Wulff N.C., Van De Kamp T., Dos Santos Rolo T., Baumbach T., Lehmann G.U.C.

in Scientific Reports, 7 (2017), 42345. DOI:10.1038/srep42345

Abstract

© The Author(s) 2017. Male genital organs are among the fastest evolving morphological structures. However, large parts of the male’s genitalia are often hidden inside the female during mating. In several bushcricket species, males bear a pair of sclerotized genital appendices called titillators. By employing synchrotron-based in vivo X-ray cineradiography on mating couples, we were able to visualize titillator movement and spermatophore attachment inside the female. Titillators are inserted and retracted rhythmically. During insertion the titillator processes tap the soft and sensillae-covered dorsal side of the female’s flap-like genital fold, which covers the opening of the female’s genitalia, without tissue penetration. Titillators thus appear to be initially used for stimulation; later they may apply pressure that forces the female’s genital fold to stay open, thereby aiding mechanically in spermatophore transfer.

Zuber M., Laass M., Hamann E., Kretschmer S., Hauschke N., Van De Kamp T., Baumbach T., Koenig T.

in Scientific Reports, 7 (2017), 41413. DOI:10.1038/srep41413

Abstract

© 2017 The Author(s). Non-destructive imaging techniques can be extremely useful tools for the investigation and the assessment of palaeontological objects, as mechanical preparation of rare and valuable fossils is precluded in most cases. However, palaeontologists are often faced with the problem of choosing a method among a wide range of available techniques. In this case study, we employ X-ray computed tomography (CT) and computed laminography (CL) to study the first fossil xiphosuran from the Muschelkalk (Middle Triassic) of the Netherlands. The fossil is embedded in micritic limestone, with the taxonomically important dorsal shield invisible, and only the outline of its ventral part traceable. We demonstrate the complementarity of CT and CL which offers an excellent option to visualize characteristic diagnostic features. We introduce augmented laminography to correlate complementary information of the two methods in Fourier space, allowing to combine their advantages and finally providing increased anatomical information about the fossil. This method of augmented laminography enabled us to identify the xiphosuran as a representative of the genus Limulitella.

Hahn S., Muller Y., Hofmann R., Moosmann J., Oktem O., Helfen L., Guigay J.-P., Van De Kamp T., Baumbach T.

in Physical Review A – Atomic, Molecular, and Optical Physics, 93 (2016), 053834. DOI:10.1103/PhysRevA.93.053834

Abstract

© 2016 American Physical Society. ©2016 American Physical Society. We analyze theoretically and investigate experimentally the transfer of phase to intensity power spectra of spatial frequencies through free-space Fresnel diffraction. Depending on λz (where λ is the wavelength and z is the free-space propagation distance) and the phase-modulation strength S, we demonstrate that for multiscale and broad phase spectra critical behavior transmutes a quasilinear to a nonlinear diffractogram except for low frequencies. On the contrary, a single-scale and broad phase spectrum induces a critical transition in the diffractogram at low frequencies. In both cases, identifying critical behavior encoded in the intensity power spectra is of fundamental interest because it exhibits the limits of perturbative power counting but also guides resolution and contrast optimization in propagation-based, single-distance, phase-contrast imaging, given certain dose and coherence constraints.

Huang D.-Y., Bechly G., Nel P., Engel M.S., Prokop J., Azar D., Cai C.-Y., Van De Kamp T., Staniczek A.H., Garrouste R., Krogmann L., Dos Santos Rolo T., Baumbach T., Ohlhoff R., Shmakov A.S., Bourgoin T., Nel A.

in Scientific Reports, 6 (2016), 23004. DOI:10.1038/srep23004

Abstract

With nearly 100,000 species, the Acercaria (lice, plant lices, thrips, bugs) including number of economically important species is one of the most successful insect lineages. However, its phylogeny and evolution of mouthparts among other issues remain debatable. Here new methods of preparation permitted the comprehensive anatomical description of insect inclusions from mid-Cretaceous Burmese amber in astonishing detail. These “missing links” fossils, attributed to a new order Permopsocida, provide crucial evidence for reconstructing the phylogenetic relationships in the Acercaria, supporting its monophyly, and questioning the position of Psocodea as sister group of holometabolans in the most recent phylogenomic study. Permopsocida resolves as sister group of Thripida + Hemiptera and represents an evolutionary link documenting the transition from chewing to piercing mouthparts in relation to suction feeding. Identification of gut contents as angiosperm pollen documents an ecological role of Permopsocida as early pollen feeders with relatively unspecialized mouthparts. This group existed for 185 million years, but has never been diverse and was superseded by new pollenivorous pollinators during the Cretaceous co-evolution of insects and flowers. The key innovation of suction feeding with piercing mouthparts is identified as main event that triggered the huge post-Carboniferous radiation of hemipterans, and facilitated the spreading of pathogenic vectors.

