Joanna Dzido

Occurrence of anisakid nematodes in Atlantic cod (Gadus morhua) and Greenland cod (Gadus ogac), West Greenland

Anisakid nematodes commonly infect gadids, and are of economic and aesthetic importance to the commercial fishing industry in Greenland as some species are pathogenic to humans. However, very little is known about the occurrence of these parasites and their impact on the hosts in Greenland waters. During a survey in 2005, stomach sample of 227 Atlantic cod (Gadus morhua) and 64 Greenland cod (Gadus ogac) was collected in Godthaab and Sisimiut fiord systems in West Greenland waters. All cod were dissected for stomach contents and anisakid nematodes were removed from the visceral cavity. Third stage larvae (L3) of three anisakid species were found, including Contracaecum osculatum (Rudolphi, 1802), Anisakis simplex (Rudolphi, 1809) and Hysterothylacium aduncum (Rudolphi, 1802). Molecular identification by PCR-RFLP indicated the presence of A. simplex s.s. and the sibling species C. osculatum B and C. The prevalence of infection by C. osculatum was higher in Greenland cod (84.3%) than in Atlantic cod (73.9%) whereas the prevalence of A. simplex showed an opposite pattern (Greenland cod 8.3%; Atlantic cod 24.2%). Only one G. morhua (1.0%) was infected by H. aduncum. No gender specific difference in both nematode species regarding prevalence of infection and mean infection intensity was evident, and there was no relationship between fish condition and the intensity of nematode infections. Standardised for size, capelin-eating cod were in better condition and more heavily infected than fish subsisting on alternative prey at the point of collection. Hence, nematode infections in the two gadids seem governed in part by feeding behaviour, and capelin appears a significant source of larval anisakids.

Anisakids of seals found on the southern coast of Baltic Sea.

In 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%).

Anisakid nematodes of Greenland halibut Reinhardtius hippoglossoides from the Barents Sea.

Abstract:  Parasitic nematodes from the body cavity of 94 Greenland halibut (Reinhardtius hippoglossoides) caught in the Barents Sea were examined. Nematode species were identified using both morphological and molecular methods. Four morphospecies were found: Anisakis simplex s.l., Contracaecum osculatum s.l., Pseudoterranova decipiens s.l., and Hysterothylacium aduncum. The most prevalent were C. osculatum s.l. (89.4%) and A. simplex s.l. (86.2%). Mean intensities for these 2 species were 7.8 and 45.2, respectively. The number of parasites was directly proportional to the fish length. The following 6 parasite species, including 3 cryptic species of Contracaecum sp., were identified using molecular methods: A. simplex sensu stricto, C. osculatum A, C. osculatum B and C (the last 2 as host records for halibut), Pseudoterranova bulbosa, and H. aduncum. Mixed infections of C. osculatum A, B, and C were observed.

MITOCHONDRIAL DNA OF ANISAKIS SIMPLEX S.S. AS A POTENTIAL TOOL FOR DIFFERENTIATING POPULATIONS

Abstract Anisakis simplex s.s. specimens from Gadus morhua, Gadus ogac, Reinhardtius hippoglossoides, Clupea harengus, Micromesistius poutassou, Pleurogrammus monopterygius, and Oncorhynchus nerka, caught in the north Atlantic and Pacific, were examined. Identity of the parasite species was confirmed using a molecular key. All specimens were used for amplifying a part of the non-coding sequence of the AT-rich region, flanked by the nad6-nad4L-trnW-trnE-rrnS-trnS2, and trnN-trnY-nad1 genes. This part of the mtDNA was chosen as a promising fragment, which could yield information regarding population differentiation. The number of samples and their geographical origin was sufficient to compare the 2 regions. The Bayesian analysis provided strong support for a population split into 2 groups, one representing A. simplex s.s. samples from the Pacific, and the other representing all the Atlantic samples. It is highly probable that observed subpopulations were constituted after the connection between the Atlantic and Pacific had been closed and movement between these 2 oceans was prevented.

Anisakidae in beluga whales Delphinapterus leucas from Hudson Bay and Hudson Strait

A total of 190 nematodes was isolated from the stomachs of 13 beluga whales Delphinapterus leucas from the Arctic part of Hudson Bay and Hudson Strait. Infection intensity ranged from 1 to 57 specimens and prevalence was 84.62%. Morphological examination of the nematodes revealed the presence of 3 species: Pseudoterranova decipiens sensu lato, Contracaecum osculatum s.l., and Anisakis simplex s.l. Molecular analysis by PCR-based restriction fragment length polymorphism (PCR-RFLP) resulted in the identification of 4 species: Pseudoterranova bulbosa, Contracaecum osculatum A and C, and Anisakis simplex sensu stricto. The nematodes were present in 3 developmental stages: L3 (159 specimens), L4 (16 larvae), and adults (15 worms: 11 males and 4 females).