Characterization of the fishing lines in Titiwai (=Arachnocampa luminosa Skuse, 1890) from New Zealand and Australia

Animals use adhesive secretions in a plethora of ways, either for attachment, egg anchorage, mating or as either active or passive defence. The most interesting function, however, is the use of adhesive threads to capture prey, as the bonding must be performed within milliseconds and under unsuitable conditions (movement of prey, variable environmental conditions, unfavourable attack angle, etc.) to be nonetheless successful. In the following study a detailed characterization of the prey capture system of the world-renowned glowworm group Arachnocampa from the macroscopic to the ultrastructural level is performed. The data reveal that the adhesive droplets consist mostly of water and display hygroscopic properties at varying humidity levels. The droplet core of Arachnocampa luminosa includes a certain amount of the elements sodium, sulphur and potassium (beside carbon, oxygen and nitrogen), while a different element composition is found in the two related species A. richardsae and A. tasmaniensis. Evidence for lipids, carbohydrates and proteins was negative on the histochemical level, however X-ray photoelectron spectroscopy confirm the presence of peptides within the droplet content. Different to earlier assumptions, the present study indicates that rather than oxalic acid, urea or uric acid are present in the adhesive droplets, presumably originating from the gut. Comparing the capture system in Arachnocampa with those of orb-spiders, large differences appear not only regarding the silky threads, but also, in the composition, hygroscopic properties and size of the mucous droplets

Characterization of the fishing lines in Titiwai (=Arachnocampa luminosa Skuse, 1890) from New Zealand and Australia

Animals use adhesive secretions in a plethora of ways, either for attachment, egg anchorage, mating or as either active or passive defence. The most interesting function, however, is the use of adhesive threads to capture prey, as the bonding must be performed within milliseconds and under unsuitable conditions (movement of prey, variable environmental conditions, unfavourable attack angle, etc.) to be nonetheless successful. In the following study a detailed characterization of the prey capture system of the world-renowned glowworm group Arachnocampa from the macroscopic to the ultrastructural level is performed. The data reveal that the adhesive droplets consist mostly of water and display hygroscopic properties at varying humidity levels. The droplet core of Arachnocampa luminosa includes a certain amount of the elements sodium, sulphur and potassium (beside carbon, oxygen and nitrogen), while a different element composition is found in the two related species A. richardsae and A. tasmaniensis. Evidence for lipids, carbohydrates and proteins was negative on the histochemical level, however X-ray photoelectron spectroscopy confirm the presence of peptides within the droplet content. Different to earlier assumptions, the present study indicates that rather than oxalic acid, urea or uric acid are present in the adhesive droplets, presumably originating from the gut. Comparing the capture system in Arachnocampa with those of orb-spiders, large differences appear not only regarding the silky threads, but also, in the composition, hygroscopic properties and size of the mucous droplets

The chemistry of stalked barnacle adhesive (Lepas anatifera)

The results of the first chemical analysis of the adhesive of Lepas anatifera, a stalked barnacle, are presented. A variety of elements were identified in scanning electron microscopy with energy dispersive spectrometry (SEM-EDS) of the adhesive, including Na, Mg, Ca, Cl, S, Al, Si, K and Fe; however, protein–metal interactions were not detected in Raman spectra of the adhesive. Elemental signatures from SEM-EDS of L. anatifera adhesive glands were less varied. Phosphorous was mostly absent in adhesive samples; supporting previous studies showing that phosphoserines do not play a significant role in adult barnacle adhesion. Disulfide bridges arising from Cys dimers were also investigated; Raman analysis showed weak evidence for S-S bonds in L. anatifera. In addition, there was no calcium carbonate signal in the attenuated total reflectance Fourier transform infrared spectra of L. anatifera adhesive, unlike several previous studies in other barnacle species. Significant differences were observed between the Raman spectra of L. anatifera and Balanus crenatus; these and a range of Raman peaks in the L. anatifera adhesive are discussed. Polysaccharide was detected in L. anatifera adhesive but the significance of this awaits further experiments. The results demonstrate some of the diversity within barnacle species in the chemistry of their adhesives

Advanced biomaterials accumulation of citrate-coated magnetic iron oxide nanoparticles by cultured brain astrocytes

Magnetic iron oxide nanoparticles (Fe-NP) are considered for various applications in the brain. However, little is known so far on the uptake and the metabolism of such nanoparticles in brain cells. Since astrocytes are strategically localized between capillaries and neurons, astrocytes are of particular interest concerning uptake and fate of nanoparticles in the brain. Using astrocyte-rich primary cultures as model system we have investigated the accumulation of citrate-coated Fe-NP by astrocytes. Viable cultured astrocytes accumulate iron from citrate-coated Fe-NP in a time-, concentration-, and temperaturedependent manner. The cellular iron content determined after 4 h of incubation increases proportional to the concentration of Fe-NP, if the particles were applied in concentrations of up to 1000 x 10 -6M of total iron. The iron accumulation from 500 or 1000 x 10 -6 M iron as Fe-NP is significantly slowed by lowering the incubation temperature from 37 to 4 degr C. Transmission electron microscopy of the cells revealed that most of the cellular Fe-NP are present in intracellular vesicles. These data demonstrate that astrocytes accumulate efficiently citrate-coated Fe-NP, most likely by an endocytotic pathway

The chemistry of stalked barnacle adhesive (lepas anatifera)

The results of the first chemical analysis of the adhesive of Lepas anatifera, a stalked barnacle, are presented. A variety of elements were identified in scanning electron microscopy with energy dispersive spectrometry (SEM-EDS) of the adhesive, including Na, Mg, Ca, Cl, S, Al, Si, K and Fe; however, protein-metal interactions were not detected in Raman spectra of the adhesive. Elemental signatures from SEM-EDS of L. anatifera adhesive glands were less varied. Phosphorous was mostly absent in adhesive samples; supporting previous studies showing that phosphoserines do not play a significant role in adult barnacle adhesion. Disulfide bridges arising from Cys dimers were also investigated; Raman analysis showed weak evidence for S-S bonds in L. anatifera. In addition, there was no calcium carbonate signal in the attenuated total reflectance Fourier transform infrared spectra of L. anatifera adhesive, unlike several previous studies in other barnacle species. Significant differences were observed between the Raman spectra of L. anatifera and Balanus crenatus; these and a range of Raman peaks in the L. anatifera adhesive are discussed. Polysaccharide was detected in L. anatifera adhesive but the significance of this awaits further experiments. The results demonstrate some of the diversity within barnacle species in the chemistry of their adhesives

A histochemical and morphological study of the mucus producing pedal gland system in Latia neritoides (Mollusca; Gastropoda; Hygrophila)

Abstract The freshwater gastropod Latia neritoides is endemic to the streams of New Zealand’s North Island. This species has evolved a unique defence system: it exudes a luminescent mucus thought to deter predators. While the bioluminescence itself has been investigated before, the underlying gland system has remained unstudied and relevant information to understand the defence system has been missing till now. For the release of the glowing mucus of L. neritoides two places of origin were assumed: the lateral foot area or the mantel cavity. In this study the focus was on the first suggestion. To gain insight into the defence system, morphological as well as histochemical analyses were performed involving all secretory gland types in the sub-epithelial foot layer. The results were compared with the foot gland system of Neritina sp., a snail living in a comparable habitat, but using a different survival strategy. The gland types of the two gastropods were compared and their mucus types were investigated. Seven subepithelial gland cell types can be distinguished in the foot region of L. neritoides. Neritina sp., in contrast, has six gland cell types of which three laterally located ones are epithelial. Both species show a pedal gland in the anterior foot region. A striking difference between the species are two prominent subepithelial gland cell types (L1l/L2l) in the lateral foot area of L. neritoides, which are missing in Neritina sp. These gland cells are distributed throughout the entire lateral foot area of L. neritoides and make up about 85% of the mucus gland cells in this area. Defence mucus and trail mucus of L. neritoides show different specificities in lectin staining, but are not equally represented in the gland cell types. Yet, based on the huge size and high density of L1l and L2L, we envision a role for these gland types in the defence system

Adhesive Droplets of Glowworm Snares (Keroplatidae: Arachnocampa spp.) Are a Complex Mix of Organic Compounds

Adhesive snares built from silks are fascinating adaptations that have rarely evolved outside spiders. Glowworms (Arachnocampa spp.) are an iconic part of the fauna of Australia and New Zealand that combine the construction of a sticky snare with a bioluminescent lure. Recently, the structure and biomechanical properties of glowworm silk have been studied in detail, but the chemical composition of its adhesive coating, and how it varies between species of Arachnocampa remained unclear, limiting an understanding of the glue function. Here, we studied the chemical composition of the water-soluble fraction of the adhesive droplets from the snares in cave and epigaeic populations of three species of Arachnocampa from mainland Australia, Tasmania, and New Zealand, using a combination of nuclear magnetic resonance and mass spectrometry. We found that glowworm glues comprise a large variety of small organic compounds, with organic acids, amino acids, amino acid derivates, alcohols, urea, and urea derivates being the major fraction, supplemented by small amounts of sugars, fatty acids, and other organic compounds. While there was a general overlap in the compounds detected in the adhesives of all tested Arachnocampa species and populations, the relative amounts differed considerably. We expect that these differences are a product of diet rather than an adaptive response to different environments, but experiments are needed for clarification. The high amount of polar substances and compounds that are hygroscopic at high humidity explains the adhesive properties of the viscous solution and its stability in damp environments. These results contribute to our understanding of the unique prey capture strategy of glowworms. Further, the comparison with convergent spider webs highlights the use of small polar compounds as plasticizers of macro-molecular bioadhesives as a general principle. This may inspire the biomimetic design of novel pressure sensitive adhesives with high performance under high humidity conditions

Under conditions of high humidity (60%), a low water loss over time (8 days) was determined (red circled line), while at a lower humidity (30%, red squared line) there was a fast weight loss (after 3 days).

<p>In relation to this, water (blue line) showed a more constant evaporation rate at 60% humidity and likewise reached its final minima after 3 days. <i>Bombyx mori</i> silkworm fibres (green line), watered for 24 h, evaporated within 2 days, showing the highest weight loss within the first 12 h.</p