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Gary Mcclelland - One of the best experts on this subject based on the ideXlab platform.
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the trouble with sealworms Pseudoterranova decipiens species complex nematoda a review
Parasitology, 2002Co-Authors: Gary McclellandAbstract:: Sealworms or codworms, larvae of ascaridoid nematodes belonging to the Pseudoterranova decipiens species complex, infect the flesh of numerous species of marine and euryhaline fish, and have proven a chronic and costly cosmetic problem for seafood processors. Moreover, the parasite may cause abdominal discomfort in humans when consumed in raw, undercooked or lightly marinated fish. In this review, the phylogeny, life cycle and distributions of sealworms are discussed along with biotic and abiotic factors which may influence distributions of these parasites in their intermediate and final hosts. Also considered here are efforts to control the problem through commercial fishing practices, fish processing technology, and the reduction of infection parameters in marine fish populations by biological means. Ironically, concern over sealworm problem has subsided in some fisheries in recent years, not as a result of falling infection parameters in fish stocks or innovations in processing technology, but as a consequence of declines in abundance and size of groundfish.
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spatial and temporal distributions of larval sealworm Pseudoterranova decipiens nematoda anisakinae in hippoglossoides platessoides pleuronectidae in eastern canada from 1980 to 1990
Journal of Materials Science, 2000Co-Authors: Gary Mcclelland, R K Misra, D. J. MartellAbstract:McClelland, G., Misra, R. K., and Martell, D. J. 2000. Spatial and temporal distributions of larval sealworm (Pseudoterranova decipiens, Nematoda: Anisakinae), in Hippoglossoides platessoides (Pleuronectidae) in eastern Canada from 1980 to 1990. – ICES Journal of Marine Science, 57: 69–88. Larval sealworm (Pseudoterranova decipiens) infections were surveyed in the fillets and napes of 28 065 Canadian plaice (Hippoglossoides platessoides), 31–40 cm in length, collected throughout Atlantic Canada between February 1980 and August 1990. Samples were taken from 11 locations in a 1980–1982 survey, and from 38 to 55 locations in 1983–1984, 1985–1986, 1987–1988, and 1989–1990 surveys. Prevalence (P) and abundance (A) of P. decipiens were greatest (P=96–100%, A=12.47–22.32) in 1989–1990 samples from the central Scotian Shelf near Sable Island, while plaice from northeastern Newfoundland and the Grand Banks were seldom infected (P<1%). Temporal trend analyses revealed that between 1980 and 1990, sealworm infection levels increased significantly in plaice in 33 of 41 locations in the Gulf of St Lawrence, on the Breton and Scotian shelves, and in the Gulf of Maine. Spatial and temporal distributions of larval P. decipiens in plaice seemed to reflect the distribution and growing abundance of grey seals (Halichoerus grypus), important definitive hosts of the parasite, but increases in levels of infection over the course of the decade may also have been promoted by a period of relatively high near-bottom temperatures in Atlantic Canadian waters in the late 1970s and early 1980s. A more recent cooling trend in near-bottom temperature or other negative influences, such as sealworm density limiting mechanisms in fish and seal hosts, may have resulted in the stabilization or decline of sealworm levels in some plaice populations in the late 1980s and early 1990s. 2000 International Council for the Exploration of the Sea
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transmission of Pseudoterranova decipiens nematoda ascaridoidea via benthic macrofauna to sympatric flatfishes hippoglossoides platessoides pleuronectes ferrugineus p americanus on sable island bank canada
Marine Biology, 1995Co-Authors: D. J. Martell, Gary McclellandAbstract:Larval ascaridoid nematodes were surveyed in three flatfish species, Hippoglossoides platessoides, Pleuronectes ferrugineus, and P. americanus, from Sable Island Bank in February and June 1989. Pseudoterranova decipiens (sealworm) abundances differed significantly with both host species, the heaviest levels being found in H. platessoides, and host length, infections generally increasing with length, but not between February and June samples. Moderate numbers of larvae were found in P. ferrugineus while P. americanus were seldom infected. Two third-stage P. decipiens larvae (L3), 3.2 and 7.0 mm in length, were recovered from the cephalothoraxes of two Mysis mixta in H. platessoides stomachs while five L3's (2.8 to 8.7 mm in length) were found among food (polychaetes, cumaceans, tanaids, amphipods) in the stomach of a P. ferrugineus. Levels of P. decipiens infection appear to be directly related to consumption of suprabenthic prey, which commonly occur in the diet of H. platessoides but are exploited less frequently by P. ferrugineus and rarely by P. americanus.
