SHORT COMMUNICATION Effect of egg clustering on the fitness of Rhipicephalus sanguineus larvae Rafael Antonio Nascimento Ramos & Alessio Giannelli & Filipe Dantas-Torres & Domenico Otranto Received: 22 November 2012 / Accepted: 28 November 2012 # Springer-Verlag Berlin Heidelberg 2012 Abstract Several biological aspects of Rhipicephalus sangui- neus have been studied, but scant information is available on the effect of egg clustering on incubation period and larval survival. Herein, R. sanguineus eggs were separated in groups composed by 1 (GI), 10 (GII), 50 (GIII), 100 (GIV), 500 (GV) and 1,000 (GVI) eggs (10 replicates), and incubation and larval survival period were recorded. No correlation was ob- served between the amount of egg batches and hatching per- centage. Larvae from GI hatched in a longer time (mean 17 days), than those of other groups (mean 14.9 days). This difference was significant in eggs from group GI vs. GV and GI vs. GVI (P <0.05). Conversely, GI displayed a shorter survival period (mean 28.7 days) compared with other groups (P <0.01). The maximum survival time was recorded in GV (mean 49.8 days). Data suggest that R. sanguineus egg clustering affects incubation period and larval survival. Introduction Ticks (Acari: Ixodida) are worldwide distributed and well adapted to different environmental conditions (Dantas-Torres 2008; Jiang et al. 2010). Their global importance relies on their blood sucking activity and role as vectors of pathogens affecting animals and human beings (Sonenshine and Mather 1994; Vantasever et al. 2008). Rhipicephalus sanguineus, also known as the “brown dog tick” or “kennel tick”, is regarded as one of the most important blood-feeding arthropods, and it is a suspected or competent vector of many pathogens (e.g., Ana- plasma platys, Ehrlichia canis, Hepatozoon canis, Babesia vogeli, Cercopithifilaria sp., Rickettsia rickettsii and Rickett- sia conorii) of veterinary and medical concern (Márquez et al. 2008; Dantas-Torres et al. 2012a, b). This tick is also acknowl- edged as a gregarious species, being usually found clustered together during the off-host phase of its life cycle (Dantas- Torres et al. 2010). Tick clustering has been described in different species (e.g., Dermacentor variabilis and Haema- physalis longicornis), most likely as a strategy to cope with prohibitive environmental conditions, such as the low relative humidity (Yoder and Knapp 1999; Yoder et al. 2004). As far as R. sanguineus is concerned, the aggregation of females affects their reproduction efficiency and egg incubation period (Dantas-Torres and Otranto 2011), and the aggregation of larvae impacts on the moulting process to nymphs (Cançado et al. 2007). In addition to current knowledge available, the effect of egg clustering on their incubation period and larval survival has been here investigated. Materials and methods Ticks Engorged females were collected from the environment in a private dog shelter located in southern Italy, highly infested by ticks throughout the year (Lorusso et al. 2010). In the labora- tory, ticks were rinsed with distilled water and dried with filter paper, being then identified as R. sanguineus, following the morphological keys proposed by Walker et al. (2000). Study design Ten engorged females, with homogeneous weight (data not shown), were placed in individual vials and kept in an R. A. N. Ramos : A. Giannelli : F. Dantas-Torres : D. Otranto (*) Dipartimento di Medicina Veterinaria, Università degli Studi di Bari, 70010 Valenzano, Bari, Italy e-mail: domenico.otranto@uniba.it F. Dantas-Torres Centro de Pesquisas Aggeu Magalhães (Fiocruz-PE), 50670-420 Recife, Pernambuco, Brazil Parasitol Res DOI 10.1007/s00436-012-3229-7