Taenia crassiceps was common in Vulpes fulva examined from southern Ontario. Metacestodes occurred naturally in Microtus pennsylvanicus, Marmota monax, Tamias striatus, and Ondatra zibethicus, and Peromyscus maniculatus, Tamiasciurus hudsonicus, and Sciurus carolinensis were infected experimentally; all rodents are new host records. Cysticerci developed into adults in dogs or foxes within 5 to 6 weeks; five coyote pups resisted infection. Development of the metacestode was followed mainly in white mice. Infections were most common subcutaneously, but also occurred in both body cavities. Mice approximately 4 weeks of age were most susceptible. Asexual reproduction occurred by exogenous, and rarely endogenous, budding from the abscolex pole beginning approximately 3 weeks after infection. Metacestodes in various stages of development were injected into mice subcutaneously, intrapleurally, but mainly intraperitoneally. Subsequent development and reproduction were similar to that following infection with eggs. Apparently all metacestodes are capable of budding. The initial rate of reproduction was higher subcutaneously and intrapleurally than intraperitoneally, but within approximately 100 days the rate became higher and continued higher intraperitoneally than elsewhere. Reproduction never reached a logarithmic rate. Metacestodes inoculated serially up to 21 times at 50-day intervals increased greatly in size and continued budding. Four other series were maintained by serial subinoculation at 50-day intervals through 23 generations without a significant change in the rate of reproduction.

No abstract

Taenia mustelae Gmelin, 1790 (= T. tenuicollis Rudolphi, 1819) is proposed as the valid name for the small-hooked cestode from European brown weasel, and Taenia martis (Zeder, 1803) n. comb. (= T. intermedia Rudolphi, 1810) is proposed for the large-hooked cestode from European marten. T. mustelae adults were found naturally in the short-tailed weasel, Mustela erminea, and T. martis adults in the pine marten, Martes americana in North America; the latter constitutes a new host record. Larvae were recovered from 10 species of rodents of which Citellus franklinii, Eutamias minimus, Marmota monax, Tamias striatus, Synaptomys cooperi, and Zapus hudsonius are new host records. Experimental infections produced by feeding T. mustelae eggs were followed in eight species of rodents. In one animal mature scoleces occurred as early as 26 days after eggs were fed, yet no fully developed scoleces were present even after 104 days in another animal in the same feeding. Such feedings of eggs produced multiscolex larvae (up to 26 scoleces), or multiscolex and uniscolex larvae simultaneously, but never uniscolex larvae exclusively, although these were found occasionally in nature. Normal, fully developed scoleces were present on larvae 318 days old. Growth of T. mustelae larvae in Peromyscus maniculatus and the host reaction is described in detail. Multiscolex larvae from a natural infection fed to a mink produced adult T. mustelae.

No abstract

Proteocephalus parallacticusMacLulich is common throughout the year in lake trout (Salvelinus namaycush).