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corynosoma wegeneri acanthocephala polymorphida and Pseudoterranova decipiens nematoda ascaridoidea larvae in scotian shelf groundfish
Canadian Journal of Fisheries and Aquatic Sciences, 1992Co-Authors: David J. Marcogliese, Gary McclellandAbstract:We examined larvae of the seal parasites Corynosoma wegeneri and Pseudoterranova decipiens in various fish species collected from Western and Sable Island banks between February 1989 and October 1990. Atlantic cod (Gadus morhua), haddock (Melanogrammus aeglefinus), American plaice (Hippoglossoides platessoides), yellowtail flounder (Pleuronectes ferrugineus), windowpane (Scophthalmus aquosus), longhorn sculpin (Myoxocephalus octodecemspinosus), and sea raven (Hemitripterus americanus) were infected by both parasites, longhorn sculpin being a new host record for C. wegeneri. Only C. wegeneri occurred in winter flounder (Pleuronectes americanus), and neither parasite was found in northern sand lance (Ammodytes dubius) or capelin (Mallotus villosus). The two parasites were most numerous in sea raven and longhorn sculpin. Corynosoma wegeneri was more prevalent in fish sampled in 1989–90 than in previous surveys of Atlantic cod and haddock from the Scotian Shelf. Pseudoterranova decipiens and C. wegeneri occur...
David J. Marcogliese - One of the best experts on this subject based on the ideXlab platform.
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review of experimental and natural invertebrate hosts of sealworm Pseudoterranova decipiens and its distribution and abundance in macroinvertebrates in eastern canada
Nammco Scientific Publications, 2014Co-Authors: David J. MarcoglieseAbstract:Experimental and natural invertebrate intermediate hosts of sealworm ( Pseudoterranova decipiens ) as well as transmission experiments of sealworm from invertebrates to fish are reviewed and summarized. Experimental hosts include copepods, mysids, cumaceans, isopods, amphipods, decapods, annelids, and molluscs. Invertebrates collected from eastern Canada between 1989 and 1995 were checked for nematode infections by microscopic examination of dissected animals or enzymatic digestion of bulk samples. Third-stage larval sealworm were found in mysids ( Neomysis americana , Mysis stenolepis ) from Passamaquoddy Bay, the Bras d’Or Lakes, inshore Cape Breton, Sable Island and Sable Island Bank. Infected amphipods ( Amphiporeia virginiana , Americorchestia megalophthalma , Gammarus spp.) were found only on Sable Island. Typical infection rates in macroinvertebrates were 1-4/1000. No sealworm infections were found in approximately 18,000 amphipods examined from Sable Island Bank, the site of the most heavily infected fishes in eastern Canada. In Wallace Lake, a brackish pond on Sable Island, infection rates were much higher in mysids than in amphipods. Estimates of rates of transmission of sealworm from invertebrates to fish were derived from infection levels in Wallace Lake and feeding experiments involving sticklebacks and invertebrate prey. It is concluded that mysids may be much more important than amphipods in transmitting sealworm to fish hosts.
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distribution and abundance of sealworm Pseudoterranova decipiens and other anisakid nematodes in fish and seals in the gulf of st lawrence potential importance of climatic conditions
Nammco Scientific Publications, 2014Co-Authors: David J. MarcoglieseAbstract:Prevalence and abundance of sealworm ( Pseudoterranova decipiens ) and other anisakid nematodes were determined in a variety of fishes from the Gulf of St. Lawrence in 1990 and 1992. Sealworm abundance and prevalence were also determined in three species of seals in the Gulf between 1988 and 1992. Atlantic cod ( Gadus morhua ) and shorthorn ( Myoxocephalus scorpius ) and longhorn sculpin ( M. octodecemspinosus ) were the fishes most heavily infected with sealworm. Grey seals ( Halichoerus grypus ) proved to be the most important definitive hosts for sealworm in the Gulf. Abundance of sealworm increased, whereas that of Anisakis simplex and contracaecine nematodes decreased, from north to south in the Gulf. Abundance of sealworm increased compared to earlier surveys in most areas of the Gulf, but decreased in both cod and grey seals during the course of this study. In contrast, abundance of Contracaecum osculatum and Phocascaris spp. in grey seals and cod continued to increase during the study period. Observed increases of nematodes are attributed to growing populations of grey seals (for sealworm) and harp seals (for Contracaecinea). Levels of A. simplex remained relatively constant between 1988 and 1992 in both grey seals and cod. There is no evidence suggesting that observed patterns in nematode abundance were due to changes in grey seal diet. Nor was there any evidence of competition between P. decipiens and C. osculatum in grey seals affecting either sealworm abundance or fecundity. The trends detected herein are attributed to climatic events in the Gulf of St. Lawrence, where water temperatures in the cold intermediate layer consistently decreased between 1986 and 1994. It is suggested that low temperatures inhibited development and hatching of sealworm eggs, but not those of C. osculatum .
