Host specificity and abundance of parasitic nematodes (Ascaridoidea) from the stomachs of five phocid species from Newfoundland and Labrador

1993 ◽  
Vol 71 (11) ◽  
pp. 2156-2166 ◽  
Author(s):  
John Brattey ◽  
Garry B. Stenson
Keyword(s):  
Newfoundland And Labrador ◽  
Phoca Vitulina ◽  
Halichoerus Grypus ◽  
Parasitic Nematodes ◽  
Fish Stocks ◽  
Cystophora Cristata ◽  
Pseudoterranova Decipiens ◽  
Large Numbers ◽  
Harbour Seals ◽  
Contracaecum Osculatum

Stomachs of 270 phocids from five species (bearded, Erignathus barbatus; hooded, Cystophora cristata; grey, Halichoerus grypus; harbour, Phoca vitulina; and ringed, P. hispida), collected off Newfoundland and Labrador during 1985–1993 were examined, and the numbers and percentages of larval and adult ascaridoid nematodes determined. Samples of adult nematodes were also identified using previously described allozymes. Bearded seals were infected mainly with Contracaecum osculatum A, C. osculatum B, and Pseudoterranova decipiens C, whereas hooded seals harboured mostly Phocascaris spp. Grey seals harboured large numbers of C. osculatum B, and small numbers of adult Anisakis simplex; harbour and grey seals were the only phocids heavily infected with P. decipiens B. Ringed seal stomachs contained fewer nematodes than other seal species and were mainly infected with C. osculatum B and Phocascaris spp. In several seal species positive, but no negative, associations in abundance were observed between nematodes. Sex ratios of adult nematodes among individual seals were heterogeneous, but changes in sex ratio suggest a bias towards female nematodes among larvae infecting fish and a selective loss of adult females during maturation. Overall, the results suggest that grey and harbour seals are the main source of larval sealworm (P. decipiens B) occurring in fish stocks off Newfoundland and Labrador, although small numbers of adult P. decipiens B also occurred in hooded seals.

Abundance and maturity of three species of parasitic anisakine nematodes (Pseudoterranova decipiens, Contracaecum osculatum, Anisakis simplex) occurring in Sable Island harbour seals (Phoca vitulina)

2002 ◽  
Vol 80 (3) ◽  
pp. 442-449 ◽  
Author(s):  
Wayne T Stobo ◽  
L Paul Fanning ◽  
Brian Beck ◽  
G Mark Fowler
Keyword(s):  
Prey Species ◽  
Phoca Vitulina ◽  
Final Host ◽  
Anisakis Simplex ◽  
Halichoerus Grypus ◽  
Commercial Fish ◽  
Pseudoterranova Decipiens ◽  
Harbour Seals ◽  
Seal Population ◽  
Contracaecum Osculatum

Three species of anisakine nematodes (Pseudoterranova decipiens, Contracaecum osculatum, Anisakis simplex) co-occur in the stomachs of Sable Island harbour seals (Phoca vitulina). The sealworm, P. decipiens, was the commonest nematode in these seals. Anisakis simplex was found in much smaller numbers, none mature, indicating that the harbour seal is not a true final host to this parasite. Contracaecum osculatum was rare but half were mature. Pseudoterranova decipiens increased in abundance with size of the seal. An inverse relationship was observed between P. decipiens abundance and the age of seals of similar size, probably owing to changes in diet. Numbers of P. decipiens may have declined over the summer, coincident with an increase in the proportion of mature worms in the stomach. From similarities between the worm infections of grey seals (Halichoerus grypus) and harbour seals, we infer that A. simplex abundance may also exhibit a decline in abundance. Contracaecum osculatum was only encountered during the latter half of the year, suggesting an association with prey species of corresponding periodicity in their distribution. We estimate that the abundance of sealworm in harbour seals is about 2.5% of that carried by the grey seal population. This could imply that harbour seals represent an insignificant vector of the sealworm infecting commercial fish species in the Northwest Atlantic, provided density-dependent relationships exist between worm abundances in different host species.

