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This study documents the natural accumulation of mollusk shells on an elevated rocky shore carved into the calcareous rocks of the La Popa formation at Punta Roca (Atlántico), covering an estimated area of 0.35 km 2 . Hydrodynamic transport and differential exposure to environmental conditions are the primary factors contributing to shell deposition. A total of 58 mollusk species were identified, including 30 bivalves and 28 gastropods. The Veneridae was the most prominent, with the highest number of species (7) and shells comprising 64.22 % of the total. Key species contributing to the accumulation include the bivalves Anomalocardia cf. flexuosa, Polymesoda cf. arctata, Leukoma pectorina, Tivela mactroides, Crassostrea rhizophorae, and the gastropod Vitta virginea. These species are primarily characteristic of estuarine environments, with the exception of T. mactroides. Notably, the first recorded occurrence of the non-native gastropod Naria turdus (Cypraeidae) on the Colombian Caribbean coast was documented. The accumulations exhibit varying degrees of abrasion, fragmentation, encrustation, and bioerosion, with some shells appearing almost intact, indicating differences in origin and transport mechanisms. The extraction of shells for ornamental purposes poses a significant challenge to this natural accumulation., Competing Interests: Declaration of competing interest We, the authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Chitin biomass is the second largest biomass resource on Earth but under-utilized. In this study, pretreated shrimp shells were converted into value-added platform chemical 5-hydroxymethylfurfural (HMF) using microwave hydrothermal treatment. Under the combined pretreatment of acid decalcification at room temperature and microwave-assisted alkali deacetylation, the HMF yield could reach 1.8 wt%. The key process parameters, including the holding temperature, holding time, and pH value, were evaluated and optimised. The highest HMF yield of 6.5 wt% was obtained at 202.6°C at a holding time of 5.8 min and a pH value of 1.5. This result demonstrates the potential of synchronously treating waste and recycling it, thereby offering a highly promising valorisation strategy for chitin-biomass utilisation.

Microscopic epibionts on molluscan shells are a component of the biodiversity of intertidal coastal areas. Because molluscan shells are discrete habitats for the epibiont community, and the molluscan basibionts belong to the local community, epibiont diversity can be evaluated hierarchically by basibiont categories including species. To evaluate the structure of epibiont diversity and effects of taxonomic resolution on the evaluation, epibionts on molluscan shells and inert surfaces were investigated at three geographically distant sites in Japan. In total, 94 species-level taxonomic units of epibionts were obtained from 31 basibiont molluscan species and inert surfaces (plastics and rock chips). The density and the species richness at the site of the lowest latitude were significantly lower than those at the other sites. The epibiont community differed between the three sites, although the major portion of the epibionts were diatoms. Between-site diversity contributed most of the total diversity of the species richness and Simpson diversity in the five levels of the hierarchical partitioning: sample (individual basibiont), basibiont species (molluscan species), surface group (bivalves, chitons + limpets, and globose gastropods), site, and the total. The taxonomic resolution did not markedly affect the variability of communities between the three sites, although the taxon richness was reduced to 51 in the genus-level analysis. The lower taxonomic resolution (genus level); however, increased the contribution of the within-sample and decreased the contribution of β diversities at the higher hierarchies, leading to a possible overestimation of biotic homogenization between the communities., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Few studies have considered the capabilities of gastropods living in minerally-deficient acidified coastal waters to compensate for outer shell corrosion or compromised growing edge shell production. We compared inner shell thickening between pristine shells (control) and corroded shells (experiment) of two related intertidal neritid gastropod species from reduced salinity and acidified environments. We predicted that the rocky-shore, Nerita chamaeleon, which has greater access to shell building biomineralization substrates, should better control shell thickness than the estuarine, Neripteron violaceum. Accordingly, N. chameleon was found to compensate perfectly for variation in the thickness of the outer calcitic blocky layer (BL). Optimal shell thickness (OST) was maintained by selective reabsorption of the aperture ridge of the distal shell (aragonitic crossed-lamellar layer, CL) and by increased internal deposition of proximal (older) shell (aragonitic protocrossed lamellar, PCL). Despite greater exposure to acidification and hyposalinity, N. violaceum showed no significant compensatory shell thickening. These findings reveal that shell thickening capability may vary greatly among intertidal gastropods and that this may be constrained by environmental biomineralization substrate availability. Such environmentally-related responses carry implications for predicted future reductions in coastal water pH and salinity., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The analysis of the DNA entrapped in ancient shells of molluscs has the potential to shed light on the evolution and ecology of this very diverse phylum. Ancient genomics could help reconstruct the responses of molluscs to past climate change, pollution, and human subsistence practices at unprecedented temporal resolutions. Applications are however still in their infancy, partly due to our limited knowledge of DNA preservation in calcium carbonate shells and the need for optimized methods for responsible genomic data generation. To improve ancient shell genomic analyses, we applied high-throughput DNA sequencing to 27 Mytilus mussel shells dated to ~111-6500 years Before Present, and investigated the impact, on DNA recovery, of shell imaging, DNA extraction protocols and shell sub-sampling strategies. First, we detected no quantitative or qualitative deleterious effect of micro-computed tomography for recording shell 3D morphological information prior to sub-sampling. Then, we showed that double-digestion and bleach treatment of shell powder prior to silica-based DNA extraction improves shell DNA recovery, also suggesting that DNA is protected in preservation niches within ancient shells. Finally, all layers that compose Mytilus shells, i.e., the nacreous (aragonite) and prismatic (calcite) carbonate layers, with or without the outer organic layer (periostracum) proved to be valuable DNA reservoirs, with aragonite appearing as the best substrate for genomic analyses. Our work contributes to the understanding of long-term molecular preservation in biominerals and we anticipate that resulting recommendations will be helpful for future efficient and responsible genomic analyses of ancient mollusc shells., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Martin-Roy et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

The Late Triassic Dockum Group in northwestern Texas preserves a rich diversity of pseudosuchian taxa, particularly of aetosaurs. In this contribution, we present Garzapelta muelleri gen. et sp. nov., a new aetosaur from the Late Triassic middle Cooper Canyon Formation (latest Adamanian-earliest Revueltian teilzones) in Garza County, Texas, based on an associated specimen that preserves a significant portion of its dorsal carapace. The carapace of G. muelleri exhibits a striking degree of similarity between that of the paratypothoracin Rioarribasuchus chamaensis and desmatosuchins. We quantitatively assessed the relationships of G. muelleri using several iterations of the matrix. Scoring the paramedian and lateral osteoderms of G. muelleri independently results in conflicting topologies. Thus, it is evident that our current matrix is limited in its ability to discern the convergence within this new taxon and that our current character lists are not fully accounting for the morphological disparity of the aetosaurian carapace. Qualitative comparisons suggest that G. muelleri is a Rioarribasuchus-like paratypothoracin with lateral osteoderms that are convergent with those of desmatosuchins. Although the shape of the dorsal eminence, and the presence of a dorsal flange that is rectangular and proportionately longer than the lateral flange are desmatosuchin-like features of G. muelleri, the taxon does not exhibit the articulation style between the paramedian and lateral osteoderms which diagnose the Desmatosuchini (i.e., a rigid interlocking contact, and an anteromedial edge of the lateral osteoderm that overlaps the adjacent paramedian osteoderm)., (© 2024 American Association for Anatomy.)

