Resilin matrix distribution, variability and function in Drosophila.

BACKGROUND: Elasticity prevents fatigue of tissues that are extensively and repeatedly deformed. Resilin is a resilient and elastic extracellular protein matrix in joints and hinges of insects. For its mechanical properties, Resilin is extensively analysed and applied in biomaterial and biomedical sciences. However, there is only indirect evidence for Resilin distribution and function in an insect. Commonly, the presence of dityrosines that covalently link Resilin protein monomers (Pro-Resilin), which are responsible for its mechanical properties and fluoresce upon UV excitation, has been considered to reflect Resilin incidence. RESULTS: Using a GFP-tagged Resilin version, we directly identify Resilin in pliable regions of the Drosophila body, some of which were not described before. Interestingly, the amounts of dityrosines are not proportional to the amounts of Resilin in different areas of the fly body, arguing that the mechanical properties of Resilin matrices vary according to their need. For a functional analysis of Resilin matrices, applying the RNA interference and Crispr/Cas9 techniques, we generated flies with reduced or eliminated Resilin function, respectively. We find that these flies are flightless but capable of locomotion and viable suggesting that other proteins may partially compensate for Resilin function. Indeed, localizations of the potentially elastic protein Cpr56F and Resilin occasionally coincide. CONCLUSIONS: Thus, Resilin-matrices are composite in the way that varying amounts of different elastic proteins and dityrosinylation define material properties. Understanding the biology of Resilin will have an impact on Resilin-based biomaterial and biomedical sciences.

Male postabdomen reveals ancestral traits of Megasecoptera among winged insects.

External male genitalia of insects are greatly diverse in form and frequently used in evolutionary context and taxonomy. Therefore, our proper recognition of homologous structures among various groups from Paleozoic and extant insect taxa is of crucial interest, allowing to understand the key steps in insect evolution. Here, we reveal structural details of two Late Carboniferous representatives of Megasecoptera (families Bardohymenidae and Brodiopteridae), such as the presence of separated coxal plates VIII and ventral expansions of coxal lobes IX. Together with the confirmed presence of abdominal styli in some other members of Palaeodictyopterida (Diaphanopterodea) this suggests that early pterygotes may have had traits more archaic than expected. Whether or not these traits point to a stem-group relationship of Palaeodictyopterida to all other Pterygota as suspected by earlier authors remains unclear at this stage. Furthermore, the present study provides an updated comparison of male postabdomen morphology among extant species of wingless Archaeognatha and representatives of early diverging groups of Pterygota from the Late Carboniferous and Early Permian, the Megasecoptera (Palaeodictyopterida), Permoplectoptera (Ephemeroptera) and Meganisoptera (Odonatoptera).

Manual of praying mantis morphology, nomenclature, and practices (Insecta, Mantodea).

This study provides a comprehensive review of historical morphological nomenclature used for praying mantis (Mantodea) morphology, which includes citations, original use, and assignment of homology. All referenced structures across historical works correspond to a proposed standard term for use in all subsequent works pertaining to praying mantis morphology and systematics. The new standards are presented with a verbal description in a glossary as well as indicated on illustrations and images. In the vast majority of cases, originally used terms were adopted as the new standard. In addition, historical morphological topographical homology conjectures are considered with discussion on modern interpretations. A new standardized formulation to present foreleg femoral and tibial spines is proposed for clarity based on previous works. In addition, descriptions for methods of collection, curation, genital complex dissection, and labeling are provided to aid in the proper preservation and storage of specimens for longevity and ease of study. Due to the lack of consistent linear morphometric measurement practices in the literature, we have proposed a series of measurements for taxonomic and morphological research. These measurements are presented with figures to provide visual aids with homologous landmarks to ensure compatibility and comparability across the Order. Finally, our proposed method of pinning mantises is presented with a photographical example as well as a video tutorial available at http://mantodearesearch.com.

Chemical disguise of myrmecophilous cockroaches and its implications for understanding nestmate recognition mechanisms in leaf-cutting ants.

