The tremendous diversity of Hymenoptera is commonly attributed to the evolution of parasitoidism in the last common ancestor of parasitoid sawflies (Orussidae) and wasp-waisted Hymenoptera (Apocrita). However, Apocrita and Orussidae differ dramatically in their species richness, indicating that the diversification of Apocrita was promoted by additional traits. These traits have remained elusive due to a paucity of sawfly genome sequences, in particular those of parasitoid sawflies. Here we present comparative analyses of draft genomes of the primarily phytophagous sawfly Athalia rosae and the parasitoid sawfly Orussus abietinus. Our analyses revealed that the ancestral hymenopteran genome exhibited traits that were previously considered unique to eusocial Apocrita (e.g., low transposable element content and activity) and a wider gene repertoire than previously thought (e.g., genes for CO2 detection). Moreover, we discovered that Apocrita evolved a significantly larger array of odorant receptors than sawflies, which could be relevant to the remarkable diversification of Apocrita by enabling efficient detection and reliable identification of hosts.

BackgroundSolar-powered sea slugs are famed for their ability to survive starvation due to incorporated algal chloroplasts. It is well established that algal-derived carbon can be traced in numerous slug-derived compounds, showing that slugs utilize the photosynthates produced by incorporated plastids. Recently, a new hypothesis suggests that the photosynthates produced are not continuously made available to the slug. Instead, at least some of the plastid’s photosynthetic products are stored in the plastid itself and only later become available to the slug. The long-term plastid-retaining slug, Elysia timida and its sole food source, Acetabularia acetabulum were examined to determine whether or not starch, a combination of amylose and amylopectin and the main photosynthate produced by A. acetabulum, is produced by the stolen plastids and whether it accumulates within individual kleptoplasts, providing an energy larder, made available to the slug at a later time.ResultsHistological sections of Elysia timida throughout a starvation period were stained with Lugol’s Iodine solution, a well-known stain for starch granules in plants. We present here for the first time, an increase in amylose concentration, within the slug’s digestive gland cells during a starvation period, followed by a sharp decrease. Chemically blocking photosynthesis in these tissues resulted in no observable starch, indicating that the starch in untreated animals is a product of photosynthetic activity.ConclusionThis suggests that kleptoplasts function as both, a nutritive producer and storage device, holding onto the polysaccharides they produce for a certain time until they are finally available and used by the starving slug to withstand extended starvation periods.

Despite its five meters length, the megamouth shark (Megachasma pelagios Taylor, Compagno & Struhsaker, 1983) is one of the rarest big sharks known in the world (117 specimens observed and documented so far). This filter-feeding shark has been assumed to be a luminous species, using its species-specific white band to produce bioluminescence as a lure trap. Another hypothesis was the use of the white band reflectivity to attract prey or for social recognition purposes. However, no histological study has ever been performed to confirm these assumptions so far. Two hypotheses about the megamouth shark's luminescence arose: firstly, the light emission may be intrinsically or extrinsically produced by specific light organs (photophores) located either on the upper jaw white band or inside the mouth; secondly, the luminous appearance might be a consequence of the reflection of prey luminescence on the white band during feeding events. Aims of the study were to test these hypotheses by highlighting the potential presence of specific photophores responsible for bioluminescence and to reveal and analyze the presence of specialized light-reflective structures in and around the mouth of the shark. By using different histological approaches (histological sections, fluorescent in situ hybridization, scanning electron microscopy) and spectrophotometry, this study allows to unravel these hypotheses and strongly supports that the megamouth shark does not emit bioluminescence, but might rather reflect the light produced by bioluminescent planktonic preys, thanks to the denticles of the white band.

Cuticular hydrocarbons (CHCs) cover the cuticle of insects and serve as desiccation barrier and as semiochemicals. While the main enzymatic steps of CHC biosynthesis are well understood, few of the underlying genes have been identified. Here we show how exploitation of intrasexual CHC dimorphism in a mason wasp, Odynerus spinipes, in combination with whole-genome sequencing and comparative transcriptomics facilitated identification of such genes. RNAi-mediated knockdown of twelve candidate gene orthologs in the honey bee, Apis mellifera, confirmed nine genes impacting CHC profile composition. Most of them have predicted functions consistent with current knowledge of CHC metabolism. However, we found first-time evidence for a fatty acid amide hydrolase also influencing CHC profile composition. In situ hybridization experiments furthermore suggest trophocytes participating in CHC biosynthesis. Our results set the base for experimental CHC profile manipulation in Hymenoptera and imply that the evolutionary origin of CHC biosynthesis predates the arthropods’ colonization of land.