Land snails exhibit an extraordinary variety of shell shapes. The way shells are constructed underlies biological and mechanical constraints that vary across gastropod clades. Here, we quantify shell geometry of the two largest groups, Stylommatophora and Cyclophoroidea, to assess the potential causes for variation in shell shape and its relative frequency. Based on micro-computed tomography scans, we estimate material efficiency through 2D and 3D generalizations of the isoperimetric ratio, quantifying the ratios between area and perimeter of whorl cross-sections (2D) and shell volume and surface (3D), respectively. We find that stylommatophorans optimize material usage through whorl overlap, which may have promoted the diversification of flat-shelled species. Cyclophoroids are bound to a circular cross-section because of their operculum; flat shells are comparatively rare. Both groups show similar solutions for tall shells, where local geometry has a smaller effect because of the double overlap between previous and current whorls. Our results suggest that material efficiency is a driving factor in the selection of shell geometry. Essentially, the evolutionary success of Stylommatophora likely roots in their higher flexibility to produce an economic shell., (© The Author(s) 2024. Published by Oxford University Press on behalf of The Society for the Study of Evolution (SSE). All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Calcium phosphates are widely studied in orthopedics and dentistry, to obtain biomimetic and antibacterial implants. However, the multi-substituted composition of mineralized tissues is not fully reproducible from synthetic procedures. Here, for the first time, we investigate the possible use of a natural, fluorapatite-based material, i.e. , Lingula anatina seashell, resembling the composition of bone and enamel, as a biomaterial source for orthopedics and dentistry. Indeed, thanks to its unique mineralization process and conditions, L. anatina seashell is among the few natural apatite-based shells, and naturally contains ions having possible antibacterial efficacy, i.e. , fluorine and zinc. After characterization, we explore its deposition by ionized jet deposition (IJD), to obtain nanostructured coatings for implantable devices. For the first time, we demonstrate that L. anatina seashells have strong antibacterial properties. Indeed, they significantly inhibit planktonic growth and cell adhesion of both Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli . The two strains show different susceptibility to the mineral and organic parts of the seashells, the first being more susceptible to zinc and fluorine in the mineral part, and the second to the organic (chitin-based) component. Upon deposition by IJD, all films exhibit a nanostructured morphology and sub-micrometric thickness. The multi-doped, complex composition of the target is maintained in the coating, demonstrating the feasibility of deposition of coatings starting from biogenic precursors (seashells). In conclusion, Lingula seashell-based coatings are non-cytotoxic with strong antimicrobial capability, especially against Gram-positive strains, consistently with their higher susceptibility to fluorine and zinc. Importantly, these properties are improved compared to synthetic fluorapatite, showing that the films are promising for antimicrobial applications.

Mysidopsis jenseni n. sp. is described from the Puget Sound area, Washington, USA from sand/rocky bottoms in depths of 8 to 15 m. This new species increases the number of American Pacific species of Mysidopsis to eight. Based on a collection of M. intii Holmquist, 1957 from coastal waters of Chile, a supplementary description of the male is presented and the female is described for the first time. The presence of a mid-dorsal lappet near the posterior margin of the carapace of females only distinguishes the new species from all other Mysidopsis species except M. velifera Brattegard, 1973 from the Caribbean. M. jenseni is further separated from its American Pacific congeners by the following combination of characters: antennal scale 34 times as long as wide with a rounded apex and distal suture; uropodal endopod with 89 spiniform setae along ventromedial margin; telson with 4654 spiniform setae along all margins. The presence of lobe-like protuberances on the basis and dactylus of thoracic endopods 38 was documented for the new species, M. intii and other species of Mysidopsis as well as species belonging to the other four genera within the Tribe Mysidopsini. A key to the species of Mysidopsis of the Pacific coasts of the Americas is given.

The carapace coloration is important for the environmental adaptation and reproductive behaviors of crustaceans. We selected red, green and white three carapace color strains of Chinese mitten crab (Eriocheir sinensis) strains. These three carapace colors have stable heritability, but the mechanism for their coloration remains unclear.Through histological observations, we have found significant differences in the composition of pigment cells and pigments within the inner membrane of the three color strains, which may be one of the reasons for the color variation. The levels of various carotenoids in both the shell and inner membrane tissues of red and green strains were significantly higher than those of the white strain, while there was no significant difference between the red and green strains. Proteomics studies have identified 2, 034 and 947 different proteins in the shell and inner membrane, respectively. In the shell, there were 18, 13 and 43 differential proteins between red and white strains, green and white strains and green and red strains, respectively. In the inner membrane, there were 44, 24 and 16 differential proteins between red and white strains, green and white strains and green and red strains, respectively. It is clear that the deposited quantity of carotenoids affects the shell formation of three color strains. Some members of the hemocyanin family showed significant variation among different strains. The study yielded two crustacyanin proteins, which were extracted from both the shell and membrane. Of the two proteins, only Crustacyanin-A1 expression showed a difference between the red and green shells strains. In conclusion, these results indicated that the carapace color formation of E. sinensis may be accomplished through pigment binding proteins (PBPs) and pigment cells, which enhance the understanding of color formation mechanism for crustacean., Competing Interests: Declaration of competing interest We confirm that all research and data presented in this paper is accurate, reliable, and unbiased. We have followed all ethical guidelines and disclosed any potential conflicts of interest to ensure transparency and integrity in our research. We believe that these disclosures do not compromise the validity or integrity of our findings., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Ultrastructural studies on the sensory apparatus of male Tantulocarida (Crustacea) have been conducted for the first time. Comparative morphological analysis with the specialized sensory structures of Thecostraca, known as lattice organs, has allowed for conclusions about possible homologies and further clarification of the phylogenetic position of Tantulocarida., (© 2023. Pleiades Publishing, Ltd.)

Marine shells are designed by nature to ensure mechanical protection from predators and shelter for molluscs living inside them. A large amount of work has been done to study the multiscale mechanical properties of their complex microstructure and to draw inspiration for the design of impact-resistant biomimetic materials. Less is known regarding the dynamic behaviour related to their structure at multiple scales. Here, we present a combined experimental and numerical study of the shells of two different species of gastropod sea snail belonging to the Turritellidae family, featuring a peculiar helicoconic shape with hierarchical spiral elements. The proposed procedure involves the use of micro-computed tomography scans for the accurate determination of geometry, atomic force microscopy and nanoindentation to evaluate local mechanical properties, surface morphology and heterogeneity, as well as resonant ultrasound spectroscopy coupled with finite element analysis simulations to determine global modal behaviour. Results indicate that the specific features of the considered shells, in particular their helicoconic and hierarchical structure, can also be linked to their vibration attenuation behaviour. Moreover, the proposed investigation method can be extended to the study of other natural systems, to determine their structure-related dynamic properties, ultimately aiding the design of bioinspired metamaterials and of structures with advanced vibration control.

