Detailed spectroscopic study of the role of Br and Sr in coloured parts of the Callinectes sapidus crab claw

Mechanical properties and clamping behaviors of snow crab claw

The high-performing biomimetic behaviors of crustaceans are the optimal results of long-time wise adaption to their living environment. One outstanding prototype is crab claw, which has the combining advantages of lightweight and high strength. To promote relevant engineering applications, it is imperative to explore its mechanical behaviors and structural characteristics. In this work, mechanical test and finite element analysis (FEA) are performed to reveal the fundamental mechanical properties and clamping behaviors of snow crab (Chionoecetes opilio) claw, respectively. A lightweight modeling method, parametric lofting modeling, for the 3D modeling of the claw is employed, which is compared with the traditional reverse engineering modeling method based on tomography image. Our results demonstrated that the hardness and modulus of the regions near the top of the claw are larger than those of the regions near of bottom of the claw. Moisture is a critical factor in controlling the tensile behavior of the claw and the wet specimens exhibit higher modulus and strength under tensile loading. Besides, The parametric lofting method is highly flexible and efficient in generating 3D geometrical model. The investigation of clamping behaviors provides not only insights into mechanical behaviors and intrinsic mechanisms but also a practical guide for their potential applications, such as designing high-performing artificial clamping muscles for clinical operations, aerospace applications, and robotics.

Wasted Biomaterials from Crustaceans as a Compliant Natural Product Regarding Microbiological, Antibacterial Properties and Heavy Metal Content for Reuse in Blue Bioeconomy: A Preliminary Study

The compliance of crab shells traditionally used as a complex natural product for agricultural soil amendment with modern biofertilizers' quality and safety requirements was investigated. Shells waste from the Blue crab, Callinectes sapidus and the Green crab, Carcinus aestuarii were tested for macronutrients, heavy metals, bacteria content, and antimicrobial properties. Such information is crucial for further utilization of the biogenic powders for any composite formulation in added-value by-products. The calcium carbonate-rich hard tissue yield was 52.13% ± 0.015 (mean ± S.D.) and 64.71% ± 0.144 from the blue and green crabs, respectively. The contents of Pb, Ni, Zn, Cr (VI), and Cu were several orders of magnitude below the prescribed limit by EU biofertilizer legislation, with Fe, Mn (not prescribed), and As being the most abundant. The content of As and Cd from the material considered here was within limits. The shells contain no colony-forming units of Salmonella spp. and compliant levels of Escherichia coli; moreover, the shell micro-powder showed dose-dependent growth inhibition of Pseudomonas aeruginosa and Staphylococcus aureus. In summary, the waste crab shells present a complex natural product as plant biofertilizer following the circular economy concepts.

Promoting hidden natural design templates in wasted shells of the mantis shrimp into valuable biogenic composite

The mineralized cuticle of the mantis shrimps Squilla Mantis which serve as natural hammers, spears and armors, have attracted research attention from various fields due to its amazing mechanical properties which were studied from evolutionary and ecological points of view. Here we aimed to valorize the astonishing mantis shrimp shell waste resulted from fishery and seafood industry as valuable biogenic composite derived from nature, potentially re-usable for novel, smart materials or added-value by-products, aspect which was not deeply considered before. Employing multi-laser Raman spectroscopy and imaging, supported by x-ray diffraction and high-resolution electron microscopy, we discover that the peripheral segments anatomically known as claws and telson, featured completely different composition and morphology, suggesting different applicability. The claw presents a bulk Mg-CaCO₃ structure reinforced with fluorapatite coating, while the carotenoid-rich telson presents a porous and anisotropic structure of an amorphous mixture of CaCO₃ and CaPO₄ in gradient deposition on the chitin-protein scaffold. Resonance Raman spectroscopy showed concentrated pools of astaxanthin carotenoid within the bright red spots visible on telson, Based on our findings, we discuss this material's potential for selective applicability, as a natural source of phosphate-carbonate minerals, antioxidants, biofertilizer, pollutant adsorbent, valuable material for regenerative medicine or even as a cell culture substrate. Knowledge-based approach on this bio-template is the basis for smart recycling of such fishery waste for sustainable development, by opening channels for blue bioeconomy avenue.

Microstructures of crab chela: A biological composite for pinching

We have investigated the microstructures and mechanical properties of four crab species Paralithodes brevipes, Eriocheir japonicas, Geothelphusa dehaani, and Telmessus acutidens and analyzed the molecular and elemental data of their chela. In the visible brown region (BR) at the distal end of the dactylus tip in Paralithodes brevipes and Eriocheir japonicas, the elastic modulus and calcium (Ca) content were lower than in the white region (WR). Near the interface between BR and WR, Ca, and carbon (C) composition changed continuously. Molecular analysis shows that the dactylus tips of the chela in P. brevipes and E. japonicas were composed of chitin and calcium carbonate. In G. dehaani and T. acutidens, the Ca concentration was homogeneous in the top portion (TP) of the dactylus dentitions. The lowest value of Ca concentration was found near the surface of the bottom portion (BP) on the dactylus dentitions. In G. dehaani, the elastic modulus distribution in the TP was maximum near the outermost surface, and gradually decreased in the inner layers; the lowest elastic modulus in the BP was near the outermost surface, and the distribution increased in the inner layer. These results show that the biological composite was as a continuous structure near the interface of the dactylus tip. Understanding the microstructures of the dactyla of crabs might help the study and development of bio-inspired composites for pinching.