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fecundity of sealworm Pseudoterranova decipiens infecting grey seals halichoerus grypus in the gulf of st lawrence canada lack of density dependent effects
International Journal for Parasitology, 1997Co-Authors: David J. MarcoglieseAbstract:Abstract Uterine egg counts were determined by means of an electronic particle counter in individual female sealworm, Pseudoterranova decipiens (Nematoda: Ascaridoidea: Anisakidae) collected from grey seals ( Halichoerus grypus ) from Anticosti Island, northern Gulf of St. Lawrence, in August and September 1992. Mean number of eggs per female was 54 916.9 (±51 866.4), with a maximum of 300 000. Egg counts were strongly correlated with worm length, and less so with host sex and age, sealworm sex ratio, and densities of Anisakis simplex and Phocascaris sp. No effect of sealworm density on worm egg counts was determined and competitive effects by Contracaecum osculatum on sealworm fecundity were not observed. Analyses demonstrated that variation in sealworm fecundity was greater among seal hosts within groups than between groups for host age and sex, density of sealworm, and density of C. osculatum . No evidence for density-dependent regulation of sealworm fecundity could be found. Variations in worm egg counts are attributed to individual host effects on worm growth and fecundity.
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transmission of the sealworm Pseudoterranova decipiens krabbe from invertebrates to fish in an enclosed brackish pond
Journal of Experimental Marine Biology and Ecology, 1996Co-Authors: David J. MarcoglieseAbstract:Abstract The life cycle and transmission dynamics of sealworm, Pseudoterranova decipiens (Krabbe), were studied in Wallace Lake, an enclosed brackish pond on Sable Island, Nova Scotia. Abundance of larval sealworm was determined in amphipods ( Gammarus spp. ), mysids ( Neomysis americana S.L. Smith), and threespine ( Gasterosteus aculeatus Linnaeus) and fourspine ( Apeltes quadracus Mitchill) sticklebacks. Sealworm larvae were more numerous in mysids (0.001–0.004 worms/host) than in amphipods (0–0.0005 worms/host), and P . decipiens abundance in mysids and fourspine stickleback was positively correlated. Amphipods outnumbered mysids in three depth zones in the lake, but density of infected mysids (1.43/m 2 ) was much higher than that of infected amphipods (0.22/m 2 ) in the vegetated zone where fish were found. Threespine and fourspine stickleback fed mainly on copepods (98% and 57% of diets, respectively), and less frequently on amphipods (1% and 23% of diets, respectively) and mysids (1% and 19% of diets, respectively). Both sticklebacks fed preferentially on mysids (Murdoch's index of preference=1.49) over amphipods (Murdoch's index=0.67). In separate feeding experiments, fourspine stickleback ingested 1.3 (±1.2) amphipods or 7.7 (±2.0) mysids per day. Calculated transmission rates suggest that these fish acquire sealworm from eating infected mysids at a rate of about 1 per month, compared to 1 every 8 yr from amphipods. Abundance of larval sealworm in N . americana on Sable Island Bank (0.002 worms/host) in January 1995 was similar to that in Wallace Lake. Results of this study demonstrate that mysids are more important than amphipods in transmission of sealworm to small benthophagous fishes in an isolated, landlocked brackish-water environment.
