Description: A total of 386 Macrourus whitsoni from Antarctic waters were examined for ecto- and endoparasites. Sixty-five M. whitsoni collected near Halley Bay (Weddell Sea) and 321 specimens from the continental slope off King George Island (South Shetland Islands) were studied for sphyriid copepods directly after being caught. A subsample of 25 specimens from the Weddell Sea and of 9 specimens from King George Island were studied for the presence of other metazoan parasites. Twenty-two species were found, including one myxozoan, six digeneans, one monogenean, three cestodes, seven nematodes, one acanthocephalan and three crustacean species/taxa. While Auerbachia monstrosa and Capillaria sp. are reported for the first time from around the Antarctic, the other parasites have been recorded earlier in the Southern Ocean. Many parasite species found have a wide zoogeographical range and a low host-specificity. The parasite fauna of M. whitsoni revealed several similarities with its congeners M. carinatus and M. holotrachys from Antarctic and sub-Antarctic waters. This can be explained by a wide host range of many macrourid deep-sea parasites, together with an overlap in distribution patterns of their hosts. Other supporting factors are host migration and a close phylogenetic relationship between the hosts, which enable the parasites to infest all three macrourids. Eight new host and 14 new locality records are established.

Description: The present study provides further data on the occurrence of Pseudoterranova decipiens in fish from two different sampling sites in the Antarctic. A total of 690 fish belonging to 33 species from the eastern Weddell Sea and 322 fish belonging to 12 species from the South Shetland Islands were examined. Altogether, 23 fish species were found to be infested and 11 new host records could be established. P. decipiens occurred at a water depth of between 80 and 820 m. Chaenocephalus aceratus and Notothenia coriiceps from the South Shetland Islands were the species with the highest prevalence (95%) and intensity (2-194 and 1-121, respectively) of infestation. Both are transport hosts, which mainly feed on benthic nototheniid fish species and accumulate the nematodes. Bathypelagic, pelagic, or mainly euphausid feeding fish species were only lightly infested, if at all. This demonstrates the benthic life cycle of P. decipiens in the Antarctic. The preferred site of infestation was the body cavity and the liver; no specimen could be isolated from the fish musculature. This might be explained by the low water temperatures. The infestation of fish from the Weddell Sea was distinctly lower than that of fish around the South Shetland Islands. Besides possible differences in final host populations at the two localities studied, the loss of eggs and larvae under the eastern Weddell Sea shelf ice and over the continental slope and differences in the availability of the first intermediate and macroinvertebrate hosts led to a lower level of infestation. Another role, although nondecisive, may be played by the reduced time of development and infectivity of eggs and larvae, respectively, in the extremely cold waters of the Weddell Sea. P. decipiens is not a rare but, rather a well-established parasite of the Antarctic fauna, which demonstrates the ability of this cosmopolitan species to complete its life cycle even under conditions of subzero temperatures.

Description: On the basis of the tentacular armature, surface ultrastructure, and morphological measurements of plerocerci obtained from the musculature of butterfishes (Stromateidae), we corroborate an earlier proposal that Otobothrium crenacolle, a commonly reported trypanorhynch cestode from the northwestern Atlantic coast, is a junior synonym of O. cysticum. This action exemplifies at least an Atlantic Ocean and Indian Ocean distribution for O. cysticum. The infection in commercially important butterfishes shows that an otobothriid trypanorhynch may heavily infect fish flesh and influence the market value of some fish species yet also be restricted to the body cavity of other fish intermediate hosts. Infections of O. cysticum in the flesh of Peprilus burti (Gulf butterfish) and P. alepidotus (harvestfish) in the Gulf of Mexico has varied annually since 1970, with samples ranging in prevalence between 20% and 100% and in mean intensity between 1 and 3,500 or more plerocerci per fish. Comparative infections in P. burti from the Gulf of Mexico and P. triacanthus (butterfish) from the Atlantic Ocean demonstrate a present geographic difference in infections. The prevalence and mean intensity in 4 collections of butterfishes ranged from 9% to 98% of the fish and from 1 to 678 plerocerci in a subsample of tissue, respectively, with prevalent and heavy infections being observed in the Gulf of Mexico fish and relatively few individuals being infected with few worms in the Atlantic fish. A slight host response in the butterfishes involving some fatty infiltration and inflammatory infiltration was associated with the metacestode. In some larger fish, encapsulations were yellow, and in a few cases, worms had degenerated. This finding and an increase in intensity with fish weight suggest a continual accumulation of the worms in association with little host resistance.

