Morphological variation of Moniliformis moniliformis (Bremser 1811) Travassos 1915 and Moniliformis clarki (Ward 1917) Chandler 1921.

A two-way fixed model analysis of variance was used to test Moniliformis moniliformis and M. clarki for inter- and intraspecific differences with respect to 7 morphological characters used to distinguish species of the genus. M. clarki was sexually dimorphic in more characters than was M. moniliformis when specimens from their usual definitive hosts, Spermophilus tridecemlineatus and Rattus norvegicus, respectively, were compared. More characters were sexually dimorphic in both species reared in hamsters, Mesocricetus auratus, than in their usual definitive hosts or M. clarki from rats. Moniliformis clarki and M. moniliformis (n = 25 each sex, each species) from their usual hosts were significantly different at the 1% level in 6 of 7 characters studied. Further M. clarki of either sex from ground squirrels did not differ significantly in any of the 7 characters from those of the same sex from rats. When reared in hamsters, the range in number of longitudinal rows of proboscis hooks of female M. moniliformis included that of M. clarki, but the 2 species were distinct in each of the other features which distinguished them in rats and ground squirrels.