Detection of odor perception in Asiatic honeybee (Apis cerana Fabricius, 1793) workers by changing membrane potential of the antennal sensilla Guntima Suwannapong a, ⁎, Paitoon Seanbualuang b , Sivaram Venkatarame Gowda c , Mark Eric Benbow d a Department of Biology, Faculty of Science, Burapha University, Chon Buri 20131, Thailand b Department of Biology, Faculty of Science, Ubon Ratchathani Rajabhat University, Ubon Ratchathani 34000, Thailand c Department of Botany, Bangalore University, Bangalore University, Bangalore 560056, India d Department of Biology, University of Dayton, Collage Park, OH 45469-2320, USA abstract article info Article history: Received 11 September 2009 Revised 26 February 2010 Accepted 1 March 2010 Keywords: Antennal sensilla Asiatic honeybee Membrane potential and odor perception The role of honeybee mandibular gland compounds is poorly understood, although they may act as alarm pheromones. We measured forager and guard bee antennal responses evoked by two major components of mandibular gland secretions of the Asiatic honeybee, Apis cerana. Membrane potentials of antennal sensilla were measured after exposure to three concentrations of the synthetic alarm pheromones 2-heptanone and (Z)-11-eicosen-1-ol using a potentiostat (EA161) connected to an e-corder (ED401) with microelectrodes. The resting membrane potential of A. cerana foragers and guards was -55.23 ± 1.44 and -56.41 ± 1.21 mV, respectively. The membrane potential of foragers after exposure to 1.0, 5.0 and 10.0% 2-heptanone was -5.32 ± 0.46, -8.41 ± 1.33 and -11.53 ± 2.16 mV, respectively. The membrane potential of guards was -5.49 ± 1.66, -8.46 ± 1.32 and -7.31 ± 3.46 mV, respectively. Exposure of foragers to 1.0, 5.0 and 10.0% (Z)-11-eicosen-1-ol induced membrane potentials of -24.00 ± 6.56, -36.36 ± 5.18 and -14.60 ± 8.20 mV, respectively; for guards they were -47.62 ± 1.46, -46.08 ± 0.87 and -9.35 ± 1.96 mV, respectively. The highest membrane potential was found in foragers exposed to 1.0% 2-heptanone. The membrane potentials of foragers were higher than that of guards except at the highest concentration (10.0%) of both pheromones. These findings suggest that antennal sensory receptors of foragers may have higher specific thresholds than those of guards. © Korean Society of Applied Entomology, Taiwan Entomological Society and Malaysian Plant Protection Society, 2010 Published by Elsevier B.V. All rights reserved. Introduction Honeybees perceive pheromones with sensory receptors located on the antennae comprising eight types of sensilla: they are sensilla ampullacae (a receptor for carbondioxide), sensilla basiconica (un- known), sensilla campaniforme (a mechanoreceptor), sensilla placo- dae (an odor receptor), sensilla trichodae type A (unknown), B, C (mechanoreceptor) and D (a gustatory receptor) (Agren, 1977). The main olfactory sensilla are sensilla placodae which are abundant over the last segment of the antenna. This sensilla type is innervated by 15 to 30 neurons which respond to flower odors and honeybee pher- omones (Claudia et al., 2002). 2-heptanone, the major component of the mandibular glands of honey bees, is an alarm pheromone and has repellent properties affecting foraging bees (Shearer and Boch, 1965; Reith et al., 1986; Yokoi and Fujisaki, 2007). This pheromone may be repellent at high concentrations and is probably deposited when a bee visits flowers which signals other bees of nectar depleted flowers (Boch and Shearer, 1971; Crew and Hasting, 1976; Balerrama et al., 1996; Gawleta et al., 2005). However, it can also be an attractant at low concentrations (Shearer and Boch, 1965; Boch and Shearer, 1971; Kerr et al., 1974; Koeniger et al., 1979; Vallet et al., 1991). The pheromone concentration secreted by workers of different ages varies. Younger bees produce low or undetectable levels of 2-heptanone and production increases with age (Ferguson and Free, 1979; Lensky, 1985; Sakamoto et al., 1990; Pankiw, 2004). Release of alarm pher- omones by guard bees alerts others workers to a source of potential danger (Maschwitz, 1964). Within the sting apparatus of honeybee workers, low concentrations of (Z)-11-eicosen-1-ol were found to repel worker bees, but at high concentrations it did not (Pickett et al., 1982; Free et al., 1983, 1988). It acts similar to isopentyl acetate as an alarm pheromone from the sting of A. mellifera; however, it is the main secre- tion of mandibular glands of four native honeybee species of Thailand (Pickett et al., 1982; Suwannapong et al., submitted for publication). The response of honeybees to specific pheromone concentrations is still unclear and not well understood. In the present study, we measured changing antennal sensilla membrane potential of Apis cerana foragers and guards in response to different concentrations of 2-heptanone and (Z)-11-eicosen-1-ol dissolved in isomolar bee saline. The objective was Journal of Asia-Pacific Entomology 13 (2010) 197–200 ⁎ Corresponding author. E-mail address: guntima@buu.ac.th (G. Suwannapong). 1226-8615/$ – see front matter © Korean Society of Applied Entomology, Taiwan Entomological Society and Malaysian Plant Protection Society, 2010 Published by Elsevier B.V. All rights reserved. doi:10.1016/j.aspen.2010.03.001 Contents lists available at ScienceDirect Journal of Asia-Pacific Entomology journal homepage: www.elsevier.com/locate/jape