Crystalline and amorphous calcium carbonate as structural components of the Calappa granulata exoskeleton

The exoskeleton of crustaceans consists of chitin biopolymers where the embedded inorganic biominerals, mainly CaCO₃, affect strongly its mechanical properties. Raman and Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopies and Transmission Electron Microscopy (TEM) are applied to investigate the CaCO₃ structure in various parts of the Calappa granulata crab exoskeleton. The shape of the main Raman peak of CaCO₃ reveals the presence of two phases which are identified as calcite and amorphous calcium carbonate (ACC). The relative concentration of the two phases in various parts of the exoskeleton is determined from the area ratio under the corresponding peaks. The results of the Ca L_3,2-edge NEXAFS analysis are in line with the Raman findings, since the energy separation of peaks that appear in the lower frequency region of the main L₂ and L₃ peaks due to crystal field splitting, is directly related to the percentage of the ACC phase in the total CaCO₃ mineral content. The C K-edge spectra are used for the determination of the extent of calcification of the exoskeleton. Furthermore, dark and bright field TEM images reveal the presence of nanocrystallites with an average size of 20 nm. The structure of the nanocrystallites, as derived from the Selected Area Electron Diffraction patterns, is calcite. The results suggest that ACC plays a structural role in the exoskeleton of Calappa granulata.

Structure and composition of the tunic in the sea pineapple Halocynthia roretzi: A complex cellulosic composite biomaterial

Biological organisms produce high-performance composite materials, such as bone, wood and insect cuticle, which provide inspiration for the design of novel materials. Ascidians (sea squirts) produce an organic exoskeleton, known as a tunic, which has been studied quite extensively in several species. However, currently, there are still gaps in our knowledge about the detailed structure and composition of this cellulosic biocomposite. Here, we investigate the composition and hierarchical structure of the tough tunic from the species Halocynthia roretzi, through a cross-disciplinary approach combining traditional histology, immunohistochemistry, vibrational spectroscopy, X-ray diffraction, and atomic force and electron microscopies. The picture emerging is that the tunic of H. roretzi is a hierarchically-structured composite of cellulose and proteins with several compositionally and structurally distinct zones. At the surface is a thin sclerotized cuticular layer with elevated composition of protein containing halogenated amino acids and cross-linked via dityrosine linkages. The fibrous layer makes up the bulk of the tunic and is comprised primarily of helicoidally-ordered crystalline cellulose fibres with a lower protein content. The subcuticular zone directly beneath the surface contains much less organized cellulose fibres. Given current efforts to utilize biorenewable cellulose sources for the sustainable production of bio-inspired composites, these insights establish the tunic of H. roretzi as an exciting new archetype for extracting relevant design principles. STATEMENT OF SIGNIFICANCE: Tunicates are the only animals able to produce cellulose. They use this structural polysaccharide to build an exoskeleton called a tunic. Here, we investigate the composition and hierarchical structure of the tough tunic from the sea pineapple Halocynthia roretzi through a multiscale cross-disciplinary approach. The tunic of this species is a composite of cellulose and proteins with two distinct layers. At the surface is a thin sclerotized cuticular layer with a higher protein content containing halogenated amino acids and cross-linked via dityrosine linkages. The fibrous layer makes up the bulk of the tunic and is comprised of well-ordered cellulose fibres with a lower protein content. Given current efforts to utilize cellulose to produce advanced materials, the tunic of the sea pineapple provides a striking model for the design of bio-inspired cellulosic composites.

Color-specific porosity in double pigmented natural 3d-nanoarchitectures of blue crab shell

3D-engineered nano-architectures with various functionalities are still difficult to obtain and translate for real-world applications. However, such nanomaterials are naturally abundant and yet wasted, but could trigger huge interest for blue bioeconomy, provided that our understanding of their ultrastructure-function is achieved. To date, the Bouligand pattern in crustaceans shell structure is believed to be unique. Here we demonstrated that in blue crab Callinectes sapidus, the 3D-nanoarchitecture is color-specific, while the blue and red-orange pigments interplay in different nano-sized channels and pores. Thinnest pores of about 20  nm are found in blue shell. Additionally, the blue pigment co-existence in specific Bouligand structure is proved for the green crab Carcinus aestuarii, although the crab does not appear blue. The pigments interplay, simultaneously detected by Raman spectroscopy in color-specific native cuticles, overturns our understanding in crustaceans coloration and may trigger the selective use of particular colored natural nanoarchitectures for broaden area of applications.