Nematode parasites in teleosts from 0 to 1540 m depth off the faroe islands (The North Atlantic)

Redescriptions of Spinitectus acipenseri and S. micracanthus (Nematoda, Cystidicolidae), with notes on the taxonomy of Spinitectus-like nematodes parasitising North American fishes

Based on light microscopical and scanning electron microscopical (SEM) examinations, two North American species of Spinitectus Fourment, 1884, S. acipenseri Choudhury & Dick, 1992 and S. micracanthus Christian, 1972 (Nematoda, Cystidicolidae) are redescribed from museum voucher specimens (S. acipenseri) and those newly collected from centrarchid and some other fishes in the Upper San Marcos River in Texas and the Santee River in South Carolina, USA. The first use of SEM to study S. acipenseri, a parasite of lake sturgeon Acipenser fulvescens Rafinesque (Acipenseridae) in Canada, made it possible to describe dorsal and ventral lips, amphids and sublabia, and the presence of a dorsal barb on the right spicule, which was confirmed to be the most characteristic feature of this species. The SEM study of S. micracanthus, a parasite mainly of centrarchids, enabled us to correctly determine the location of the excretory pore in relation to rings of cuticular spines in the male, and to describe the exact structure of the tip of the male tail, sublabia, phasmids and the presence of a median ventral protuberance on the male tail. Some taxonomic problems of North American species of Spinitectus are discussed. Filaria serrata Linton, 1901 is considered a junior synonym of S. oviflagellis Fourment, 1884. To date, there are 13 valid species of Spinitectus parasitising fishes in North America. Keys to species of Spinitectus-like nematodes from fishes in North American waters are provided.

New records of spirurid nematodes (Nematoda, Spirurida, Guyanemidae, Philometridae & Cystidicolidae) from marine fishes off New Caledonia, with redescriptions of two species and erection of Ichthyofilaroides n. gen

Recent examinations of spirurid nematodes (Spirurida) from deep-sea or coral reef marine fishes off New Caledonia, collected in the years 2006–2009, revealed the presence of the following five species: Ichthyofilaroides novaecaledoniensis (Moravec et Justine, 2009) n. gen., n. comb. (transferred from Ichthyofilaria Yamaguti, 1935) (females) (Guyanemidae) from the deep-sea fish Hoplichthys citrinus (Hoplichthyidae, Scorpaeniformes), Philometra sp. (male fourth-stage larva and mature female) (Philometridae) from Epinephelus maculatus (Serranidae, Perciformes), Ascarophis (Dentiascarophis) adioryx Machida, 1981 (female) (Cystidicolidae) from Sargocentron spiniferum (Holocentridae, Beryciformes), Ascarophis (Ascarophis) nasonis Machida, 1981 (males and females) from Naso lituratus and N. unicornis (Acanthuridae, Perciformes), and Ascarophisnema tridentatum Moravec et Justine, 2010 (female) from Gymnocranius grandoculis (Lethrinidae, Perciformes). Two species, I. novaecaledoniensis and A. nasonis, are redescribed based on light microscopical (LM) and scanning electron microscopical (SEM) examinations, the latter used in these species for the first time. Morphological data on the specimen of A. tridentatum from the new host species are provided. Philometra sp. (from E. maculatus) most probably represents a new gonad-infecting species of this genus. The newly established genus Ichthyofilaroides n. gen. is characterized mainly by the presence of a small buccal capsule and by the number and distribution of cephalic papillae in the female; it is the sixth genus in the Guyanemidae.

A new species of Hamaticolax (Copepoda: Bomolochidae) from Helicolenus dactylopterus (Delaroche, 1809) (Scorpaeniformes: Sebastidae) in NW Mediterranean deep waters and notes on patterns of host use and host-specificity of the genus

Hamaticolax juanji n. sp. is described from specimens collected from the blackbelly rosefish Helicolenus dactylopterus Delaroche 1809 (Scorpaeniformes: Sebastidae). It is the second Hamaticolax species described and reported from the Mediterranean Sea, after Ha. resupinus Pérez-i-García, Carrassón and Boxshall, 2017. It is distinguished from Ha. resupinus by the presence of only one dorsal naked seta on the third segment of the antennule (vs. four), two unequal short naked setae in distal part of the antenna (vs. four), and the absence of a minute spine on the third endopodal segment of leg 1, among others. It is differentiated from Ha. prolixus Cressey 1969 by a comparatively reduced fourth pedigerous somite, the presence of two naked setae on the third segment of the antennule (vs. three), two naked setae and three curved claws in the distal part of the apical segment of the antenna (vs. three and four), an outer naked seta on the basis of leg 2, and by larger length/width ratio of the third endopodal segment, among others. Hamaticolax juanji n. sp. also has relatively longer inner setae on the first and second endopodal segments of leg 4 than the two former species. Patterns of host-use and host-specificity of the genus Hamaticolax are also discussed. The frequently observed low host-specificity of its members may be better explained by host ecological similarity and host availability phenomena, rather than by host phylogenetic distance.

