Variation and Criteria for Generic and Specific Determination of Diphyllobothriid Cestodes

Abstract

In a recent publication, Vik (1964) p. 6, observed, “Although the genus Diphyllobolhrium Cobbold, 1858, has been revised several times (Liihe, 1910, Cohn, 1912, Stunkard, 1949, Wardle and McLeod, 1952, and Yamaguti, 1959) since the type species was described by Cobbold in 1858, the systematics of the group are still in a state of confusion and identification is made difficult by discrepancies in original and subsequent descriptions. However, the significant facts here are that Diphyllobothrium species from land mammals and fish-eating birds, those about whose life cycle we know most, do not seem to be especially host specific; and that in tapeworm specimens of the same species—factors such as the age of the worm, age and nutrition of the host, degree of crowding in the intestines, etc., as well as the species of host used, may result in marked differences in appearance.” This appraisal of the situation is modest and conservative.