Taxonomic Status of Ixodes didelphidis (Acari: Ixodidae)

Ixodes didelphidis 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. loricatus (CSP, PSP, and TRJ colonies). We analyzed the spiracular plate morphology of F1 adult ticks from each tick colony, compared their biological data, 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 from single females from the four colonies showed variations that invalidate morphological parameters for differentiation of I. loricatus and I. didelphidis. Biological data of the BMG, CSP, and TRJ colonies were similar. The biology of the 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 showed 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 of I. loricatus and I. didelphidis. RESUMO Ixodes didelphidis Fonseca e Aragão foi descrito no Brazil em 1952 como uma nova espécie de carrapato que se diferenciava de Ixodes loricatus Neumann através do padrão da placa espiracular. Nós criamos em laboratório quatro colônias de carrapatos de diferentes áreas geográficas, iniciadas a partir de fêmeas ingurgitadas originalmente identificadas como I. didelphidis (colônia BMG) e I. loricatus (colônias CSP, PSP, e TRJ). Nós analisamos a morfologia da placa espiracular dos adultos F1 de cada colônia, comparamos seus dados biológicos e fizemos uma análise molecular do segundo espaço transcrito interno do rDNA (ITS2) para verificar a validade da espécie I. didelphidis. A análise da placa espiracular de adultos provenientes de uma mesma fêmea de cada uma das colônias demonstrou resultados controversos que invalidam os parâmetros morfológicos publicados para diferenciação de I. loricatus e I. didelphidis. Os dados biológicos das colônias BMG, CSP, e TRJ foram similares. As variações nas seqüências do ITS2 entre as colôn