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corynosoma wegeneri acanthocephala polymorphida and Pseudoterranova decipiens nematoda ascaridoidea larvae in scotian shelf groundfish
Canadian Journal of Fisheries and Aquatic Sciences, 1992Co-Authors: David J. Marcogliese, Gary McclellandAbstract:We examined larvae of the seal parasites Corynosoma wegeneri and Pseudoterranova decipiens in various fish species collected from Western and Sable Island banks between February 1989 and October 1990. Atlantic cod (Gadus morhua), haddock (Melanogrammus aeglefinus), American plaice (Hippoglossoides platessoides), yellowtail flounder (Pleuronectes ferrugineus), windowpane (Scophthalmus aquosus), longhorn sculpin (Myoxocephalus octodecemspinosus), and sea raven (Hemitripterus americanus) were infected by both parasites, longhorn sculpin being a new host record for C. wegeneri. Only C. wegeneri occurred in winter flounder (Pleuronectes americanus), and neither parasite was found in northern sand lance (Ammodytes dubius) or capelin (Mallotus villosus). The two parasites were most numerous in sea raven and longhorn sculpin. Corynosoma wegeneri was more prevalent in fish sampled in 1989–90 than in previous surveys of Atlantic cod and haddock from the Scotian Shelf. Pseudoterranova decipiens and C. wegeneri occur...
M. D. B. Burt - One of the best experts on this subject based on the ideXlab platform.
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cell mediated immune response of rainbow trout oncorhynchus mykiss to larval Pseudoterranova decipiens nematoda ascaridoidea following sensitization to live sealworm sealworm extract and nonhomologous extracts
Canadian Journal of Fisheries and Aquatic Sciences, 1993Co-Authors: N R Ramakrishna, M. D. B. Burt, B M MackinnonAbstract:The delaved-type hypersensitivity (DTH) reaction (an in vivo manifestation of cell-mediated immunity) was studied in rainbow trout (Oncorhynchus mykiss) exposed to sealworm Pseudoterranova decipiens infections. Test fish immunized with sealworm extract and live intact worms, were compared with control fish which received either phosphate-buffered saline (negative control) or nonhomologous cestode or nematode antigens (positive control). Test fish immunized with sealworm extract produced a typical DTH reaction to live sealworm, challenge. The DTH reaction was similar to that in mammals and showed lymphoid and mononuclear cell infiltration. The electron microscopical studies revealed the presence of activated macrophages and plasma cells in the reaction zone. The specific response, following immunization with homologous antigens, supports the existence of T-cell function with anamnesis in rainbow trout exposed to sealworm antigens. However, when the test fish were immunized with live sealworms and later cha...
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tissue response of fish to invasion by larval Pseudoterranova decipiens nematoda ascaridoidea
Canadian Journal of Fisheries and Aquatic Sciences, 1991Co-Authors: N R Ramakrishna, M. D. B. BurtAbstract:The histopathology of Pseudoterranova decipiens (L3) in experimentally infected rainbow trout (Oncorhynchus mykiss) and naturally infected Atlantic cod (Gadus morhua) was similar. The chronic granulomatous inflammatory reaction included polymorphonuclear neutrophils, macrophages, lymphocytes, epithelioid cells, and fibroblasts. Giant cells were also found but only in the experimentally infected rainbow trout. Mature capsules around the larvae consisted of an inner layer, composed of macrophages which underwent epithelioid transformation and later gradually degenerated, and an outer layer, composed of fibroblasts and collagen fibres. A layer of lipofuscin was adjacent to the parasite in older cod infections but this was absent in all of the newly formed capsules in the experimentally infected rainbow trout.
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biochemical characterization of third stage larval sealworm Pseudoterranova decipiens nematoda anisakidae in canadian atlantic waters using isoelectric focusing of soluble proteins
Canadian Journal of Fisheries and Aquatic Sciences, 1991Co-Authors: Tracey E Appleton, M. D. B. BurtAbstract:Isoelectric focusing (IEF) was performed on soluble protein extracts from whole specimens of third-stage larval sealworm (Pseudoterranova decipiens) recovered from the musculature of three fish intermediate host species: Atlantic cod (Gadus morhua), sea raven (Hemitripterus americanus), and rainbow smelt (Osmerus mordax). The fish were collected at various sites in the Canadian Atlantic, and IEF revealed the occurrence of two "variants" within what has previously been considered a single, uniform species of P. decipiens in these waters. The larvae were characterized by the absence ("type I" L3's) or presence ("type II" L3's) of a sharp, dark-staining protein band with a mean pl of 6.46 pH units. Type I larvae were predominant at two sites sampled in the lower Bay of Fundy, while type II larvae were predominant at three sites sampled in the Gulf of St. Lawrence region.
