Cestodes and Nematodes of Antarctic Fishes and Birds

Tapeworms (Platyhelminthes, Cestoda) from marine chondrichthyans of the Southwestern Atlantic Ocean, and the sub-Antarctic and Antarctic islands: a checklist

A parasite-host list of cestodes parasitizing chondrichthyans in the Southwest Atlantic off Argentina and surrounding waters of Antarctica is compiled based on the available literature. The list is based on published descriptions and redescriptions of species, and newly collected worms during the current study. A total of 57 valid species belonging to 28 genera of the orders Cathetocephalidea, Diphyllidea, Gyrocotylidea, Lecanicephalidea, Onchoproteocephalidea, Phyllobothriidea, Rhinebothriidea, "Tetraphyllidea", and Trypanorhyncha is listed. Information on hosts, localities, specimens in collections and comments on tapeworms are also included. A host-parasite list including chimaeras (1 order, 1 genus), batoids (4 orders, 10 genera), and sharks (3 orders, 5 genera) is provided. Tapeworm diversity, distribution range, and host associations are discussed. The cestodes orders Phyllobothriidea and Rhinebothriidea exhibit the highest species richness, with 13 and 12 species, respectively. Onchoproteocephalideans and rhinebothriideans have the broadest geographic distribution in the study area. Regarding hosts, arhynchobatid skates are the group most frequently associated with cestodes. However, further collecting efforts are necessary to understand whether this data reflect the real diversity and host association of these parasites or is a result of a bias in sampling.

Infection patterns of helminth community in black rockcod Notothenia coriiceps in West Antarctica over a 6-year term

Patterns of the rockcod Notothenia coriiceps infection with helminths were analysed to understand the dynamics of parasite communities in this Antarctic fish and to test their stability over time. The study was performed using helminth samples collected from 183 N. coriiceps in 2014-2015 and 2020-2021 in the vicinity of the Ukrainian Antarctic station (UAS) "Akademik Vernadsky", Galindez Island, Argentine Islands, West Antarctica. Overall, 25 helminth taxonomical categories (nine trematodes, four cestodes, five nematodes, and seven acanthocephalans) were subjected to analysis. A direct comparison of the helminth population characteristics showed that nine species significantly changed their infection parameters during the 6 years between the samples. Seven of them (Pseudoterranova sp., Contracaecum sp., Ascarophis nototheniae, monolocular metacestodes, bilocular metacestodes, Metacanthocephalus rennicki, and Diphyllobothrium sp.) were found to have a significant impact on the differences between helminth infracommunities in 2014-2015 and 2020-2021. Most studied patterns of helminth component community appeared to show a stable tendency, and observed fluctuations were close to the steady trend. Slight but significant changes in the infection patterns observed in this study might have been caused by changes in the populations of intermediate, paratenic, and definitive hosts of helminths (marine invertebrates, mammals, and birds), which participate in helminth transmission in Antarctic ecosystems.

Parasites of Three Closely Related Antarctic Fish Species (Teleostei: Nototheniinae) from Elephant Island

BACKGROUND

Studies of parasite communities and patterns in the Antarctic are an important knowledge base with the potential to track shifts in ecological relations and study the effects of climate change on host-parasite systems. Endemic Nototheniinae is the dominant fish group found in Antarctic marine habitats. Through their intermediate position within the food web, Nototheniinae link lower to higher trophic levels and thereby also form an important component of parasite life cycles. The study was set out to gain insight into the parasite fauna of Nototheniops larseni, N. nudifrons and Lepidonotothen squamifrons (Nototheniinae) from Elephant Island (Antarctica).

METHODS

Sampling was conducted at three locations around Elephant Island during the ANT-XXVIII/4 expedition of the research vessel Polarstern. The parasite fauna of three Nototheniine species was analysed, and findings were compared to previous parasitological and ecological research collated from a literature review.

RESULTS

All host species shared the parasites Neolebouria antarctica (Digenea), Corynosoma bullosum (Acanthocephala) and Pseudoterranova decipiens E (Nematoda). Other parasite taxa were exclusive to one host species in this study. Nototheniops nudifrons was infected by Ascarophis nototheniae (Nematoda), occasional infections of N. larseni with Echinorhynchus petrotschenkoi (Acanthocephala) and L. squamifrons with Elytrophalloides oatesi (Digenea) and larval tetraphyllidean Cestoda were detected.

CONCLUSION

All examined fish species' parasites were predominantly euryxenous regarding their fish hosts. The infection of Lepidonotothen squamifrons with Lepidapedon garrardi (Digenea) and Nototheniops larseni with Echinorhynchus petrotschenkoi represent new host records. Despite the challenges and limited opportunities for fishing in remote areas, future studies should continue sampling on a more regular basis and include a larger number of fish species and sampling sites within different habitats.

Helminth Assemblages of the Antarctic Black Rockcod, Notothenia coriiceps (Actinopterygii: Nototheniidae) in Coastal Waters near Galindez Island (Argentine Islands, West Antarctic): Temporal Changes in the Endoparasite Community

PURPOSE

Analysis and comparison of the helminth assemblages in Antarctic rockcod Notothenia coriiceps collected near the UAS "Akademik Vernadsky" (Argentine Islands, West Antarctica) in 2002 and 2014-2015 were performed to characterise the parasite community and investigate the temporal changes in helminth assemblages and infection parameters.

