Taxonomic Status ofIxodes didelphidis(Acari: Ixodidae)

Ixodes didelphidis Fonseca & Araga ˜o 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 identiÞed as I. didelphidis (BMG colony) and I. loricatus (CSP, PSP, and TRJ colonies).We analyzed the spiracular plate morphology of F 1 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 F 1 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 intraspeciÞc variations found in other ticks species.The morphological and biological results, in conjunction with the ITS2 analysis, supported the conspeciÞcity of I. loricatus and I. didelphidis.RESUMO Ixodes didelphidis Fonseca e Araga ˜o foi descrito no Brazil em 1952 como uma nova espe ´cie de carrapato que se diferenciava de Ixodes loricatus Neumann atrave ´s do padra ˜o da placa espiracular.No ´s criamos em laborato ´rio quatro colo ˆnias de carrapatos de diferentes a ´reas geogra ´Þcas, iniciadas a partir de fe ˆmeas ingurgitadas originalmente identiÞcadas como I. didelphidis (colo ˆnia BMG) e I. loricatus (colo ˆnias CSP, PSP, e TRJ).No ´s analisamos a morfologia da placa espiracular dos adultos F 1 de cada colo ˆnia, comparamos seus dados biolo ´gicos e Þzemos uma ana ´lise molecular do segundo espac ¸o transcrito interno do rDNA (ITS2) para veriÞcar a validade da espe ´cie I. didelphidis.A ana ´lise da placa espiracular de adultos provenientes de uma mesma fe ˆmea de cada uma das colo ˆnias demonstrou resultados controversos que invalidam os para ˆmetros morfolo ´gicos publicados para diferenciac ¸a ˜o de I. loricatus e I. didelphidis.Os dados biolo ´gicos das colo ˆnias BMG, CSP, e TRJ foram similares.As variac ¸o ˜es nas sequ ¨e ˆncias do ITS2 entre as colo ˆnias de carrapatos (amplitude: 1,3Ð4,9%) e a a ´rvore de similaridade com as dista ˆncias de nucleotõ ´deos mostraram que as dista ˆncias entre as amostras foram similares ao esperado para variac ¸o ˜es intra-especõ ´Þcas encontradas em outras espe ´cies de carrapatos.Os resultados morfolo ´gicos, biolo ´gicos e moleculares fornecem evide ˆncias para considerarmos I. loricatus e I. didelphidis como a mesma espe ´cie. KEY WORDS Ixodes loricatus, Ixodes didelphidis, spiracular plate, biology, second internal transcribed spacerDuring the last two decades, several studies have been conducted on the biology, epidemiology, and taxonomic status of various members of the genus Ixodes, as well as their interaction with various pathogens.Recent investigations determined the capability of Ixodes ticks for transmitting Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt & Brenner sensu lato genospecies to humans or domestic and wild animals, indicating the tick potential for maintaining enzootic foci of borreliosis (Gray 1998, Oliver 1999).More than 35 species of Ixodes have been reported in the Neotropical zoogeographic region, but this genus is one of the most difÞcult to distinguish taxonomically and there are still several doubtful species throughout the world (Clifford et al. 1973).We followed the protocol, which agrees with Ethical Principles in Animal Research adopted by Brazilian College of Animal Experimentation (COBEA), and was approved by the Biomedical Sciences Institute/USP-Ethical Committee for Animal Research (CEEA).Permits and approvals are on Þle in the ofÞce of T.T.S.S.