BACKGROUND: Cockroaches of the genus Attaphila regularly occur in leaf-cutting ant colonies. The ants farm a fungus that the cockroaches also appear to feed on. Cockroaches disperse between colonies horizontally (via foraging trails) and vertically (attached to queens on their mating flights). We analysed the chemical strategies used by the cockroaches to integrate into colonies of Atta colombica and Acromyrmex octospinosus. Analysing cockroaches from nests of two host species further allowed us to test the hypothesis that nestmate recognition is based on an asymmetric mechanism. Specifically, we test the U-present nestmate recognition model, which assumes that detection of undesirable cues (non-nestmate specific substances) leads to strong rejection of the cue-bearers, while absence of desirable cues (nestmate-specific substances) does not necessarily trigger aggression. RESULTS: We found that nests of Atta and Acromyrmex contained cockroaches of two different and not yet described Attaphila species. The cockroaches share the cuticular chemical substances of their specific host species and copy their host nest's colony-specific cuticular profile. Indeed, the cockroaches are accepted by nestmate but attacked by non-nestmate ant workers. Cockroaches from Acromyrmex colonies bear a lower concentration of cuticular substances and are less likely to be attacked by non-nestmate ants than cockroaches from Atta colonies. CONCLUSIONS: Nest-specific recognition of Attaphila cockroaches by host workers in combination with nest-specific cuticular chemical profiles suggest that the cockroaches mimic their host's recognition labels, either by synthesizing nest-specific substances or by substance transfer from ants. Our finding that the cockroach species with lower concentration of cuticular substances receives less aggression by both host species fully supports the U-present nestmate recognition model. Leaf-cutting ant nestmate recognition is thus asymmetric, responding more strongly to differences than to similarities.

The Jurassic Bajanzhargalanidae (Insecta: Grylloblattida?): New genera and species, and data on postabdominal morphology.

The presumed phylogenetic link between extant ice-crawlers (Grylloblattidae = 'crown-Grylloblattida') and fossil species of the taxon concept Grylloblattida sensu Storozhenko (2002) is essentially based on postabdominal morphology. However, the fossil data are limited, and the interpretation is open to debate. Here we investigate a sample of a poorly known fossil 'grylloblattidan' family, the Bajanzhargalanidae, collected from the Daohugou locality (Middle Jurassic, China). We describe Sinonele fangi gen. nov., sp. nov., Sinonele hei gen. nov., sp. nov., Sinonele phasmoides gen. nov., sp. nov., and Sinonele mini gen. nov., sp. nov. Thanks to the abundance and exceptional preservation of the material, we could document wing venation intra-specific variability, provide cues to identify male and female individuals, describe and tentatively interpret various body structures of both sexes, and discuss them with a broad pterygotan phylogenetic perspective. The Bajanzhargalanidae exhibit a puzzling combination of postabdominal characters leaving us inconclusive on their affinities, or lack thereof, with crown-Grylloblattida. Our contribution suggests that a substantial effort will be needed to further investigate postabdominal structures from comparatively ancient fossil insects preserved as rock imprints, because of their broad morphological disparity.

Identifying possible sister groups of Cryptocercidae+Isoptera: a combined molecular and morphological phylogeny of Dictyoptera.

Termites (Isoptera) offer an alternative model for the development of eusociality which is not dependent on a high degree of relatedness as found between sisters in hymenopterans (bees, wasps, ants). Recent phylogenetic studies have established that termites belong within the cockroaches as sister to the subsocial Cryptocercidae. Cryptocercidae shares several important traits with termites, thus we need to understand the phylogenetic position of Cryptocercidae+Isoptera to determine how these traits evolved. However, placement of Cryptocercidae+Isoptera is still uncertain. We used both molecular (12S, 16S, COII, 18S, 28S, H3) and morphological characters to reconstruct the phylogeny of Dictyoptera. We included all previously suggested sister groups of Cryptocercidae+Isoptera as well as taxa which might represent additional major cockroach lineages. We used Bayes factors to test different sister groups for Cryptocercidae+Isoptera and assessed character support for the consensus tree based on morphological characters and COII amino acid data. We used the molecular data and fossil calibration to estimate divergence times. We found the most likely sister groups of Cryptocercidae+Isoptera to be Tryonicidae, Anaplecta or Tryonicidae+Anaplecta. Anaplecta has never previously been suggested as sister group or even close to Cryptocercidae+Isoptera, but was formerly placed in Blaberoidea as sister to the remaining taxa. Topological tests firmly supported our new placement of Anaplecta. We discuss the morphological characters (e.g. retractable genitalic hook) that have contributed to the previous placement of Anaplecta in Blaberoidea as well as the factors that might have contributed to a parallel development of genitalic features in Anaplecta and Blaberoidea. Cryptocercidae+Isoptera is placed in a clade with Tryonicidae, Anaplecta and possibly Lamproblattidae. Based on this, we suggest that wood-feeding, and the resultant need to conserve nitrogen, may have been an important factor in the development of termite eusociality. Nocticolidae was placed as sister group to Latindia+Paralatindia (both Corydiidae), this clade was in turn placed as sister group to the remaining Corydiidae. The Nocticolidae+Corydiidae clade is supported by both morphological and COII amino acid changes. Our divergence time estimates placed the split between Mantodea and Blattodea at 273mya (middle Permian) and the splits between the major blattodean lineages no later than 200mya (end of Triassic).