Parasite fauna of Antarctic Macrourus whitsoni (Gadiformes: Macrouridae) in comparison with closely related macrourids

BACKGROUND

The extreme, isolated environment within the Antarctic Convergence has fuelled the evolution of a highly endemic fauna with unique adaptations. One species known from this area is the Whitson's grenadier Macrourus whitsoni (Regan, 1913). While closely related species occurring in the Northern Hemisphere were targets of a variety of studies, knowledge on M. whitsoni is scarce, including not only its ecology but also its parasite fauna. Parasites, an often overlooked but important component of every ecosystem, can provide important insights into host ecology, including feeding habits, food web interactions and distribution patterns. The aim of our study was to increase the currently limited knowledge on the ecology of M. whitsoni and its parasite life-cycles.

METHODS

In this study, parasite fauna and stomach content of 50 specimens of M. whitsoni were sampled off Elephant and King George Islands. Fish samples were morphological, food ecological and parasitological examined and parasites morphological and partly molecular identified. To evaluate the findings, results were compared with other macrourid species.

RESULTS

The parasite fauna of M. whitsoni revealed 9 genera and 17 species. Stomach content analysis indicated Amphipoda and Mysida as the primary food source. Considering the parasites of M. whitsoni, the highest diversity was found within the Digenea, while prevalence was highest for the Acanthocephala and Nematoda. The diverse parasite fauna of M. whitsoni together with the stomach content analysis, suggests a benthopelagic mode of life. Furthermore, an extensive evaluation of the parasite fauna of species of the Macrourinae was conducted, which is probably the most thorough one yet, to compare the findings with closely related host fish species. A similarity analysis revealed a strong connection between the parasite fauna composition and geographical distribution, with a clear separation between the parasite faunas in fishes sampled in the Pacific and the Atlantic Oceans.

CONCLUSIONS

Due to the isolated habitat within the Antarctic Conversion, the parasite fauna of M. whitsoni differs clearly from those of closely related and closely occurring species of the genus Macrourus. Our study revealed an endemically dominated parasite fauna, with parasites often host-specific to M. whitsoni. The comparison with the faunas of other species of the Macrourinae revealed a largely endemic parasite fauna, which emphasizes again the isolated character of the Antarctic shelf regions.

Molecular identification of Hysterothylacium aduncum specimens isolated from commercially important fish species of Eastern Mediterranean Sea using mtDNA cox1 and ITS rDNA gene sequences

The presence of a Raphidascarid parasitic nematode Hysterothylacium aduncum (Rudolphi, 1802) in two sparid fish (Sparus aurata and Diplodus vulgaris) and one soleid fish (Solea solea) was investigated in this study. A total of 868 individuals; 385 S. aurata, 437 D. vulgaris and 46 S. solea were collected from the Mersin Bay between February 2013 and January 2014 and examined. Variations in the prevalence, mean intensity, and mean abundance of the parasite were 14.55%, 2.05, and 0.30 for S. aurata, 4.12%, 2.44, and 0.10 for D. vulgaris, and 15.22%, 3.29, and 0.50 for S. sole respectively. Nucleotide sequences of 1398 base pair long fragment of 18S rRNA-ITS1-5.8S rRNA-ITS2-28S rRNA region and 641 base pair long fragment of mtDNA cytochrome c oxidase I (cox1) gene were used in molecular identification of isolated parasites at species level. All the parasite samples were identified as H. aduncum based on nucleotide sequence comparisons. Both ITS rDNA and mtDNA cox1 sequences revealed a genetic variation among H. aduncum specimens isolated from different fish species, while only mtDNA cox1 sequences were indicating a mean genetic distance of 0.010 among H. aduncum specimens of the same host species.

