Neuropeptides and their G protein-coupled receptors (GPCRs) play a central role in the physiology of insects. One large family of insect neuropeptides are the adipokinetic hormones (AKHs), which mobilize lipids and carbohydrates from the insect fat body. Other peptides are the corazonins that are structurally related to the AKHs but represent a different neuropeptide signaling system. We have previously cloned an orphan GPCR from the malaria mosquito Anopheles gambiae that was structurally intermediate between the A. gambiae AKH and corazonin GPCRs. Using functional expression of the receptor in cells in cell culture, we have now identified the ligand for this orphan receptor as being pQVTFSRDWNAamide, a neuropeptide that is structurally intermediate between AKH and corazonin and that we therefore named ACP (AKH/corazonin-related peptide). ACP does not activate the A. gambiae AKH and corazonin receptors and, vice versa, AKH and corazonin do not activate the ACP receptor, showing that the ACP/ receptor couple is an independent and so far unknown peptidergic signaling system. Because ACP is structurally intermediate between AKH and corazonin and the ACP receptor between the AKH and corazonin receptors, this is a prominent example of receptor/ligand co-evolution, probably originating from receptor and ligand gene duplications followed by mutations and evolutionary selection, thereby yielding three independent hormonal systems. The ACP signaling system occurs in the mosquitoes A. gambiae, Aedes aegypti, and Culex pipiens (Diptera), the silkworm Bombyx mori (Lepidoptera), the red flour beetle Tribolium castaneum (Coleoptera), the parasitic wasp Nasonia vitripennis (Hymenoptera), and the bug Rhodnius prolixus (Hemiptera). However, the ACP system is not present in 12 Drosophila species (Diptera), the honeybee Apis mellifera (Hymenoptera), the pea aphid Acyrthosiphon pisum (Hemiptera), the body louse Pediculus humanus (Phthiraptera), and the crustacean Daphnia pulex, indicating that it has been lost several times during arthropod evolution. In particular, this frequent loss of hormonal systems is unique for arthropods compared with vertebrates.

BackgroundThe red flour beetle Tribolium castaneum is an emerging insect model organism representing the largest insect order, Coleoptera, which encompasses several serious agricultural and forest pests. Despite the ecological and economic importance of beetles, most insect olfaction studies have so far focused on dipteran, lepidopteran, or hymenopteran systems.ResultsHere, we present the first detailed morphological description of a coleopteran olfactory pathway in combination with genome-wide expression analysis of the relevant gene families involved in chemoreception. Our study revealed that besides the antennae, also the mouthparts are highly involved in olfaction and that their respective contribution is processed separately. In this beetle, olfactory sensory neurons from the mouthparts project to the lobus glomerulatus, a structure so far only characterized in hemimetabolous insects, as well as to a so far non-described unpaired glomerularly organized olfactory neuropil in the gnathal ganglion, which we term the gnathal olfactory center. The high number of functional odorant receptor genes expressed in the mouthparts also supports the importance of the maxillary and labial palps in olfaction of this beetle. Moreover, gustatory perception seems equally distributed between antenna and mouthparts, since the number of expressed gustatory receptors is similar for both organs.ConclusionsOur analysis of the T. castaneum chemosensory system confirms that olfactory and gustatory perception are not organotopically separated to the antennae and mouthparts, respectively. The identification of additional olfactory processing centers, the lobus glomerulatus and the gnathal olfactory center, is in contrast to the current picture that in holometabolous insects all olfactory inputs allegedly converge in the antennal lobe. These findings indicate that Holometabola have evolved a wider variety of solutions to chemoreception than previously assumed.Electronic supplementary materialThe online version of this article (doi:10.1186/s12915-016-0304-z) contains supplementary material, which is available to authorized users.

The adult insect brain is composed of neuropils present in most taxa. However, the relative size, shape, and developmental timing differ between species. This diversity of adult insect brain morphology has been extensively described while the genetic mechanisms of brain development are studied predominantly in Drosophila melanogaster. However, it has remained enigmatic what cellular and genetic mechanisms underlie the evolution of neuropil diversity or heterochronic development. In this perspective paper, we propose a novel approach to study these questions. We suggest using genome editing to mark homologous neural cells in the fly D. melanogaster, the beetle Tribolium castaneum, and the Mediterranean field cricket Gryllus bimaculatus to investigate developmental differences leading to brain diversification. One interesting aspect is the heterochrony observed in central complex development. Ancestrally, the central complex is formed during embryogenesis (as in Gryllus) but in Drosophila, it arises during late larval and metamorphic stages. In Tribolium, it forms partially during embryogenesis. Finally, we present tools for brain research in Tribolium including 3D reconstruction and immunohistochemistry data of first instar brains and the generation of transgenic brain imaging lines. Further, we characterize reporter lines labeling the mushroom bodies and reflecting the expression of the neuroblast marker gene Tc-asense, respectively.Electronic supplementary materialThe online version of this article (doi:10.1007/s00427-016-0542-7) contains supplementary material, which is available to authorized users.

