In Drosophila melanogaster olfactory sensory neurons (OSNs) establish synapses with projection neurons (PNs) and local interneurons within antennal lobe (AL) glomeruli. Substantial knowledge regarding this circuitry has been obtained by functional studies, whereas ultrastructural evidence of synaptic contacts is scarce. To fill this gap, we studied serial sections of three glomeruli using electron microscopy. Ectopic expression of a membrane-bound peroxidase allowed us to map synaptic sites along PN dendrites. Our data prove for the first time that each of the three major types of AL neurons is both pre-and postsynaptic to the other two types, as previously indicated by functional studies. PN dendrites carry a large proportion of output synapses, with approximately one output per every three input synapses. Detailed reconstructions of PN dendrites showed that these synapses are distributed unevenly, with input and output sites partially segregated along a proximal-distal gradient and the thinnest branches carrying solely input synapses. Moreover, our data indicate synapse clustering, as we found evidence of dendritic tiling of PN dendrites. PN output synapses exhibited T-shaped presynaptic densities, mostly arranged as tetrads. In contrast, output synapses from putative OSNs showed elongated presynaptic densities in which the T-bar platform was supported by several pedestals and contacted as many as 20 postsynaptic profiles. We also discovered synaptic contacts between the putative OSNs. The average synaptic density in the glomerular neuropil was about two synapses/mm 3 . These results are discussed with regard to current models of olfactory glomerular microcircuits across species. J. Comp. Neurol. 524:1920-1956, 2016. INDEXING TERMS: Drosophila melanogaster; olfactory system; glomerulus; projection neuron; ultrastructure; synaptic microcircuitsThe neural circuitry of the antennal lobe (AL) of the vinegar fly Drosophila melanogaster is one of the principal models for the study of how chemosensory information is processed in the brain. Thus it has been investigated intensively with a variety of anatomical, physiological, and genetic methods (Stocker, 1994;Vosshall and Stocker, 2007;Wilson, 2011). Very little is known, however, about the synaptic circuitry, synapse structure, numbers, and identity of pre-and postsynaptic components of this brain center.The olfactory sensory neurons (OSNs) located in the antennae and maxillary palps send axons to the AL, where they form synapses with different types of interneurons within functional and morphological units called glomeruli (Stocker, 1994;Couto et al., 2005). These generic structural features of glomerular anatomy are preserved across species (Hildebrand and Shepherd, 1997;Ache and Young, 2005;Martin et al., 2011). Olfactory glomeruli are spherical structures of synaptic neuropilThis is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work...

IntroductionBelow ground orientation in insects relies mainly on olfaction and taste. The economic impact of plant root feeding scarab beetle larvae gave rise to numerous phylogenetic and ecological studies. Detailed knowledge of the sensory capacities of these larvae is nevertheless lacking. Here, we present an atlas of the sensory organs on larval head appendages of Melolontha melolontha. Our ultrastructural and electrophysiological investigations allow annotation of functions to various sensory structures.ResultsThree out of 17 ascertained sensillum types have olfactory, and 7 gustatory function. These sensillum types are unevenly distributed between antennae and palps. The most prominent chemosensory organs are antennal pore plates that in total are innervated by approximately one thousand olfactory sensory neurons grouped into functional units of three-to-four. In contrast, only two olfactory sensory neurons innervate one sensillum basiconicum on each of the palps. Gustatory sensilla chaetica dominate the apices of all head appendages, while only the palps bear thermo-/hygroreceptors. Electrophysiological responses to CO2, an attractant for many root feeders, are exclusively observed in the antennae. Out of 54 relevant volatile compounds, various alcohols, acids, amines, esters, aldehydes, ketones and monoterpenes elicit responses in antennae and palps. All head appendages are characterized by distinct olfactory response profiles that are even enantiomer specific for some compounds.ConclusionsChemosensory capacities in M. melolontha larvae are as highly developed as in many adult insects. We interpret the functional sensory units underneath the antennal pore plates as cryptic sensilla placodea and suggest that these perceive a broad range of secondary plant metabolites together with CO2. Responses to olfactory stimulation of the labial and maxillary palps indicate that typical contact chemo-sensilla have a dual gustatory and olfactory function.

Background: Mitochondrial genomes are widely utilized for phylogenetic and population genetic analyses among animals. In addition to sequence data the mitochondrial gene order and RNA secondary structure data are used in phylogenetic analyses. Arachnid phylogeny is still highly debated and there is a lack of sufficient sequence data for many taxa. Ricinulei (hooded tickspiders) are a morphologically distinct clade of arachnids with uncertain phylogenetic affinities.

In patients with bifurcated lesions treated by provisional stenting technique, EES compared with SES is associated with similar procedural performance and better 3-dimensional reconstruction and quantitative coronary analysis result in the SB. Both DES are associated with low rates of major adverse events and angiographic failure. (Sirolimus Versus Everolimus-Eluting Stent Randomized Assessment in Bifurcated Lesions and Clinical Significance of Residual Side-Branch Stenosis [SEA-SIDE]; NCT00697372).

A fossil trigonotarbid (Arachnida: Trigonotarbida) assigned to Palaeocharinus sp. from the Early Devonian (c. 410 Ma) Rhynie cherts of Aberdeenshire, Scotland, UK is described, speciWcally for a previously unrecognised feature of the distal end of the pedipalp. This exhibits a small chela formed from a movable, unpaired apotele articulating against a slightly shorter, Wxed projection from the inferior surface of the tarsus. Among other arachnids, this morphology has only previously been observed in the rare and enigmatic Carboniferous-Recent taxon Ricinulei. This character oVers explicit support for a monophylum (Trigonotarbida + Ricinulei); a hypothesis previously based on opisthosomal characters which (if correct) would draw Ricinulei within the so-called Pantetrapulmonata clade (i.e. spiders and their closest relatives). Our data is not consistent with Ricinulei's traditional position as sister-group of mites (Acari) and is an example of how considering extinct taxa may help to resolve the position of a 'diYcult' living group.