Taxonomic status of Ixodes didelphidis (Acari: Ixodidae)

Ixodes didelphilis Fonseca & Aragão was described in Brazil in 1952 as a new tick species that differed from Ixodes loricatus Neumann by the spiracular plate pattern. We have reared four tick colonies from different geographic areas in the laboratory that were started from single engorged females originally identified as I. didelphidis (BMG, colony ) and I. Iocicatus (CSP, PSP, and TRJ colonies). We analyzed the spiracular plate morphology of F1 adult ticks from each tick colony, compared their biological 11th, and performed a molecular analysis of the second internal transcribed rDNA spacer (ITS2) to test the validity of the species I. didelphidis. The spiracular plate analysis of laboratory F1 adult ticks yielded single females from the four colonies showed variations that invalidate morphological parameters for differentiation of loricatus and I. didelphidis. Biological data of the BMC, CSP, and TRJ colonies were similar. The biology ofthe PSP colony was not evaluated. The ITS2 sequence variations observed between the tick colonies ranged from 1.3 to 4.9%, and the similarity tree constructed by the neighbor-joining method with nucleotide distances showerl that the distances between the samples were similar to what is expected for intraspecific variations found in other ticks species. The morphological and biological results, in conjunction with the ITS2 analysis, supported the conspecificity I. loricatus and I. didelphidis.