Four species of the genus Tetrabothrius were reported from three species of Antarctic flying seabirds. There were: Tetrabothrius (Culmenamniculus) gracilis Nybelin, 1916 and Tetrabothrius (Oriana) minutus Szpotańska, 1917 from Macronectes giganteus (Gmelin, 1789); Tetrabothrius (Oriana) filiformis Nybelin, 1916 from Larus dominicanus Lichtenstein, 1823 and Tetrabothrius (Culmenamniculus) cylindraceus Rudolphi, 1849 from Stercorarius antarcticus lonnbergi (Mathews, 1912). M. giganteus is a new host for T. (Culmenamniculus) gracilis and T. (Oriana) minutus, and L. dominicanus is a new host for T. (Oriana) filiformis. The South Shetland Islands are a new locality for T. (Oriana) minutus and T. (Culmenamniculus) gracilis.
In total, 1446 Antarctic and subantarctic teleosts were examined for nematodes. One species, Ascarophis nototheniae Johnston et Mawson, 1945, is reported. New data on the biometrical variability and the occurrence or absence of this species are given. Three areas of the West Antarctic (the South Shetland Islands, South Georgia and South Orkneys) as well as three areas of the East Antarctic (Davis Sea, Weddell Sea and off Adelie Land) are new geographical localities for this nematode species. Also, 21 fish species represent new host records for A. nototheniae. Two predatory channichthyid species, Chaenocephalus aceratas and Cryodraco antarcticus are the most strongly infected fishes in all examined areas, except the Weddell Sea.
In total, 400 teleosts of 32 species (7 families) were examined. Cercoids of Tetraphyllidea (about 41 thousands) occurred in 204 host specimens of 26 species. Three morphological forms of cercoids were recognized. They were cercoids with bothridia divided into two and three loculi, and cercoids with subcylindrical bothridia. All forms were found in fishes from the Weddell Sea for the first time. Cercoids with bilocular bothridia were the most abundant form (90.7% of all specimens); cercoids with trilocular bothridia and cercoids with subcylindrical bothridia were less numerous (6.6 and 2.7% of all specimens, respectively). Cercoids concentrated in obligatory or facultative predators, whereas pelagic and bentho-pelagic fishes feeding on crill, were rarely infected. Chionodraco hamatus was the most heavily infected - prevalence 100%, relative density 903.
Four nematode species are reported from bony fishes caught in the Weddell Sea. Two species of cystidicolids, Cystidicola beatriceinsleyae (Holloway et Kiewer, 1969) and Ascarophis nototheniae Johnston et Mawson, 1945, were found in Lycodichthys antarcticus Pappenheim, 1911, whereas one capillariid, Capillaria (Procapillaria) sp., and one anisakid, Paranisakiopsis weddelliensis sp. nov., in Macrourus whitsoni Regan, 1913. Capillaria (Procapillaria) sp. (only females were found) is characterised by: body 17.6-26.0 mm long; stichosome composed of 46-49 stichocytes; presence of a vulvar appendage, and eggs 77-82 × 37-42 µm. This is the first Capillaria species reported from fishes in the Antarctic. Paranisakiopsis weddelliensis sp. nov. is characterised by: body length of male and female 40-48 and 55-62 mm, respectively; lips up to 200 µm and interlabia up to 140 µm long; inconspicuous dentigerous ridge on each lip; 8-10 pairs of preanal and 4 pairs of postanal papillae; spicules equal or subequal, 420-620 µm; eggs 83-85 × 63-65 µm. P. weddelliensis is the first representative of this genus reported from the Antarctic.
Bony fishes (Teleostei) play an important role in the completion of life cycles of helminth parasites in the Antarctica. These fishes may be definitive, second intermediate or paratenic hosts of the helminths. The most species-rich taxon is Digenea. Virtually all of these digeneans use teleosts as definitive hosts. Only one species, Otodistomum cestoides, occurs as the adult stage in skates (Chondrichthyes), with teleosts as its second intermediate host. Among 14 cestode species maturing in fishes only one, Parabothriocephalus johnstoni, occurs in a bony fish, Macrourus whitsoni, whereas the others are parasites of Chondrichthyes (cartilaginous fishes). Antarctic Chondrichthyes are not infected with nematode and acanthocephalan species. Specificity to the intermediate and/or paratenic hosts of the majority of Antarctic helminths is wide, whereas that for definitive hosts is often narrower, restricted to one order or sometimes even to one or two host species. Almost all of 73 helminth species maturing in Antarctic fishes are endemics. Only 4 digenean and one nematode species are cosmopolitan or bipolar.