In the early 19th century, long before the discovery of the dinosaurs, scientists and the public alike were faced with the realization that strange beasts, wholly extinct, were once populating Earth's ancient oceans. In no small part, this realization was through the discovery of the first plesiosaurs (and ichthyosaurs) along the Dorset coast of England in the seaside town of Lyme Regis. There was this large marine reptile resembling a large sea turtle, but with four evenly shaped flippers and looking as though a large snake had been pulled through its carapace. It was soon to be named scientifically Plesiosaurus, in reference to its greater similarity to living reptiles than the Ichthyosaurus (Figure 1). While the Ichthyosaurus was relatively easily understood as a fish-shaped reptile descended from land-living ancestors, the Plesiosaurus was beyond comprehension, even though incomplete skeletons had been unearthed already in the early 18th century. Plesiosaurs seemed so alien that the first complete skeleton, discovered by the famed Mary Anning a little more than 200 years ago (Figure 1A), was considered a fake by the leading anatomist of the day, the Baron Georges Cuvier in Paris. Only study of the original specimen convinced him of the authenticity of this animal but reinforced his seminal insight that there is extinction., Competing Interests: Declaration of interests The author declares no competing interests., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Shell color shows broad variation within mollusc species and despite information on the genetic pathways involved in shell construction and color has recently increased, more studies are needed to understand its genetic architecture. The common cockle (Cerastoderma edule) is a valuable species from ecological and commercial perspectives which shows important variation in shell color across Northeast Atlantic. In this study, we constructed a high-density genetic map, as a tool for screening common cockle genome, which was applied to ascertain the genetic basis of color variation in the species. The consensus genetic map comprised 19 linkage groups (LGs) in accordance with the cockle karyotype (2n = 38) and spanned 1073 cM, including 730 markers per LG and an inter-marker distance of 0.13 cM. Five full-sib families showing segregation for several color-associated traits were used for a genome-wide association study and a major QTL on chromosome 13 associated to different color-traits was detected. Mining on this genomic region revealed several candidate genes related to shell construction and color. A genomic region previously reported associated with divergent selection in cockle distribution overlapped with this QTL suggesting its putative role on adaptation., (© 2022. The Author(s).)

Biological armors derive their mechanical integrity in part from their geometric architectures, often involving tessellations: individual structural elements tiled together to form surface shells. The carapace of boxfish, for example, is composed of mineralized polygonal plates, called scutes, arranged in a complex geometric pattern and nearly completely encasing the body. In contrast to artificial armors, the boxfish exoskeleton grows with the fish; the relationship between the tessellation and the gross structure of the armor is therefore critical to sustained protection throughout growth. To clarify whether or how the boxfish tessellation is maintained or altered with age, we quantify architectural aspects of the tessellated carapace of the longhorn cowfish Lactoria cornuta through ontogeny (across nearly an order of magnitude in standard length) and in a high-throughput fashion, using high-resolution microCT data and segmentation algorithms to characterize the hundreds of scutes that cover each individual. We show that carapace growth is canalized with little variability across individuals: rather than continually adding scutes to enlarge the carapace surface, the number of scutes is surprisingly constant, with scutes increasing in volume, thickness, and especially width with age. As cowfish and their scutes grow, scutes become comparatively thinner, with the scutes at the edges (weak points in a boxy architecture) being some of the thickest and most reinforced in younger animals and thinning most slowly across ontogeny. In contrast, smaller scutes with more variable curvature were found in the limited areas of more complex topology (e.g., around fin insertions, mouth, and anus). Measurements of Gaussian and mean curvature illustrate that cowfish are essentially tessellated boxes throughout life: predominantly zero curvature surfaces comprised of mostly flat scutes, and with scutes with sharp bends used sparingly to form box edges. Since growth of a curved, tiled surface with a fixed number of tiles would require tile restructuring to accommodate the surface's changing radius of curvature, our results therefore illustrate a previously unappreciated advantage of the odd boxfish morphology: by having predominantly flat surfaces, it is the box-like body form that in fact permits a relatively straightforward growth system of this tessellated architecture (i.e., where material is added to scute edges). Our characterization of the ontogeny and maintenance of the carapace tessellation provides insights into the potentially conflicting mechanical, geometric, and developmental constraints of this species but also perspectives into natural strategies for constructing mutable tiled architectures., (© 2022 The Authors. Journal of Anatomy published by John Wiley & Sons Ltd on behalf of Anatomical Society.)

Boxfish (Ostraciidae) have peculiar body shapes, with conspicuous keels formed by their bony carapaces. Previous studies have proposed various hydrodynamic roles for these keels, including reducing drag during swimming, contributing to passive stabilization of the swimming course, or providing resistance against roll rotations. Here, we tested these hypotheses using computational fluid dynamics simulations of five species of Ostraciidae with a range of carapace shapes. The hydrodynamic performance of the original carapace surface models, obtained from laser scanning of museum specimens, was compared with models where the keels had been digitally reduced. The original carapaces showed no reduced drag or increased passive stability against pitch and yaw compared to the reduced-keel carapaces. However, consistently for all studied species, a strong increase in roll drag and roll-added mass was observed for the original carapaces compared to the reduced-keel carapaces, despite the relatively small differences in keel height. In particular, the damping of roll movement by resistive drag torques increased considerably by the presence of keels. Our results suggest that the shape of the boxfish carapace is important in enabling the observed roll-free forward swimming of boxfish and may facilitate the control of manoeuvres.

Horseshoe crab (order Xiphosura) has a large and thick carapace that has evolved as a protective tool to defend against predators and resist impacts from surf-zone turbulence. The naturally occurring spatial variation in the mechanical properties of the carapace cuticle need to be investigated to understand their regulatory mechanism and the underlying design strategies. In this work, we used a combination of high-resolution optical microscopy, scanning electron microscopy, (SEM) and energy-dispersive X-ray spectroscopy (EDS) to evaluate the multiscale microstructure and elemental composition of the cuticle of tri-spine horseshoe crab (Tachypleus tridentatus). The moduli, ultimate strengths, and failure strains of the three individual layers and the entire cuticle were systematically characterized in both the dry and hydrated states. The failure behaviors and energy absorption of the cuticle involved stress stiffening, toughness mechanism and environmental adaptation were analyzed qualitatively and quantitatively and then correlated with the morphological features in different cuticle regions. The mechanical properties are primarily influenced by the endocuticle thickness ratio; a higher thickness ratio corresponds to more stacking of the vertical lamellae, leading to a lower modulus, weaker strength, and greater elongation of the endocuticle. Radial energy is absorbed primarily by the endocuticle, with the energy absorbed in the radial direction being nearly twice that absorbed in the circumferential direction. This is attributed to the larger failure strain and relatively small decrease in the stress plateau in the radial direction. The findings provide a deeper understanding of how nature modulates the cuticle's mechanical properties and inspiration for developing high-performance synthetic composites., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The fossil history of turtle and whale barnacles (Coronuloidea: Chelonibiidae, Platylepadidae, Coronulidae and †Emersoniidae) is fragmentary and has only been investigated in part. Morphological inferences and molecular phylogenetic analyses on extant specimens suggest that the roots of whale barnacles (Coronulidae) are to be found among the chelonibiid turtle barnacles, but the hard-part modifications that enabled early coronuloids to attach to the cetacean skin are still largely to be perceived. Here, we reappraise a fossil chelonibiid specimen from the Miocene of insular Tanzania that was previously referred to the living species Chelonibia caretta. This largely forgotten specimen is here described as the holotype of the new species †Chelonibia zanzibarensis. While similar to C. caretta, †C. zanzibarensis exhibits obvious external longitudinal parietal canals occurring in-between external longitudinal parietal septa that abut outwards to form T-shaped flanges, a character so far regarded as proper of the seemingly more derived Coronulidae and Platylepadidae. Along with these features, the presence of a substrate imprint on the shell exterior indicates that †C. zanzibarensis grasped its host's integument in much the same way as coronulids and platylepadids, albeit without the development of macroscopic parietal buttresses and bolsters. Thin section analyses of the inner parietal architecture of some extant and extinct coronuloids conclusively demonstrate that vestiges of comparable external parietal microstructures are present in some living members of Chelonibiidae. This observation strengthens the unity of Coronuloidea while significantly contributing to our understanding of the evolution of the coronuloid shell structure in adapting to a diverse spectrum of hosts., (© 2021 The Authors. Integrative Zoology published by International Society of Zoological Sciences, Institute of Zoology/Chinese Academy of Sciences and John Wiley & Sons Australia, Ltd.)