Ascaridoid Nematodes from the Stomach of Harp Seals, Phoca groenlandica, from Newfoundland and Labrador

1992 ◽  
Vol 49 (5) ◽  
pp. 956-966 ◽  
Author(s):  
John Brattey ◽  
I-Hsun Ni
Keyword(s):  
Newfoundland And Labrador ◽  
Sex Ratios ◽  
Condition Index ◽  
Fish Stocks ◽  
Phoca Groenlandica ◽  
Pseudoterranova Decipiens ◽  
Large Numbers ◽  
Pinniped Species ◽  
Nematode Abundance ◽  
Contracaecum Osculatum

Stomachs of 488 harp seals, Phoca groenlandica, collected off Newfoundland and Labrador during 1984–88, contained four species of ascaridoid nematodes. Seals had high prevalences and abundances of Contracaecum osculatum B and Phocascaris sp. but were rarely infected with Anisakis simplex B or Pseudoterranova decipiens B (sealworm). Nematode abundance increased with age, and distribution of each species among seals was highly aggregated. Gastric lesions, often associated with clusters of nematodes, occurred in 13.8% of 405 seals. Female seals with large numbers of nematodes had a higher body condition index (sculp weight) than lightly infected females. Overall sex ratios of C. osculatum B and Phocascaris sp. were biased toward females, but sex ratios of adult nematodes among individual seals were heterogeneous. Most nematodes recovered were third- or fourth-stage larvae; adults of C. osculatum B and Phocascaris sp. were also common, but no mature females of A. simplex B or P. decipiens B were found. Harp seals are probably unimportant in the transmission of A. simplex but may be partly responsible for sealworm found in fish stocks off Newfoundland and Labrador. More information on other pinniped species is needed to assess more precisely the relative importance of harp seals in sealworm transmission.

Mercury in Seals from Eastern Canada

1973 ◽  
Vol 30 (6) ◽  
pp. 843-846 ◽  
Author(s):  
D. E. Sergeant ◽  
F. A. J. Armstrong
Keyword(s):  
Phoca Vitulina ◽  
Halichoerus Grypus ◽  
Eastern Canada ◽  
Small Pelagic Fish ◽  
Marine Food Web ◽  
Cystophora Cristata ◽  
Pagophilus Groenlandicus ◽  
Harbour Seals ◽  
Order Of Magnitude ◽  
Marine Food

Mercury concentrations in the tissues of four species of seals from individual localities in eastern Canada were highest in liver (usually 1–100 ppm) but up to 387 ppm and lowest in blubber (usually 0.1 ppm). Levels in muscle ranged from < 0.16 to 2.35 ppm. Values similar to those in muscle were found in the few specimens of heart, intestine, and lungs analyzed, and higher values in kidney and hair. Ratios of mercury in the liver to that in the muscle for adult seals were much greater than those found in two species of freshwater fish and three species of domestic animals exposed to wide ranges of mercury concentrations in their food. The ratios for seal pups, however, resembled those in the other animals.Mercury in seals increased with age and appeared to vary with the position in the marine food web of the organisms which they eat. Harp seals (Pagophilus groenlandicus), which feed on small pelagic fish and crustaceans, accumulated an order of magnitude less mercury than grey (Halichoerus grypus) and harbour (Phoca vitulina) seals, which live on large pelagic and benthic fish and cephalopods. However, grey and harbour seals are resident in eastern Canadian waters, which presumably contain higher mercury levels than arctic waters, where harp seals spend about half the year. Yet hood seals (Cystophora cristata), which spent more than half the year in arctic waters but feed on large fish and cephalopods, had mercury levels as high as grey and harbour seals.

scholarly journals Patterns of abundance and maturity among three species of parasitic nematodes (Pseudoterranova decipiens, Contracaecum osculatum, Anisakis simplex) co-existing in Sable Island grey seals (Halichoerus grypus)

2001 ◽  
Vol 3 ◽  
pp. 149 ◽  
Author(s):  
G Mark Fowler ◽  
Wayne T Stobo
Keyword(s):  
Prey Species ◽  
Final Host ◽  
Anisakis Simplex ◽  
Halichoerus Grypus ◽  
Parasitic Nematodes ◽  
Breeding Period ◽  
Cetacean Species ◽  
Pseudoterranova Decipiens ◽  
Contracaecum Osculatum ◽  
Winter Breeding

The abundance and maturity of three species of anisakine nematode (Pseudoterranova decipiens, Contracaecum osculatum, Anisakis simplex) that co-occurred in the stomachs of Sable Island grey seals were examined in relation to seal growth and seasonal considerations. Sealworm (P. decipiens), the predominant nematode in these seals, typically reached numbers of 400 to 2000 worms per stomach. C. osculatum and A. simplex were usually found in much smaller numbers of 40 to 100 and 20 to 60 worms, respectively, per stomach. All three species initially increased in abundance as the seals grew, but after most of a seals’ growth had been attained P. decipiens abundance continued to increase with age, A. simplex numbers either continued to increase or were simply maintained, while C. osculatum abundance declined. Numbers of both P. decipiens and A. simplex declined during winter breeding/pupping and summer moulting fasts or partial fasts, and rose during the regular feeding periods between the fasts. Conversely, numbers of C. osculatum rose during the breeding period, and also during the moulting period in younger seals. We believe this could be attributed to some degree of feeding on prey species in the immediate vicinity of Sable Island that were not preferred during focused feeding periods, and that the inclination to feed during fasting periods decreased as seals grew. An inverse relationship between worm abundance and worm maturity, attributable to the seasonal changes in rates of ingestion of immature worms, was more pronounced for C. osculatum than P. decipiens. C. osculatum was usually represented by much higher proportions of mature worms than P. decipiens. This could be entirely related to the longer periods of time dedicated to feeding than spent breeding or moulting, but higher mortality rates of immature C. osculatum or greater longevity of mature C. osculatum could also have occurred. A. simplex, generally associated with cetacean species as final hosts, rarely matured in grey seals. We have doubts that the grey seal could be considered a final host for A. simplex.

