From material collected by into a residence house at Rio de Janeiro city, using an aspirator machine during four continues hours in all house, it was captured 1,284 Rhipicephalus sanguineus including 289 females; one of them showed a mutagenic alteration like an asymmetry of opistosome, and monstrosity like a two anus. The first register of this phenomenon in R. sanguineus is reported.
tick; mutagenic occurence; asymmetry