Hard external armors have to defend against a lifetime of threats yet are traditionally understood by their ability to withstand a single attack. Survival of bivalve mollusks thus can depend on the ability to repair shell damage between encounters. We studied the capacity for repair in the intertidal mussel Mytilus californianus by compressing live mussels for 15 cycles at ∼79% of their predicted strength (critically fracturing 46% of shells), then allowing the survivors 0, 1, 2 or 4 weeks to repair. Immediately after fatigue loading, mussel shells were 20% weaker than control shells that had not experienced repetitive loading. However, mussels restored full shell strength within 1 week, and after 4 weeks shells that had experienced greater fatiguing forces were stronger than those repetitively loaded at lower forces. Microscopy supported the hypothesis that crack propagation is a mechanism of fatigue-caused weakening. However, the mechanism of repair was only partially explained, as epifluorescence microscopy of calcein staining for shell deposition showed that only half of the mussels that experienced repetitive loading had initiated direct repair via shell growth around fractures. Our findings document repair weeks to months faster than demonstrated in other mollusks. This rapid repair may be important for the mussels' success contending with predatory and environmental threats in the harsh environment of wave-swept rocky coasts, allowing them to address non-critical but weakening damage and to initiate plastic changes to shell strength. We highlight the significant insight gained by studying biological armors not as static structures but, instead, as dynamic systems that accumulate, repair and respond to damage., Competing Interests: Competing interests The authors declare no competing or financial interests., (© 2021. Published by The Company of Biologists Ltd.)

This paper presents the compressive behavior of tortoise carapace at high strain rates and its protection mechanisms under impact loading. Both experimental and numerical results are reported. Tortoise is a land-based desert-dwelling animal taxonomically classified in the order of Testudines. The carapace is the dome-shaped upper part of the tortoise shell that protects its body from predator attacks. The carapace structure is composed of four layers formed as a composite structure with a porous core. The outer surface is keratin scutes made of fibrous structural proteins. The remaining layers are bone-like materials which are dorsal cortex, cancellous interior and ventral cortex. The compressive behavior at high rate of deformation is examined using split Hopkinson pressure bar (SHPB) technique. The results shown in the stress-strain plot illustrate a strain-rate hardening effect. The impact test is conducted using a gas gun with 6.35-mm diameter steel bearing balls as projectiles. The responses of carapace sample under a range of impact velocities are investigated to analyze its protection mechanisms. The numerical model of impact test is created to obtain an insight into mechanical behaviors of the carapace structure that cannot be observed in the experiments. The strain rate dependent material model is defined based on the SHPB test results. The distributions of stress and rebound velocity are presented and discussed.

The turtle carapace is a biological armor exhibiting enhanced protection performance. Despite considerable efforts to characterize the structure-property relations of the turtle carapace, how the design of soft keratin-collagen bi-layer coating contributes to the protection of this biological armor remains largely unknown. In this study, calculations are carried out for fracture of the turtle carapace subjected to impact loading. The dynamic fracture of the bone layer, plastic deformation of the keratin-collagen bi-layer, and delamination at the keratin-collagen and collagen-bone interfaces are accounted for in the analyses. We reveal that plastic deformation and interfacial delamination within the soft bi-layer coating are two toughening mechanisms controlling the resistance to dynamic crack growth in the bone layer of the turtle carapace. The architecture of the keratin-collagen bi-layer coating enables large plastic deformation in the collagen layer and multiple delaminations within the bi-layer coating, preventing crack propagation in the bone layer. It is found that the dynamic fracture of bone layer in the turtle carapace depends on the stiffness mismatch and yield stress contrast between the keratin layer and the collagen layer. As the stiffness mismatch increases, small plastic deformation of the bi-layer coating occurs and the plastic deformation of collagen layer tends to emerge in the vicinity of the keratin-collagen interface, suppressing interfacial delamination and leading to weak resistance to fracture of the bone layer. The intermediate level of yield stress contrast can activate large plastic deformation and multiple delaminations within the bi-layer coating, mitigating fracture of the bone layer., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Multiphasic calcium phosphate (Ca-P) has widely been explored for bone graft replacement. This study represents a simple method of developing osteoinductive scaffolds by direct printing of seashell resources. The process demonstrates a coagulation-assisted extrusion-based three-dimensional (3D) printing process for rapid fabrication of multiphasic calcium phosphate-incorporated 3D scaffolds. These scaffolds demonstrated an interconnected open porous architecture with improved compressive strength and higher surface area. Multiphasic calcium phosphate (Ca-P) and hydroxyapatite present in the multi-scalar naturally resourced scaffold displayed differential protein adsorption, thus facilitating cell adhesion, migration, and differentiation, resulting in enhanced deposition of the extracellular matrix. The microstructural and physicochemical attributes of the scaffolds also lead to enhanced stem cell differentiation as witnessed from gene and protein expression analysis. Furthermore, the histological study of subcutaneous implantation evidently portrays promising biocompatibility without foreign body reaction. Neo-tissue in-growth was manifested with abundant blood vessels, thus indicative of excellent vascularization. Notably, cartilaginous and proteoglycan-rich tissue deposition indicated ectopic bone formation via an endochondral ossification pathway. The hierarchical interconnected porous architectural tribology accompanied with multiphasic calcium phosphate composition manifests its successful implication in enhancing stem cell differentiation and promoting excellent tissue in-growth , thus making it a plausible alternative in bone tissue engineering applications.

The Manila clam, Ruditapes philippinarum , is an ecologically and economically important marine bivalve species. In this study, we conducted transcriptomic sequencing of two different shell color strains (O and Z) before color appearance (uncolored juvenile clam) and pigmented shell color (colored juvenile clam) and investigated the analysis of the differential expression patterns of specific genes associated with pigmentation by RNA-seq and time course qPCR analysis. The transcription level of 16 differentially expressed genes (DEGs) related with shell color was analyzed by qRT-PCR to validate the performance of RNA-seq from Illumina sequence data where most of them were up-regulated. Two genes were down-regulated after the occurrence of zebra clam stripes compared with uncolored zebra clam. The trend of gene expression obtained by qPCR was basically consistent with that of RNA-seq. The synthesis of melanin in bivalves plays potential roles in the pigmentation of the shell and is closely related to the formation of the surface pattern. The porphyrin metabolism combined with tyrosinase and melanogenesis signaling pathway is a novel finding in shell color determination of R. philippinarum . This study sheds light on the pigmentation and coloration mechanism of the Manila clam.

