title: Ultrastructure of chemoreceptive tarsal sensilla in an armored harvestman and evidence of olfaction across Laniatores (Arachnida, Opiliones).
abstract: Harvestmen (Arachnida, Opiliones) are especially dependent on chemical cues and are often regarded as animals that rely mainly on contact chemoreception. Information on harvestman sensilla is scarce when compared to other arachnid orders, especially concerning internal morphology. Using scanning (SEM) and transmission (TEM) electron microscopy, we investigated tarsal sensilla on the distal tarsomeres (DT) of all leg pairs in Heteromitobates discolor (Laniatores, Gonyleptidae). Furthermore, we explored the typological diversity of sensilla present on the DT I and II in members of the suborder Laniatores, which include two thirds of the formally described opilionid fauna, using species from 17 families representing all main laniatorian lineages. Our data revealed that DT I and II of H. discolor are equipped with wall-pored falciform hairs (two types), wall-pored sensilla chaetica (two types) and tip-pored sensilla chaetica, while DT III and IV are mainly covered with trichomes (non-sensory) and tip-pored sensilla chaetica. The ultrastructural characteristics support an olfactory function for all wall-pored sensilla and a dual gustatory/mechanoreceptive function for tip-pored sensilla chaetica. Based on our comparative SEM survey, we show that wall-pored sensilla occur in all investigated Laniatores, demonstrating their widespread occurrence in the suborder and highlighting the importance of both legs I and II as the sensory appendages of laniatorean harvestmen. Our results provide the first morphological evidence for olfactory receptors in Laniatores and suggest that olfaction is more important for harvestmen than previously thought.
authors.affiliation: Laboratório de Ecologia Sensorial e Comportamento de Artrópodes, Escola de Artes, Ciências e Humanidades, Universidade de São Paulo, Rua Arlindo Béttio, 1000, Ermelino Matarazzo, São Paulo, SP 03828-000, Brazil; Programa de Pós-Graduação em Zoologia, Instituto de Biociências, Universidade de São Paulo, Rua do Matão, 321, Travessa 14, São Paulo, SP 05508-090, Brazil.
authors.forename: Guilherme
authors.initials: G
authors.lastname: Gainett
authors.affiliation: Zoological Institute and Museum, Department of General and Systematic Zoology, Universität Greifswald, Loitzer Str. 26, D-17489, Greifswald, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Michalik
authors.affiliation: Zoological Institute and Museum, Department of General and Systematic Zoology, Universität Greifswald, Loitzer Str. 26, D-17489, Greifswald, Germany.
authors.forename: Carsten H G
authors.initials: CH
authors.lastname: Müller
authors.affiliation: Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA.
authors.forename: Gonzalo
authors.initials: G
authors.lastname: Giribet
authors.affiliation: Department of Forensic Toxicology, Institute of Legal Medicine, University of Greifswald, Kuhstrasse 30, 17489 Greifswald, Germany.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Talarico
authors.affiliation: Laboratório de Ecologia Sensorial e Comportamento de Artrópodes, Escola de Artes, Ciências e Humanidades, Universidade de São Paulo, Rua Arlindo Béttio, 1000, Ermelino Matarazzo, São Paulo, SP 03828-000, Brazil; Programa de Pós-Graduação em Zoologia, Instituto de Biociências, Universidade de São Paulo, Rua do Matão, 321, Travessa 14, São Paulo, SP 05508-090, Brazil; Programa de Pós-Graduação em Ecologia e Evolução, Universidade Federal de São Paulo, Campus Diadema, Rua Professor Artur Riedel, 275, Jardim Eldorado, Diadema, SP 09972-270, Brazil.
authors.forename: Rodrigo H
authors.initials: RH
authors.lastname: Willemart
mesh_terms: D000818:Animals; D001097:Arachnida / Q000502:physiology / Q000648:ultrastructure*; D002628:Chemoreceptor Cells / Q000648:ultrastructure; D005121:Extremities / Q000033:anatomy & histology; D005260:Female; D008297:Male; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D058618:Sensilla / Q000648:ultrastructure; D012903:Smell / Q000502:physiology
keywords: Chemoreceptors; Goniosomatinae; Gonyleptidae; Olfaction; Sensory morphology; Wall pores