The mason wasp Odynerus spinipes shows an exceptional case of intrasexual cuticular hydrocarbon (CHC) profile dimorphism. Females of this species display one of two CHC profiles (chemotypes) that differ qualitatively and quantitatively from each other. The ratio of the two chemotypes was previously shown to be close to 1:1 at three sites in Southern Germany, which might not be representative given the Palearctic distribution of the species. To infer the frequency of the two chemotypes across the entire distributional range of the species, we analyzed with GC–MS the CHC profile of 1042 dry-mounted specimens stored in private and museum collections. We complemented our sampling by including 324 samples collected and preserved specifically for studying their CHCs. We were capable of reliably identifying the chemotypes in 91% of dry-mounted samples, some of which collected almost 200 years ago. We found both chemotypes to occur in the Far East, the presumed glacial refuge of the species, and their frequency to differ considerably between sites and geographic regions. The geographic structure in the chemotype frequencies could be the result of differential selection regimes and/or different dispersal routes during the colonization of the Western Palearctic. The presented data pave the route for disentangling these factors by providing information where to geographically sample O. spinipes for population genetic analyses. They also form the much-needed basis for future studies aiming to understand the evolutionary and geographic origin as well as the genetics of the astounding CHC profile dimorphism that O. spinipes females exhibit.

The mason wasp Odynerus spinipes shows an exceptional case of intrasexual CHC dimorphism. Females of this species express one of two cuticular hydrocarbon (CHC) profiles (chemotypes) that differ qualitatively and quantitatively from each other. The ratio of the two chemotypes was previously shown to be close to 1:1 at three sites in Southern Germany, which might not be representative given the Palearctic distribution of the species. To infer the frequency of the two chemotypes across the entire distributional range of the species, we analyzed with GC-MS the CHC profiles of 1,042 dry-mounted specimens stored in private and museum collections. We complemented our sampling by including 324 samples collected and preserved specifically for studying their CHCs. We were capable of reliably identifying the chemotypes in 91% of dry-mounted samples, some of which collected almost 200 years ago. We found both chemotypes to occur in the Far East, the presumed glacial refuge of the species, and their frequency to differ considerably between sites and geographic regions. The geographic structure in the chemotype frequencies could be the result of differential selection regimes and/or different dispersal routes during the colonization of the Western Palearctic. The presented data pave the route for disentangling these factors by providing information where to geographically sample O. spinipes for population genetic analyses. They also form the much-needed basis for future studies aiming to understand the evolutionary and geographic origin as well as the genetics of the astounding CHC dimorphism that O. spinipes females exhibit.

Cuticular hydrocarbons (CHCs) cover the cuticle of insects and serve as desiccation barrier and for chemical communication. While the main enzymatic steps of CHC biosynthesis are well understood, few of the underlying genes have been identified. Here we show how exploitation of intrasexual CHC dimorphism in a mason wasp, Odynerus spinipes, in combination with whole-genome sequencing and comparative transcriptomics facilitated identification of such genes. RNAi-mediated knockdown of twelve candidate gene orthologs in honey bees, Apis mellifera, confirmed nine genes impacting CHC profile composition. Most of them have predicted functions consistent with current knowledge of CHC metabolism. However, we found first-time evidence for a fatty acid amide hydrolase also influencing CHC profile composition. In situ hybridization experiments furthermore suggest trophocytes participating in CHC biosynthesis. Our results set the base for experimental CHC profile manipulation in Hymenoptera and imply that the evolutionary origin of CHC biosynthesis predates the arthropods’ colonization of land.

Background: The remarkable resistance to ionizing radiation found in anhydrobiotic organisms, such as some bacteria, tardigrades, and bdelloid rotifers has been hypothesized to be incidental to the desiccation resistance. Both stresses produce reactive oxygen species and cause damage to DNA and other macromolecules, including DNA. However, this hypothesis has only been investigated in a few species and it is so far not possible to determine how universal it is. Results: In this study, we analyzed the transcriptomic response of the bdelloid rotifer Adineta vaga to desiccation and to low- (X-rays) and high- (Fe) LET radiation in order to highlight the molecular and genetic mechanisms triggered by both stresses. We detected a transcriptomic response common to desiccation and both radiations with the over-expression of highly expressed genes mainly involved in DNA repair, protein modifications, or coding for Heat Shock Proteins, histones variants, enhancers but also many genes with unknown functions. We also discovered a distinct transcriptomic response specific to rehydration, which involved the over-expression of genes encoding Late Embryogenesis Abundant proteins, Heat Shock Proteins, and glucose repressive proteins. Moreover, we identified numerous genes encoding antioxidants that are constitutively highly expressed, which may contribute to the bdelloid rotifer resistance. Conclusions: These results suggest that the extreme resistance of bdelloid rotifers to radiation might indeed be inherited from and a consequence of their capacity to resist complete desiccation. This study paves the way for functional experiments targeting promising candidate proteins playing central roles in radiation and desiccation resistance.