Many biological structures use liquid crystals as self-organizing templates for their formation. We review and analyse evidence that the crossed-lamellar biomineral microstructure of mollusc shells may be formed from such a liquid-crystal precursor. STATEMENT OF SIGNIFICANCE: Many biological structures use liquid crystals as self-organizing templates for their formation. We review and analyse evidence that the crossed-lamellar biomineral microstructure of mollusc shells may be formed from such a liquid-crystal precursor., (Copyright © 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

Biological waste from marine sources is discarded into various water bodies which leads to dramatic increase in the water pollution near coastal areas. This animal waste consists of bioactive compounds such as fatty acids, amino acids, and chitin which can be used in agricultural and pharmaceutical sectors. The aim of the current study was to extract chitosan (CS) from the discarded shells of Carinosquilla multicarinata and prepare anti-inflammatory drug diclofenac potassium (DP) encapsulated chitosan nanoparticles (DP-CSNPs). The CS was extracted, purified and physicochemical and morphological properties were characterized such as viscosity (1.44cPs), molecular weight (~57 kDa), degree of deacetylation (83%). The DP-CSNPs were prepared by ionic gelation of extracted chitosan with tripolyphosphate (TPP) anions by varying chitosan, TPP, and drug concentrations. SEM imaging showed that DP-CSNPs were nano-sized (248 nm) along with small, spherical, and uniformity in shape. The endothermic peak appeared at 180°C while performing the thermal analysis of DP-CSNPs by differential scanning calorimetry (DSC). The Loading capacity (LC) and encapsulation efficiency (EE) were determined for all combinations while maximum EE (79.42%), LC (42.08%), and +0.00459 mV for Zeta potential were found for nanoparticles synthesized from CS with 2.5mg/mL concentration and 1mg/mL of TPP and drug concentrations. Moreover, in vitro drug release study was performed at simulated biological fluid (pH 7.4) and at 10th hr maximum (80%) of the drug was released from DP-CSNPs. Therefore, this waste source would be a better model system for the drug release. Implications : Dumping of marine waste into deep ocean has led to dramatic increase in water pollution leading to the endangerment of various oceanic animals. This discarded waste can be used sustainably for the isolation of various biopolymers into the ultimate use for human community. The work provides a detailed guide into the method of extraction of low molecular weight chitosan and preparation of nanoparticles for the delivery of anti-inflammatory drug diclofenac.

Molluscan shells are composed of calcium carbonates, with small amounts of extracellular matrices secreted from mantle epithelial cells. Many types of shell matrix proteins (SMPs) have been identified from molluscan shells or mantle cells. The pen shell Atrina pectinata (Pinnidae) has two different shell microstructures, the nacreous and prismatic layers. Nacreous and prismatic layer-specific matrix proteins have been reported in Pteriidae bivalves, but remain unclear in Pinnidae. We performed transcriptome analysis using the mantle cells of A. pectinata to screen the candidate transcripts involved in its prismatic layer formation. We found Asprich and nine highly conserved prismatic layer-specific SMPs encoding transcript in P. fucata, P. margaritifera, and P. maxima (Tyrosinase, Chitinase, EGF-like proteins, Fibronectin, valine-rich proteins, and prismatic uncharacterized shell protein 2 [PUSP2]) using molecular phylogenetic analysis or multiple alignment. We confirmed these genes were expressed in the epithelial cells of the mantle edge (outer surface of the outer fold) and the mantle pallium. Phylogenetic character mapping of these SMPs was used to infer a possible evolutionary scenario of them in Pteriomorphia. EGF-like proteins, Fibronectin, and valine-rich proteins encoding genes each evolved in the linage leading to four Pteriomorphia (Mytilidae, Pinnidae, Ostreidae, and Pteriidae), PUSP2 evolved in the linage leading to three Pteriomorphia families (Pinnidae, Ostreidae, and Pteriidae), and chitinase was independently evolved as SMPs in Mytilidae and in other Pteriomorphia (Pinnidae, Ostreidae, and Pteriidae). Our results provide a new dataset for A. pectinata SMP annotation, and a basis for understanding the evolution of prismatic layer formation in bivalves.

Molluscs defend themselves against predation and environmental stressors through the possession of mineralized shells. Mussels are widely used to predict the effects of abiotic factors such as salinity and pH on marine calcifiers in the context of changing ocean conditions. Shell matrix proteins are part of the molecular control regulating the biomineralization processes underpinning shell production. Under changing environmental conditions, differential expression of these proteins leads to the phenotypic plasticity of shells seen in many mollusc species. Low salinity decreases the availability of calcium and inorganic carbon in seawater and consequently energetic constraints often lead to thin, small and fragile shells in Mytilid mussels inhabiting Baltic Sea. To understand how the modulation of shell matrix proteins alters biomineralization, we compared the shell proteomes of mussels living under full marine conditions in the North Sea to those living in the low saline Baltic Sea. Modulation of proteins comprising the Mytilus biomineralization tool kit is observed. These data showed a relative increase in chitin related proteins, decrease in SD-rich, GA-rich shell matrix proteins indicating that altered protein scaffolding and mineral nucleation lead to impaired shell microstructures influencing shell resistance in Baltic Mytilid mussels. Interestingly, proteins with immunity domains in the shell matrix are also found to be modulated. Shell traits such as periostracum thickness, organic content and fracture resistance qualitatively correlates with the modulation of SMPs in Mytilid mussels providing key insights into control of biomineralization at molecular level in the context of changing marine conditions., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

During billions of years of evolution, creatures in nature have possessed nearly perfect structures and functions for survival. Multiscale structures in biological materials over several length scales play a pivotal role in achieving structural and functional integrity. Fiber, as a common principal structural element in nature, can be easily constructed in different ways, thus resulting in various natural structures. In this review, we summarized the decades of investigations on a typical biological structure constructed by fiber aragonites in mollusk shells. Crossed-lamellar structure, as one of the most widespread structures in mollusk shells, reconciles the strength-toughness trade-off dilemma successfully due to the presence of highly-hierarchical architectures. This distinctive structure includes several orders of sub-lamellae, and the different order lamellae present a cross-ply feature in one macro crossed-lamellar layer. When a mollusk shell has more than one macro-layer, the crossed-lamellar structure exhibits various forms of architectures including 0°/90°, 0°/90°/0° typical-sandwich, 15°/75°/0° quasi-sandwich, and 0°/90°/0°/90° arranged modes. The fracture resistance and the relevant toughening mechanisms are directly related to the highly-hierarchical crossed-lamellar structures on different length scales. This article is aimed to review the different arranged modes of crossed-lamellar structures existing in nature, with special attention to their impact on the mechanical behavior and salient toughening mechanisms over several length scales, for seeking the design guidelines for the fabrication of bio-inspired advanced engineering materials that are adaptive to different loading conditions., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Hyoliths (hyolithids and orthothecids) were one of the most successful early biomineralizing lophotrochozoans and were a key component of the Cambrian evolutionary fauna. However, the morphology, skeletogenesis and anatomy of earliest members of this enigmatic clade, as well as its relationship with other lophotrochozoan phyla remain contentious. Here, we present a new orthothecid, Longxiantheca mira gen. et sp. nov. preserved as part of secondarily phosphatized small shelly fossil assemblage from the lower Cambrian Xinji Formation of North China. Longxiantheca mira retains some ancestral traits of the clade with an undifferentiated disc-shaped operculum, a simple conical conch with apical septa and a two-layered microstructure of aragonitic fibrous bundles. The operculum interior exhibits impressions of soft tissues, including muscle attachment scars, mantle epithelial cells and a central kidney-shaped platform interpreted as a support structure in association with its presumptive feeding apparatus. The muscular system in orthothecids appears to be similar to that in hyolithids, suggesting a consistent anatomical configuration among the total group of hyoliths. The new finding of shell secreting cells demonstrates a mantle regulating the mode of growth for the operculum. Investigations of shell microstructures support the placement of hyoliths as total group molluscs with an unsettled position within the phylum Mollusca.