Peppermint (Mentha piperita) and albendazole against anisakiasis in an animal model

OBJECTIVES

Therapy against anisakiasis requires invasive techniques to extract L3 , and an effective drug against this nematode is needed. The aim of this study was to determine the efficacy of peppermint essential oil (EO) and its main components against the parasite in comparison to albendazole, a drug currently prescribed to treat anisakiasis.

METHODS

We conducted in vitro experiments and studied an experimental model simulating the human infection in Wistar rats. We used polymerase chain reaction restriction fragment length polymorphism to identify A. simplex s.s. and A. pegreffii and determine any differences in their pathogenicity and susceptibility to the treatments.

RESULTS

The in vitro and in vivo experiments both showed that the larvicidal activity of peppermint EO, menthol, menthone and menthyl acetate is higher than that of albendazole. Large stomach lesions were observed in 46.7% of the albendazole-treated rats, whereas no gastrointestinal lesions were detected in those treated with peppermint EO, menthol, menthyl acetate or menthone.

CONCLUSIONS

In this animal model, treatment with peppermint EO or its main components was more effective than was treatment with albendazole. Lesions were more frequently produced by A. simplex s.s. larvae than by A. pegreffii larvae.

A scoring system approach for the parasite predictive assessment of fish lots: a proof of concept with anisakids

A total of 982 individuals distributed in 11 lots belonging to 10 fish species from three Atlantic FAO fishing areas were sampled and examined to detect the presence of anisakid larvae in fish muscle. After hazard identification by genetic sequencing and exposure assessment by anatomic extent and demographic characterization of infection, all data were fitted for each fish species to a new proposed scoring schema of parasite prediction. In the absence of a criterion standard method for inspection and precise definition of the quantum satis for parasites in contaminated fish lots, the inspection rating scheme called SADE (Site of infection, Assurance of quality, Demography, Epidemiology) may help fish industries to precisely handle and to evaluate the likely outcome of infected fish lots after being diagnosed. For this purpose, a supporting flow diagram for decision was defined and suggested. This new performance assessment tool has the aim of staging fish lots, thus helping in planning manufacture, commercial, and research decisions during self-management programs. This novel scoring system provides an improved inspection format by implementing the occurrence stratification for parasites to guide Hazard Analysis and Critical Control Points (HACCP) programs for the uniform exchange of information among fish industries, administration and researchers, thus facilitating standardization and communication. In the future, this scoring version could be validated (in terms of classification and wording) for similar overall predictive purposes in other muscular parasites infecting seafood products.

Epidemiology and molecular identification of Anisakis pegreffii (Nematoda: Anisakidae) in the horse mackerel Trachurus trachurus from northern Morocco

Anisakis infection parameters were studied in horse mackerel (Trachurus trachurus) taken from two areas of northern Morocco (Tetouan and Tangier), which showed a mean prevalence of 54.9%. Identification of the ITS1–5.8S–ITS2 fragment by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) showed A. pegreffii to be the dominant species; no A. simplex s.s. were detected. The presence of A. pegreffii in horse mackerel was not influenced by the sex (P= 0.46) or catch area (Atlantic versus Mediterranean, P= 0.52) of the fish, but was significantly related to their length, weight, liver weight and gonad weight, and to the season of their capture (P< 0.05). A low prevalence (8.6%) and mean intensity (1.0) was detected in the muscle, probably related to the reduced ability of A. pegreffii to penetrate muscle. The risk of the presence of A. pegreffii in the muscle was fivefold higher in fish caught during the summer than during any other season. Susceptible members of the human population can minimize the risk of infection by avoiding the consumption of larger horse mackerel specimens during the summer.

Anisakis simplex s.l. parasitization in mackerel (Scomber japonicus) caught in the North of Morocco--prevalence and analysis of risk factors

Consumption of mackerel (Scomber japonicus) is very widespread in Morocco, where its production is an important economic pillar. We investigated the prevalence of infection by Anisakis spp. in mackerel caught in Moroccan waters, analyzing infection risk factors. The prevalence was generally higher in fish from the Atlantic (67.9%) than from the Mediterranean (57.0%), but they did not differ in the mean abundance, intensity, or prevalence of muscle parasitization. A. pegreffii was the predominant species (82.6% of larvae) followed by the hybrid A. simplex s.s./A. pegreffii (16.3%). Only one L3 of A. simplex s.s. was found in a specimen of S. japonicus from the Atlantic. Mackerel infection was associated with total fish weight, gonad weight, catch area, and catch season. However, muscle infection was associated solely with total weight and parasite loads. The consumption of lower-weight mackerel may be a good prophylactic measure against human anisakiasis.

