The ecology of Echinococcus multilocularis (Cestoda: Taeniidae) on St. Lawrence Island, Alaska. II. Helminth populations in the definitive host.

The helminths of 1,579 arctic foxes from St. Lawrence Island were investigated by standard methods. The foxes, obtained mainly during the winter from fur trappers, harbored 22 species of helminths. Four of those were trematodes, viz., Maritrema afanassjewi Belopol'skaia, 1952, Orthosplanchnus pygmaeus Iurakhno, 1967, Plagiorchis elegans (Rudolphi, 1802) and Alaria marcianae (LaRue, 1917), each of which occurred in a single host. Two species of cestodes, Diphyllobothrium dendriticum (Nitzsch, 1824) and Mesocestoides kirbyi Chandler, 1940, were uncommon (in 2.7 and 1.3% of the foxes, respectively). Taenia polyacantha Leuckart, 1856 and Echinococcus multilocularis Leuckart, 1863 were present in about 80% of the foxes, and Taenia crassiceps (Zeder, 1800) in less than 10%. The specimens of Taenia spp. from the autumn-winter sample were usually destrobilate. In about 2% of the foxes, acanthocephalans of six species occurred. Four of those, of the genus Corynosoma Lühe, 1904, were common in marine mammals of the region; a fifth, Corynosoma clavatum Goss, 1940, has been reported previously only from marine birds of the Southern Hemisphere; and the sixth, Polymorphus cf. minutus (Goeze, 1782), has been found widely in waterfowl of the Northern Hemisphere. Of the nematodes, Sobolophyme baturini Petrov, 1930, Cylicospirura felineus (Chandler, 1925), and Physaloptera sp. were rare (with each in only one to three foxes). Trichinella nativa Boev et Britov, 1972 and Crenosoma vulpis (Dujardin, 1844) were uncommon (1.5 and 4%, respectively). The nematodes most often present were Toxascaris leonina (von Linstow, 1902) (89%) and Uncinaria stenocephala (Railliet, 1884) (40%). Several of the rare to uncommon helminths probably were transported to the island by foxes immigrating from the adjacent continents via the pack ice.

Postoncospheral development and cycle of Taenia polyacantha Leuckart, 1856 (Cestoda: Taeniidae). First part.

The postoncospheral development and cycle of Taenia polyacantha Leuckart, 1856, an holarctic species of cestode, were investigated in the laboratory as well as in the tundra of northern Alaska. Foxes, Alopex lapogus (L.) and Vulpes vulpes (L.), serve as final host of T. polyacantha; the northern vole, Microtus oeconomus (Pallas), and the brown lemming, Lemmus sibiricus (Kerr), are important as the intermediate host. As determined in experimentally infected voles and lemmings, the oncosphere of T. polyacantha transformed to a primary vesicle in the liver. On the 6th day postexposure, coinciding with its migration to the peritoneal cavity, the larval cestode consisted of a minute aggregation of secondary vesicles. By 9-10 days postexposure, the secondary vesicles dissociated, thereafter developing independently to infective cysticerci by 30-40 days postexposure. At an age of about 60 days, the infective larvae began to undergo further growth and morphological modification, which led to acquisition of some strobilar characteristics by the forebody. Such late transformation of a cysticercus to a more advanced form of larva is known otherwise only in Taenia martis (Zeder, 1803). Differences in numbers and sizes of rostellar hooks provided the basis for recognition of two taxa at the infraspecific level: Taenia p. polyacantha Leuckart, 1856, distributed in Eurasia to the south of the zone of tundra, and T. p. arctica ssp. nov., present throughout the holarctic tundra. Observations concerning interactions of T. polyacantha and its hosts are discussed.

Antibodies to marine caliciviruses in the Pacific walrus (Odobenus rosmarus divergens Illiger).

Sera from 155 Pacific walruses (Odobenus rosmarus divergens Illiger), sampled in the Chukchi Sea during the summer of 1983, were tested for serum neutralizing (SN) antibodies to six marine calicivirus serotypes. Serotypes tested included San Miguel sea lion virus (SMSV) types 1, 5, 8, and 10, previously isolated from northern fur seals (Callorhinus ursinus Linné) in the Bering Sea; walrus calicivirus (WCV), previously isolated from walrus feces collected off sea ice in the Chukchi Sea; and Tillamook calicivirus (TCV), a bovine isolate from Oregon of suspected marine origin. No antibodies were found to SMSV-1, SMSV-10, or TCV. Antibodies to SMSV-5 were found in two animals (titers 1:20 and 1:160); antibodies to SMSV-8 were found in four animals (all 1:20); and antibodies to WCV were found in one animal (titer 1:40). Antibodies to WCV have been found in the Pacific walrus previously; however, this represents the first report of antibodies to any of the SMSV serotypes in this marine mammal.

Nasal mites (Acari:Halarachnidae) in the spotted seal, Phoca largha Pallas, and other pinnipeds of Alaskan waters.

The nasal passages of 349 pinnipeds of seven species were examined for halarachnid mites. Each of seven Steller sea lions (Eumetopias jubatus), 75 of 99 harbor seals (Phoca vitulina), and four of 71 spotted seals (P. largha) were infected, but none of 28 walruses (Odobenus rosmarus), 43 ringed seals (Phoca hispida), 58 ribbon seals (P. fasciata), and 43 bearded seals (Erignathus barbatus) was infected. The sea lions harbored Orthohalarachne attenuata (Banks, 1910) and O. diminuata (Doetschman, 1944), and the harbor and spotted seals harbored Halarachne halichoeri Allman, 1847. The finding of H. halichoeri in the spotted seals is a new host record.