Anne Jantschke

The diamondback moth, Plutella xylostella , has developed strategies to overcome the challenging waxy surfaces of plants. Females can lay their eggs on pruinose Brassicaceae plants using a secretion from their colleterial glands, which acts as an egg adhesive. The present microscopic analyses, along with contact angle and force measurements, show that this secretion wets hydrophilic glass surfaces significantly better than hydrophobic ones, forming superthin layers with limited volume. Consequently, the pull-off forces required to remove the eggs are significantly greater on hydrophilic glass (23 mN) compared to hydrophobic glass (2 mN), indicating adhesive strengths of 198 and 29 kPa, respectively. The safety factors, which indicate how many times the weight of the egg (23 µg) corresponds to the pull-off force, are remarkably high: 101,689 for hydrophilic surfaces and 8517 for hydrophobic ones. Egg adhesion to plants varies depending on plant surface structures. Pull-off forces significantly decrease with the increasing number of plant epicuticular wax crystals. For example, safety factors measure 1795 on young adaxial white cabbage leaves and reach as high as 25,461 on the petioles of older Chinese cabbage leaves. This attachment ability is facilitated by the predominantly protein and lipid composition of the egg adhesive, alongside the structural matrices created by plant wax crystals and trichomes embedded within the adhesive. Raman spectroscopy of the untreated solidified egg adhesive reveals characteristic amide I and III bands, a β -sheet structural motif, and the presence of aromatic amino acids phenylalanine and tyrosine, as well as saturated fatty acids. Based on a comprehensive discussion with previous findings, we propose that there is a trade-off between secure egg adhesion and the selection of oviposition sites that match the offspring’s preferences and provide enemy-free spaces. Understanding P. xylostella ’s egg adhesion mechanisms and the characteristics of the adhesive substance may contribute to the improvement of pest control strategies, including physical measures, and the advancement of bioinspired adhesives. Moreover, our study should stimulate future integrative and multidisciplinary research on insect egg adhesives, promoting a comprehensive understanding from various perspectives.

Functional capacities of lead halide perovskites are strongly dependent on their morphology, crystallographic texture, and internal ultrastructure on the nano‐ and the meso‐scale. In the last decade, significant efforts are directed towards the development of novel synthesis routes that would overcome the morphological constraints provided by the physical and crystallographic properties of these materials. In contrast, various living organisms, such as unicellular algae, have the ability to mold biogenic crystals into a vast variety of intricate nano‐architectured shapes while keeping their single crystalline nature. Here, using the cell wall of the dinoflagellate L. granifera as a model, sustainably harvested biogenic calcite is successfully transformed into nano‐structured perovskites. Three variants of lead halide perovskites CH₃NH₃PbX₃ are generated with X = Cl⁻, Br⁻ and I⁻; exhibiting emission peak‐wavelength ranging from blue, to green, to near‐infrared, respectively. The approach can be used for the mass production of nano‐architectured perovskites with desired morphological, textural and, consequently, physical properties exploiting the numerous templates provided by calcite forming unicellular organisms.

Calcareous foraminifer shells (tests) represent one of the most important archives for paleoenvironmental and paleoclimatic reconstruction. To develop a mechanistic understanding of the relationship between environmental parameters and proxy signals, knowledge of the fundamental processes operating during foraminiferal biomineralization is essential. Here, we apply microscopic and diffraction‐based methods to address the crystallographic and hierarchical structure of the test wall of different hyaline foraminifer species. Our results show that the tests are constructed from micrometer‐scale oriented mesocrystals built of nanometer‐scale entities. Based on these observations, we propose a mechanistic extension to the biomineralization model for hyaline foraminifers, centered on the formation and assembly of units of metastable carbonate phases to the final mesocrystal via a non‐classical particle attachment process, possibly facilitated by organic matter. This implies the presence of metastable precursors such as vaterite or amorphous calcium carbonate, along with phase transitions to calcite, which is relevant for the mechanistic understanding of proxy incorporation in the hyaline foraminifers.

An increasing area of shallow-marine benthic habitats, specifically in the Baltic Sea, is affected by seasonal oxygen depletion. To place the current spread of oxygen deficiency into context and quantify the contribution of anthropogenic ecosystem perturbation to this development, high-resolution archives for the pre-instrumental era are needed. As recently demonstrated, shells of the bivalve mollusk, Arctica islandica fulfil this task with molar Mn/Ca_shell ratios as proxies for dissolved oxygen (DO) levels in the water column. Since the ocean quahog is inhomogeneously distributed in the Baltic Sea and may not be present in museum collections or found throughout sedimentary sequences, the present study evaluated whether two other common bivalves, Astarte elliptica and Astarte borealis can be used interchangeably or alternatively as proxy DO recorders. Once mathematically resampled and corrected for shell growth rate-related kinetic effects and (some) vital effects, Mn/Ca_shell data of all three species (age ten onward in A. islandica) were statistically significantly (p < 0.0001) linearly and inversely correlated to DO concentration in the free water column above seafloor (r = –0.66 to –0.75, corresponding to 43 to 56% explained variability). A. elliptica may provide slightly more precise DO data (1σ error of ±1.5 mL/L) than A. islandica or A. borealis ( ± 1.6 mL/L), but has a shorter lifespan. Both Astarte species show a stronger correlation with DO than A. islandica, because their biomineralization seems to be less severely hampered by oxygen and salinity stress. In turn, A. islandica grows faster resulting in less time-averaged data. During youth, the ocean quahog typically incorporates a disproportionately large amount of manganese into its shell, possibly because food intake occurs directly at the sediment-water interface where Mn-rich porewater diffuses out of the sediment. With increasing age, however, A. islandica seems to generate a gradually stronger inhaling water current and takes in a larger proportion of water farther away from the fluffy layer. As demonstrated here, all three studied species can be used as DO archives, though species-specific limitations should be kept in mind.

Highly reflective crystals of the nucleotide base guanine are widely distributed in animal coloration and visual systems. Organisms precisely control the morphology and organization of the crystals to optimize different optical effects, but little is known about how this is achieved. Here we examine a fundamental question that has remained unanswered after over 100 years of research on guanine: what are the crystals made of? Using solution-state and solid-state chemical techniques coupled with structural analysis by powder XRD and solid-state NMR, we compare the purine compositions and the structures of seven biogenic guanine crystals with different crystal morphologies, testing the hypothesis that intracrystalline dopants influence the crystal shape. We find that biogenic “guanine” crystals are not pure crystals but molecular alloys (aka solid solutions and mixed crystals) of guanine, hypoxanthine, and sometimes xanthine. Guanine host crystals occlude homogeneous mixtures of other purines, sometimes in remarkably large amounts (up to 20% of hypoxanthine), without significantly altering the crystal structure of the guanine host. We find no correlation between the biogenic crystal morphology and dopant content and conclude that dopants do not dictate the crystal morphology of the guanine host. The ability of guanine crystals to host other molecules enables animals to build physiologically “cheaper” crystals from mixtures of metabolically available purines, without impeding optical functionality. The exceptional levels of doping in biogenic guanine offer inspiration for the design of mixed molecular crystals that incorporate multiple functionalities in a single material.