Males of Ichthyofilaria argentinensis Incorvaia, 1999 and I. bergensis (Wülker, 1930) (Dracunculoidea:Guyanemidae): new morphological aspects and emendation of the generic diagnosis

Abstract: The adult male of dracunculoid nematode Ichthyofilaria argentinensis Incorvaia, 1999 (Guyanemidae) is described for the first time based on specimens found in the swimbladder of its type host, Merluccius hubbsi Marini (Merlucciidae), caught off the coast of Buenos Aires, Argentina (western Atlantic Ocean). In addition, the males of Ichthyofilaria bergensis (Wülker, 1930) Køie, 1993 are redescribed from specimens collected from the body cavity and visceral surface of Molva macrophthalma (Rafinesque) (Lotidae) caught in the western Mediterranean Sea, off the coast of Sardinia. Light and scanning electron microscopy examinations revealed some new morphological features for the genus, such as a pair of deirids located near the end of muscular oesophagus, the body wall conspicuously twisted immediately anterior to the cloaca, the presence of a copulatory plate, one pair of adcloacal papillae and a pair of phasmids situated on the posterior half of the tail. On the basis of this material, the generic diagnosis of Ichthyofilaria is modified to include some of these newly observed features, as well as to indicate the absence of spicules. The diagnosis of Guyanemidae is extended to include that a copulatory plate and/or two spicules may be present as characteristics for this family.

Two new species of cystidicolid nematodes from the digestive tract of the deep-sea fish Coryphaenoides mediterraneus (Giglioli) (Macrouridae) from the Mid-Atlantic Ridge

Two new nematode species, Ascarophis longiovata n. sp. and Neoascarophis longispicula n. sp. (Cystidicolidae), are described from the digestive tract of the marine deep-water fish, the Mediterranean grenadier Coryphaenoides mediterraneus (Giglioli), from the Mid-Atlantic Ridge. The former species is characterised mainly by the structure of the mouth (large pseudolabia, each with well-developed dorsal and ventral extension and small apical protrusion; submedian labia almost absent), the large, elongate-oval, non-filamented eggs (60-66 x 18-27 microm), a cervical inflation of the cuticle, bifurcate deirids, and the length of the spicules (315-360 and 120-147 microm), whereas the latter (only males available) can be distinguished by the length of the spicules (960-1,149 and 258-351 microm) and their length ratio (1:1.91-2.71), the shape of the deirids (bifurcate, with long, narrow posterior arms), and the location of the excretory pore and deirids well posterior to the level of the nerve-ring.

Anisakid parasites of the pouting (Trisopterus luscus) from the Cantabrian Sea coast, Bay of Biscay, Spain

An epidemiological survey was undertaken of anisakids in 139 specimens (length: 13.2–24.5 cm) of pouting or bib (Trisopterus luscus) captured off the coast of northern Spain in the Cantabrian Sea. Third-stage larvae of two species of nematodes, Anisakis larvae type I and Hysterothylacium aduncum, were isolated. One adult female H. aduncum was also detected in the intestine of one pouting. Total prevalence of anisakids was 88.5%. Hysterothylacium aduncum and Anisakis showed, respectively, prevalence of 87.8% and 22.3%, mean intensity of 19.7 and 3.5, and mean abundance of 17.3 and 0.8. Analysis of infection parameters as a function of host length revealed a much higher prevalence in pouting specimens with length < 20 cm (94.4% for H. aduncum; 28.0% for Anisakis) than in those with length ≥ 20 cm (65.6% for H. aduncum; 3.1% for Anisakis). The high mean intensity of Anisakis in muscle of parasitized pouting (5.9) may pose human health risks, although these are minimized by eating only thoroughly cooked pouting, as is the custom in Spain.

Composition and structure of the parasite faunas of cod, Gadus morhua L. (Teleostei: Gadidae), in the North East Atlantic

Background

Although numerous studies on parasites of the Atlantic cod, Gadus morhua L. have been conducted in the North Atlantic, comparative analyses on local cod parasite faunas are virtually lacking. The present study is based on examination of large samples of cod from six geographical areas of the North East Atlantic which yielded abundant baseline data on parasite distribution and abundance.

