cosmopolitan, zoonotic parasites

Parasites of the nematode genus Anisakis are associated with aquatic organisms. They can be found in a variety of marine hosts including whales, crustaceans, fish and cephalopods and are known to be the cause of the zoonotic disease anisakiasis, a painful inflammation of the gastro-intestinal tract caused by the accidental consumptions of infectious larvae raw or semi-raw fishery products. Since the demand on fish as dietary protein source and the export rates of seafood products in general is rapidly increasing worldwide, the knowledge about the distribution of potential foodborne human pathogens in seafood is of major significance for human health. Studies have provided evidence that a few Anisakis species can cause clinical symptoms in humans. The aim of our study was to interpolate the species range for every described Anisakis species on the basis of the existing occurrence data. We used sequence data of 373 Anisakis larvae from 30 different hosts worldwide and previously published molecular data (n = 584) from 53 field-specific publications to model the species range of Anisakis spp., using a interpolation method that combines aspects of the alpha hull interpolation algorithm as well as the conditional interpolation approach. The results of our approach strongly indicate the existence of species-specific distribution patterns of Anisakis spp. within different climate zones and oceans that are in principle congruent with those of their respective final hosts. Our results support preceding studies that propose anisakid nematodes as useful biological indicators for their final host distribution and abundance as they closely follow the trophic relationships among their successive hosts. The modeling might although be helpful for predicting the likelihood of infection in order to reduce the risk of anisakiasis cases in a given area.     

The metazoan parasites of swordfish from Atlantic tropical–equatorial waters

The metazoan parasite fauna composition of the swordfish Xiphias gladius is reported from 145 (72 females and 73 males) specimens caught in Atlantic tropical–equatorial waters during June to July 2006 and August 2007. Seventeen metazoan taxa (two monogeneans, two digeneans, one acanthocephalan, four cestodes, seven nematodes and one copepod) were identified by morphological and genetic methodologies. Among those identified, Anisakis brevispiculata, Anisakis paggiae and the acanthocephalan Bolbosoma vasculosum are new host records. Dominant species were: the anisakid nematode larvae Anisakis physeteris, Anisakis brevispiculata, Hysterothylacium incurvum and Hysterothylacium corrugatum (s.l.), the adult cestode Fistulicola plicatus, the plerocercoid Hepatoxylon squali and the monogeneans Tristoma integrum and Tristoma coccineum, which showed high prevalences and intensities. The relationship between metazoan parasites and host size and sex was investigated for the first time. No statistically significant correlation was found between host sex and parasite burden. Infection levels with T. integrum and T. coccineum were observed to be significantly negatively correlated to host size. Infection levels by endoparasites observed in X.gladius from Atlantic tropical‐equatorial area may be related to host feeding behaviour and the availability of the parasites’ intermediate and final hosts in the area studied. Anisakids of the genus Anisakis, were identified genetically to species level, and were considered to be promising biological tags for the characterization of X.gladius stocks.     

Salinity gradient shapes distance decay of similarity among parasite communities in three marine fishes

Published data were used to compare the distance decay of similarity in parasite communities of three marine fish hosts: Atlantic cod Gadus morhua, the dab Limanda limanda and the flounder Platichthys flesus in two adjacent areas that differ with respect to the strength of a salinity gradient. In the Baltic Sea, which exhibits a strong salinity gradient from its connection with the North Sea in the west to its head in the north‐east, parasite communities in all three fish hosts showed a significant decline of similarity with increasing distance. In contrast, among host populations in the North Sea, which is a fully marine environment, there was no such decline or only a weak relationship. The results suggest that environmental gradients like salinity can be strong driving forces behind patterns of distance decay in parasite communities of fishes.     

Recruitment of stock of deepwater redfish <Emphasis Type="Italic">Sebastes mentella</Emphasis> (Scorpaeniformes,Scorpaenidae) in the pelagial of the Irminger Sea and adjacent waters

Results of comparative analysis of several ecologo-populational characteristics and fauna of parasites of deepwater redfish Sebastes mentella from the pelagial of the Irminger Sea and slopes of Greenland are provided. It was established that the nursery area of the species in this part of the northern Atlantic is located in the shelf and shallow-water sites of the Greenland slopes. Near the nursery area, at deepwater sites of the Greenland slope, aggregations of mainly immature specimens (68–86%) with an average length of 35–38 cm are located, and, in the oceanic pelagial, there are mainly mature specimens (91–95%) with a length of more than 30 cm. Considerable similarity and specific features of fauna of parasites of S. mentella from the southeastern slope of Greenland and the pelagial of the Irminger Sea indicate the belonging of fish aggregations in these areas to a single intraspecies group and the migration of maturing specimens from the slope to the pelagial. A conclusion is made that the aggregations of S. mentella in the pelagial of the Irminger and Labrador seas represent a pelagic ecological group formed by rapidly maturing specimens; a near-bottom ecological group at deepwater sites of the slope of Greenland is formed by slowly maturing specimens. No mass migration of the redfish from deepwater areas to shallow sites of the slope and to the oceanic pelagial of the northern Atlantic was recorded.     