Jesus S Hernandezorts - One of the best experts on this subject based on the ideXlab platform.
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description microhabitat selection and infection patterns of sealworm larvae Pseudoterranova decipiens species complex nematoda ascaridoidea in fishes from patagonia argentina
Parasites & Vectors, 2013Co-Authors: Isabel Blascocosta, Maria Villoramontero, Nestor A Garcia, Jesus S Hernandezorts, Francisco Javier Aznar, Enrique A. Crespo, Francisco E MonteroAbstract:Background: Third-stage larvae of the Pseudoterranova decipiens species complex (also known as sealworms) have been reported in at least 40 marine fish species belonging to 21 families and 10 orders along the South American coast. Sealworms are a cause for concern because they can infect humans who consume raw or undercooked fish. However, despite their economic and zoonotic importance, morphological and molecular characterization of species of Pseudoterranova in South America is still scarce. Methods: A total of 542 individual fish from 20 species from the Patagonian coast of Argentina were examined for sealworms. The body cavity, the muscles, internal organs, and the mesenteries were examined to detect nematodes. Sealworm larvae were removed from their capsules and fixed in 70% ethanol. For molecular identification, partial fragments of the mitochondrial cytochrome c oxidase subunit 1 gene (cox1) were amplified for 10 isolates from 4 fish species. Morphological and morphometric data of sealworms were also obtained. Results: A total of 635 larvae were collected from 12 fish species. The most infected fish was Prionotus nudigula, followed by Percophis brasiliensis, Acanthistius patachonicus, Paralichthys isosceles, and Pseudopercis semifasciata. Sequences obtained for the cox1 of sealworms from A. patachonicus, P. isosceles, P. brasiliensis and P. nudigula formed a reciprocally monophyletic lineage with published sequences of adult specimens of Pseudoterranova cattani from the South American sea lion Otaria flavescens, and distinct from the remaining 5 species of Pseudoterranova. A morphological description, including drawings and scanning electron microscopy photomicrographs of these larvae is provided. Sealworms collected from Argentinean fishes did not differ in their diagnostic traits from the previously described larvae of P. cattani. However a discriminant analysis suggests that specimens from P. nudigula were significantly larger than those from other fishes. Most of the sealworms were collected encapsulated from the muscles and, to a lesser degree, from the mesenteries and the liver. Conclusions: We provided the first molecular identification, morphological description and microhabitat characterization of sealworm larvae from the Argentinean Patagonian coast. We also reported the infection levels of sealworms on 20 fish species in order to elucidate the life cycle of these nematodes in this area.
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description microhabitat selection and infection patterns of sealworm larvae Pseudoterranova decipiens species complex nematoda ascaridoidea in fishes from patagonia argentina
Parasites & Vectors, 2013Co-Authors: Isabel Blascocosta, Maria Villoramontero, Nestor A Garcia, Jesus S Hernandezorts, Francisco Javier Aznar, Enrique A. Crespo, J A Raga, Francisco E MonteroAbstract:Third-stage larvae of the Pseudoterranova decipiens species complex (also known as sealworms) have been reported in at least 40 marine fish species belonging to 21 families and 10 orders along the South American coast. Sealworms are a cause for concern because they can infect humans who consume raw or undercooked fish. However, despite their economic and zoonotic importance, morphological and molecular characterization of species of Pseudoterranova in South America is still scarce. A total of 542 individual fish from 20 species from the Patagonian coast of Argentina were examined for sealworms. The body cavity, the muscles, internal organs, and the mesenteries were examined to detect nematodes. Sealworm larvae were removed from their capsules and fixed in 70% ethanol. For molecular identification, partial fragments of the mitochondrial cytochrome c oxidase subunit 1 gene (cox 1) were amplified for 10 isolates from 4 fish species. Morphological and morphometric data of sealworms were also obtained. A total of 635 larvae were collected from 12 fish species. The most infected fish was Prionotus nudigula, followed by Percophis brasiliensis, Acanthistius patachonicus, Paralichthys isosceles, and Pseudopercis semifasciata. Sequences obtained for the cox 1 of sealworms from A. patachonicus, P. isosceles, P. brasiliensis and P. nudigula formed a reciprocally monophyletic lineage with published sequences of adult specimens of Pseudoterranova cattani from the South American sea lion Otaria flavescens, and distinct from the remaining 5 species of Pseudoterranova. A morphological description, including drawings and scanning electron microscopy photomicrographs of these larvae is provided. Sealworms collected from Argentinean fishes did not differ in their diagnostic traits from the previously described larvae of P. cattani. However a discriminant analysis suggests that specimens from P. nudigula were significantly larger than those from other fishes. Most of the sealworms were collected encapsulated from the muscles and, to a lesser degree, from the mesenteries and the liver. We provided the first molecular identification, morphological description and microhabitat characterization of sealworm larvae from the Argentinean Patagonian coast. We also reported the infection levels of sealworms on 20 fish species in order to elucidate the life cycle of these nematodes in this area.
