Contents lists available at ScienceDirect Ticks and Tick-borne Diseases journal homepage: www.elsevier.com/locate/ttbdis Morphodifferentiation of Gené’s organ in engorged Amblyomma sculptum Berlese, 1888 female ticks (Acari: Ixodidae) Marcelo Francisco dos Santos a,b , Magna Aparecida Maltauro Soares a , Maria Anete Lallo b , Darci Moraes Barros-Battesti c , Solange de Lima-Netto c , Diva Denelle Spadacci-Morena a, ⁎ a Laboratório de Fisiopatologia, Instituto Butantan, São Paulo, Brazil b Programa de Pós-Graduação em Patologia Ambiental e Experimental, Universidade Paulista, São Paulo, Brazil c Laboratório de Parasitologia, Instituto Butantan, São Paulo, Brazil ARTICLE INFO Keywords: Amblyomma sculptum Gené’s organ Engorged Morphology Histochemistry Egg wax ABSTRACT The Gené’s organ (GO) secretes a waxy substance on eggs that reduces water loss and has antimicrobial prop- erties. The current study evaluated morphological and histochemical aspects of GO in Amblyomma sculptum from the period of post-feeding – when ticks detach from the host – to the stage just before oviposition. In this species, GO is composed of a corpus and two pairs of glands, namely, cranial and caudal. Glandular cells are joined laterally by a system of interdigitating membranes with junctional complexes. Histochemistry showed that lipid droplets became more evident as GO developed, while glycogen gradually disappeared, and proteins were de- tected only near the onset of oviposition. The ultrastructural results revealed a marked distension of the cuticle filled with an amorphous material. Glandular cells showed poor endoplasmatic reticulum, many mitochondria mainly in the basal cell poles and a very developed basal labyrinth. We concluded that the development of GO in A. sculptum ticks was continuous and progressive, and it started after detachment from the host. Additionally, the ultrastructure study suggests that gland cells have an important absorption ability and a low synthetic activity, which indicates that the majority of wax precursors are derived from haemolymph. 1. Introduction Gené’s organ (GO), which is present only in female ticks, is a spe- cialized structure required for the production of the wax that is de- posited on the surface of the eggs during oviposition (Arthur, 1953; Lees and Beament, 1948). The layer of wax deposited on the eggshell reduces water loss (Lees and Beament, 1948) and exhibits anti-micro- bial properties (Lima-Netto et al., 2012, 2011; Arrieta et al., 2006). Furthermore, the sticky wax causes the eggs to adhere to each other, which reduces the total surface area of the egg mass (Booth, 1992; Lees and Beament, 1948). In addition, the wax likely reduces the absorption of pesticides from the environment, and the compounds present in it may act as pheromones, as in other arthropods (Howard and Blomquist, 1982; Nelson and Sukkestad, 1970). The sequence of events in the morphodifferentiation of GO during oviposition has been documented in detail in Ornithodoros moubata (Murray), Ixodes ricinus (Linnaeus) (Lees and Beament, 1948), and Dermacentor reticulatus (Fabricius) (Siebertz and Gothe, 2000). How- ever, in these studies, only unfed or ovipositing ticks were used. Thus, a study showing the kinetics as well as the morphological and histochemical changes occurring in GO throughout the reproductive process has never been conducted. Amblyomma sculptum Berlese, 1888 is one of the most commonly studied ticks in Brazil. It currently has serious implications for public health and is quite resistant to tick-controlling pesticides (Moraes-Filho, 2017; George et al., 2008; Horta et al., 2004). To the best of our knowledge, no reports have described GO in A. sculptum. The current study describes the morphology of GO for engorged A. sculptum from host detachment to immediately before oviposition. A histochemical study was also conducted to identify the chemical nature of the cellular constituents that compose the organ. 2. Materials and methods 2.1. Animals Adult male and female A. sculptum ticks were collected from vege- tation by a CO 2 trap (Oliveira et al., 2000) in the Parque Ecológico do Tietê (Núcleo Engenheiro Goulart, São Paulo, Brazil – 23° 49′ South latitude and 46° 52′ West longitude). These ticks were fed on rabbits in https://doi.org/10.1016/j.ttbdis.2018.01.004 Received 6 April 2017; Received in revised form 26 December 2017; Accepted 12 January 2018 ⁎ Corresponding author at: Laboratory of Pathophysiology, Butantan Institute, Avenida Dr. Vital Brazil, 1500, São Paulo, SP, CEP 05503-900, Brazil. E-mail address: diva.morena@butantan.gov.br (D.D. Spadacci-Morena). Ticks and Tick-borne Diseases xxx (xxxx) xxx–xxx 1877-959X/ © 2018 Elsevier GmbH. All rights reserved. Please cite this article as: Santos, M.F.d., Ticks and Tick-borne Diseases (2018), https://doi.org/10.1016/j.ttbdis.2018.01.004