Materials and Methods

A total of 826 fish was sampled in the Baltic, Celtic, Irish and North seas, Icelandic waters and Trondheimsfjord (Norway) in 2002 (spring and autumn) and 2003 (spring). The gills and internal organs (oesophagus, stomach, intestine, pyloric caeca, liver, heart, spleen, gall bladder and gonads) were examined for macroparasites following a standardised protocol. The taxonomic consistency of the identification was ensured thorough the entire study.

Results

We discuss some problems in parasite identification, outline the composition of the parasite faunas in cod in the six North East Atlantic regions, provide novel data on parasite prevalence and abundance and a comparative assessment of the structure of the regional parasite faunas with respect to the higher-level taxonomic groupings, host specificity and zoogeographical distribution of the parasites. Altogether 57 different parasite forms were found including seven new host records (Diclidophora merlangi, Rhipidocotyle sp., Fellodistomum sp., Steringotrema sp., Cucullanus sp., Spinitectus sp., and Chondracanthus ornatus). The predominant groups of cod parasites were trematodes (19 species) and nematodes (13 species) including larval anisakids which comprised 58.2% of the total number of individuals.

Conclusion

Our study reveals relatively rich regional parasite faunas in cod from the North East Atlantic which are dominated by generalist parasites with Arcto-Boreal distribution. Further, it provides more detailed data on the distribution in the North East Atlantic of the majority of cod parasites which may serve as baselines for future studies on the effect of climate change. Based on the faunal comparisons, predictions can be made in relation to the structure and diversity of the parasite communities in the North East Atlantic regions studied.

Parasite communities of eels Anguilla anguilla in freshwater and marine habitats in Iceland in comparison with other parasite communities of eels in Europe

Ninety-five eels from one marine and three freshwater localities in Iceland were examined for parasites. Twenty species were found, 12 from marine habitat, 12 from freshwater and 4 species were found in both habitats. These are: Eimeria anguillae, Chilodonella hexasticha, Trichodina fultoni, T. jadranica, Myxidium giardi, Myxobolus kotlani, two Zschokkella spp., Derogenes varicus, Deropristis inflata, Diplostonmum sp., Plagioporus angulatus, Podocotyle atomon, Anisakis simplex (larva), Eustrongylides sp. (larva), Hysterothylacium aduncum (larva), Raphidascaris acus (larval and adult stages), Bothriocephalus claviceps, Proteocephalus macrocephalus, and a pseudophyllidean larva. Thirteen of these species are new parasite records from Icelandic waters. The component community of marine eels was characterized by low diversity and a high dominance of a single species. Overall, seven species of helminths were observed, up to five different species occurring in an individual fish. The component community of the freshwater eels was species-poor with low diversity and relatively high dominance of single species. A between-sites difference in the freshwater eels was considerable; only Diplositonun sp. was found at more then one sampling site. Similar to previous studies, there is a total replacement of freshwater macroparasite species by marine ones in saline waters. But unlike research abroad in which species richness decreases with higher salinity, the marine eels in Iceland have considerably higher richness than the freshwater ones. The parasite communities of freshwater eels in Iceland are, in general species-poorer, less diverse and having higher Berger Parker (BP) dominance than other eel communities in Europe. Marine eels have on the other hand comparable species richness, are less diverse and with a high BP dominance.

Endoparasites of the blue whiting, Micromesistius poutassou from north-west Spain

The communities of metazoan endoparasites of blue whiting, Micromesistius poutassou, in waters of north-west Spain were analysed and a geographical comparison made with other localities. Four hundred blue whiting collected in July 1999 and September 2000 were examined for parasites, excluding the head and gills. Six species were found: Anisakis simplex s.l. (L3), A. physeteris (L3), Hysterothylacium aduncum (L2 and L3), Stephanostomum lophii (metacercaria), S. pristis (adult), and Prosorhynchus crucibulum (metacercaria). The latter is a new host record, and A. physeteris is reported for the first time in blue whiting from the north-east Atlantic. Host gender was not a significant predictor of abundance of any helminth species, and host length was only weakly and positively related to the abundance of A. simplex. Infracommunities were species-poor, with 56% of fish harbouring only one parasite species, and 92% up to two species. Infracommunities were strongly dominated by A. simplex (389 fish) or S. lophii (6 fish). Fish length or gender, and the year of capture, did not affect species richness nor the degree of dominance. There were no significant pair-wise associations between species. Infracommunities were basically composed of several allogenic parasites with different life histories that converge in the blue whiting through the local food web. The parasite fauna of blue whiting in the study area was poor and distinctive compared with that of other localities in the north-east North Atlantic. These peculiarities might primarily be related to the composition of the local community of definitive hosts, although there might also be some influence of the geographical distribution of parasites.

