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Flexible protective armors are found in large animals such as fish skins, snake skins, and pangolin scales. For small-sized invertebrates, such armors are paid less attention and overlooked. Chitons, a type of marine mollusk, possess mineralized armors covering the whole dorsal body. The dorsal scales in the girdle tissue are well known, in this study, we reported hidden mineralized scales in the ventral side of chiton Acanthopleura loochooana girdles for the first time. The ventral surface is covered with scales with ca. 40 μm in length, forming continuous but overlapped scales. Additionally, scales are formed from aragonitic spicule-like and square-like scales, embedded in the cuticle layer. Nanoindentation testing results showed that the hardness and elastic modulus of ventral scales were ∼20 % higher compared to those in the dorsal scales, exhibiting good hardness and wear resistance. The combination of the ventral scales and cuticle, along with the regular arrangement of ventral scales, may allow chitons to simultaneously address complex and variable attachment interfaces while also providing wear-resistant protection. This study provides insights for designing protective structures that balance flexibility and durability. Biomineralization is universal in nature and provides protection and support for animals. However, mineralization of dermal skin is not commonly seen. Herein, for the first time, we reported hidden minerals covering the whole ventral side of skin in a small marine animal, chitons. Calcium carbonate minerals are arranged regularly and manifest different morphology in different regions. Additionally, these minerals are embedded in a continuous cuticle layer covering the whole animal. The material also indicates a higher wear-resistant property. This study extends our understanding of the diverse functionality of biominerals and provides a prototype for designing wear-resistant materials. [Display omitted] [ABSTRACT FROM AUTHOR]

The chiton (Polyplacophora) occupies a significant position in molluscan evolutionary history as one of the most primitive groups within the phylum Mollusca. Acanthochitona defilippii (Tapparone-Canefri 1874) (Chitonida: Acanthochitonidae) is a commonly found intertidal chiton species in South Korea. In this study, we characterized the complete mitochondrial genome of A. defilippii (14,999 bp long), comprising 13 protein-coding genes (PCGs), 22 transfer RNA genes, two ribosomal RNA genes, and an A + T rich region (166 bp). The base composition is as follows: 31.82% for A, 11.63% for C, 16.69% for G, and 39.86% for T. We reconstructed a maximum likelihood (ML) tree to elucidate phylogenetic relationships among the eight chitonid families using the nucleotide sequences of all PCGs. The ML tree revealed that A. defilippii clustered with Acanthochitona avicula (BP 100) within the family Acanthochitonidae. Acanthochitonidae formed a sister group with Mopaliidae. The results could provide a valuable understanding the phylogenetic relationships of chitonid species.

Chiton articulatus is a species of mollusk living in the tropical Pacific intertidal rocky shores of Mexico. This species feeds on solid waste organic sources, including hard crustose algae that grow on rocky substrates, by grazing on them with its radula, a flexible chitinous membrane lined with mineralized major lateral teeth. In this study, the composition, morphology, and resulting mechanics of the mature teeth of this species, which have yet to be examined, are revealed. The results show the presence of multiphasic mature teeth, each consisting of aligned hard magnetite nanoparticles on the leading edge of the tooth underneath which are magnetite lamellae, followed by goethite, lepidocrocite, and eventually hydroxyapatite near the trailing edge. This multiregional structure demonstrates a gradation in hardness as well as different microstructural features integrated with tough interfaces. The combination of these microstructural and phase arrangements results in an abrasion‐resistant tough structure with a self‐sharpening ability. The results of this work will help contribute to developing new bioinspired designs while also helping to understand the evolution and feeding habits of these intriguing invertebrates. [ABSTRACT FROM AUTHOR]