Ecologal and parasitological chracteristics of redfish <Emphasis Type="Italic">Sebastes mentella</Emphasis> (Scorpaeniformes: Sebastidae) from the Norwegian Sea and adjacent waters

Special traits of ecology, zoogeography, formation of fauna of parasites, and occurrence of external lesions are investigated in redfish Sebastes mentella from the Norwegian Sea and the adjacent area of the Barents Sea. A considerable weakening of connection with bottom biocenoses in redfish in the pelagial of the Norwegian Sea indicates that it lives here for most of its annual life cycle. In redfish from south of the open part of the Norwegian Sea, there are noticeable differences in the fauna of parasites and in occurrence of external lesions from those in the fish from the north and east of this sea while traits characteristic of redfish from the Irminger Sea are present.     

Structure and specific features of formation of aggregations of deepwater redfish <Emphasis Type="Italic">Sebastes mentella</Emphasis> (Scorpaenidae) in the Norwegian Sea pelagial

Results of studies of the structure and specific features of formation of aggregations of deepwater redfish Sebastes mentella in the Norwegian Sea pelagial are provided. Data on the biological characteristics of S. mentella from different regions of the Norwegian Sea pelagial do not allow us to consider its aggregations as separate populations. On the basis of comparative analysis of the structure of aggregations in the Norwegian Sea and of population parameters and specific features of the life cycle of S. mentella in different parts of the Atlantic Ocean, its complex intraspecies organization at sites of overlapping of two largest populations—North Atlantic and Norwegian-Barents Sea-was established. The formation of pelagic aggregations in the water area of the Norwegian Sea occurs due to migration of maturing and mature individuals from the adjoining water areas. In the southern areas of the Norwegian Sea, dominant recruitment comes from the pelagial of the northeastern part of the Irminger Sea, which is promoted by the direction of streams of the North-Atlantic Current; it is not excluded either that fish can migrate to the southern part of the sea from the slopes of the Faeroes, Faeroes-Icelandic threshold, and the western coast of Norway. Migration to the northern areas of the sea is mainly performed by rapidly maturing fish from the rearing region from the western slopes of the Barents Sea and Spitsbergen Archipelago. The presence of seasonal migrations hinders the formation in the pelagial of perch isolated groups and promotes their migration.     

Anisakis spp. larvae in three mesopelagic and bathypelagic fish species of the central Mediterranean Sea

In this work 437 fish samples of species belonging to the families Myctophidae (Electrona risso and Diaphus metopoclampus) and Phosichthyidae (Vinciguerria attenuata) were examined for the presence of Anisakidae larvae. The study was performed with fishes in the central Mediterranean Sea, particularly in the Strait of Sicily and in the Strait of Messina. The visual inspection and chloro-peptic analysis revealed the presence of nematode parasites with prevalence values between 2.9% in Electrona risso samples and 5.4% in Vinciguerria attenuata samples. A positive correlation was found between standard length (SL) and prevalence of infestation in D. metopoclampus samples (p < 0.05). The larvae examined were morphologically ascribed, at genus level, to Anisakis morphotypes I and II and molecularly identified as Anisakis pegreffii, Anisakis ziphidarum and Anisakis physeteris, in 67%, 9% and 24% of the fish samples examined. Overall, A. pegreffii and A. ziphidarum larvae were isolated in 14 and 2 specimens of D. metopoclampus respectively, A. physeteris larvae were found in 3 E. risso and 2 V. attenuata. A positive correlation was found between standard length and prevalence of infestation in D. metopoclampus samples (p < 0.05). First information is provided on the presence of Anisakis spp. larvae of the myctophid fish species E. risso, D. metopoclampus and V. attenuata from the Central Mediterranean. It is also confirmed the role of lanternfishes (Myctophidae) as paratenic hosts for Anisakis spp.     