New data on the morphology of Spinitectus oviflagellis Fourment, 1884 (Nematoda: Cystidicolidae) from the pyloric caeca of Macrourus berglax (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.

Anisakid parasites of two forkbeards (Phycis blennoides and Phycis phycis) from the Mediterranean coasts of Andalucía (Southern Spain)

An epidemiological survey of anisakids was carried out on 209 specimens of greater forkbeard (Phycis blennoides) and 58 of forkbeard (Phycis phycis) captured off the Mediterranean coasts of Andalucía (southern Spain). Four species of nematodes were identified: Anisakis simplex s.l., Anisakis physeteris, Hysterothylacium aduncum and Hysterothylacium fabri. The total prevalence was 62.06% in the forkbeard and 58.85% in the greater forkbeard. The highest values of prevalence (56.90%), mean intensity (5.21) and mean abundance (2.96) were all obtained for H. fabri in the forkbeard. The most frequent parasite in the greater forkbeard was H. aduncum with 51.20% prevalence and values of 3.00 and 1.53 for mean intensity and mean abundance, respectively. The infestation parameters were also analyzed according to the host length, observing a maximum of parasitized fish (91.67%) in samples of P. blennoides longer than 40 cm, while in P. phycis, the highest prevalence (82.35%), conditioned by H. fabri parasitization, was found in fish with lengths between 30 and 35 cm.

Structure of Anisakis simplex s.l. populations in a region sympatric for A. pegreffii and A. simplex s.s

The aim of this study was to determine the genetic structure of A. simplex s.l. populations. This was done by applying PCR-RFLP and RAPD-PCR to 42 specimens morphologically identified as third stage larvae of A. simplex s.l. Of these larvae, 59.26% of those of Mediterranean origin are identified by PCR-RFLP as A. pegreffii. In Atlantic waters, this percentage dropped to 20.00% while A. simplex s.s. represents 66.67%. However, findings seem to suggest that the taxonomic status of both species should be reconsidered owing to: (i) the high gene flow value that we detected between A. simplex s.s. and A. pegreffii; (ii) the short genetic distance between both members of the A. simplex complex; (iii) the fact that hybrid genotypes represent 16.67% of the parasites analyzed and are represented in all the populations studied, except for the Cantabrian one. When the genetic variation is estimated between the 42 individual A. simplex s.l. specimens studied these can be classified into four groups. The genetic distances and gene flow between three of them are compatible with the existence of three different genetic populations. The fourth is comprised of a single specimen of L3, identified both by PCR-RFLP and by RAPD-PCR as a new genotype.

The life-cycle of the flatfish nematode Cucullanus heterochrous

Mature specimens of Cucullanus heterochrous Rudolphi, 1802 (Nematoda: Cucullanidae) were obtained from the intestine of the flounder, Platichthys flesus, from Danish waters. Eggs embryonate in seawater but do not hatch. Fully developed larvae pressed out of eggs are 430 microm long with amphids and dereids and enclosed within the cuticle of a previous larval stage. Infective larvae are believed to be in their third stage. Experimental studies showed that the polychaetes, Nereis spp., Scoloplos armiger, Brada villosa and Capitella sp., may act as intermediate hosts. In N. diversicolor the larvae increase their length to 1 mm within four weeks (15 degrees C) without moulting. Experimental infections showed that larvated eggs are not infective to fish, whereas >550 microm long larvae from polychaetes survived in 4-24 cm long flounders and plaice, Pleuronectes platessa. Third-stage larvae 550 microm to 1.1 mm long were found in the submucosa of the intestine one week post infection. At a length of about 800 microm to 1.4 mm they moult to fourth-stage larvae. Fourth-stage larvae, immature and mature worms occur in the intestine and rectum. Fourth-stage larvae and adults survived experimental transfer from one flounder to another. Similar developmental stages survived for two weeks in the intestine of experimentally infected cod, Gadus morhua.