The chiton (Polyplacophora) occupies a significant position in molluscan evolutionary history as one of the most primitive groups within the phylum Mollusca. Acanthochitona defilippii (Tapparone-Canefri 1874) (Chitonida: Acanthochitonidae) is a commonly found intertidal chiton species in South Korea. In this study, we characterized the complete mitochondrial genome of A. defilippii (14,999 bp long), comprising 13 protein-coding genes (PCGs), 22 transfer RNA genes, two ribosomal RNA genes, and an A + T rich region (166 bp). The base composition is as follows: 31.82% for A, 11.63% for C, 16.69% for G, and 39.86% for T. We reconstructed a maximum likelihood (ML) tree to elucidate phylogenetic relationships among the eight chitonid families using the nucleotide sequences of all PCGs. The ML tree revealed that A. defilippii clustered with Acanthochitona avicula (BP 100) within the family Acanthochitonidae. Acanthochitonidae formed a sister group with Mopaliidae. The results could provide a valuable understanding the phylogenetic relationships of chitonid species. [ABSTRACT FROM AUTHOR]

Poliplacóforos, conhecidos popularmente por quítons, são moluscos marinhos que apresentam ocorrência em todas as partes do mundo. As estruturas morfológicas externas destes indivíduos contribui para sua adesão em regiões irregulares do substrato consolidado. O objetivo do presente estudo foi caracterizar a assembleia de quítons quanto a sua composição, abundância e ocorrência com coabitantes em substratos duros em praias no litoral oeste do Ceará, nordeste do Brasil. O estudo foi realizado na Praia da Pedra Rachada localizada na cidade de Paracuru e na Praia do Farol localizada em Camocim. As praias rochosas de Camocim e Paracuru foram representadas por três espécies de Polyplacophora: Acanthochitona sp., Ischnochiton striolatus e Ischnoplax pectinata. Foram encontrados 697 organismos, destes, 56% eram da espécie I. striolatus, seguidos de I. pectinata com 33%, Acanthochitona sp. com 11%. Quando comparadas as duas áreas amostradas, Paracuru apresentou uma abundância de 488 indivíduos, e Camocim, apresentou uma abundância de 209 indivíduos. Os organismos apresentaram abundância diferente entre os tipos de substratos e coabitantes. Um total de 30 indivíduos ocorreram somente em substrato liso composto por seixos, sendo as espécies I. pectinata, Achantochitona sp., I. striolatus; e 26 ocorreram em arenito, sendo das espécies I. pectinada e I. striolatus. Foram observados quitons coabitando substratos com algas, gastrópodes, ostras, esponjas, poliquetas, coral, cracas, ascidías e em associações. As espécies I. striolatus e I. pectinata são comumente abundantes nas regiões estudadas e são necessários novos estudos para a compreensão das relações ecológicas dos quítons com os substratos consolidado de regiões costeiras.

Introduction: Chitons are marine molluscs, mostly grazers, resistant to tidal conditions and often living in crevices of rocks. The Oman Sea is located in the southeast of Iran and the northwest of the Indian Ocean and is heavily influenced by the monsoon winds of the Indian Ocean. Due to the occurrence of the monsoon process, the Makoran Sea has a rich variety of marine species, including molluscs. The aim of the present research was to investigate the density and distribution of Acanthopleura vaillantii in the beaches of Pozm, Konarak, Tis, Kolbe Ghawasi, Darya Bozorg and Ramin in winter 2018 and summer 2019.Materials and Methods: In this study, the density and distribution of A. vaillantii was investigated in transects perpendicular to the sea and in the tidal zone, using a quadrat (1*1 m2). in the tidal zone of six stations on the coasts of Pozm, Konarak, Tis, Kolbe Ghavasi, Darya Bozorg and Ramin. A number of samples in each station were taken to the laboratory to measure biological parameters such as length, total wet weight, soft tissue moisture content, tissue moisture percentage and dry weight percentage. In each station, physical and chemical factors of water (temperature-salinity and acidity) were measured and recorded by WTW device. Results: Investigations showed that the highest average density in the winter of 2018 was in Ramin station and was equal to 11.27 ± 1.46 m2. In total, Ramin station had the highest average density in winter and summer with a value of 19.15 ± 2.67 m2. Also, the lowest average density was related to the diving hut station in summer and the first transect of the lower part of the tide, which was not recorded due to the presence of a sandy bed. In total, the average density for two seasons was 0.85 ± 0.26 m2 at the Kolbeh ghavasi station. Also, the statistical test showed a significant difference between the stations (P