In many insect species olfaction is a key sensory modality. However, examination of the chemical ecology of insects has focussed up to now on insects living above ground. Evidence for behavioral responses to chemical cues in the soil other than CO2 is scarce and the role played by olfaction in the process of finding host roots below ground is not yet understood. The question of whether soil-dwelling beetle larvae can smell their host plant roots has been under debate, but proof is as yet lacking that olfactory perception of volatile compounds released by damaged host plants, as is known for insects living above ground, occurs. Here we show that soil-dwelling larvae of Melolontha hippocastani are well equipped for olfactory perception and respond electrophysiologically and behaviorally to volatiles released by damaged host-plant roots. An olfactory apparatus consisting of pore plates at the antennae and about 70 glomeruli as primary olfactory processing units indicates a highly developed olfactory system. Damage induced host plant volatiles released by oak roots such as eucalyptol and anisol are detected by larval antennae down to 5 ppbv in soil air and elicit directed movement of the larvae in natural soil towards the odor source. Our results demonstrate that plant-root volatiles are likely to be perceived by the larval olfactory system and to guide soil-dwelling white grubs through the dark below ground to their host plants. Thus, to find below-ground host plants cockchafer larvae employ mechanisms that are similar to those employed by the adult beetles flying above ground, despite strikingly different physicochemical conditions in the soil.

Neuropeptides are a highly diverse group of signaling molecules that affect a broad range of biological processes in insects, including development, metabolism, behavior, and reproduction. In the central nervous system, neuropeptides are usually considered to act as neuromodulators and cotransmitters that modify the effect of "classical" transmitters at the synapse. The present study analyzes the neuropeptide repertoire of higher cerebral neuropils in the brain of the red flour beetle Tribolium castaneum. We focus on two integrative neuropils of the olfactory pathway, the antennal lobes and the mushroom bodies. Using the technique of direct peptide profiling by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry, we demonstrate that these neuropils can be characterized by their specific neuropeptide expression profiles. Complementary immunohistological analyses of selected neuropeptides revealed neuropeptide distribution patterns within the antennal lobes and the mushroom bodies. Both approaches revealed consistent differences between the neuropils, underlining that direct peptide profiling by mass spectrometry is a fast and reliable method to identify neuropeptide content.

We present a fast, nondestructive, and quantitative approach to characterize the morphology of capillary silica-based monolithic columns by reconstruction from confocal laser scanning microscopy images. The method comprises column pretreatment, image acquisition, image processing, and statistical analysis of the image data. The received morphological data are chord length distributions for the bulk macropore space and skeleton of the silica monolith. The morphological information is shown to be comparable to that derived from transmission electron microscopy, but far easier to access. The approach is generally applicable to silica-based capillary columns, monolithic or particulate. It allows the rapid acquisition of hundreds of longitudinal and cross-sectional images in a single session, resolving a multitude of morphological details in the column.

To estimate the prevalence and pattern of conjuctival squamous cell carcinoma (CSCC) in patients with HIV infection. DESIGN: A hospital based cross sectional study. SETTING: Kenyatta National Hospital (KNH) and Kikuyu Eye Unit (KEU) during the period November 2003 and May 2004. SUBJECTS: Four hundred and nine HIV positive patients. RESULTS: Four hundred and nine HIV positive patients aged 25 to 53 years were screened. Male to Female ratio was 1:1. One hundred and three had conjunctival growths. Thirty two had histologically proven conjunctiva squamous cell carcinoma (CSCC). Estimated prevalence of CSCC among HIV positive patients was 7.8%. The average duration of growth of the conjunctival masses was 21.8 months. The average size of the lesions at the time of presentation was 6.6 mm. Twenty two (68.8%) patients had primary CSCC, while ten (31.2%) had recurrent lesions. The pattern of the histopathology results was: fifteen (46.9%) patients had poorly differentiated squamous cell carcinoma; nine (28%) had moderately differentiated squamous cell carcinoma; five patients (15.6%) had CIN; two patients (6.3%) had dysplasia and one patient (3.1%) had a well differentiated squamous cell carcinoma. CONCLUSIONS: Prevalence of CSCC in HIV/AIDS patients was 7.8%. Patients present late with advanced lesions. Recurrence rates from previous surgery are high. The often uncharacteristic complaints and findings on presentation complicate the clinical diagnosis. Active search for early manifestations of CSCC in HIV / AIDS patients, complete surgical excision and close follow up is necessary. Alternative treatment methods and techniques like the topical use of antimetabolites should be explored further.

Arthropoda is comprised of four major taxa: Hexapoda, Crustacea, Myriapoda and Chelicerata. Although this classification is widely accepted, there is still some debate about the internal relationships of these groups. In particular, the phylogenetic position of Collembola remains enigmatic. Some molecular studies place Collembola into a close relationship to Protura and Diplura within the monophyletic Hexapoda, but this placement is not universally accepted, as Collembola is also regarded as either the sister group to Branchiopoda (a crustacean taxon) or to Pancrustacea (crustaceans + hexapods). To contribute to the current debate on the phylogenetic position of Collembola, we examined the brains in three collembolan species: Folsomia candida, Protaphorura armata and Tetrodontophora bielanensis, using antennal backfills, series of semi-thin sections, and immunostaining technique with several antisera, in conjunction with confocal laser scanning microscopy and three-dimensional reconstructions. We identified several neuroanatomical structures in the collembolan brain, including a fan-shaped central body showing a columnar organization, a protocerebral bridge, one pair of antennal lobes with 20-30 spheroidal glomeruli each, and a structure, which we interpret as a simply organized mushroom body. The results of our neuroanatomical study are consistent with the phylogenetic position of Collembola within the Hexapoda and do not contradict the hypothesis of a close relationship of Collembola, Protura and Diplura.