A bulky waste, oyster shell (OS), was calcinated at 400-800°C to produce Ca-rich products (OS 400 -OS 800 ) to reduce the human health risk of soil cadmium (Cd) and arsenic (As). Thermogravimetric analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), and BET method were used to characterize OS and its calcined products. OS and OS 400 -OS 700 removed little Cd and As from water, whereas OS 800 removed 1508 mg Cd or 514 mg As per kg of OS 800 from solutions of 1032 mg Cd/L or 257 mg As/L via adsorption and precipitation. Adding OS 800 at a 2% dose to a Cd- and As-contaminated soil lowered its exchangeable Cd from 60% to 27%, and reduced Cd content in the edible part of vegetable Bok Choy from 2.80 to 0.048 mg/kg and As from 1.73 to 0.47 mg/kg. Converting OS to soil amendment has the dual benefits to soil remediation and sustainable oyster aquaculture.

Mollusk shells can provide important information regarding environmental parameters. It is known that shell morphology is affected by both natural and anthropogenic factors. However, few studies have investigated alterations in shell morphology over a historical perspective and considering chemical contamination and climate changes. The present study assessed shell form (shape and size) variations of limpet (Lottia subrugosa) shells sampled from 1950 to 1981 (past) in comparison with organisms obtained in 2018 (present). Differences between shells from the past and present (2018) were detected, being shell weight and height the two most important affected parameters. The differences observed were attributed to the possible increase in contamination over the years due to human population growth and to climate change. Additionally, when shells from the past were evaluated according to the decade they were sampled, results indicate that it was necessary an interval of 40 years to shell form be altered within populations., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Through biological evolution, bivalve mollusks developed shells to improve the utilization of metabolic energy and provide protection against external threats. In addition to the mechanical optimization of the microstructure, the design of the macroscopic shape of a bivalve shell naturally becomes a potential approach to achieving the aforementioned purposes. While the functions of some features of mollusk shells have been studied, the role of the suture-serrate margins, a common morphology of bivalve shell edges, in the global mechanical behaviors of bivalve shells requires further exploration. Here, we present how the serrate margins contribute to the global mechanical properties of bivalve shells. The results of the compression tests employed on a typical bivalve, M. mercenaria, showed that the complete bivalve shells with suture-serrate margins perform better in terms of strength and work to fracture than those without the margins under the same conditions (dry and wet). The primary failure types observed during compression reveal that the failure mechanisms of valve shells are dependent on the suture-serrate margin morphology and water content. Using numerical simulations, the mechanical functions of the suture-serrate margins were demonstrated. Specifically, serrate margins provide mutual resistance by "locking" complementary valves to redistribute and eliminate stress concentrations around pre-existing defects, thereby enhancing the mechanostability and strength of the entire structure., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Shrimp processing and consumption generate large amounts of waste shrimp shell (WSS) rich in chitin and protein. Herein, we successfully synthesized WSS-based hydrochar (WSH) adsorbent through deproteinization and deacetylation followed by hydrothermal carbonization (HTC) and acid washing. For comparison, another hydrochar (CCH) adsorbent was synthesized from HTC of commercial chitosan under identical conditions. Specifically, WSH contained rich nitrogen-containing functional groups with a long aliphatic chains structure. Acid etching of calcium carbonate in WSS led to a higher specific surface area of WSH (12.65 m 2 /g) which was nearly 6 times higher than that of CCH (2.13 m 2 /g). The lower deacetylation degree of WSH was responsible for higher amide I and amino groups retained therein. Under an optimal initial solution pH of 4.0, WSH could rapidly achieve a superb adsorption capacity of 755.08 mg/g for methyl orange molecule. Moreover, the adsorption process followed a pseudo-second-order kinetics model and was well described by a monolayer adsorption pattern based on the Langmuir isotherm model with correlation coefficients higher than 0.9989. Prominent adsorption performance of WSH for methyl orange was mainly attributed to electrostatic interactions, while steric hindrance effect had a detrimental impact on the adsorption capacity of CCH. Superb adsorption capacity and excellent regeneration performance suggest WSH could be a promising and affordable adsorbent candidate for anionic dye removal., (Copyright © 2019 The Authors. Published by Elsevier Ltd.. All rights reserved.)

This study describes shell-exchange behavior in the hermit-crab-like tanaidacean Macrolabrum sp. (Pagurapseudidae: Pagurapseudinae) under captive conditions. I observed one shell exchange by Macrolabrum sp., the behavioral sequence of which was as follows: a shell-carrying tanaidacean 1) grasped the edge of the aperture of an empty gastropod shell with its right cheliped; 2) inspected the condition inside the shell four times by inserting the anterior portion of its body into the shell; and 3) moved into the shell, posterior end (pleotelson) first. The elapsed time from the initial grasping of the empty shell to completing the move into it was 2 min 20 sec. In contrast to a Pagurapseudes tanaidacean and hermit crabs, the individual of Macrolabrum sp. did not examine the external surface of the shell during the single shell exchange observed.

Fossil cephalopods are frequently encrusted by epibionts; however, determining whether encrustation occurred prior to or post-mortem to the host, and whether the final environment of deposition corresponds to the habitat of encrustation is complex. The present paper describes cirripede epibionts, their calcareous bases and their attachment scars on 6 post-mortem shells of Nautilus macromphalus, collected from deep water off New Caledonia. The cirripedes have left both cemented calcareous bases of Hexelasma and scars associated with bioerosion and discoloration produced by verrucomorph barnacles. Live cirripedes included a Metaverruca recta, with articulated opercular plates and organic tissue (on a shell that had been exposed on the sea floor for at least 150 years), and specimens of Hexelasma velutinum, one of which was partly attached to an internal surface of a shell. The disposition of verrucomorphs indicates that most Nautilus shells were colonized post-mortem rather than during a floating stage. However, as cirripedes are known to have colonized living Nautilus, some Hexelasma, preserved only as calcareous eroded bases, may represent specimens that settled on a living Nautilus. The degree of bioerosion and discoloration induced by verrucomorph barnacles varies according to the surface preservation of Nautilus shells, with deeper and discolored traces preserved on old and degraded shells. Traces made by verrucomorphs described here are ellipsoidal and a new ichnotaxon, Anellusichnus ellipticus, is proposed to accommodate them. Importantly, verrucomorphs and other cirripede taxa with membranous bases that were attached to pristine shells may not leave any substantial scars, and, thus, will be difficult to detect in the fossil record., (© 2019 The Authors. Integrative Zoology published by International Society of Zoological Sciences, Institute of Zoology/Chinese Academy of Sciences and John Wiley & Sons Australia, Ltd.)