Bjorn Berland - One of the best experts on this subject based on the ideXlab platform.
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Pseudoterranova decipiens species A and B (Nematoda, Ascaridoidea): nomenclatural designation, morphological diagnostic characters and genetic markers
Systematic Parasitology, 2000Co-Authors: Simonetta Mattiucci, Giuseppe Nascetti, Bjorn Berland, Rossella Cianchi, David I. Gibson, Luciano BulliniAbstract:Five genetically distinct and reproductively isolated species have been detected previously within the morphospecies Pseudoterranova decipiens from the Arctic-Boreal, Boreal and Antarctic. Morphological analysis was carried out on male specimens identified by genetic (allozyme) markers, allowing the detection of significant differences at a number of characters between two members of the P. decipiens complex, namely P. decipiens A and B. On the basis of such differences, the nomenclatural designation for the two species is discussed. The names Pseudoterranova krabbei n. sp. and P. decipiens (sensu stricto) are proposed for species A and B, respectively. Morphological and genetic differentiation between the two species is shown using multivariate analysis. Allozyme diagnostic keys for routine identification of the four members of the P. decipiens complex, namely P. decipiens (s.s.), P. krabbei , P. bulbosa and P. azarasi , irrespective of sex and life-history stage, are provided.
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Development to third-stage larvae occurs in the eggs of Anisakis simplex and Pseudotetranova decipiens (Nematoda, Ascaridoidea, Anisakidae)
Canadian Journal of Fisheries and Aquatic Sciences, 1995Co-Authors: Marianne Køie, Bjorn Berland, Michäel D.b. BurtAbstract:Two moults occur during larval development in the eggs of Anisakis simplex (Rudolphi, 1809) and Pseudoterranova decipiens (Krabbe, 1878) from the North Atlantic. Live larvae forced out of eggs in sea water by coverslip pressure shortly before spontaneous hatching were surrounded by the thin cuticle of the first-stage larva. Infective larvae from naturally hatched eggs are loosely ensheathed in the thick cuticle of the second-stage larva. Thus, it is the third-stage larva that emerges from the egg of both species and not the second-stage larva as previously believed. The thin, smooth, fragile cuticle of the first-stage larva remains in the egg. The striated, cocoon-like cuticle of the second-stage larva of A. simplex may increase the buoyancy of the third-stage larva. The tail tip of the cuticle of the second-stage larva of P. decipiens is sticky and adheres the sheathed third-stage larva to the substrate.