Abstract This paper presents the first teratological records for Peruvian waters of Chiton cumingsii Frembly, 1827 and Chiton granosus Frembly, 1827, both species very common in the Southeast Pacific. We found five abnormal individuals in C. cumingsii, and two in C. granosus, including the first recorded splitting abnormalities for these species. An individual of C. cumingsii with a new insertion plate in the tail valve was also observed. We observed that splitting abnormalities in Polyplacophora can be classified as perfect or imperfect, depending on whether the splitted valves are clearly recognized as individual fragments or not. Coalescence between the splitted valves seems to be a common phenomenon, and this coalescence can be homogeneous or heterogeneous. As both species show a combination of hypomerism, coalescence and splitting, we suggest that they are probably interrelated and represent an attempt of the developmental mechanisms of chitons to overcome a valve malformation.

In the present study, the complete mitochondrial genome of Lepidozona coreanica was sequenced and described. The complete mitogenome sequence of L. coreanica is 16,572 bp long and contains 13 protein-coding genes (PCGs), 22 transfer RNA (tRNA) genes, and two ribosomal RNA (rRNA) genes. The base composition was AT biased (70.1%). The 13 PCGs of L. coreanica and the other 15 species of Polyplacophora were used for phylogenetic analysis using maximum-likelihood methods. The results showed that L. coreanica, Ischnochiton hakodadensis, and Chaetopleura apiculata are sister groups of the three lineages.

An unusual new genus and species of chiton, Boreacanthus griphus n. g. &n. sp. isdescribed from the shallow subtidal depths of the central Aleutian Islands, and is tentatively placed in the family Mopaliidae Dall, 1889. The tail valve of the new taxon has a caudal sinus typical of the family Mopaliidae, but differs from all other known members of Mopaliidae in possessing pustulose tegmental sculpture and spike-like, calcareous girdle elements. [ABSTRACT FROM AUTHOR]

In the present study, the complete mitochondrial genome of Lepidozona coreanica was sequenced and described. The complete mitogenome sequence of L. coreanica is 16,572 bp long and contains 13 protein-coding genes (PCGs), 22 transfer RNA (tRNA) genes, and two ribosomal RNA (rRNA) genes. The base composition was AT biased (70.1%). The 13 PCGs of L. coreanica and the other 15 species of Polyplacophora were used for phylogenetic analysis using maximum-likelihood methods. The results showed that L. coreanica, Ischnochiton hakodadensis, and Chaetopleura apiculata are sister groups of the three lineages. [ABSTRACT FROM AUTHOR]

Over hundreds of millions of years, organisms have evolved architected structures via precise control over hierarchically assembled components, including the integration of dissimilar materials. One such example is found in the radula system of chitons, intertidal mollusks that feed on algae growing on the rock. Their radula consists of multiple rows of ultrahard teeth, each integrated with a foldable belt-like substrate via a stiff, yet flexible stylus, which is essential for efficient rasping during the feeding process. Here, we investigate the nano and micro-scale components and architectures as well as regional mechanical properties of the stylus, and their subsequent role during the rasping of Cryptochiton stelleri. Three important factors were determined to contribute to the regio-specific stiffness of the stylus: the presence of mineral components, highly oriented chitinous fibers, and a chemically cross-linked protein matrix. All these factors are varied throughout the stylus. There is a high mineral content on the trailing edge close to the tooth and a cross-linked matrix on the leading edge, both with orientational specific oriented chitin fibers that provide force transduction to the tooth. Conversely, there is a significant lack of mineral or cross-linked matrix in the proximal end as well as a low degree of fiber orientation, resulting in a flexible region that can accommodate torsion and flexure during rasping. Understanding the graded composite structure of the stylus and applying this unique design to various engineering fields such as soft robotics, biotechnology, and the medical industry, can inspire the production of high-performance materials. Graphical Abstract [ABSTRACT FROM AUTHOR]