Schwermann A.H., dos Santos Rolo T., Caterino M.S., Bechly G., Schmied H., Baumbach T., van de Kamp T.

in eLife, 5 (2016), e12129. DOI:10.7554/eLife.12129

Abstract

© Schwermann et al. External and internal morphological characters of extant and fossil organisms are crucial to establishing their systematic position, ecological role and evolutionary trends. The lack of internal characters and soft-tissue preservation in many arthropod fossils, however, impedes comprehensive phylogenetic analyses and species descriptions according to taxonomic standards for Recent organisms. We found well-preserved three-dimensional anatomy in mineralized arthropods from Paleogene fissure fillings and demonstrate the value of these fossils by utilizing digitally reconstructed anatomical structure of a hister beetle. The new anatomical data facilitate a refinement of the species diagnosis and allowed us to reject a previous hypothesis of close phylogenetic relationship to an extant congeneric species. Our findings suggest that mineralized fossils, even those of macroscopically poor preservation, constitute a rich but yet largely unexploited source of anatomical data for fossil arthropods.

Kuhsel S., Bruckner A., Schmelzle S., Heethoff M., Bluthgen N.

in Insect Science (2016). DOI:10.1111/1744-7917.12362

Abstract

© 2016 Institute of Zoology, Chinese Academy of Sciences. Body mass, volume and surface area are important for many aspects of the physiology and performance of species. Whereas body mass scaling received a lot of attention in the literature, surface areas of animals have not been measured explicitly in this context. We quantified surface area-volume (SA/V) ratios for the first time using 3D surface models based on a structured light scanning method for 126 species of pollinating insects from 4 orders (Diptera, Hymenoptera, Lepidoptera, and Coleoptera). Water loss of 67 species was measured gravimetrically at very dry conditions for 2 h at 15 and 30 °C to demonstrate the applicability of the new 3D surface measurements and relevance for predicting the performance of insects. Quantified SA/V ratios significantly explained the variation in water loss across species, both directly or after accounting for isometric scaling (residuals of the SA/V ∼ mass2/3 relationship). Small insects with a proportionally larger surface area had the highest water loss rates. Surface scans of insects to quantify allometric SA/V ratios thus provide a promising method to predict physiological responses, improving the potential of body mass isometry alone that assume geometric similarity.

Mangold S., Van De Kamp T., Steininger R.

in Journal of Physics: Conference Series, 712 (2016), 012141. DOI:10.1088/1742-6596/712/1/012141

Abstract

The usefulness of full field transmission spectroscopy is shown using the example of mandible of the stick insect Peruphasma schultei. An advanced data evaluation tool chain with an energy drift correction and highly reproducible automatic background correction is presented. The results show significant difference between the top and the bottom of the mandible of an adult stick insect.

van de Kamp T., Riedel A., Greven H.

in Arthropod Structure and Development, 45 (2016) 14-22. DOI:10.1016/j.asd.2015.10.002

Abstract

© 2015 Elsevier Ltd.The elytral cuticle of 40 beetle species, comprising 14 weevils (Curculionoidea) and 26 representatives of other taxa, is examined. All weevils and 18 other species have an endocuticle with prominent macrofibers, which corresponds to a modified pseudo-orthogonal cuticle. Angles between successive layers of macrofibers range between 30° and 90°, but are constantly less than 60° in weevils. In all Curculionoidea, as well as in one buprestid and one erotylid species exo- and endocuticle are densely interlocked. In the weevil Sitophilus granarius, transmission electron microscopy revealed vertical microfibrils extending from the exocuticle between the macrofibers of the underlaying endocuticle. Vertical microfibrils connecting successive macrofiber layers of the endocuticle were observed in S. granarius and Trigonopterus nasutus. Distinct cuticular characters are traced on a beetle phylogeny: the angles between unidirectional endocuticle layers; the presence and the shape of endocuticular macrofibers; and the interlocking of exo- and endocuticle. While character traits seem to be more or less randomly distributed among Coleoptera, the Curculionoidea have a uniform groundplan: The “weevil-specific” combination of characters includes 1) interlocking of exo- and endocuticle, 2) an endocuticle with distinct ovoid macrofibers embedded in a matrix and 3) comparatively small angles between successive endocuticular layers. Thus, phylogenetic constraints appear equally important to functional factors in the construction of the weevil elytron.

