Host specificity of Laelaps (Acari: Laelapidae) in central Brazil.

A study of associations between small mammals and ectoparasites in two adjacent nature reserves near Brasilia, Federal District, Brazil, revealed that ectoparasitic mites of the genus Laelaps Koch are host specific. Data on the prevalence and intensity of mite infestations were combined with measures of the reproductive activity of mite populations to estimate the association of each host-mite pair. Twelve morphologically distinct species of Laelaps occurred in monoxenous and oligoxenous associations with the cricetid rodent genera Oryzomys, Nectomys, Rhipidomys, and Calomys. Nine were referred to species recognized at the time of the study; three were described as new species in a recent publication. When mites initially assigned as the same species infested more than one host species, an examination of the morphological variation within and among mite specimens supported the hypothesis that mites infesting different hosts were reproductively isolated populations. Dispersal pathways apparently were restricted, occurring primarily between conspecific individuals. In one instance, two morphologically similar groups of Laelaps paulistanensis Fonseca were associated with two closely related rodent species, Oryzomys fornesi Massoia and O. nigripes (Olfers). Although the data presented here indicate that these two groups of mites are conspecific, further study is warranted.