Larval anisakids parasitizing the blue whiting, Micromesistius poutassou, from Motril Bay in the Mediterranean region of southern Spain

A total of 301 blue whiting, Micromesistius poutassou Risso, 1826, ranging in length from 17 to 28 cm, from Motril Bay (Mediterranean coast, south Spain) were examined for anisakid nematodes, as these fish are common items in the Spanish Mediterranean diet. Three anisakid species were morphologically identified with a total prevalence of 10.63%. Anisakis simplex s.l. Rudolphi, 1809 had a prevalence value of 6.65%, compared with 2.66% for A. physeteris Baylis, 1923 and 2.33% for Hysterothylacium aduncum Rudolphi, 1802. Variations in prevalence values with season and host size are discussed. Allozyme markers (leucine aminopeptidase-1) were used to identify anisakid nematodes assigned to the A. simplex complex and all examined larvae were found to correspond genetically to A. pegreffii Nascetti et al., 1986.

Life cycle and seasonal dynamics of Cucullanus cirratus O.F. Müller, 1777 (Nematoda, Ascaridida, Seuratoidea, Cucullanidae) in Atlantic cod, Gadus morhua L

Mature specimens of Cucullanus cirratus O.F. Müller, 1777 (Cucullanidae) were obtained from the pyloric caeca and intestine of Atlantic cod, Gadus morhua L., from Danish waters. Eggs embryonate in seawater. Third-stage larvae about 400 µm long, with amphids and dereids, hatch from the egg. Experimental studies indicated that third-stage larvae were infective to calanoid and cyclopoid copepods and sand gobies, Pomatoschistus minutus (Pisces, Gobiidae). Larvae entered the haemocoel of copepods but did not grow. In gobies, the third-stage larvae entered the intestinal mucosa and grew to 800 µm in length within 6 months. They were not encapsulated. Experimental infections of cod (8-30 cm long) showed that free-living third-stage larvae are not infective, whereas >700 µm long third-stage larvae from gobies survived in the cod. Third-stage larvae 700-1200 µm long occur in the stomach mucosa, where they develop and moult to fourth-stage larvae. The fourth-stage larvae then migrate to the pyloric caeca and anterior part of the intestine, where they moult and develop to the mature adult stage. No developmental stage became encapsulated. Naturally infected cod (>20 cm total length) harboured moulting third-stage larvae and <2 mm long fourth-stage larvae 2 months post capture. Naturally infected 4- to 5-month-old codlings (8-10 cm total length) harboured 2-3 mm long fourth-stage larvae only, indicating that they acquired the third-stage larvae as planktivorous fry only a few centimetres long. Cucullanus cirratus may have a life-cycle that involves copepod transport hosts and fish (gobies or cod fry) intermediate hosts. Postcyclic development occurs in gadoids when an infected cod is consumed by another cod (cannibalism). Examinations of 350 (8-78 cm total length) naturally infected cod showed that group 1 and older cod are infected throughout the year, with maximum prevalence of third-stage larvae in spring and summer. The greatest prevalence of gravid worms was observed in autumn.

The life cycle of Contracaecum osculatum (Rudolphi, 1802) sensu stricto (Nematoda, Ascaridoidea, Anisakidae) in view of experimental infections

Hatched, ensheathed third-stage larvae of Contracaecum osculatum, 300-320 microns long, were shown to be infective to copepods, to nauplius larvae of Balanus and to small specimens of fishes (sticklebacks, O-group eelpout). Other fishes such as gobies and small flatfishes became infected by ingesting infected crustaceans. Cod were infected by being given infected small fishes. In the crustacean paratenic hosts, little growth of the larvae occurred, if any. In the liver sinusoids of sticklebacks and gobies the length of most of the unencapsulated third-stage larvae had not even doubled within 6 months of infection. The fate of larvae (max. 2 mm long) given to cod via infected intermediate fish hosts was apparently decided by the size of the larvae only. Small larvae became encapsulated and eventually died in the liver and wall of the gastrointestinal tract. Larger larvae migrated to the liver parenchyma, where some grew to a length of as much as 10 mm. The growth of the larvae in sticklebacks was shown not to be affected by an increase in temperature (infected fish being transferred from 8 degrees to 14 degrees and 20 degrees C), by the intensity of infection and, partly, by the age of infection (e.g. some 2-week-old and 6-month-old larvae were of identical size). In the liver and mesentery of plaice the third-stage larvae developed via copepod paratenic hosts to infectivity (i.e. to more than 4 mm in length), showing that the life cycle may be completed with an optional paratenic invertebrate host and only one intermediate fish host.(ABSTRACT TRUNCATED AT 250 WORDS)