Scientists at the Max Planck Institute for Chemical Ecology in Jena, Germany, have now quantified and mapped the functional units of the olfactory center in the brains of vinegar flies responsible for the perception of odors. They found out that the so-called olfactory glomeruli in the antennal lobe, the insect analogue of the olfactory bulb of mammals, differ from each other in their architecture. The morphology and the structure of these spherical brain units provide information about the ecological relevance of the odors they process, especially with regard to the flies’ odor-guided behavior.
When insects search for food, a sexual mate or the ideal place for laying eggs – somewhere where the hatching larvae have a good chance to survive – they have to rely on their sense of smell. They use their olfactory organs, the antennae, to detect odor molecules in their environment.
These odors are processed in the so-called antennal lobe, the actual olfactory center of the insect brain, which consists of spherical structures: the olfactory glomeruli. Here, inside the olfactory glomeruli, different groups of olfactory neurons form conjunctions or synapses which enable different environmental odors to be processed.
Until now, scientists had assumed that olfactory glomeruli share a pretty homogeneous architecture and that particular functions of the different glomeruli can be attributed primarily to special olfactory receptors on the membranes of the olfactory sensory neurons.
A research team of the Department of Evolutionary Neuroethology has now shown for the first time that the neuronal composition of each glomerulus is unique and highly specific. “Each glomerulus processes different odors in a unique way. The odors, on the other hand, differ in their impact on the behavior of the vinegar flies,” explains Silke Sachse, the leader of the study.
The researchers scrutinized the neuronal architecture of the olfactory glomeruli in the vinegar fly Drosophila melanogaster and linked the morphological differences they observed to the respective functions. They labeled different neurons in single glomeruli, and counted and anatomically described these. In order to achieve this, they used transgenic Drosophila lines which expressed the photoactivatable green fluorescent protein (PA-GFP) in the neurons and high-resolution confocal microscopy.
“As assumed, but until now not experimentally proven, glomeruli which contained many olfactory sensory neurons were generally bigger than were the glomeruli with fewer olfactory sensory neurons. This means that the anatomical shape of a glomerulus already provides information about how sensitive it will respond to a certain odor,” Veit Grabe, one of the first authors of the study, reports. The scientists also investigated whether there were any differences between male and female flies: Glomeruli which processed the Drosophila sex pheromones were bigger in males which were able to perceive the female attractants from large distances.
Moreover, the researchers counted the so-called projection neurons which are responsible for the transmission of odor stimuli to higher regions of the olfactory system. Glomeruli containing highly specific olfactory sensory neurons – namely, those which process only one single odor – seem to exhibit more projection neurons than glomeruli which process many different odors. More projection neurons make sure that information is transferred to higher brain regions in a faster and more reliable way to result in rapid odor-guided decisions.
In order to link the morphology of a glomerulus to its function, the research team determined another important parameter by means of electrophysiological analysis: “Lifetime sparseness” indicates how many different odors can activate an olfactory receptor. If a receptor is activated by a large variety of odors, it has very low “sparseness” and is therefore a very broad-range receptor. The higher the “sparseness” of a receptor, the fewer odors it is able to perceive.
An extreme case would be a highly specific receptor which responds only to a single odor. Odors which are very attractive to vinegar flies include their own pheromones, but also odors which provide clues about where to find a food source, such as overripe fruit. Some of these attractive odors may elicit oviposition in females, because they provide information about a place where larvae can hatch and have a good chance to survive. However, important odors may also be deterrents – and warning signals – because they contain information about lethal dangers, such as toxic substances in a potential food source or parasites.
“The complete quantitative mapping of all olfactory sensory neurons linked together in each olfactory glomerulus helped us to create an extended morphological basis for a better understanding of the role and function these units in the olfactory system have,” co-author Amelie Baschwitz summarizes.
Because these new insights are not limited to the vinegar fly, and may also apply to other animals or even humans, they have far-reaching significance. [KG/AO]
Grabe, V., Baschwitz, A., Dweck, H. K. M., Lavista-Llanos, S., Hansson, B., Sachse, S. (2016). Elucidating the neuronal architecture of olfactory glomeruli in the Drosophila antennal lobe. Cell Reports. DOI: 10.1016/j.celrep.2016.08.063
Dr. Silke Sachse, Max Planck Institute for Chemical Ecology, Hans-Knöll-Str. 8, 07745 Jena, Tel. +49 3641 57-1405, E-Mail email@example.com
Contact and Media Requests:
Angela Overmeyer M.A., Max Planck Institute for Chemical Ecology, Hans-Knöll-Str. 8, 07743 Jena, +49 3641 57-2110, E-Mail firstname.lastname@example.org
Download high-resolution images via http://www.ice.mpg.de/ext/downloads2016.html
http://www.ice.mpg.de/ext/index.php?id=evolutionary-neuroethology&L=0 Department of Evolutionary Neuroethology
Angela Overmeyer | Max-Planck-Institut für chemische Ökologie
Zebrafish's near 360 degree UV-vision knocks stripes off Google Street View
22.06.2018 | University of Sussex
New cellular pathway helps explain how inflammation leads to artery disease
22.06.2018 | Cedars-Sinai Medical Center
In a recent publication in the renowned journal Optica, scientists of Leibniz-Institute of Photonic Technology (Leibniz IPHT) in Jena showed that they can accurately control the optical properties of liquid-core fiber lasers and therefore their spectral band width by temperature and pressure tuning.
Already last year, the researchers provided experimental proof of a new dynamic of hybrid solitons– temporally and spectrally stationary light waves resulting...
Scientists from the University of Freiburg and the University of Basel identified a master regulator for bone regeneration. Prasad Shastri, Professor of...
Moving into its fourth decade, AchemAsia is setting out for new horizons: The International Expo and Innovation Forum for Sustainable Chemical Production will take place from 21-23 May 2019 in Shanghai, China. With an updated event profile, the eleventh edition focusses on topics that are especially relevant for the Chinese process industry, putting a strong emphasis on sustainability and innovation.
Founded in 1989 as a spin-off of ACHEMA to cater to the needs of China’s then developing industry, AchemAsia has since grown into a platform where the latest...
The BMBF-funded OWICELLS project was successfully completed with a final presentation at the BMW plant in Munich. The presentation demonstrated a Li-Fi communication with a mobile robot, while the robot carried out usual production processes (welding, moving and testing parts) in a 5x5m² production cell. The robust, optical wireless transmission is based on spatial diversity; in other words, data is sent and received simultaneously by several LEDs and several photodiodes. The system can transmit data at more than 100 Mbit/s and five milliseconds latency.
Modern production technologies in the automobile industry must become more flexible in order to fulfil individual customer requirements.
An international team of scientists has discovered a new way to transfer image information through multimodal fibers with almost no distortion - even if the fiber is bent. The results of the study, to which scientist from the Leibniz-Institute of Photonic Technology Jena (Leibniz IPHT) contributed, were published on 6thJune in the highly-cited journal Physical Review Letters.
Endoscopes allow doctors to see into a patient’s body like through a keyhole. Typically, the images are transmitted via a bundle of several hundreds of optical...
13.06.2018 | Event News
08.06.2018 | Event News
05.06.2018 | Event News
22.06.2018 | Materials Sciences
22.06.2018 | Earth Sciences
22.06.2018 | Life Sciences