Ticks and Tick-borne Diseases 1 (2010) 75–99 Contents lists available at ScienceDirect Ticks and Tick-borne Diseases journal homepage: www.elsevier.de/ttbdis Original article Nymphs of the genus Amblyomma (Acari: Ixodidae) of Brazil: descriptions, redescriptions, and identification key Thiago F. Martins a , Valeria C. Onofrio b , Darci M. Barros-Battesti b , Marcelo B. Labruna a,∗ a Department of Preventive Veterinary Medicine and Animal Health, Faculty of Veterinary Medicine, University of São Paulo, São Paulo, SP, Brazil b Laboratory of Parasitology, Butantan Institute, São Paulo, SP, Brazil article info Article history: Received 23 January 2010 Received in revised form 12 March 2010 Accepted 14 March 2010 Available online 20 April 2010 Keywords: Amblyomma Nymphs Description Identification key Brazil abstract Together with the larval stage, the nymphal stage of ticks of the genus Amblyomma are the most aggres- sive ticks for humans entering areas inhabited by wildlife and some domestic animals in Brazil. However, due to the absence of morphological descriptions of the nymphal stage of most Brazilian Amblyomma species, plus the lack of an identification key, little or nothing is known about the life history of Ambly- omma spp. nymphs in the country. In the present study, morphological description of the nymphal stage, illustrating important external characters through scanning electron microscopy, is provided for nymphs of 15 Amblyomma species that occur in Brazil, for which the nymphal stage had never been described: A. aureolatum, A. auricularium, A. calcaratum, A. coelebs, A. fuscum, A. humerale, A. incisum, A. latepunctatum, A. naponense, A. nodosum, A. ovale, A. pacae, A. pseudoconcolor, A. scalpturatum, A. varium. In addition, the nymphal stage of 12 Amblyomma species, which had been previously described, are redescribed: A. brasiliense, A. cajennense, A. dissimile, A. dubitatum, A. longirostre, A. oblongoguttatum, A. parkeri, A. parvum, A. romitii, A. rotundatum, A. tigrinum, A. triste. The descriptions and redescriptions totalized 27 species. Only 2 species (A. geayi, A. goeldii) out of the 29 Amblyomma species established in Brazil are not included in the present study. A dichotomous identification key is included to support taxonomic identification of the nymphal stage of 27 Amblyomma species established in Brazil. © 2010 Elsevier GmbH. All rights reserved. Introduction The genus Amblyomma (Acari: Ixodidae) is currently repre- sented by 130 valid tick species (Nava et al., 2009a, 2009b), 29 of which (22.3%) are established in Brazil (Dantas-Torres et al., 2009). While the adult stage of these 29 species has been morphologi- cally well described, resulting in good identification keys, the same cannot be said for the immature stages (Guglielmone et al., 2003; Onofrio et al., 2006). The nymphal stage of 17 Amblyomma species from Brazil remains undescribed. This scenario has precluded the construction of identification keys. Consequently, taxonomic iden- tification to species level of field-collected Amblyomma nymphs has been a laborious and very difficult task, sometimes impossible. For example, species identification of field-collected Amblyomma nymphs in recent studies in Brazil were possible only because these nymphs were reared to the adult stage in the laboratory or because molecular methods were applied, such as DNA sequencing of molecular markers previously determined for each species through the adult stage (Labruna et al., 2007; Ogrzewalska et al., 2009). ∗ Corresponding author at: Faculdade de Medicina Veterinária e Zootecnia, Uni- versidade de São Paulo, Av. Prof. Orlando Marques de Paiva 87, Cidade Universitária, 05508-270 São Paulo, SP, Brazil. Tel.: +55 11 3091 1394; fax: +55 11 3091 7928. E-mail address: labruna@usp.br (M.B. Labruna). Herein, we describe the nymphal stage of 15 Amblyomma species for the first time and redescribe the nymphal stage of another 12 Amblyomma species from Brazil. In addition to providing scanning electron micrographs of the nymphs, we also include an identifi- cation key for the 27 Amblyomma species evaluated in the present study. Materials and methods During 2000–2009, tick colonies of 23 Amblyomma species from Brazil were maintained in the laboratory of the Faculty of Veteri- nary Medicine of the University of São Paulo at different periods for different purposes. Unfed nymphs, 15–30 days old, of the first laboratory generation (F 1 ) of each species were killed in hot water (70–80 ◦ C) and immediately preserved in 70% alcohol until further processing for description or redescription. In addition, alcohol- preserved F 1 unfed nymphs from laboratory colonies of 3 other Amblyomma species were kindly provided by colleagues from other institutions, as stated in the Acknowledgments. All these 26 tick colonies started with field-collected ticks as stated in Table 1. Species identification of the tick colonies was undertaken during the adult stage (F 0 ) using specific identification keys and corre- sponding morphological redescriptions available in the current literature (Robinson, 1926; Aragão and Fonseca, 1961; Jones et 1877-959X/$ – see front matter © 2010 Elsevier GmbH. All rights reserved. doi:10.1016/j.ttbdis.2010.03.002