Johnston’s Organ

Kyle Parks, Chip Austin, Rafael Achury, Keon Mook Seong

I. Introduction

II. Podcast

Click here to listen to the audio file via SoundCloud.

III. Transcript

Kyle: Hello, today we’re going to talk about the Johnston’s Organ. I’m Kyle Parks

Chip: I’m Chip

Koen: I’m Koen

Kyle: And Rafa did a bunch of research but he didn’t record with us. The Johnston’s Organ is a synapomorphy for the class Insecta. It’s located on the pedicel of the antennae. Uh, it’s a chordonatal organ, which means it’s a stretch receptor and it’s made up of an array of scolopidia. There can be quite a lot and there can be just a few depending on the type of insect. Scolopidia are the most fundamental mechanoreceptor in insects.

Chip: An individual scolpidium is comprised of four cell types that include one or more bipolar sensory cells, a glial cell, an attachment cell, and a scolopale. It is usually attach to the cuticle at both end and can thus measure the amount of cuticular distortion. Integumental movements causes the scolopale to lengthen, compressing the dendrite and triggering receptor potential by affecting the opening of ion channels. Movement of the flagellum relative to the pedicel may have a number of causes, so Johnston’s organs can serve a variety of functions in any one insect. It’s so sensitive that different scolopidia are stimulated in different amounts depending on the direction from which the antennae are being moved by stimuli. In grasshoppers, bees, lepidopterans, and some flies, and probably other insects, this organ acts as an indicator of velocity and orientation in flight. For example, wind blowing on the face of blow flies causes the arista to act as a lever, rotating the third antennal segment on the second segment. The antenna will tremble even in a steady airflow and the resulting minute movement is enough to stimulate some neurons of the Johnston’s Organ.

Kyle: The Johnston’s Organ can detect extremely fine movements of the flagellum, including vibrations caused by sound waves, vibrations in the substrate that the insect is standing on, and vibrations caused by the rate of airflow over the flagellum. It has even been shown to be sensitive enough to detect gravitational fields and electromagnetic fields created by other insects. During the waggle dance of honey bees, workers communicate to other bees in the colony the location distance and quality of a food source they have found. They do this by a set of repetitive movements that other bees observe. The flagellum of the bees that are observing the dancing bee are actually charged and move very minutely in response to the electromagnetic field of the dancing bee.

Koen: In termites, it seems like they use their Johnston’s Organ for the detection of the direction of gravity. The filament of the antenna tends to at the joint which is monitored by Johnston’s organ.

Chip: This structure is also crucial in allowing aquatic insects to perceive and navigate their environment. It’s used in Gyrinid beetles to perceive ripples on the surface of the water as they jostle the antennae. This allows them to avoid collisions with other organisms living in the water. In addition, they have their own form of insect echolocation in which they create ripples of their own and detect which ones bounce back off of obstacles.

Kyle: Sound waves that cause the flagellum to vibrate are detected by the Johnston’s organ. Because of this it is often the primary sound-perceiving organ in insects.

Chip: This makes hearing in insects and vertebrates quite similar as they both depend on mechanoreceptor to perceive and interpret sound.

Kyle: Male mosquitos can detect the specific vibrational patterns caused by the wing-beat frequencies of conspecific females. They can therefore use their Johnston’s organ to locate suitable mates. Johnston’s organs can be especially elaborate in Diptera, with some species having as many as 20,000 scolopidia associated with their Johnston’s organ. In Drosophila melanogaster it’s been demonstrated that the females can detect the male’s wing vibrations and respond to them during courtship. On top being a defining character of insects, the Johnston’s organ is used in a variety of diverse applications in insect behavior.

IV. References

Sun, Y, L Liu, Y Ben-Shahar, JS Jacobs, DF Eberl, & WJ Welsh. 2009. TRPA channels distinguish gravity sensing from hearing in Johnston’s organ. PNAS. 106: 13606-13611

Boekhoff-Falk, G. 2005. Hearing in Drosophila: Development of Johnston’s organ and emerging parallels to vertebrate ear development. Developmental Dynamics. 232: 550-558

Sane, SP, A Dieudonne, MA WIllis, & TL Daniel. 2007. Antennal Mechanosensors Mediate Flight Control in Moths. Science. 315: 863-866

Cator, LJ, BJ Arthur, LC Harrington, & RR Hoy. 2009. Harmonic Convergence in the Love Songs of the Dengue Vector Mosquito. Science. 323: 1077-1079

Vande Berg, JS. 2005. Fine structural studies of Johnston’s organ in the tobacco hornworm moth, Manduca sexta (Johannson). Journal of Morphology. 133: 439-455

Greggers, U, G Koch, V Schmidt, A Durr, A Floriou-Servou, D Piepenbrock, MC Gopfert, & R Menzel. 2013. Reception and learning of electric fields in bees. PNAS. 280

Chapman, RF. 1998. The Insects: Structure and Function. Fourth Edition. Harvard University Press, Cambridge, Massachusetts, USA.