Description: Fifty specimens of Notothenia coriiceps caught in Potter Cove, King George Island, were examined for ecto- and endoparasites. Of the 22 parasite species found, 18 were helminths, 2 were hirudineans and 2 were crustaceans. The isopod Aega antarctica and an unidentified hirudinean are reported for the first time from this fish host. Dominant parasites were the adults of Aspersentis megarhynchus, the invasive stage of Corynosoma spp. (cystacanth) and the adults of Macvicaria pennelli, with respective prevalences of infestation of 94, 76 and 74%. The preferred sites of infestation were the pylorus and intestine, where five different larval (nematodes and cestodes) and eight adult (digeneans and acanthocephalans) parasite species were found. No adult nematodes and cestodes were found and no parasites could be isolated from the musculature. The results of the present study are related to previous findings on the parasite fauna of N. coriiceps. The comparison implies a high parasite diversity in this benthic Antarctic fish species. Most parasites found appear to have a wide range of distribution within Antarctic waters together with a low host specificity. Besides its role as final host for several species of trematodes and acanthocephalans, N. coriiceps serves as transmitter of parasite larvae to piscivorous birds and seals. It is concluded that the parasite fauna in Antarctic fish species provides important insights into the different habitat use and trophic relationship of their fish hosts.

Description: Copepoda (Calanus finmarchicus n=1,722, Paraeuchaeta norvegica n=1,955), Hyperiidae (n=3,019), Euphausiacea (Meganyctiphanes norvegica n=4,780), and the fishes Maurolicus muelleri (n=500) and Pollachius virens (n=33) were collected in the Norwegian Deep (northern North Sea) during summer 2001 to examine the importance of pelagic invertebrates and vertebrates as hosts of Anisakis simplex and their roles in the transfer of this nematode to its final hosts (Cetaceans). Third stage larvae (L3) of A. simplex were found in P. norvegica, M. muelleri and P. virens. The prevalence of A. simplex in dissected P. norvegica was 0.26%, with an intensity of 1. Prevalences in M. muelleri and P. virens were 49.6% and 100.0%, with mean intensities of 1.1–2.6 (total fish length ≥6.0–7.2) and 193.6, respectively. All specimens of C. finmarchicus and M. norvegica examined were free of anisakid nematode species and no other parasites were detected. P. norvegica, which harboured the third stage larvae, is the obligatory first intermediate host of A. simplex in the investigated area. Though there was no apparent development of larvae in M. muelleri, this fish can be considered as the obligatory second intermediate host of A. simplex in the Norwegian Deep. However, it is unlikely that the larva from P. norvegica can be successfully transmitted into the cetacean or pinniped final hosts, where they reach the adult stage. An additional growth phase and a second intermediate host is the next phase in the life cycle. Larger predators such as P. virens serve as paratenic hosts, accumulating the already infective stage from M. muelleri. The oceanic life cycle of A. simplex in the Norwegian Deep is very different in terms of hosts and proposed life cycle patterns of A. simplex from other regions, involving only a few intermediate hosts. In contrast to earlier suggestions, euphausiids have no importance at all for the successful transmission of A. simplex in the Norwegian Deep. This demonstrates that this nematode is able to select definite host species depending on the locality, apparently having a very low level of host specificity. This could explain the wide range of different hosts that have been recorded for this species, and can be seen as the reason for the success of this parasite in reaching its marine mammal final hosts in an oceanic environment.