Antennal sensilla of the stonefly Dinocras cephalotes (Plecoptera: Perlidae) Manuela Rebora a, * , Jos  e Manuel Tierno de Figueroa b , Silvana Piersanti a a Dipartimento di Chimica, Biologia e Biotecnologie, University of Perugia, 06121, Italy b Departamento de Zoología, Facultad de Ciencias, Universidad de Granada, 18071, Granada, Spain article info Article history: Received 23 June 2016 Accepted 7 October 2016 Available online xxx Keywords: Aquatic insects Plecoptera Mechanoreceptors Gustatory sensilla Olfactory sensilla Ultrastructure abstract Plecoptera, one of the most primitive groups of Neoptera, are important aquatic insects usually employed as bioindicators of high water quality. Notwithstanding the well-developed antennae of the adult, its sensory abilities are so far not well known. The present paper describes at ultrastructural level under scanning and transmission electron microscopy the antennal sensilla of the adult stonefly Dinocras cephalotes (Plecoptera, Perlidae). Adult males and females show a filiform antenna constituted of a scape, a pedicel and a flagellum composed of very numerous segments with no clear sexual dimorphism in the number and distribution of the antennal sensilla. The most represented sensilla are sensilla trichodea, with different length, whose internal structure reveal their mechanosensory func- tion, sensilla chaetica, with an apical pore, with an internal structure revealing a typical gustatory function, porous pegs representing single-walled olfactory sensilla, digitated pegs with hollow cuticular spoke channels representing double-walled olfactory sensilla, pegs in pits for which we hypothesize a thermo-hygrosensory function. The diversity of described sensilla is discussed in relation to known biological aspects of the studied species. This opens new perspectives in the study of the behavior of these aquatic insects during their adult stage. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction Aquatic insects include organisms associated with an aquatic or semiaquatic environment in one or more of their life stages. Among them, Plecoptera are one of the most primitive groups of Neoptera (Zwick, 2000). Particularly the Perlidae family are among the main macroinvertebrate predators in streams (Merritt and Cummins, 2006) and one of the insect families with lower toler- ance to water pollution and environmental alterations, being usually employed as bioindicators of high water ecological quality (Rosenberg et al., 2008). Perlidae are also the most diverse family among Plecoptera (with more than 1000 described species) and the most widely distributed within this insect order (spreaded over Holarctic, Oriental, Afrotropical and Neotropical Regions) (Fochetti and Tierno de Figueroa, 2008a,b). Plecoptera sensory systems have been the object of studies mainly focused on the nymphal stages in the stonefly Paragnetina media (Walker, 1852) (Kapoor, 1985, 1987, 1991; see review in Gaino and Rebora, 1999), while little attention has been paid to the sensilla of adults [e.g., Gnatzy and Rupprecht (1972) and Rupprecht and Gnatzy (1974) on the sensilla on the ventral vesicle on the 9th sternum of a few Nemouroidean stoneflies], notwithstanding that stoneflies possess very developed antennae, thus differing from the short ones visible on the adults of other aquatic insects such as Ephemeroptera and Odonata. In an old paper by Slifer (1979), the antennae of the adult stonefly Allocapnia recta (Claassen, 1924) have been analyzed under scanning electron microscope and light microscope but no infor- mation on the internal structure of the antennal sensilla has been given. Crespo in a review on chemosensation in aquatic insects (2011) reports that, notwithstanding that stonefly adult antennae are well developed, no research has been performed on the sensory biology of these structures and nothing is known about the sensory mo- dalities used by stoneflies during their adult stage. The same author considers that “It would be very surprising if those well-developed antennae had been retained without being advantageous for the insect's life”. The aim of the present paper is to describe at ultrastructural level under scanning and transmission electron microscope the * Corresponding author. Fax: þ39 0755855733. E-mail address: manuela.rebora@unipg.it (M. Rebora). Contents lists available at ScienceDirect Arthropod Structure & Development journal homepage: www.elsevier.com/locate/asd http://dx.doi.org/10.1016/j.asd.2016.10.009 1467-8039/© 2016 Elsevier Ltd. All rights reserved. Arthropod Structure & Development xxx (2016) 1e10 Please cite this article in press as: Rebora, M., et al., Antennal sensilla of the stonefly Dinocras cephalotes (Plecoptera: Perlidae), Arthropod Structure & Development (2016), http://dx.doi.org/10.1016/j.asd.2016.10.009