Dictyocaulus hadweni, Chapin, 1925

A. Danks, Hannah, Sobotyk, Caroline, N. Saleh, Meriam, Kulpa, Matthew, L. Luksovsky, Joe, Jones, Lee C & Verocai, Guilherme G., 2022, Opening a can of lungworms: Molecular characterization of Dictyocaulus (Nematoda: Dictyocaulidae) infecting North American bison (Bison bison), International Journal for Parasitology: Parasites and Wildlife 18, pp. 128-134 : 132

4.2. Novel species or Dictyocaulus hadweni ?

The lack of adult Dictyocaulus specimens isolated from North American plains bison for detailed morphologic assessment hampers direct comparison with the description of D. hadweni , a species that has been considered invalid by Dikmans (1936), following reassessment of its type-specimens. The original description of D. hadweni is relatively poor, contains confusing if not erroneous morphological comparisons with other Dictyocaulus species, and male specimens were considered virtually indistinguishable from those of D. viviparus from cattle. The most recent revision of the genus Dictyocaulus also failed to recognize D. hadweni as a valid species ( Gibbons and Khalil, 1988). Nevertheless, the morphological differentiation among adult male and female can be rather challenging, and recent studies integrating classical and molecular approaches have recognized two new species in Eurasian cervids, namely D. capreolus and D. cervi , and a proposed susbspecies infecting the European bison, D. v. viviparus ( Gibbons and Khalil, 1988; Gibbons and H¨oglund, 2002; Pyziel et al., 2017, 2020). Overall, these recent advances around the biodiversity of the genus Dictyocaulus suggest that cryptic species may yet to be recognized, especially since our analysis identified a previously uncharacterized species genetically distinct from both D. viviparus and the proposed subspecies D. v. bisontis described in European bison ( Pyziel et al., 2020) .

Our laboratory has begun acquiring adult nematode specimens from North American plains bison for a detailed morphological characterization in tandem with the confirmation of the species identity based on our ITS2 and cox1 data. Future studies should include experimental infections with Dictyocaulus of cattle to elucidate transmissibility as well as additional fecal samples from cattle which co graze with bison.