The exoskeleton of the female genitalic region in Petrobiellus takunagae (Insecta: Archaeognatha): insect-wide terminology, homologies, and functional interpretations.

The exoskeleton of the female genitalic region (abdominal venters 7-9) in Petrobiellus takunagae (Machilidae-Petrobiellinae) is studied using light microscopy and SEM. Sclerites are distinguished from membrane by the degree of cuticular flexibility. However, the microsculpture of the cuticle is shown to be useful in characterising the heterogeneity of the cuticle and in detecting weak sclerotisations. The morphology of Petrobiellus is compared with that in Trigoniophthalmus alternatus (Machilidae-Machilinae) described previously. While venter 7 is similar, venters 8 and 9 show many differences in the presence/absence or fusion/separation of particular sclerites. This suggests female genitalic morphology to be a valuable character system for phylogenetic and taxonomic work in Archaeognatha. Comparison with other insect orders is aimed at detecting homologous structures and conditions. Important points are: (1) Petrobiellus has a sclerotised genital lobe posteriorly on venter 7, similar to Zygentoma and Dictyoptera; it bears the gonopore. (2) Petrobiellus has a posterior sclerite on venter 9 that is very similar to a sclerite of Odonata. (3) The morphology of the coxal lobes of venter 9 (gonoplacs) suggests their function as a sheath of the ovipositor. From female genitalic morphology we deduce the process of oviposition, describing an external egg transportation tract.

The gonangulum: a reassessment of its morphology, homology, and phylogenetic significance.

The gonangulum is a sclerite in the female genitalic region of insects. Its presence or full development has long been considered an apomorphy supporting Zygentoma + Pterygota. Recent studies of female genitalia in several insect orders (K.-D. Klass and co-workers) revealed many new data on the gonangulum and homologous sclerotisations (laterocoxa LC9). Herein the gonangulum area is described (including articulations, muscle attachments, sulci) and compared among Archaeognatha, Zygentoma, Odonata, Dermaptera, Dictyoptera, and Notoptera. A wider perspective is provided to the topic by addressing some novel issues: identification of LC9 sclerotisations in non-insect taxa and in insects that secondarily lack an ovipositor; occurrence of homonomous sclerotisations in other abdominal segments of both sexes; morphological interpretation of LC9; and the role of paedomorphosis in LC9 evolution. As a result, there is currently no support for any insect lineage from this character system. For gonangulum-related characters both a significant intra-ordinal variation and frequent homoplasy are demonstrated using various Odonata, Dermaptera, and Dictyoptera as examples. Divergent fates of LC9 in simplified genitalia are shown using a dermapteran and an odonatan. We view all this as a showcase of how a renewed and more detailed examination of a character system can dramatically change the phylogenetic evidence drawn from it.

Postembryonic development of the unique antenna of Mantophasmatodea (Insecta).

The postembryonic antennal development and life cycle of a member of the insect order Mantophasmatodea (Lobatophasma redelinghuysense) was investigated using a series of annulus counts and a time sequence of head capsule measurements. The life cycle comprised six instars. Females achieved significantly larger head capsules from instar 2 onwards, resulting in adult females having a larger mean head capsule diameter (2.58 mm) than males (2.27 mm). Antennae of first instar larvae comprised a smooth four-segmented basiflagellum and a seven-segmented, sensilla-rich distiflagellum. Lengthening of the basiflagellum was achieved by the addition of two annuli per moult, generated by division of the basal annulus (meriston). Annulus number and the unique annulation pattern of the distiflagellum remained constant until adulthood. The segmentation pattern of adult antennae (comprising a basiflagellum and a distiflagellum of 14 and seven annuli respectively) and mode of antennal elongation was consistent for all 11 species examined. Subdivisions in basiflagellar annuli were observed in adults of all species examined, although they are not considered to be true annular divisions. The structure of the mantophasmatodean antenna appears to be autapomorphic within Insecta, bearing little resemblance to that of Grylloblattodea, Dictyoptera or Phasmatodea, all putative sister groups of the Mantophasmatodea. However, the mode of flagellar elongation most closely resembles that of Isoptera, Blattaria and Dermaptera.