Bruckner A., Wehner K., Neis M., Heethoff M.

in Acarologia, 56 (2016).

Abstract

© Brückner A. et al. Oribatid mites represent a diverse group of soil micro-arthropods. They have evolved a broad range of defensive chemical and morphological traits (e.g. sclerotization, ptychoidy, biomineralization). Chemical defense, rather than sclerotization, can provide protection against large predators (staphylinid beetles) and many oribatid mite species are also well protected against gamasid soil mites using morphological traits (“enemy-free-space hypothesis”). However, since predatory mites and staphylinid beetles have different types of attacking and feeding, the adaptive values of chemical and morphological traits might differ accordingly. We used the oribatid model species Archegozetes longisetosus Aoki and the common gamasid mite Stratiolaelaps miles Berlese in a predator-prey experiment. We tested for effects of chemical defense (treatments with and without oil gland secretions) and sclerotization (treatments with unsclerotized tritonymphs and sclerotized adults) in an orthogonal design. In contrast to attacks by large predators, chemical defense was mostly ineffective against gamasid mites. Sclerotization, however, had a positive effect. Hence, in a natural environment with diverse types of predators, the “enemy-free space” seems only realizable by combinations of chemical and morphological protective traits.

Greven H., Van De Kamp T., Dos Santos Rolo T., Baumbach T., Clemen G.

in Vertebrate Zoology, 65 (2015) 81-99.

Abstract

A study on the cranial morphology, especially on the tooth bearing (dental) systems of several preserved developmental stages (from early premetamorphic larvae, in which most skull elements were already present and ossified or ossified in part, to transformed adult) of the smooth newt Lissotriton vulgaris (Salamandridae) was undertaken. We used μCT (to visualize the ossified elements in general and their relationships to each other) and an overall Alizarinred staining (to at best visualize teeth, replacement teeth, tooth buds and, after removing the oral mucosa, the course of dental laminae). Specimens cleared and stained with Alzarinred and Alcianblue were shown to be less suitable for our questions. In one case we used histological sections to follow the course of dental laminae, and in a second case scanning electron microscopy to show the structure of teeth in detail. The general sequence, growth, and changes of the bony elements including the “dental systems”, especially around metamorphosis, known from several other salamandrids are largely confirmed. Concerning the “tooth systems”, metamorphic events include the late appearance of the maxillae, resorption of the coronoids and palatines including their tooth-patches, remodelling of the vomer, i.e. resorption of the vomerine larval tooth-patch, formation of the edentate vomerine plate, and outgrowth of the monstichously dentate vomerine bar (typical for salamandrids). We show evidence that the larval vomer is not completey resorbed and that, unlike what has been described for Salamandra salamandra, the development of the vomerine bar is probably preceded by a shift of the dental lamina towards the middle of the palate, leaving a broad area between larval vomer and dental lamina. We hypothesize that the connective tissue in this area ossifies later and extends posteriorly forming the vomerine bar. It is noteworthy that in nearly all larvae vomer and intact pterygopalatinum were very close together either on one side or on both sides leading in overwintered larvae to the fusion of the vomer and the palatinal portion of the pterygopalatinum, primarily on one side. The zone of fusion is always characterized by a buccal notch. We think that in L. vulgaris the formation of “vomeropterygopalatina” is supported by the close proximity of the two bones and that these bones may fuse due to an imbalance between differentiation- and growth rate (indirectly caused by low temperatures). Approximation and especially fusion of the two bones correspond with the extension of the vomerine dental lamina into the area of the palatine, which temporally provides the latter with teeth. Overwintered larvae show further deviations concerning growth and differentiation of the mouth roof, which can be also interpreted as signs of delayed metamorphosis. They retain, for example, a largely intact dentate palatine, but with some regression of its tooth-patch, while the larval vomer is enlarged anteriorly and posteriorly and its number of teeth has increased; and the largely intact pterygopalatinal bony bridge. Further, maxillae begin to ossify. All larvae obviously have reached a late premetamorphic larval stage before the delay has started.