Shells are very common objects in the world, often used for decorations, collections, academic research, etc. With tens of thousands of species, shells are not easy to identify manually. Until now, no one has proposed the recognition of shells using machine learning techniques. We initially present a shell dataset, containing 7894 shell species with 29622 samples, where totally 59244 shell images for shell features extraction and recognition are used. Three features of shells, namely colour, shape and texture were generated from 134 shell species with 10 samples, which were then validated by two different classifiers: k-nearest neighbours (k-NN) and random forest. Since the development of conchology is mature, we believe this dataset can represent a valuable resource for automatic shell recognition. The extracted features of shells are also useful in developing and optimizing new machine learning techniques. Furthermore, we hope more researchers can present new methods to extract shell features and develop new classifiers based on this dataset, in order to improve the recognition performance of shell species.

Introduction: Crab shell ( Portunus pelagicus ) has the potential to be a source of hydroxyapatite biomaterials that used as bone grafts. Before clinical application, crab shell graft should be tested for its biocompatibility in vitro on human gingival fibroblast., Aim: This study aimed to determine the biocompatibility of Portunus pelagicus hydroxyapatite graft on human gingival fibroblast cell culture., Material and Methods: Human gingival fibroblast cell cultures were divided into control group and treatment group with the addition of hydroxyapatite graft powder from Portunus pelagicus at a concentration of 100 ppm, 50 ppm, and 25 ppm. The synthesis process of hydroxyapatite was conducted by heating at 1000°C then characterizing the compound with SEM-EDX. All samples were incubated in α-MEM medium, then were given MTT material. The cultures on the plate were examined using ELISA reader. The results were analyzed using a Oneway Anova., Results: The percentage of living cells throughout all treatment group shown results that exceeded the LD50 parameter. The highest percentage of living cells was at 25 ppm concentration group., Conclusion: The hydroxyapatite graft powder from crab shells is biocompatible with human gingival fibroblast cell culture., Competing Interests: There are no conflicts of interest., (© 2019 Michael Josef Kridanto Kamadjaja, Janery Fidelia Abraham, Harry Laksono.)

The extreme environmental conditions that prevail in cities are known to cause selection pressures leading to adaptive changes in wild, city-dwelling, organisms (urban evolution). The urban heat island, elevated temperatures in the city centre due to a combination of generation, reflection, and trapping of heat, is one of the best recognised and most widespread urban environmental factors. Here, we use a citizen-science approach to study the effects of urban heat on genetically-determined shell colour in the land snail Cepaea nemoralis in the Netherlands. We use smartphone applications to obtain colour data on almost 8000 snails throughout the country. Our analysis shows that snails in urban centres are more likely to be yellow than pink, an effect predicted on the basis of thermal selection. Urban yellow snails are also more likely to carry dark bands at the underside of the shell; these bands might affect thermoregulation in yet underexplored ways., Competing Interests: Competing interestsThe authors declare no competing interests.

In this work we evaluate the mechanical properties of Chamelea gallina shells, collected at various locations in the Adriatic Sea, through compression tests. We present an analytical model for the extraction of the material Young's modulus and ultimate strength, based on the approximation of the valves with a simpler geometry. The effect of porosity and the computation of the energy dissipated at fracture are also discussed. Results show a dependence of the mechanical performance on the location at which the samples were collected, i.e. latitude, and thus the environmental factors can affect the rigidity, strength and toughness of the shells. These findings integrate preliminary results published in a previous work., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Organisms with long generation times require phenotypic plasticity to survive in changing environments until genetic adaptation can be achieved. Marine calcifiers are particularly vulnerable to ocean acidification due to dissolution and a reduction in shell-building carbonate ions. Long-term experiments assess organisms' abilities to acclimatize or even adapt to environmental change. Here we present an unexpected compensatory response to extensive shell dissolution in a highly calcium-carbonate-dependent organism after long-term culture in predicted end-century acidification and warming conditions. Substantial shell dissolution with decreasing pH posed a threat to both a polar ( Liothyrella uva) and a temperate ( Calloria inconspicua) brachiopod after 7 months and 3 months exposure, respectively, with more extensive dissolution in the polar species. This impact was reflected in decreased outer primary layer thickness in the polar brachiopod. A compensatory response of increasing inner secondary layer thickness, and thereby producing a thicker shell, was exhibited by the polar species. Less extensive dissolution in the temperate brachiopod did not affect shell thickness. Increased temperature did not impact shell dissolution or thickness. Brachiopod ability to produce a thicker shell when extensive shell dissolution occurs suggests this marine calcifier has great plasticity in calcification providing insights into how similar species might cope under future environmental change.

Over the past decade, many skeletal matrix proteins that are possibly related to calcification have been reported in various calcifying animals. Molluscs are among the most diverse calcifying animals and some gastropods have adapted to terrestrial ecological niches. Although many shell matrix proteins (SMPs) have already been reported in molluscs, most reports have focused on marine molluscs, and the SMPs of terrestrial snails remain unclear. In addition, some terrestrial stylommatophoran snails have evolved an additional unique calcified character, called a "love dart," used for mating behavior. We identified 54 SMPs in the terrestrial snail Euhadra quaesita, and found that they contain specific domains that are widely conserved in molluscan SMPs. However, our results also suggest that some of them possibly have evolved independently by domain shuffling, domain recruitment, or gene co-option. We then identified four dart matrix proteins, and found that two of them are the same proteins as those identified as SMPs. Our results suggest that some dart matrix proteins possibly have evolved by independent gene co-option from SMPs during dart evolution events. These results provide a new perspective on the evolution of SMPs and "love darts" in land snails.

Sandwich structure consisting of three crossed-lamellar layers (inner, middle and outer) is one of the most common structures found in mollusk shells, and is normally arranged in a 0°/90°/0° or 90°/0°/90° mode. However, the Cymbiola nobilis seashell in the present study is observed to exhibit a unique quasi-sandwich structure, where the inner and middle layers have an ~15° rotation in comparison with those of typical sandwich structures, resulting in a 15°/75°/0° or 75°/15°/90° mode. This has been identified as the weak/tough/weak and tough/weak/tough modes, and the sample arranged in the 15°/75°/0° mode with a tough layer in the middle has a higher strength than that arranged in the 75°/15°/90° mode with a weak layer in the middle. The fracture resistances of these two types of structural arrangements depend mainly on crack propagation. The interfaces between the macrolayers can effectively arrest the crack propagation especially when the tough layer is positioned in the middle (15°/75°/0° mode), hence increasing the strength and toughness of materials. Salient toughening mechanisms involving crack deflection together with zig-zag crack propagation paths as well as the fiber pull-out of second-order lamellae are identified. Moreover, triangular fracture paths with a convex morphology are observed to form due to the concurrent occurrence of fiber fracturing and channel cracking in single 1st-order lamellae. These findings shed light on the superb crack propagation resistance of the unique quasi-sandwich structure in the C. nobilis shell, thus paving the way for the development of bio-inspired advanced structural materials., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Scanning electron microscopy, X-ray diffraction and Fourier transformed infrared spectroscopy have been used to characterize the microstructure and instrumented microindentation for the determination of the mechanical properties of Charonia Lampas Lampas shell. Both elastic modulus and hardness are found to be dependent on the texture of the three distinct layers. From the analysis of load-depth curves, the shell exhibits small viscoelastic behaviour at low indentation loads and mainly elastoplastic behaviour at higher loads. These phenomena were attributed to the influence of the organic matter present in the shell. Both elastic modulus and hardness are found to be load-dependent in each layer in relation to their microstructure and, accordingly, to the anisotropy of the predominant mineral part. At a macroscopic scale, this tendency is explained by using a rule of mixture and jointly by the anisotropy of the aragonite. The Bull and Page model is subsequently applied to the hardness variation in order to compute the macrohardness which is the characteristic hardness number of a material and the hardness parameter related to the indentation size effect. This model describes well the experimental results for the relative higher depths, and deviates for the small depths due to the effect of the viscoelastic behaviour which then requires a more appropriate model to describe this phenomenon., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Atlantiid heteropods are zooplanktonic marine snails which have a calcium carbonate shell and single swimming fin. They actively swim to hunt prey and vertically migrate. Previous accounts of atlantiid heteropod swimming described these animals sculling with the swimming fin while the shell passively hung beneath the body. Here, we show, via high-speed stereophotogrammetric measurements of body, fin and shell kinematics, that the atlantiid heteropod Atlanta selvagensis actively flaps both the swimming fin and shell in a highly coordinated wing-like manner in order to swim in the intermediate Reynolds number regime ( Re =10-100). The fin and shell kinematics indicate that atlantiid heteropods use unsteady hydrodynamic mechanisms such as clap-and-fling and delayed stall. Unique features of atlantiid heteropod swimming include the coordinated pairing of dissimilar appendages, use of the clap and fling mechanism twice during each stroke cycle, and the fin's extremely large stroke amplitude, which exceeds 180 deg., Competing Interests: Competing interestsThe authors declare no competing or financial interests., (© 2018. Published by The Company of Biologists Ltd.)

