The function of resilin in beetle wings Haas, Fabian; Gorb, Stanislav; Blickhan, Reinhard
Proceedings - Royal Society. Biological sciences/Proceedings - Royal Society. Biological Sciences,
07/2000, Letnik:
267, Številka:
1451
Journal Article
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This account shows the distribution of elastic elements in hind wings in the scarabaeid Pachnoda marginata and coccinellid Coccinella septempunctata (both Coleoptera). Occurrence of resilin, a ...rubber-like protein, in some mobile joints together with data on wing unfolding and flight kinematics suggest that resilin in the beetle wing has multiple functions. First, the distribution pattern of resilin in the wing correlates with the particular folding pattern of the wing. Second, our data show that resilin occurs at the places where extra elasticity is needed, for example in wing folds, to prevent material damage during repeated folding and unfolding. Third, resilin provides the wing with elasticity in order to be deformable by aerodynamic forces. This may result in elastic energy storage in the wing.
Many biological attachment devices of insects, spiders and geckos consist of arrays of hairs (setae), which are terminated by contact elements of different shapes. However, the most frequently ...observed shape is a thin plate-like spatula. In spite of a rather wide range of sizes, most spatulae of different animals are not uniform, but rather possess a gradient in thickness and width. Here we show that the spatulae of insects and geckos become gradually thinner and wider approaching the end. This geometrical effect is explained in the present paper, by using a numerical approach for the modelling of the van der Waals adhesion and friction between the contact elements and the substrate. The approach suggests that the observed negative thickness gradient contributes to the improvement of the adhesion resistance, whereas the positive width gradient increases the stability of the detachment, probably a key factor in controlling the animal walking.
The fly Calliphora vicina (Diptera, Calliphoridae) bears attachment pads (pulvilli) covered with setae on their ventral sides. These structures enable attachment to smooth vertical surfaces and ...ceilings. The contact between the terminal setal tips (spatulae) and various substrates was visualised using various experimental techniques combined with conventional scanning electron microscopy (SEM) and cryo-SEM. The results show that the setal endplates are highly flexible structures that form contact with the surface by bending their tips in the distal direction. With conventional SEM, a comparison of partly attached endplates with unattached endplates demonstrated the presence of a distinct marginal bulge. As observed with cryo-SEM, the bulge continuously disappeared as a larger area of the endplate came into contact. Two explanations of this result are suggested. First, the volume between the bulge, the mid-part of the endplate and the substrate may be filled with a fluid secretion that is released into the contact area in the endplate region. Second, the flexible central part of the endplate may jump into contact with the substrate during contact formation.
•Mucilage envelope is the second adhesive system present in the Commicarpus helenae anthocarps.•For the first time the mucilage structure, morphology and basic chemical composition was ...studied.•Mucilage belongs to the cellulosic type and possess very long cellulosic fibrils.•We discuss the role of two independent adhesive systems for anthocarp attachment and dispersal.
Mucilaginous diaspores (seeds, fruits, anthocarps) responsible for the plant dispersion are known for many diverse plant families. The anthocarp of Commicarpus helenae demonstrates a unique double adhesive system represented by the apical gland-like emergences, which are sticky even without hydration, and mucilaginous cells, which form a mucilage envelope around the whole anthocarp after hydration. In this study, we characterised the type of mucilage, its internal structure, and discussed its biological function. We found that the mucilage was a type of cellulose possessing very long spirally coiled cellulosic fibrils embedded in a mass of hydrophilic pectins. The cellulose fibrils build the main scaffold for the rest of polysaccharides. All of the components are arranged into a net-like spatial structure. The mucilage of C. helenae may play diverse roles e.g., in epizoochory/endozoochory, anchoring the diaspore to the soil and enabling germination due to the presence of water attracted by the pectins. The mucilage envelope, which forms rapidly after hydration (from rain or capillary water condensation), facilitating adhesion to the soil and simultaneously providing optimised germination conditions. The presence of the second adhesive systems in C. helenae i.e., mucilaginous cells producing mucilage seems to be an adaptation with different ecological functions.
The impeding effect of plant surfaces covered with three-dimensional wax on attachment and locomotion of insects has been shown previously in numerous experimental studies. The aim of this study was ...to examine the effect of different parameters of crystalline wax coverage on insect attachment. We performed traction experiments with the beetle Coccinella septempunctata and pull-off force measurements with artificial adhesive systems (tacky polydimethylsiloxane semi-spheres) on bioinspired wax surfaces formed by four alkanes of varying chain lengths (C36H74, C40H82, C44H90, and C50H102). All these highly hydrophobic coatings were composed of crystals having similar morphologies but differing in size and distribution/density, and exhibited different surface roughness. The crystal size (length and thickness) decreased with an increase of the chain length of the alkanes that formed these surfaces, whereas the density of the wax coverage, as well as the surface roughness, showed an opposite relationship. Traction tests demonstrated a significant, up to 30 fold, reduction of insect attachment forces on the wax surfaces when compared with the reference glass sample. Attachment of the beetles to the wax substrates probably relied solely on the performance of adhesive pads. We found no influence of the wax coatings on the subsequent attachment ability of beetles. The obtained data are explained by the reduction of the real contact between the setal tips of the insect adhesive pads and the wax surfaces due to the micro- and nanoscopic roughness introduced by wax crystals. Experiments with polydimethylsiloxane semi-spheres showed much higher forces on wax samples when compared to insect attachment forces measured on these surfaces. We explain these results by the differences in material properties between polydimethylsiloxane probes and tenent setae of C. septempunctata beetles. Among wax surfaces, force experiments showed stronger insect attachment and higher pull-off forces of polydimethylsiloxane probes on wax surfaces having a higher density of wax coverage, created by smaller crystals.
This study represents an investigation of surface-related plant–insect interactions. Surface micro-morphology of leaflets in pea (
Pisum sativum
) with wild-type crystalline surface waxes (waxy) and ...with reduced crystalline surface waxes (glossy) caused by a mutation (
wel
) were studied using various microscopy techniques. The free surface energy of these plant surfaces was estimated using contact angles of droplets of three different liquids. The morphological study of the attachment system in the ladybird beetle
Cryptolaemus montrouzieri
was combined with measurements of attachment (traction) forces, generated by beetles on these plant substrates. Differences were found in wax crystal shape, dimensions, and density between the adaxial and abaxial surfaces of waxy and glossy plants. The crystalline wax was not completely eliminated in the glossy plant: it was only slightly reduced on the adaxial side and underwent greater changes on the abaxial side. The free surface energy for both surfaces of both pea types was rather low with strongly predominating dispersion component. Insects generated low traction forces on all intact plant surfaces studied, except the abaxial surface of the glossy plant, on which the force was greater. After being treated with chloroform, all the surfaces allowed much higher traction forces. It is demonstrated that the difference in the crystal length and density of the epicuticular wax coverage within the observed range did not influence wettability of surfaces, but affected insect attachment. The reduction in insect attachment force on plant surfaces, covered with the crystalline wax, is explained by the decrease of the real contact area between setal tips of beetles and the substrate.
Among a suite of abiotic and biotic factors, the hydrodynamic regime strongly influences the success of seagrass recruitment through sexual propagules. Uprooting of propagules by drag forces exerted ...by currents and waves is one of the main causes for the failed establishment and the consequent recruitment. Substrate type and stability play a key role in determining the success of colonization through sexual propagules, as seedling establishment probabilities proved to be significantly higher on rocky bottoms than on unstable unconsolidated substrates. In this research, the current and wave flow intensity that
Posidonia oceanica
seedlings anchored to rocky substrates can withstand before uprooting were evaluated and the influence of substrate complexity on seedling anchorage success and anchorage strength was investigated.
P. oceanica
seedlings withstood the current velocity of 70 cm s
–1
and increased orbital flow velocities up to 25 cm s
–1
. Seedling adhesion strength ranged from 3.92 to 29.42 N. Results of the present study corroborate the hypothesis that substrate complexity at scales relevant to the size of propagules is a crucial feature for
P. oceanica
seedling establishment. The intensity of unidirectional and oscillatory flow that seedlings can withstand without being dislodged assessed in this study support the hypothesis that
P. oceanica
sexual propagules, once adhered to a consolidated substrate, are able to tolerate high hydrodynamic stress. The results of the present study contribute to re-evaluation of the habitat requirements of
P. oceanica
, assessing the range of hydrodynamic conditions that this species can tolerate during the early stages of its life history.
Using a cryo-scanning electron microscope, we studied microstructure of the slippery zone in nine
Nepenthes
taxa. For
N. fusca
,
N. macrophylla
,
N. mirabilis
,
N. ventricosa
,
N. dicksoniana,
and
N. ...veitchii
, it was examined here for the first time. Three types of the slippery zone were distinguished among the studied taxa: (1) with well-developed crystalline wax coverage, (2) with greatly reduced wax coverage, and (3) without wax crystals. These data were combined with morphometrical measurements of the two pitcher zones primarily relevant to prey catching and retaining: the slippery zone and the peristome. In species with fully developed wax coverage, the slippery zone was longer and the peristome was narrower compared to those with reduced or lacking crystalline wax. We found statistically significant negative correlation between the relative length of the slippery zone and the relative width of the peristome. Based on the analysis of the relationship between the microstructure of the slippery zone and pitcher macromorphology, two main types of pitchers in
Nepenthes
are proposed: (a) traps based predominantly on the waxy slippery zone and (b) peristome-based traps.
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