Review of the population structure and ecology of S. mentella in the Irminger sea and adjacent waters

Significant controversies exist over the three types of Sebastes mentella found in the Irminger Sea and adjacent waters. Preliminary genetic studies have given evidence for the existence of three distinct groups, characterized using several molecular genetic markers. The biological or ecological significance of these between-group differences has, however, not been evaluated. In the present paper, we review the life cycle of S. mentella in this area, based on published data. Spawning of S. mentella in the Irminger Sea takes place in a single area above Reykjanes Ridge. The larvae drift towards East Greenland from where they are carried to West Greenland (NAFO Subareas 0+1). Later they return to East Greenland where the main nursery area has been identified. There is evidence for a migration of juvenile fish from the nursery area into the open Irminger Sea, where many different cohorts spawn. We also compare these ecological data with the genetic results and we conclude that the observed genetic differences can be derived from possible genetic drift, selection or mostly from temporal variation (age dependency). which has also been reported for other species with as high longevity as S. mentella. We conclude that S. mentella in the Irminger Sea and adjacent waters comprises one single population.     

Molecular Analysis of Anisakis Type I Larvae in Marine Fish from Three Different Sea Areas in Korea

Anisakiasis, a human infection of Anisakis L3 larvae, is one of the common foodborne parasitic diseases in Korea. Studies on the identification of anisakid larvae have been performed in the country, but most of them have been focused on morphological identification of the larvae. In this study, we analyzed the molecular characteristics of 174 Anisakis type I larvae collected from 10 species of fish caught in 3 different sea areas in Korea. PCR-RFLP and sequence analyses of rDNA ITS and mtDNA cox1 revealed that the larvae showed interesting distribution patterns depending on fish species and geographical locations. Anisakis pegreffii was predominant in fish from the Yellow Sea and the South Sea. Meanwhile, both A. pegreffii and A. simplex sensu stricto (A. simplex s.str.) larvae were identified in fish from the East Sea, depending on fish species infected. These results suggested that A. pegreffii was primarily distributed in a diverse species of fish in 3 sea areas around Korea, but A. simplex s.str. was dominantly identified in Oncorhynchus spp. in the East Sea.     

Biological and ecological characteristics of deepwater redfish <Emphasis Type="Italic">Sebastes mentella</Emphasis> (Scorpaenidae) at different depths in the pelagial of the Irminger Sea

Results of comparative analysis of several ecological and biological indices of Sebastes mentella from the northern Atlantic (the Irminger Sea, Reykjanes Ridge) inhabiting different depths, 0–500 and 501–1000 m, are provided. A considerable similarity in the rates of linear and weight growth, sexual maturation, composition of parasitofauna, the degree of invasion by parasites of most species, specific features of invasion by copepod Sphyrion lumpi, as well as the pattern of pigment formations on the skin of S. mentella from two studied layers, testify to the absence of isolated groups of this species in the pelagial of the Irminger Sea. It was established that the formation of perch aggregations at a depth larger than 500 m takes place due to a partial redistribution from the upper layer of individuals aged 5 to 18 years and a complete departure to large depths of perch individuals older than 18 years. A conclusion was made that it is incorrect to use as a criterion for the intraspecies differentiation of the perch the insignificant differences in the occurrence of pigment formations on the skin that are the result of age changes in fish and an obvious pathology of this phenomenon. A decrease in the occurrence of melanin inclusions in the muscular tissue of fish at a depth larger than 500 m is also related to age changes and the change in the diet of the perch. Vertical variation, in particular biological parameters in pelagic aggregations, was determined by specific features of biology, ecology, and the life cycle of the species. In establishing measures of control of the international fishery in the pelagial of the Irminger Sea, it is necessary to proceed from the unity of aggregations of S. mentella throughout the vertical of their distribution.     

Biogeographical patterns of marine larval trematode parasites in two intermediate snail hosts in Europe

Aim We used published inventories of trematodes in Littorina littorea (L.) and Hydrobia ulvae (Pennant) in European seas to search for two basic biogeographical patterns in the spatial occurrence of various trematode species: (1) do parasite distribution and richness patterns in the two host snails overlap with known ecoregions of free‐living organisms; and (2) does trematode species richness in the snails follow latitudinal or longitudinal gradients? Location North East Atlantic. Methods We used multidimensional scaling (MDS), analysis of similarity (ANOSIM) and analysis of variance (ANOVA) to test whether there were overlaps of parasite distribution and richness with known ecoregions of free‐living organisms. In addition, we used linear regression analyses to test whether trematode richness in snails (corrected for sampling effort) was correlated with the latitude or longitude of the sampling sites. Results When corrected for sampling effort, mean trematode species richness per site did not differ among the different ecoregions in L. littorea. In contrast, in H. ulvae, mean species richness was much lower for sites from the Celtic Sea compared with sites from the Baltic Sea and the North Sea. Based on the results of MDS analyses, trematode species composition was distinct among ecoregions; in particular, communities from the Baltic Sea differed markedly from communities in the Celtic Sea, for both snail species. Latitude and longitude were not significantly correlated with parasite species richness in either snail species. Most trematode species had restricted distributions, and only three species in L. littorea and five species in H. ulvae occurred at more than 50% of the sites. Main conclusions There is more structure in the large‐scale distribution of trematodes in gastropods than one would expect from the large‐scale dispersal capabilities of their bird and fish final hosts. We propose mechanisms based both on limited dispersal via fish and bird final hosts and on gradients in environmental factors to explain the observed patterns.     