Fatal Interspecies Mating Attempts of a Grey Seal (Halichoerus grypus) with Harbour Seals (Phoca vitulina) on the German North Sea Coast

2020 ◽  
Vol 174 ◽  
pp. 166
Author(s):  
K. Hülskötter ◽  
S. Rohner ◽  
S. Groß ◽  
J. Lakemeyer ◽  
M. Fähndrich ◽  
...  
Keyword(s):  
North Sea ◽  
Phoca Vitulina ◽  
Halichoerus Grypus ◽  
Grey Seal ◽  
Harbour Seals ◽  
Sea Coast ◽  
North Sea Coast

Anisakids of seals found on the southern coast of Baltic Sea

2014 ◽  
Vol 59 (1) ◽  
Author(s):  
Michał Skrzypczak ◽  
Jerzy Rokicki ◽  
Iwona Pawliczka ◽  
Katarzyna Najda ◽  
Joanna Dzido
Keyword(s):  
Baltic Sea ◽  
Life Stage ◽  
Adult Life ◽  
Sensu Stricto ◽  
Halichoerus Grypus ◽  
Slight Excess ◽  
Pseudoterranova Decipiens ◽  
Pusa Hispida ◽  
Contracaecum Osculatum ◽  
Anisakid Nematodes

AbstractIn the present study 5 grey seals (Halichoerus grypus), 3 common seals (Phoca vitulina) and 1 ringed seal (Pusa hispida) bycaught or stranded on the Polish Baltic Sea coast in years 2000-2006 were investigated for the infestation of parasitic anisakid nematodes. 749 of anisakids were found. The most common were: Contracaecum osculatum (59.3%) and Pseudoterranova decipiens (31.0%). There were also small numbers of Anisakis simplex (0.8%). After performing RFLP three sibling species were found. C. osculatum was identified as C. osculatum C, P decipiens was identified as P. decipiens sensu stricto and A. simplex — A. simplex sensu stricto. Nematodes found in seals were mostly in L4 and adult life stage — both of them were equal with some minor variations among the specimens. Sex ratio was also equal, but there was slight excess of males in some cases. There was a minority of L3 larvae belonging to A. simplex species (0.8%).

Sealworm (Pseudoterranova decipiens) infections in demersal fish from two areas in Norway

1994 ◽  
Vol 72 (4) ◽  
pp. 598-608 ◽  
Author(s):  
Tor Jensen ◽  
Karin Andersen ◽  
Sophie des Clers
Keyword(s):  
Gadus Morhua ◽  
Demersal Fish ◽  
Phoca Vitulina ◽  
Halichoerus Grypus ◽  
Shallow Waters ◽  
Benthic Fish ◽  
Pseudoterranova Decipiens ◽  
Average Abundance ◽  
Myoxocephalus Scorpius ◽  
Southern Norway

Fish from Torbjørnskjær, in the outer Oslofjord in southern Norway, and from Vega in Nordland in central Norway were examined for infections of the larval nematode Pseudoterranova decipiens transmitted by seals. Three sites were sampled between 1990 and 1992, two (S1 and S2) in Torbjørnskjær and one (S3) in Vega, and 3361 fish were examined in total. In Torbjørnskjær, fish were collected from shallow waters (S1) near skerries where a colony of common seals (Phoca vitulina) regularly haul out, and from deeper waters outside these skerries (S2). In Vega, an extensive zone of rocks and shallow water is inhabited by a colony of grey seals (Halichoerus grypus) and some common seals. In Vega, fish were caught from the littoral zone to 40–50 m depth, except for cusk (Brosme brosme), which were caught in deeper waters. Only demersal and benthic fish were infected in both areas, infection levels being highest in shallow waters close to the rocks (sites S1 and S3). Sculpins (Myoxocephalus scorpius) had the highest infection levels (an average abundance of 36 and 23 worms per fish, respectively), with cod (Gadus morhua) and cusk also heavily infected; the latter species was found only at Vega. Two somewhat different transmission routes to seals are suggested for the two areas.

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