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.

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., Cecilia A., dos Santos Rolo T., Vagovic P., Baumbach T., Riedel A.

in Arthropod Structure and Development, 44 (2015) 509-523. DOI:10.1016/j.asd.2015.07.004

Abstract

© 2015 Elsevier Ltd.The thorax morphology, especially the muscles and the tracheal system of three flightless species of Cryptorhynchinae is examined by digital 3D reconstructions based on synchrotron X-ray microtomography and compared to other Curculionidae. Wings, metanepisternites, and muscles functional in flight are fully reduced in the species examined: Kyklioacalles roboris (Curtis), Trigonopterus scharfi Riedel and Trigonopterus vandekampi Riedel. All three share the same set of thoracic muscles, but differences exist in the shape and size of muscles. Both Trigonopterus species examined have a conspicuous fan-shaped branch of Musculus mesosterni primus contracting pro- and mesothorax, interpreted as an adaption to their thanatosis defense strategy. Trigonopterus vandekampi furthermore shows a marked increase in the size of two metacoxal muscles, which may be functional in this species’ thanatosis blocking mechanisms. The metathoracic spiracle of all Trigonopterus species is located at the side of the metaventrite externally and not in the subelytral space as in other beetles. It is hypothesized that this translocation was triggered by the need to improve oxygen supply during thanatosis, when both the mesothoracic spiracle and the subelytral cavity are tightly sealed from the outside.

Yang X., Hofmann R., Dapp R., Van De Kamp T., Dos Santos Rolo T.T., Xiao X., Moosmann J., Kashef J., Stotzka R.

in Optics Express, 23 (2015) 5368-5387. DOI:10.1364/OE.23.005368

Abstract

© 2015 Optical Society of America. High-resolution, three-dimensional (3D) imaging of soft tissues requires the solution of two inverse problems: phase retrieval and the reconstruction of the 3D image from a tomographic stack of two-dimensional (2D) projections. The number of projections per stack should be small to accommodate fast tomography of rapid processes and to constrain X-ray radiation dose to optimal levels to either increase the duration of in vivo time-lapse series at a given goal for spatial resolution and/or the conservation of structure under X-ray irradiation. In pursuing the 3D reconstruction problem in the sense of compressive sampling theory, we propose to reduce the number of projections by applying an advanced algebraic technique subject to the minimisation of the total variation (TV) in the reconstructed slice. This problem is formulated in a Lagrangian multiplier fashion with the parameter value determined by appealing to a discrete L-curve in conjunction with a conjugate gradient method. The usefulness of this reconstruction modality is demonstrated for simulated and in vivo data, the latter acquired in parallel-beam imaging experiments using synchrotron radiation.

Schmelzle S., Norton R.A., Heethoff M.

in Zoologischer Anzeiger, 254 (2015) 27-40. DOI:10.1016/j.jcz.2014.09.002

Abstract

© 2014 Elsevier GmbH. The most complex mechanical defense of oribatid mites is ptychoidy, in which the animals can retract their legs and gnathosoma into the idiosoma and encapsulate by deflecting the prodorsum. Since Acari lack most antagonistic musculature, extension of appendages is facilitated through hemolymph pressure that in mites mostly is generated by dorso-ventral compression of the opisthosoma. The hardened notogaster of box mites requires a different system of pressure generation that is also able to accommodate huge hemolymph movement accompanying ptychoidy. We compared the functional morphology of ptychoidy in one model species from each of the two ptyctime superfamilies, Euphthiracaroidea and Phthiracaroidea, using synchrotron X-ray microtomography and high-speed videography. We show that the two groups evolved very different functional modes of hydrostatic pressure control. While euphthiracaroids employ a lateral compression of the notogaster using all muscles of the opisthosomal compressor system, phthiracaroids employ a dorsoventral compression generated by only the notogaster lateral compressor and additionally the postanal muscle; these retract the temporarily unified ventral plates into the idiosoma, revealing the poam as an integral part of the opisthosomal compressor system in this group. The primitive mode of operation for generating hemolymph pressure in the Ptyctima probably was lateral compression, as molecular studies indicate that Phthiracaroidea evolved within Euphthiracaroidea. In this hypothesis, dorsoventral compression evolved secondarily in phthiracaroid mites, but whether the immediate ancestors of Ptyctima used lateral or dorsoventral compression remains to be determined.

Heethoff M., Rall B.C.

in Chemoecology, 25 (2015) 53-61. DOI:10.1007/s00049-014-0184-z

Abstract

© 2015, Springer Basel. Morphological and chemical defences are widespread anti-predator mechanisms in most domains of life, and play an important role in understanding predator–prey interactions. Classical concepts of dynamical protection (‘inducible defence’) include the morphological changes in certain crustaceans or the production of chemicals in many plants. Permanently stored defensive secretions are, to our knowledge, ignored in food web ecology. We show that this kind of chemical defence is highly dynamic and may loose its effect over time (‘reducible defence’). Combining experimental and theoretical approaches, we show that chemical defence also changes the time budget of predators and decreases the strength of the functional response. However, this may be counteracted by increasing predator density—an effect we call ‘apparent facilitation’. The interplay of ‘reducible defence’ and ‘apparent facilitation’ may substantially contribute to stability in terrestrial ecosystems.

Smith J.L., Palermo N.A., Theobald J.C., Wells J.D., Heethoff M.

in Journal of Insect Science, 15 (2015). DOI:10.1093/jisesa/iev114

Abstract

© The Author 2015. Male Chrysomya megacephala (F.) blow fly compound eyes contain an unusual area of enlarged dorsal facets believed to allow for increased light capture. This region is absent in females and has been hypothesized to aid in mate tracking in low light conditions or at greater distances. Many traits used in the attraction and capture of mates are allometric, growing at different rates relative to body size. Previous reports concerning C. megacephala eye properties did not include measurements of body size, making the relationship between the specialized eye region and body size unclear. We examined different morphological features of the eye among individuals of varying sizes. We found total eye size scaled proportionately to body size, but the number of enlarged dorsal facets increased as body size increased. This demonstrated that larger males have an eye that is morphologically different than smaller males. On the basis of external morphology, we hypothesized that since larger males have larger and a greater number of dorsally enlarged facets, and these facets are believed to allow for increased light capture, larger males would be active in lower light levels than smaller males and females of equal size. In a laboratory setting, larger males were observed to become active earlier in the morning than smaller males, although they did not remain active later in the evening. However, females followed the same pattern at similar light levels suggesting that overall body size rather than specialized male eye morphology is responsible for increased activity under low light conditions.

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.