METHODS

All specimens of N. coriiceps (n = 194) were caught at depths of 10-30 m. Parasites (22,856 helminth specimens and 15,057 cysts) were collected manually and identified based on their morphology. Statistical analysis of the quantitative data was performed using the Quantitative Parasitology 3.0 (QP 3.0), Paleontological Statistics (PAST v. 3.1), and PRIMER 6 software.

RESULTS

Twenty-seven species of four taxonomic groups were recorded: trematodes (8 species), cestodes (4), nematodes (5), and acanthocephalans (10). Helminth samples collected in 2002 and 2014-2015 showed a rather high similarity in species composition. The species richness was higher in the sample collected in 2014-2015, while the evenness and diversity in the two samples were similar. The dissimilarity between helminth infracommunities in the two samples appeared to be statistically significant. Larval cestodes Diphyllobotrium sp., the acanthocephalan Metacanthocephalus rennicki, and the trematode Neoleoburia antarctica were found to make the most significant impact on the dissimilarity.

CONCLUSIONS

The analysis of the composition and structure of helminth community in N. coriiceps revealed the changes that have happened during the last decade. At least some of the changes are attributed to the changes in marine ecosystems in Western Antarctica.

Checklist of the cestode parasites of wild birds of Argentina

An annotated checklist of the cestode parasites of Argentinean wild birds is presented, as the result of a compilation of parasitological papers published between 1900 and April 2021. This review provides data on hosts, geographical distribution, sites of infection, location of material deposited in helminthological collections, references and taxonomic comments. A host/parasite list is also provided. During this period, 38 papers were published that gather information about 34 cestode nominal species and 11 taxa identified at generic level, belonging to three orders, ten families and 35 genera. The highest number of cestode taxa was recorded in the family Hymenolepididae, with 12 nominal species and two taxa identified at generic level, followed by Dilepididae, with eight nominal species and three taxa identified at generic level. Of the 1042 species of birds reported in Argentina, only 29 (2.8%) were reported as hosts of adult cestodes. The families of birds with the highest number of reported taxa were Laridae and Anatidae, with 20 and 14 taxa, respectively.

Emerging global novelty in phyllobothriidean tapeworms (Cestoda: Phyllobothriidea) from sharks and skates (Elasmobranchii)

New genera are erected for three clades of tapeworms originally discovered using molecular sequence data. The morphological features of each are characterized after examination of specimens with light and scanning electron microscopy. Rockacestus gen. nov. parasitizes skates. Ruhnkebothrium gen. nov. parasitizes hammerhead sharks. Yamaguticestus gen. nov. parasitizes small squaliform sharks and catsharks. The novelty of these genera is supported by a taxonomically comprehensive molecular phylogenetic analysis of the D1–D3 region of the 28S rDNA gene, which, with the addition of newly generated sequence data, is the first to include representation of 15 of the 18 genera of phyllobothriideans plus the three new genera. Five new species are described from elasmobranchs in the western Atlantic Ocean, the Gulf of California, Chile, the Falkland Islands and South Africa to help circumscribe the new genera. Two of the genera provide appropriate generic homes for ten species of phyllobothriideans from catsharks and skates with uncertain generic affinities and thus resolve longstanding taxonomic issues. Given that these genera parasitize some of the most poorly sampled groups of elasmobranchs (i.e. hammerhead sharks, squaliform sharks, catsharks and skates), based on the strict degree of host specificity observed, we predict that further work on other members of these groups will yield as many as 200 additional species in these three genera of tapeworms globally. This brings the total number of genera in the Phyllobothriidea to 21.

Lighten up the dark: metazoan parasites as indicators for the ecology of Antarctic crocodile icefish (Channichthyidae) from the north-west Antarctic Peninsula

Due to its remote and isolated location, Antarctica is home to a unique diversity of species. The harsh conditions have shaped a primarily highly adapted endemic fauna. This includes the notothenioid family Channichthyidae. Their exceptional physiological adaptations have made this family of icefish the focus of many studies. However, studies on their ecology, especially on their parasite fauna, are comparatively rare. Parasites, directly linked to the food chain, can function as biological indicators and provide valuable information on host ecology (e.g., trophic interactions) even in remote habitats with limited accessibility, such as the Southern Ocean. In the present study, channichthyid fish (Champsocephalus gunnari: n = 25, Chaenodraco wilsoni: n = 33, Neopagetopsis ionah: n = 3, Pagetopsis macropterus: n = 4, Pseudochaenichthys georgianus: n = 15) were collected off South Shetland Island, Elephant Island, and the tip of the Antarctic Peninsula (CCAML statistical subarea 48.1). The parasite fauna consisted of 14 genera and 15 species, belonging to the six taxonomic groups including Digenea (four species), Nematoda (four), Cestoda (two), Acanthocephala (one), Hirudinea (three), and Copepoda (one). The stomach contents were less diverse with only Crustacea (Euphausiacea, Amphipoda) recovered from all examined fishes. Overall, 15 new parasite-host records could be established, and possibly a undescribed genotype or even species might exist among the nematodes.