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Specimens of Biacetabulum macrocephalum McCrae, 1962 (Cestoda: Caryophyllidae) were first described from the white sucker, Catostomus commersoni (Lacépède) in Colorado. The white sucker appears to be its major host species in a few other states often in the Mississippi River basin. We have collected and examined this uncommon cestode, also from C. commersoni in Tichigan Lake, a tributary of the Mississippi River and from the Root River in SE Wisconsin. We update our first and only 1986 account of our Wisconsin population, with new observations and measurements, and compare with those in the original and other descriptions. The morphology of B. macrocephalum is revisited using light microscopy revealing new features. Emphasis is placed on the morphological variability of its scolex and reproductive structures especially its ovarian arms and pre- and post-ovarian vitellaria. Measurements of 10 specimens from the Root River provided an opportunity to review the taxonomy and description of the species, distinguish locality differences, and correct and update other statements and concepts by other observers. The disconnected distribution of worms from the same host species in separate waters of various states is described. |