Six previously undescribed spiromeroterpenoids, chermesins I-N (1-6), were isolated and identified from the marine-sourced fungus Penicillium chermesinum AS-400. Their structures were determined by nuclear magnetic resonance and mass spectroscopic data, and the relative and absolute configurations were confirmed based on nuclear Overhauser effect spectroscopic experiments, electronic circular dichroism (ECD) calculations and X-ray crystallographic analysis, and by comparisons of ECD Cotton effects with those of known congeners as well. Structurally, compound 1 represents the first example of spiromeroterpenoid demethylated at C-4. The isolated compounds exhibited inhibitory activities against several aquatic and human pathogenic bacteria with MIC values ranging from 4 to 64 μg/mL., Competing Interests: Declaration of competing interest The authors declare that they have no competing financial interest or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2025 Elsevier Ltd. All rights reserved.)

Introducing biological structures into materials design is expected to develop strong and tough structural materials. However, multiple interfaces are introduced simultaneously. They are always the weakest part of load transfer, becoming a critical vulnerability and failure-prone area. Here, it is the first found that the chiton achieves superior mechanical properties just by incorporating a unique sinusoidal interlocking interface into cross-lamellar architecture. These special interlocking interfaces make the chiton shell achieve damage delocalization and increase the resistance to crack initiation and propagation. Meanwhile, this "pre-engineered" path significantly increases the travel path of the cracks and balances the strength and toughness under quasi-static and impact loading. Inspired by this, a novel chiton-inspired composite is proposed. Through coupling the cross-lamellar structures and sinusoidal interlocking interfaces, its strength and toughness are increased by 88% and 107% under quasi-static loading, as well as by 17.8% and 52.4% under impact loading, respectively. These unusual interfaces make up the weak point of cross-lamellar structures and provide insights into the longer evolution of structural materials., (© 2024 Wiley‐VCH GmbH.)

Chiton teeth in the radula are one of the hardest biomaterials in nature. Chiton uses radula to scrape algae on hard surfaces. The ultrastructure and composition of teeth are well known while how they move is less clear. This study used an array of material characterizations including soft-tissue micro-computed tomography (micro-CT), histology, scanning electron microscopy, and proteomics to investigate the tissue that may control the movement of the radula of Acanthopleura loochooana. Surprisingly, unusually complex muscle fibers were found around the radula. 54 muscle fibers with diameters of around 130 µm were anchored to the second and third shell plates. These muscle fibers are in close contact with the radula and cartilage beneath the radula. Proteomics using a recently published chiton genome as a reference confirmed the proteins related to energy metabolism, calcium metabolism, as well as a cartilage oligomeric matrix protein in the muscle. qPCR found that the above proteins were highly expressed in the radula muscle compared to the foot. Taken together, this study provides insights into the complex tissue structures that control the movement of the radula, which may inspire robotics design relating to hard-soft tissue interfaces.

This study documents a new deep-sea chiton from the Haima cold seeps. Thermochiton xui. nov. is the third species of the genus Thermochiton and the first occurrence of this genus in the South China Sea. This species is identified by its morphological characteristics and the molecular sequence of a Thermochiton species is reported for the first time. The placement of the new species is determined in the phylogenetic tree of Ischnochitonidae by Maximum Likelihood (ML) and Bayesian inference (BI) methods, based on the sequences of the mitochondrial cytochrome c oxidase subunit I (COI), 16S ribosomal DNA (16S), and nuclear 28S ribosomal DNA (28S) gene regions. Bayesian evolutionary analysis with an uncorrelated relaxed clock approach indicated that this new species is estimated to have diverged from its most closely related shallow-water ischnochitonid taxa 5.10–10.07 million years ago in the Late Miocene. A regional ocean general circulation model was used to estimate the potential dispersal ability of the three species of Thermochiton. Because it is highly unlikely for one species to have spread between the northwest and southwest Pacific to the localities in which this genus has been found to date, we propose that ