Arthropod Exoskeletons Research Articles

Unwinding a spiral of cellulose nanocrystals for stimuli-responsive stretchable optics

Cellulose nanocrystals (CNCs) derived from biomass spontaneously organize into a helical arrangement, termed a chiral nematic structure. This structure mimics the organization of chitin found in the exoskeletons of arthropods, where it contributes to their remarkable mechanical strength. Here, we demonstrate a photonic sensory mechanism based on the reversible unwinding of chiral nematic CNCs embedded in an elastomer, leading the materials to display stimuli-responsive stretchable optics. Vivid interference colors appear as the film is stretched and disappear when the elastomer returns to its original shape. This reversible optical effect is caused by a mechanically-induced transition of the CNCs between a chiral nematic and pseudo-nematic arrangement.

Planctomycetes in boreal and subarctic wetlands: diversity patterns and potential ecological functions.

Members of the phylum Planctomycetes are common inhabitants of boreal Sphagnum peat bogs and lichen-dominated tundra wetlands. These bacteria colonize both oxic and anoxic peat layers and reach the population size of 107 cells per gram of wet peat. The 16S rRNA gene sequences from planctomycetes comprise 5%-22% of total 16S rRNA gene reads retrieved from peat samples. Most abundant peat-inhabiting planctomycetes affiliate with the families Isosphaeraceae and Gemmataceae, and with as-yet-uncultured Phycisphaera-related group WD2101. The use of metatranscriptomics to assess the functional role of planctomycetes in peatlands suggested the presence of versatile hydrolytic capabilities in these bacteria. This evidence was further confirmed by the analysis of genome-encoded capabilities of isolates from wetlands. Large (up to 12 Mbp) genomes of planctomycetes encode wide repertoires of carbohydrate-active enzymes including many unclassified putative glycoside hydrolases, which suggests the presence of extremely high glycolytic potential in these bacteria. Experimental tests confirmed their ability to grow on xylan, pectin, starch, lichenan, cellulose, chitin and polysaccharides of microbial origin. These results provide an insight into the ecological roles of peat-inhabiting planctomycetes and suggest their participation in degradation of plant-derived polymers, exoskeletons of peat-inhabiting arthropods as well as exopolysaccharides produced by other bacteria.

Chitin synthesis and degradation in Lepeophtheirus salmonis: Molecular characterization and gene expression profile during synthesis of a new exoskeleton

Animals with exoskeleton need to molt to grow and develop. Molting is well described in some arthropods especially insects. Chitin is a polymer of N-acetylglucosamine, and one of the major components of the exoskeleton of arthropods. Chitin is synthesized and degraded by a series of enzymes during the molting cycle. However, the presence and function of these enzymes are largely unknown in copepods such as the ectoparasite salmon louse (Lepeophtheirus salmonis) a major pest in salmonid aquaculture. Here we describe six genes found in the L. salmonis genome (LsCHS1, LsCHS2, LsGFAT, LsGNA1, LsAGM, and LsUAP) with high homology to enzymes in the chitin synthesis pathway. The transcription profiles of these enzymes together with three chitinases enzymes (LsChi1, LsChi2, and LsChi4), which have been characterized before, were examined during the synthesis of a new exoskeleton and revealed a dynamical expression concurrent with the morphological changes during the molt cycle. Further understanding of chitin metabolism and its regulation may prove useful tool to develop new pesticides.

Chitosan as a Bone Scaffold Biomaterial.

The current standard of care for bone reconstruction, whether secondary to injury, nonunion, cancer resection, or idiopathic bone loss, is autologous bone grafting. Alternatives to autograft and allograft bone substitutes currently being researched are synthetic and natural graft materials that are able to guide bone regeneration. One promising material currently being researched is chitosan, a highly versatile, naturally occurring polysaccharide, derived from the exoskeleton of arthropods that is comprised of glucosamine and N-acetylglucosamine. Research on chitosan as a bone scaffold has been promising. Chitosan is efficacious in bone regeneration due to its lack of immunogenicity, its biodegradability, and its physiologic features. Chitosan combined with growth factors and/or other scaffold materials has proven to be an effective alternative to autologous bone grafts. Additionally, current studies have shown that it can provide the additional benefit of a local drug delivery system. As research in the area of bone scaffolding continues to grow, further clinical research on chitosan in conjunction with growth factors, proteins, and alloplastic materials will likely be at the forefront.

Techno-economic Sensitivity Analysis of Large Scale Chitosan Production Process from Shrimp Shell Wastes

Chitin is one the most abundant natural amino-polysaccharides in nature, it is found in the exoskeleton of many arthropods on earth, being the main component of these ones. Great quantities of crustaceans are processed daily for human consumption, generating big shell wastes to should be correctly treated and give them a final disposal that not bringing environmental concerns to fishing industry. There are potential uses of these shell wastes, and one of them is the extraction of chitosan from chitin present in these wastes. In this work was developed the economic evaluation and the techno-economic sensitivity analysis of the large-scale production of chitosan from shrimp shell wastes via depigmentation, demineralization, deproteinization and deacetylation of chitin, using the ethanol-based route, which employs ten units of operation, in order to analyze the behavior of the process under changes of the techno-economic environment of the process as break-even point, on-stream efficiency, raw material cost, among others. Results shows that for a processing capacity of 57,000 t/y of shell waste with a plant life of 15 y, located in North Colombia, the critical techno-economic variables were raw material costs which with an increase in 100 % of price decreases the Profit After Taxes (PAT) close to zero, product selling price and normalized variable operating costs (NVOC).

Chitinases as Antibacterial Proteins: A Systematic Review

Chitinases are hydrolases that catalyze the cleavage of the β-1,4-Oglycosidic linkages in chitin, a polysaccharide abundantly found in nature. Chitin is an important structural component of the cell wall of most fungi and the exoskeleton of arthropods, including insects and crustaceans. These enzymes are widespread in the living world, being found in organisms from all three domains of life. Due to their hydrolytic activity on chitin, chitinases have great biotechnological potential in different areas, such as human health, agriculture and food technology. The antifungal, insecticidal and nematicidal effects of many chitinases have been intensively investigated in the scientific literature, aiming to exploit these properties to protect crops against phytopathogenic fungi and insect pests and parasitic nematodes. On the other hand, the effects of chitinases on bacteria have been underexploited, possibly because chitin is not present in bacterial cell walls. The aim of this study was to search the scientific literature for works describing chitinases with antibacterial activity. Three bibliographic databases were searched using the keywords “chitinase” and “antibacterial” as descriptors and the chosen articles were selected according to specific inclusion and exclusion criteria. As a result, we identified only 5 reports wherein 6 purified chitinases have been shown experimentally to have antibacterial activity. Three out of these 6 antibacterial chitinases were shown to be bifunctional enzymes, which have chitinase and lysozyme activity. The possible mechanism of action of these antibacterial chitinases is discussed, highlighting their potential as antibacterial agents. Key-words: Antimicrobial, Chitin, Lysozyme, Peptidoglycan, Hydrolases.

Genome Analysis of Fimbriiglobus ruber SP5T, a Planctomycete with Confirmed Chitinolytic Capability.

Members of the bacterial order Planctomycetales have often been observed in associations with Crustacea. The ability to degrade chitin, however, has never been reported for any of the cultured planctomycetes although utilization of N-acetylglucosamine (GlcNAc) as a sole carbon and nitrogen source is well recognized for these bacteria. Here, we demonstrate the chitinolytic capability of a member of the family Gemmataceae, Fimbriiglobus ruber SP5T, which was isolated from a peat bog. As revealed by metatranscriptomic analysis of chitin-amended peat, the pool of 16S rRNA reads from F. ruber increased in response to chitin availability. Strain SP5T displayed only weak growth on amorphous chitin as a sole source of carbon but grew well with chitin as a source of nitrogen. The genome of F. ruber SP5T is 12.364 Mb in size and is the largest among all currently determined planctomycete genomes. It encodes several enzymes putatively involved in chitin degradation, including two chitinases affiliated with the glycoside hydrolase (GH) family GH18, GH20 family β-N-acetylglucosaminidase, and the complete set of enzymes required for utilization of GlcNAc. The gene encoding one of the predicted chitinases was expressed in Escherichia coli, and the endochitinase activity of the recombinant enzyme was confirmed. The genome also contains genes required for the assembly of type IV pili, which may be used to adhere to chitin and possibly other biopolymers. The ability to use chitin as a source of nitrogen is of special importance for planctomycetes that inhabit N-depleted ombrotrophic wetlands.IMPORTANCE Planctomycetes represent an important part of the microbial community in Sphagnum-dominated peatlands, but their potential functions in these ecosystems remain poorly understood. This study reports the presence of chitinolytic potential in one of the recently described peat-inhabiting members of the family Gemmataceae, Fimbriiglobus ruber SP5T This planctomycete uses chitin, a major constituent of fungal cell walls and exoskeletons of peat-inhabiting arthropods, as a source of nitrogen in N-depleted ombrotrophic Sphagnum-dominated peatlands. This study reports the chitin-degrading capability of representatives of the order Planctomycetales.

Termiticidal activity of chitosan against the subterranean termites Reticulitermes flavipes and Reticulitermes virginicus.

Chitosan is a derivative form of chitin, which is the major component of exoskeletons of arthropods and the cell walls of fungi. The antimicrobial activity of chitosan against lepidopterans, aphids, fungi and bacteria has been extensively investigated, but only one report on the termiticidal effect of chitosan on termites has been published. In this study, we examined the termiticidal activity of chitosan by exposing single colonies of Reticulitermes flavipes (Kollar) and Reticulitermes virginicus Banks to wood treated with six different concentrations of chitosan solutions. Termite mortality and percent mass loss of wood samples after exposure to termites for 4 weeks were calculated. High termite mortality (≥ 94%) occurred during exposure of R. flavipes termites to chitosan-treated wood with ≥38 mg g-1 treatment concentrations (≥ 2% chitosan), while <50% termite mortality was observed at lower treatment concentrations (11-15 mg g-1 ; 0.5% and 1% chitosan). For R. virginicus, 100% mortality was observed at all levels of treatment concentrations. A decrease in the percent mass loss of the wood sample was apparent in samples treated with solutions with an increasing chitosan concentration, with a significant difference (P < 0.05) between lower and higher treatment concentrations. Treatment retention in wood samples upon leaching was also determined and showed retention levels of between 0 and 30 mg g-1 chitosan retention. This study investigated the exposure of subterranean termites to chitosan as a wood preservative. The results show that chitosan treatments at sufficiently high loadings could protect wood against termites, preferably under non-leaching conditions. © 2018 Society of Chemical Industry.

Diet composition and habitat use of coyotes on the Chattahoochee National Forest in northeast Georgia

Coyotes (Canis latrans) are a recent addition to southeastern ecosystems and regional studies are needed to understand their ecological role. Most studies from the southeast are concentrated on diets from animals on the coastal plain. Here we report on the diet and habitat use of coyotes on the Chattahoochee National Forest, which is located in northeast Georgia at the southern terminus of the Appalachian Mountains. Seventeen total scat samples were collected from March through May 2014. Habitat types and GPS coordinates of each sample were also recorded. Gray squirrel (65%) was the most common food item and occurred along with plant matter (53%) and arthropod exoskeletons (35%), suggesting that these food items were likely scavenged. Wild hog (18%), identified by adult guard hairs, also appeared to be scavenged. Small mammals and perching birds comprised a large portion of the diets, whereas white-tail deer were rarely recorded. Two competitors, bobcat and gray fox, were also identified in the scat samples. The most common habitat types were edges and logging roads, with little utilization of open hardwoods.

Direct chitin conversion to N-doped amorphous carbon nanofibers for high-performing full sodium-ion batteries

Currently, renewable and low-cost electrode materials are being intensively pursued to meet the development of sustainable electrochemical energy-storage systems. Chitin, which is the second most abundant biopolymer throughout the natural world and can be sourced cheaply from the exoskeletons of arthropods and shells of cephalopods, has many attractive properties such as renewability, nontoxicity, intrinsically fibrous structure and high nitrogen content. In this study, nitrogen-doped amorphous carbon nanofibers (NACF) fabricated by direct pyrolysis of chitin, were used as the anode material in sodium-ion batteries (SIBs) for the first time. The NACF electrode delivered a high reversible capacity of 320.6mAhg−1 with excellent rate capability and long cyclability. The superior electrochemical performance can mainly be attributed to synergistic effects of the unique one-dimensional mesoporous nanofibers facilitating the transmission of electrons/electrolyte, and the N-doped amorphous nanostructure increasing electrical conductivity and number of active sites. Furthermore, a sodium-ion full cell was constructed by coupling the NACF electrode with a Prussian blue cathode, and it delivered 115mAhg−1 while retaining 90% of the capacity after 200 cycles. Our work will hopefully inspire the research community to explore other advanced materials with value-added attributes that can be generated by appropriate treatment of renewable bio-waste.

Evolution of Acidic Mammalian Chitinase Genes (CHIA) Is Related to Body Mass and Insectivory in Primates.

Insects are an important food resource for many primates, but the chitinous exoskeletons of arthropods have long been considered to be indigestible by the digestive enzymes of most mammals. However, recently mice and insectivorous bats were found to produce the enzyme acidic mammalian chitinase (AMCase) to digest insect exoskeletons. Here, we report on the gene CHIA and its paralogs, which encode AMCase, in a comparative sample of nonhuman primates. Our results show that early primates likely had three CHIA genes, suggesting that insects were an important component of the ancestral primate diet. With some exceptions, most extant primate species retain only one functional CHIA paralog. The exceptions include two colobine species, in which all CHIA genes have premature stop codons, and several New World monkey species that retain two functional genes. The most insectivorous species in our sample also have the largest number of functional CHIA genes. Tupaia chinensis and Otolemur garnettii retain three functional CHIA paralogs, whereas Tarsius syrichta has a total of five, two of which may be duplications specific to the tarsier lineage. Selection analyses indicate that CHIA genes are under more intense selection in species with higher insect consumption, as well as in smaller-bodied species (<500 g), providing molecular support for Kay's Threshold, a well-established component of primatological theory which proposes that only small primates can be primarily insectivorous. These findings suggest that primates, like mice and insectivorous bats, may use the enzyme AMCase to digest the chitin in insect exoskeletons, providing potentially significant nutritional benefits.

Activation of Vibrio cholerae quorum sensing promotes survival of an arthropod host.

Vibrio cholerae colonizes the human terminal ileum to cause cholera and the arthropod intestine and exoskeleton to persist in the aquatic environment. Attachment to these surfaces is regulated by the bacterial quorum sensing signal transduction cascade, which allows bacteria to assess the density of microbial neighbors. Intestinal colonization with V. cholerae results in expenditure of host lipid stores in the model arthropod Drosophila melanogaster. Here we report that activation of quorum sensing in the Drosophila intestine retards this process by repressing V. cholerae succinate uptake. Increased host access to intestinal succinate mitigates infection-induced lipid wasting to extend survival of V. cholerae-infected flies. Therefore, quorum sensing promotes a more favorable interaction between V. cholerae and an arthropod host by reducing the nutritional burden of intestinal colonization.

N-acetylglucosamine, the building block of chitin, inhibits growth of Neurospora crassa

N-acetylglucosamine (GlcNAc) is the monomer of the polysaccharide chitin, an essential structural component of the fungal cell wall and the arthropod exoskeleton. We recently showed that the genes encoding the enzymes for GlcNAc catabolism are clustered in several ascomycetes. In the present study we tested these fungi for growth on GlcNAc and chitin. All fungi, containing the GlcNAc gene cluster, could grow on GlcNAc with the exception of four independent Neurospora crassa wild-type isolates, which were however able to grow on chitin. GlcNAc even inhibited their growth in the presence of other carbon sources. Genes involved in GlcNAc catabolism were strongly upregulated in the presence of GlcNAc, but during growth on chitin their expression was not increased. Deletion of hxk-3 (encoding the first catabolic enzyme, GlcNAc-hexokinase) and ngt-1 (encoding the GlcNAc transporter) improved growth of N. crassa on GlcNAc in the presence of glycerol. A crucial step in GlcNAc catabolism is enzymatic conversion from glucosamine-6-phosphate to fructose-6-phosphate, catalyzed by the glucosamine-6-phosphate deaminase, DAM-1. To assess, if DAM-1 is compromised in N. crassa, the orthologue from Trichoderma reesei, Trdam1, was expressed in N. crassa. Trdam1 expression partially alleviated the negative effects of GlcNAc in the presence of a second carbon source, but did not fully restore growth on GlcNAc. Our results indicate that the GlcNAc-catabolism pathway is bypassed during growth of N. crassa on chitin by use of an alternative pathway, emphasizing the different strategies that have evolved in the fungal kingdom for chitin utilization.

Elemental characterization of the exoskeleton in the whipscorpions Mastigoproctus giganteus and Typopeltis dalyi (Arachnida: Thelyphonida)

AbstractThe arthropod cuticle is a structurally diverse secretion that is largely composed of lipids, proteins, and α‐chitin that function together in protection, prey capture, and as a skeletal framework for efficient and diverse means of locomotion. Aquatic, aerial, and terrestrial arthropods are well known to enrich their cuticles with trace elements that are proposed to strengthen or otherwise enhance specific regions of the exoskeleton. In this study, we provide evidence that whipscorpions (vinegaroons) enrich their exoskeleton with up to 14 trace elements. We use energy‐dispersive x‐ray spectroscopy (EDS) to provide the first comparisons of trace element composition in two species of Thelyphonida: Mastigoproctus giganteus (female) and Typopeltis dalyi (female and male). We analyzed the chemical composition of eight regions that have sensory, locomotory, taxonomic, protective, and/or predatory significance: the flagellum, prosoma, tarsal claws of the walking legs, tarsi of the antenniform legs, chelicerae, and the terminal three segments of the pedipalps. Our results reveal the presence of 14 trace elements across both species (12 elements in T. dalyi, 10 elements in M. giganteus), and only four elements are present at significant levels (≥1% weight): Si, Cl, Ca, and Zn. The flagellum, antenniform leg tarsi, and prosoma keel lack these elements in both species, while the chelicerae of all species are enriched with Ca, Zn, and Cl, and the tarsal claws are enriched with Zn. Significantly, we note the presence of Si in the prosomal carapace (but not the keel) of males and females of Typopeltis only, which appears to be the first evidence of this transition metal in the arthropod exoskeleton. We discuss the significance of these chemical enrichments in whipscorpions and provide hypotheses about their functional significance.

Identification of the key chitinase genes in Tetranychus cinnabarinus (Boisduval) based on the expression and sequence characteristic analysis

Chitin is an important content in the exoskeletons of arthropods, and its hydrolyzation is catalyzed by chitinases during the process of molting, thus, the chitinases are considered as ideal target to interfere the growth of arthropods. This study intends to clarify the characteristic of the chitinases during the development of Tetranychus cinnabarinus, and screen out important genes as potential control targets. The results showed that the total enzyme concentration of chitinases was significantly higher in larva, the first and second nymph than that in egg and adult. Base on the transcriptome data, six unigenes encoding chitinases were identified and their expression patterns in different developmental stages were detected. The expressions of TcCHIT1 and TcCHIT10 showed high abundance during the molting process and their expression change during the developmental stages was consistent with the enzyme concentration. The full-length of these two genes were further cloned, and the structural characteristics of their proteins were analyzed by constructing the three-dimensional structure model. The results provide basic information to understand the characteristic of chitinases in T. cinnabarinus and might be considered as target for control.

Identification of the Eucalyptus grandis chitinase gene family and expression characterization under different biotic stress challenges.

Eucalyptus grandis (W. Hill ex Maiden) is an Australian Myrtaceae tree grown for timber in many parts of the world and for which the annotated genome sequence is available. Known to be susceptible to a number of pests and diseases, E. grandis is a useful study organism for investigating defense responses in woody plants. Chitinases are widespread in plants and cleave glycosidic bonds of chitin, the major structural component of fungal cell walls and arthropod exoskeletons. They are encoded by an important class of genes known to be up-regulated in plants in response to pathogens. The current study identified 67 chitinase gene models from two families known as glycosyl hydrolase 18 and 19 (36 GH18 and 31 GH19) within the E. grandis genome assembly (v1.1), indicating a recent gene expansion. Sequences were aligned and analyzed as conforming to currently recognized plant chitinase classes (I-V). Unlike other woody species investigated to date, E. grandis has a single gene encoding a putative vacuolar targeted Class I chitinase. In response to Leptocybe invasa(Fisher & La Salle) (the eucalypt gall wasp) and Chrysoporthe austroafricana (Gryzenhout & M.J. Wingf. 2004) (causal agent of fungal stem canker), this Class IA chitinase is strongly up-regulated in both resistant and susceptible plants. Resistant plants, however, indicate greater constitutive expression and increased up-regulation than susceptible plants following fungal challenge. Up-regulation within fungal resistant clones was further confirmed with protein data. Clusters of putative chitinase genes, particularly on chromosomes 3 and 8, are significantly up-regulated in response to fungal challenge, while a cluster on chromosome 1 is significantly down-regulated in response to gall wasp. The results of this study show that the E. grandis genome has an expanded group of chitinase genes, compared with other plants. Despite this expansion, only a single Class I chitinase is present and this gene is highly up-regulated within diverse biotic stress conditions. Our research provides insight into a major class of defense genes within E. grandis and indicates the importance of the Class I chitinase.

The search for all of the victims and all of the killers

Carnivorous plants often claim the name “insectivorous” for the simple reason that most carnivorous traps usually contain insects, and, even when not insects, trapped prey are usually close cousins of the insects from within the Phylum Arthropoda. An example of this is when bladderworts (Utricularia spp.; Lentibulariaceae) trap crustaceans such as amphipods and copepods, which are arthropods, like insects. Indeed, Darwin’s book on the carnivorous plants recognizes this fact with its title Insectivorous Plants. Splitting open a pitcher from Sarracenia leucophylla, as an example, usually reveals one chitinous arthropod exoskeleton after another.

Chitosan oligosaccharide: Biological activities and potential therapeutic applications.

Chitosan oligosaccharide (COS) is an oligomer of β-(1➔4)-linked d-glucosamine. COS can be prepared from the deacetylation and hydrolysis of chitin, which is commonly found in the exoskeletons of arthropods and insects and the cell walls of fungi. COS is water soluble, non-cytotoxic, readily absorbed through the intestine and mainly excreted in the urine. Of particular importance, COS and its derivatives have been demonstrated to possess several biological activities including anti-inflammation, immunostimulation, anti-tumor, anti-obesity, anti-hypertension, anti-Alzheimer's disease, tissue regeneration promotion, drug and DNA delivery enhancement, anti-microbial, anti-oxidation and calcium-absorption enhancement. The mechanisms of actions of COS have been found to involve the modulation of several important pathways including the suppression of nuclear factor kappa B (NF-κB) and mitogen-activated protein kinases (MAPK) and the activation of AMP-activated protein kinase (AMPK). This review summarizes the current knowledge of the preparation methods, pharmacokinetic profiles, biological activities, potential therapeutic applications and safety profiles of COS and its derivatives. In addition, future research directions are discussed.

Identification of microbial populations driving biopolymer degradation in acidic peatlands by metatranscriptomic analysis.

Northern peatlands play a crucial role in the global carbon balance, serving as a persistent sink for atmospheric CO2 and a global carbon store. Their most extensive type, Sphagnum-dominated acidic peatlands, is inhabited by microorganisms with poorly understood degradation capabilities. Here, we applied a combination of barcoded pyrosequencing of SSU rRNA genes and Illumina RNA-Seq of total RNA (metatranscriptomics) to identify microbial populations and enzymes involved in degrading the major components of Sphagnum-derived litter and exoskeletons of peat-inhabiting arthropods: cellulose, xylan, pectin and chitin. Biopolymer addition to peat induced a threefold to fivefold increase in bacterial cell numbers. Functional community profiles of assembled mRNA differed between experimental treatments. In particular, pectin and xylan triggered increased transcript abundance of genes involved in energy metabolism and central carbon metabolism, such as glycolysis and TCA cycle. Concurrently, the substrate-induced activity of bacteria on these two biopolymers stimulated grazing of peat-inhabiting protozoa. Alveolata (ciliates) was the most responsive protozoa group as confirmed by analysis of both SSU rRNA genes and SSU rRNA. A stimulation of alphaproteobacterial methanotrophs on pectin was consistently shown by rRNA and mRNA data. Most likely, their significant enrichment was due to the utilization of methanol released during the degradation of pectin. Analysis of SSU rRNA and total mRNA revealed a specific response of Acidobacteria and Actinobacteria to chitin and pectin, respectively. Relatives of Telmatobacter bradus were most responsive among the Acidobacteria, while the actinobacterial response was primarily affiliated with Frankiales and Propionibacteriales. The expression of a wide repertoire of carbohydrate-active enzymes (CAZymes) corresponded well to the detection of a highly diverse peat-inhabiting microbial community, which is dominated by yet uncultivated bacteria.

Axially aligned organic fibers and amorphous calcium phosphate form the claws of a terrestrial isopod (Crustacea).

Skeletal elements that are exposed to heavy mechanical loads may provide important insights into the evolutionary solutions to mechanical challenges. We analyzed the microscopic architecture of dactylus claws in the woodlice Porcellio scaber and correlated these observations with analyses of the claws' mineral composition with energy dispersive X-ray spectrometry (EDX), electron energy loss spectroscopy (EELS) and selected area electron diffraction (SAED). Extraordinarily, amorphous calcium phosphate is the predominant mineral in the claw endocuticle. Unlike the strongly calcified exocuticle of the dactylus base, the claw exocuticle is devoid of mineral and is highly brominated. The architecture of the dactylus claw cuticle is drastically different from that of other parts of the exoskeleton. In contrast to the quasi-isotropic structure with chitin-protein fibers oriented in multiple directions, characteristic of the arthropod exoskeleton, the chitin-protein fibers and mineral components in the endocuticle of P. scaber claws are exclusively axially oriented. Taken together, these characteristics suggest that the claw cuticle is highly structurally anisotropic and fracture resistant and can be explained as adaptations to predominant axial loading of the thin, elongated claws. The nanoscale architecture of the isopod claw may inspire technological solutions in the design of durable machine elements subjected to heavy loading and wear.