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sealworm Pseudoterranova decipiens infection in common seals phoca vitulina and potential intermediate fish hosts from the outer oslofjord
International Journal for Parasitology, 1995Co-Authors: Paul Eric Aspholm, Karl I Ugland, Kjell Andreas Jodestol, Bjorn BerlandAbstract:Abstract Infection with Pseudoterranova decipiens in 45 common seals ( Phoca vitulina ) from the outer Oslofjord was investigated. Seals were cellected before and during the phocine distemper virus epizootic in 1988 when the seal population in the area was reduced from about 350 to 100. In 1989, cod ( Gadus morhua ) and other fish species were sampled for comparison with earlier investigations on prevalence and abundance of P. decipiens infection in fishes from the outer Oslefjord. Seventy-two per cent of cod were infected with P. decipiens larvae in shallow waters between the seal skerries; the corresponding abundance was 2.2. At other fishing sites at increasing distances from the seal colony, abundance dropped to 0.05 – 0.20. Otoliths recovered from stomachs and scats indicated that gadids ( Micromesistius poutassu, Trisopterus esmarkii and G. morhua ) made up more than 80% of the seal diet. Bullrout ( Myxocephalus scorpius ) was also heavily infected with P. decipiens (prevalence 93% and abundance 8.4), but was not found in the seal diet. However, uninfected cod that enter shallow water from the surronading deep waters became infected when they feed on bullrout. Recruitment to mature stock of P. decipiens occurs when highly infected cod are eaten by seals. The number of reproducing P. decipiens is very low in comunon seals. Only 2 seals (i.e. less than 5% of the sample) were simultaneonaly infected with mature werms of both sexes. The dramatic reduction of the seal stock in the outer Oslofjord by the epizootic did not seem to affect the abundance of P. decipiens in its intermediate hosts.
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on the ecology and distribution of Pseudoterranova decipiens c nematoda anisakidae in an intermediate host hippoglossoides platessoides in northern norwegian waters
International Journal for Parasitology, 1992Co-Authors: G. A. Bristow, Bjorn BerlandAbstract:Abstract The distribution of Pseudoterranova decipiens C helps demonstrate the ecological basis of this genetically defined sibling species. In northern Norwegian waters the major fish intermediate host is Hippoglossoides platessoides . Overall prevalence, mean intensity and intensity range in H. platessoides were 15%, 16.5 and 1–165, respectively. Outside the range of its only known definitive host, the seal Erignathus barbatus , the parasite was not found in the same intermediate host.
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genetic evidence for three species within Pseudoterranova decipiens nematoda ascaridida ascaridoidea in the north atlantic and norwegian and barents seas
International Journal for Parasitology, 1991Co-Authors: Giuseppe Nascetti, S Damelio, Simonetta Mattiucci, Bjorn Berland, Rossella Cianchi, J.w. Smith, P. Orecchia, J Brattey, Luciano BulliniAbstract:Abstract Genetic variation of 1017 specimens of codworm, Pseudoterranova decipiens, collected from fish and seals at 23 sampling locations in the North Atlantic and Norwegian and Barents Seas, was analysed on the basis of 16 enzyme loci. Three reproductively isolated species, provisionally designated P. decipiens A, B and C, were detected, showing distinct alleles at the following loci: Mdh-1, 6Pgdh, Np, Pgm, Est-2 (between species A and B); Mdh-3, 6Pgdh, Np, Sod-1, Adk, Pgm, Est-2, Mpi (between A and C); Mdh-1, Mdh-3, Sod-1, Adk, Pgm, Est-2, Mpi (between B and C). One F, hybrid was observed between P. decipiens A and B, but this apparently does not lead to any gene exchange between the two species, which do not show any evidence of introgression. No hybrids or introgressed individuals were observed between P. decipiens C and either A or B. Genetic distances among conspecific populations were low (average Nei's D 0.001–0.005), even though they were collected thousands of kilometres apart, indicating high levels of gene flow within each of the three species. The values of Nei's index D were 0.44 between P. decipiens A and B, 0.57 between B and C, and 0.79 between A and C. Estimated evolutionary divergence times, using Nei's formula, range from 2 to 4 million years. Differences between P. decipiens A, B and C were also found with respect to genetic variability, morphology, geographical distribution and hosts. Mean heterozygosity values of 0.08, 0.05 and 0.02 were obtained for P. decipiens A, B and C, respectively. Preliminary morphological examination of adult males, previously identified by multilocus electrophoresis, revealed differences in the relative size and pattern of caudal papillae. P. decipiens B is widespread in the study area, whereas P. decipiens A was found only in the North-East Atlantic and Norwegian Sea. In this area P. decipiens A is most common in the grey seal, Halichoerus grypus, while the common seal, Phoca vitulina, is the main host for P. decipiens B. In Canadian Atlantic waters, where P. decipiens A is apparently absent, P. decipiens B infects both grey and common seals; a few specimens were also found in the hooded seal, Cystophora cristata. The only definitive host so far identified for P. decipiens C is the bearded seal, Erignathus barbatus; P. decipiens C appears to be widespread, occurring in both the North-West Atlantic and Barents Sea.
