The performance of vertebrate ears is controlled by auditory efferents that originate in the brain and innervate the ear, synapsing onto hair cell somata and auditory afferent fibers [1-3]. Efferent activity can provide protection from noise and facilitate the detection and discrimination of sound by modulating mechanical amplification by hair cells and transmitter release as well as auditory afferent action potential firing [1-3]. Insect auditory organs are thought to lack efferent control [4-7], but when we inspected mosquito ears, we obtained evidence for its existence. Antibodies against synaptic proteins recognized rows of bouton-like puncta running along the dendrites and axons of mosquito auditory sensory neurons. Electron microscopy identified synaptic and non-synaptic sites of vesicle release, and some of the innervating fibers co-labeled with somata in the CNS. Octopamine, GABA, and serotonin were identified as efferent neurotransmitters or neuromodulators that affect auditory frequency tuning, mechanical amplification, and sound-evoked potentials. Mosquito brains thus modulate mosquito ears, extending the use of auditory efferent systems from vertebrates to invertebrates and adding new levels of complexity to mosquito sound detection and communication.

Animals rely on mechanosensory feedback from proprioceptors to control locomotory body movements. Unexpectedly, we found that this movement control requires visual opsins. Disrupting the Drosophila opsins NINAE or Rh6 impaired larval locomotion and body contractions, independently of light and vision. Opsins were detected in chordotonal proprioceptors along the larval body, localizing to their ciliated dendrites. Loss of opsins impaired mechanically evoked proprioceptor spiking and cilium ultrastructure. Without NINAE or Rh6, NOMPC mechanotransduction channels leaked from proprioceptor cilia and ciliary Inactive (Iav) channels partly disappeared. Locomotion is shown to require opsins in proprioceptors, and the receptors are found to express the opsin gene Rh7, in addition to ninaE and Rh6. Besides implicating opsins in movement control, this documents roles of non-ciliary, rhabdomeric opsins in cilium organization, providing a model for a key transition in opsin evolution and suggesting that structural roles of rhabdomeric opsins preceded their use for light detection.

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Although many algorithms have been developed in the last two decades to detect damage in civil structures using dynamic properties, few studies have considered the challenge imposed by the variability of these properties due to changing environmental conditions. To address this concern, a statistically based analysis is proposed herein to analyze the distribution of identified structural parameters over an unknown number of external conditions and to effectively reduce their influence on the localization of damage. The proposed SHM scheme can be divided into three main steps: (1) identification of modal properties using acceleration responses of the structure to ambient loads under the influence of environmental conditions; (2) characterization of the structure as a function of the detected dynamic properties and an identification model (ID-model) representative of the system; and (3) accommodation of the influence of external conditions by means of a principal component analysis of the identified parameters. An analytical model of a four story, two-bay by two-bay building developed by the IASCM-ASCE Task Group on SHM benchmark problems is used to demonstrate the effectiveness of the proposed technique. The robustness of the technique is tested by considering modeling errors, as well as a considerable amount of sensor noise. Nine structural configurations are investigated with various temperatures and temperature gradients. The results indicate that the method is effective for detecting and locating damage.

Highlights d Drosophila mechanosensation requires opsins but no retinal chromophore d Mechanosensory opsin function is independent of the retinal attachment site d Mechanosensation involves visual chromophore pathway components d Mechanosensory organs express chromophore pathway genes

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Sensing environmental temperatures is essential for the survival of ectothermic organisms. In Drosophila , two of the most used methodologies to study temperature preferences (T P ) and the genes involved in thermosensation are two-choice assays and temperature gradients. Whereas two-choice assays reveal a relative T P , temperature gradients can identify the absolute T p . One drawback of gradients is that small ectothermic animals are susceptible to cold-trapping: a physiological inability to move at the cold area of the gradient. Often cold-trapping cannot be avoided, biasing the resulting T P to lower temperatures. Two mathematical models were previously developed to correct for cold-trapping. These models, however, focus on group behaviour which can lead to overestimation of cold-trapping due to group aggregation. Here we present a mathematical model that simulates the behaviour of individual Drosophila in temperature gradients. The model takes the spatial dimension and temperature difference of the gradient into account, as well as the rearing temperature of the flies. Furthermore, it allows the quantification of cold-trapping and reveals unbiased T P. Additionally, our model reveals that flies have a range of tolerable temperatures, and this measure is more informative about the behaviour than commonly used T P . Online simulation is hosted at http://igloo.uni-goettingen.de . The code can be accessed at https://github.com/zerotonin/igloo .

The yellow fever mosquito Aedes aegypti employs olfaction to locate humans. We applied CRISPR-Cas9 genome engineering and neural activity mapping to define the molecular and cellular logic of how the mosquito brain is wired to detect human odorants. We determined that the breath volatile carbon dioxide (CO2) is detected by the largest unit of olfactory coding in the primary olfactory processing center of the mosquito brain, the antennal lobe. Synergistically, CO2 detection gates synaptic transmission from defined populations of olfactory sensory neurons, innervating unique antennal lobe regions tuned to the human sweat odorant L-(+)-lactic acid. Our data suggests that simultaneous detection of signature human volatiles rapidly disinhibits a multimodal olfactory network for hunting humans in the mosquito brain.