Tautochondria dolichoura n. g., n. sp., a copepod parasitic on the bathypelagic fish Anoplogaster cornuta (Valenciennes) in the western North Atlantic

Tautochondria dolichoura is described based on a specimen taken from a bathypelagic fish, Anoplogaster cornuta (Valenciennes), collected near the Grand Banks, southeast of Newfoundland. It is a siphonostome copepod of the family Hyponeoidae. The appendages of Hyponeo australis Heegaard taken from Paralepis rissoi off the Kuril Islands are compared with the new form from the North Atlantic. A discussion on the affinity of this rarely known family is also given. ac]19860428     

Presence of the telescope fish Mendosoma lineatum in Patagonian waters,a new species in the ichthyological fauna from the south‐west Atlantic Ocean

The presence of the telescope fish Mendosoma lineatum in Patagonian waters of Argentina is reported. Mendosoma lineatum is the second species of the Latridae recorded in the south‐west Atlantic Ocean and its presence in Patagonia is an addition to both the ichthyological fauna of the Argentinean Sea and the south‐west Atlantic Ocean.     

Molecular identification and infection levels of Anisakis species (Nematoda: Anisakidae) in the red scorpionfish Scorpaena scrofa (Scorpaenidae) from the Aegean Sea

The red scorpionfish Scorpaena scrofa (Scorpaenidae) is a high commercial value marine fish species along the Mediterranean coasts. Anisakiasis is a fish–borne parasitic zoonoses caused by Anisakis larvae in consumers. To date, there are only a few epidemiological studies on the presence and molecular identification of Anisakis larvae infecting S. scrofa. A total of 272 S. scrofa captured from the Gulf of Izmir in the Turkish Aegean coasts (FAO 37.3.1) were examined for Anisakis larvae between March 2019 and March 2020. The prevalence, mean intensity and mean abundance of Anisakis larvae were 9.6% (95% CI 6.5–13.7%), 2.8 (95% CI 1.88–5.19), and 0.27 (95% CI 0.15–0.56), respectively. All Anisakis larvae were collected from the viscera and body cavity of S. scrofa. Anisakis pegreffii, A. typica, and A. ziphidarum were genetically identified by RFLP analysis of the ITS region. These species were also confirmed by cox2 sequence analysis. A weak positive and statistically significant correlation between the total length (ρS 0.204; p = 0.001) and total weight (ρS 0.200; p = 0.001) of S. scrofa and the number of Anisakis larvae was observed. This survey presents the first molecular detection of A. typica and A. ziphidarum in S. scrofa. Thus, this fish species is a new host for A. typica and A. ziphidarum. This is also the first report of the presence of A. ziphidarum in the Aegean Sea.     

Anisakis – A food-borne parasite that triggers allergic host defences

Anisakis is a parasitic nematode which infects fish and marine invertebrates, including crustaceans and molluscs. Ingestion of contaminated seafood can cause acute gastrointestinal diseases. Infection can be accompanied by severe allergic reactions such as urticaria, angioedema and anaphylaxis. Diagnosis of allergy due to Anisakis currently relies on the detection of serum IgE antibodies to allergenic proteins and a history of reactions upon exposure to fish. Anisakis proteins demonstrate considerable immunological cross-reactivity to proteins of related nematodes and other invertebrates such as crustaceans and house dust-mites. In contrast, very limited molecular associations with other parasite groups are observed, including trematodes and cestodes. This review outlines current knowledge on Anisakis as a food-borne parasite, with special focus on the underlying immunological mechanisms resulting in allergic host defence responses.     

Relationships between otolith and fish size from Mediterranean and north‐eastern Atlantic species to be used in predator–prey studies

Regressions between fish length and otolith size are provided for 40 species from the north‐eastern Atlantic Ocean and 142 species from the Mediterranean Sea. Regressions were also estimated at genus level. Most of the regressions (c. 84%) explained a high percentage of the deviance (>75%).     

Ascaridoid parasites infecting in the frequently consumed marine fishes in the coastal area of China: A preliminary investigation

Marine fishes represent the important components of the diet in the coastal areas of China and they are also natural hosts of various parasites. However, to date, little is known about the occurrence of ascaridoid parasites in the frequently consumed marine fishes in China. In order to determine the presence of ascaridoid parasites in the frequently consumed marine fishes in the coastal town Huizhou, Guangdong Province, China, 211 fish representing 45 species caught from the South China Sea (off Daya Gulf) were examined. Five species of ascaridoid nematodes at different developmental stages were detected in the marine fishes examined herein, including third-stage larva of Anisakis typica (Diesing, 1860), third and fourth-stage larvae of Hysterothylacium sp. IV-A of Shamsi, Gasser & Beveridge, 2013, adult and third-stage larvae of Hysterothylacium zhoushanense Li, Liu & Zhang, 2014, adults and third-stage larvae of Raphidascaris lophii (Wu, 1949) and adults of Raphidascaris longispicula Li, Liu & Zhang, 2012. The overall prevalence of infection is 18.0%. Of them, Hysterothylacium sp. IV-A with the highest prevalence (17.5%) and intensity (mean = 14.6) of infection was the predominant species. The prevalence and intensity of A. typica were very low (1/211 of marine fish infected with an intensity of one parasite per fish). The morphological and molecular characterization of all nematode species was provided. A cladistic analysis based on ITS sequence was constructed in order to determine the phylogenetic relationships of these ascaridoid parasites obtained herein. The present study provided important information on the occurrence and diagnosis of ascaridoid nematodes in the commercially important marine fishes from the South China Sea. The low level of infection and the species composition of ascaridoid nematodes seem to indicate the presence of low risk of human anisakidosis when local population consumed these marine fishes examined herein.     

Genetic markers in the study of Anisakis typica (Diesing, 1860): larval identification and genetic relationships with other species of Anisakis Dujardin, 1845 (Nematoda: Anisakidae)

Genetic variation at 21 gene-enzyme systems was studied in a sample of an adult population of Anisakis typica (Diesing, 1860) recovered in the dolphin Sotalia fluviatilis from the Atlantic coast of Brazil. The characteristic alleles, detected in this population, made it possible to identify as A. typica, Anisakis larvae with a Type I morphology (sensu Berland, 1961) from various fishes: Thunnus thynnus and Auxis thazard from Brazil waters, Trachurus picturatus and Scomber japonicus from Madeiran waters, Scomberomorus commerson, Euthynnus affinis, Sarda orientalis and Coryphaena hippurus from the Somali coast of the Indian Ocean, and Merluccius merluccius from the Eastern Mediterranean. Characteristic allozymes are given for the identification, at any life-stage and in both sexes, of A. typica and the other Anisakis species so far studied genetically. The distribution of A. typica in warmer temperate and tropical waters is confirmed; the definitive hosts so far identified for this species belong to delphinids, phocoenids and pontoporids. The present findings represent the first established records of intermediate/paratenic hosts of A. typica and extend its range to Somali waters of the Indian Ocean and to the Eastern Mediterranean Sea. A remarkable genetic homogeneity was observed in larval and adult samples of A. typica despite their different geographical origin; interpopulation genetic distances were low, ranging from D _Nei=0.004 (Eastern Mediterranean versus Somali) to D _Nei=0.010 (Brazilian versus Somali). Accordingly, indirect estimates of gene flow gave a rather high average value of Nm = 6.00. Genetic divergence of A. typica was, on average, D _Nei=1.12 from the members of the A. simplex complex (A. simplex s.s, A. pegreffii, A. simplex C) and D _Nei=1.41 from A. ziphidarum, which all share Type I larvae; higher values were found from both A. physeteris (D _Nei=2.77)     

New data on the morphology of <Emphasis Type="Italic">Spinitectus oviflagellis</Emphasis> Fourment, 1884 (Nematoda: Cystidicolidae) from the pyloric caeca of <Emphasis Type="Italic">Macrourus berglax</Emphasis> (Macrouridae) in the eastern Greenland Sea

Specimens of a little-known nematode, Spinitectus oviflagellis Fourment, 1884, the type-species of Spinitectus Fourment, 1884, were collected mainly from the pyloric caeca of a marine deep-water fish, the onion-eye grenadier Macrourus berglax Lacépède (a new host record), in the eastern Greenland Sea, North Atlantic Ocean. Studies using light and scanning electron microscopy revealed some taxonomically important, previously unreported features of S. oviflagellis, such as the detailed structure of the cephalic end, the position of the excretory pore and the presence of ventral pre-anal cuticular ridges (area rugosa) in the male, which indicated a certain degree of intraspecific biometrical variability in this species. S. oviflagellis is compared with similar congeneric species parasitising marine fishes.