In order to provide reference for the development of relevant dredging and processing machinery of the manila clam (Ruditapes philippinarum), the clam shell´s microstructure, phase composition, microhardness, nanoindentation hardness and elastic modulus were investigated, the quasi static compression and orthogonal compression tests of live clams were carried out as well. The shell consists of the outer, middle, and inner layer, which correspond with the composite prismatic structure, crossed-lamellar structure, and homogeneous structure, respectively. X-ray diffraction (XRD) results indicated that all the three layers are made up of pure aragonite phase, the outer layer of the shell displays greater intensity and more diffraction peaks than the middle and inner layer. The microhardness of the inner layer, ~ 3.00 GPa, is harder than the middle and outer layer. Both in the middle and outer layers, the microhardnesses of the vertical section perpendicular to the growth lines are obviously higher than that of the cross section parallel to the growth lines. The similar trend was observed in nanoindentation hardness (H) and elastic modulus (E), but the H/E ratios between three layers and two sections are close to 0.05. The quasi static compressive strengths of live clams with loading along the X (beak horizontal), Y (beak upward and umbo downward), and Z (beak vertical) orientations were tested, and the differences were identified. The lowest strength was found with loading orientation Z, the Weibull strength at 50% probabilities of fracture force is just 153 N. The results of the orthogonal compression tests demonstrated that the fracture force of clams varies from approximately 100 N to 400 N, the effect of the clams´ age on fracture force is more significant (p < 0.01) than loading orientation and loading speed. Therefore, the clams´ age and ultimate load of fracture should be taken into account during clam production mechanization, for the purpose of maintaining the clams´ integrity and survival prior to sale., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Turtle shell rattles are percussion instruments used by Indigenous peoples of the Americas in ceremonial contexts to keep rhythm. Archaeological investigations in the southeastern United States produced several complete and partial Eastern box turtle (Terrapene carolina) shell rattles from mortuary contexts dating from the Archaic (ca. 8000-1000 BC) through Mississippian periods (ca. AD 800-1500). Fragmentary turtle remains, some identified as Eastern box turtle, are frequently recovered from non-mortuary contexts. Traditionally, these fragmentary remains are attributed to food waste. Given the archaeological and ethnographic evidence for turtle shell rattles, we need to consider how fragmentary remains might fit into the chaîne opératoire of rattle production. This paper presents the results of an experimental study designed to identify one such chaîne opératoire of rattle production. During this experiment, the data on taphonomic processes such as manufacturing marks, use-wear, and breakage patterns, were recorded. We then tested the taphonomic findings from the experimental study and an object trait list we compiled from known rattle specimens and documentary sources with archaeological turtle remains recovered from non-mortuary contexts at two Mississippian period (ca. AD 1000-1450) sites in Middle Tennessee. Historic indigenous groups are known to have, and still do into the present-day, make and use turtle shell rattles in the region. Ultimately, we determined that "food refuse" should not be the default interpretation of fragmentary box turtle remains, and instead the taphonomic history and contextual associations must be considered in full. The experimental process of crafting turtle shell rattles enhances our understanding of an ancient musical instrument and the success rate of identifying musical artifacts and distinguishing between other modified turtle remains in the archaeological record. This study expands our knowledge of ancient music in North America and prompts re-analysis of curated turtle remains in museums for rattle-related modifications., Competing Interests: The authors have declared that no competing interests exist.

The pasiphaeid shrimp genus Eupasiphae Wood-Mason Alcock, 1893 (Caridea: Pasiphaeidae) currently includes four bathypelagic species: Eupasiphae latirostris (Wood-Mason, 1891), E. gilesii (Wood-Mason, 1892), E. serrata Rathbun, 1902 and E. paucidentata Crosnier, 1988. The present work describes a further new species, Eupasiphae ostrovski n. sp., on the basis of material sampled at the continental shelf and slope of the Central Brazilian coast at depths of 200 - 2000 m. The new species is somewhat similar to E. paucidentata, only known from Madagascar, but can be easily distinguished from all other congeneric species by the number and shape of lateral carinae at carapace and by the middorsal carina of the carapace being without teeth anteriorly and with 0-3 posteriorly. The new species is the first Eupasiphae representative known from the southwestern Atlantic.

Musculoskeletal disorders in the elderly have significantly increased due to the increase in an ageing population. The treatment of these diseases necessitates surgical procedures, including total joint replacements such as hip and knee joints. Over the years a number of treatment options have been specifically established which are either permanent or use temporary natural materials such as marine skeletons that possess unique architectural structure and chemical composition for the repair and regeneration of bone tissue. This review paper will give an overview of presently used materials and marine structures for hard tissue repair and regeneration, drugs of marine origin and other marine products which show potential for musculoskeletal treatment.

This study examined the effects on nitrate removal when adding sulfur granules and crushed seashells to a woodchip bioreactor treating aquaculture effluents. Using a central composite design, the two components were added at three levels (0.000, 0.125 and 0.250 m 3 /m 3 bioreactor volume) to 13 laboratory-scale woodchip bioreactors, and a response surface method was applied to find and model the optimal mixture ratios with respect to reactor performance. Adding 0.125 m 3 /m 3 sulfur granules improved the total N removal rate from 3.27 ± 0.38 to 8.12 ± 0.49 g N/m 3 /d compared to pure woodchips. Furthermore, the inclusion of crushed seashells together with sulfur granules helped to maintain the pH above 7.4 and prevent a production (i.e., release) of nitrite. According to the modeled response surfaces, a sulfur granule:crushed seashell:woodchip mixture ratio containing about 0.2 m 3 sulfur granules and 0.1 m 3 crushed seashells per m 3 reactor volume would give the best results with respect to high N removal and minimal nitrite release. In conclusion, the study showed that N removal in woodchip bioreactors may be improved by adding sulfur granules and seashells, contributing to the optimization of woodchip performance in treating aquaculture effluents.