Phylogeny of the Heelwalkers (Insecta: Mantophasmatodea) based on mtDNA sequences, with evidence for additional taxa in South Africa.

We examined the phylogeny of Mantophasmatodea from southern Africa (South Africa, Namibia) using approx. 1300 bp of mitochondrial DNA sequence data from the genes encoding COI and 16S. The taxon sample comprised multiple specimens from eight described species (Namaquaphasma ookiepense, Austrophasma rawsonvillense, A. caledonense, A. gansbaaiense, Lobatophasma redelinghuysense, Hemilobophasma montaguense, Karoophasma botterkloofense, K. biedouwense) and four undescribed species of Austrophasmatidae; three specimens of Sclerophasma paresisense (Mantophasmatidae); and two specimens of Praedatophasma maraisi and one of Tyrannophasma gladiator (not yet convincingly assigned to any family). For outgroup comparison a broad selection from hemimetabolous insect orders was included. Equally weighted parsimony analyses of the combined COI+16S data sets with gaps in 16S scored as a fifth character state supported Austrophasmatidae and all species and genera of Mantophasmatodea as being monophyletic. Most species were highly supported with 98-100% bootstrap/7-39 Bremer support (BS), but K. biedouwense had moderate support (87/4) and A. caledonense low support (70/1). Mantophasmatodea, Austrophasmatidae, and a clade Tyrannophasma gladiator+Praedatophasma maraisi were all strongly supported (99-100/12-25), while relationships among the two latter clades and Mantophasmatidae remain ambiguous. Concerning the relationships among genera of Austrophasmatidae, support values are moderately high for some nodes, but not significant for others. We additionally calculated the partitioned BS values of COI and 16S for all nodes in the strict consensus of the combined tree. COI and 16S are highly congruent at the species level as well as at the base of Mantophasmatodea, but congruence is poor for most intergeneric relationships. In forthcoming studies, deeper relationships in the order should be additionally explored by nuclear genes, such as 18S and 28S, for a reduced sample of specimens.

Wood-feeding cockroaches as models for termite evolution (Insecta: Dictyoptera): Cryptocercus vs. Parasphaeria boleiriana.

Isoptera are highly specialized cockroaches and are one of the few eusocial insect lineages. Cryptocercus cockroaches have appeared to many as ideal models for inference on the early evolution of termites, due to their possible phylogenetic relationship and several shared key attributes in life history. Recently, Pellens, Grandcolas, and colleagues have proposed the blaberid cockroach Parasphaeria boleiriana to be an alternative model for the early evolution in termites. We compare the usefulness of Cryptocercus and P. boleiriana as models for termite evolution. Cryptocercus and lower Isoptera (1) can both feed on comparatively recalcitrant wood, (2) have an obligate, rich and unique hypermastigid and oxymonadid fauna in the hindgut, (3) transfer these flagellates to the next generation by anal trophallaxis, (4) have social systems that involve long-lasting biparental care, and, finally, (5) are strongly suggested to be sister groups, so that the key attributes (1)-(4) appear to be homologous between the two taxa. On the other hand, P. boleiriana (1) feeds on soft, ephemeral wood sources, (2) shows no trace of the oxymonadid and hypermastigid hindgut fauna unique to Cryptocercus and lower Isoptera, nor does it have any other demonstrated obligate relationship with hindgut flagellates, (3) is likely to lack anal trophallaxis, (4) has only a short period of uniparental brood care, and (5) is phylogenetically remote from the Cryptocercus+Isoptera clade. These facts would argue against any reasonable usage of P. boleiriana as a model for the early evolution of Isoptera or even of the clade Cryptocercus+Isoptera. Cryptocercus thus remains an appropriate model-taxon-by-homology for early termite evolution. As compared to P. boleiriana, some other Blaberidae (such as the Panesthiinae Salganea) appear more useful as model-taxa-by-homoplasy for the early evolution of the Cryptocercus+Isoptera clade, as their brooding behavior is more elaborate than in P. boleiriana.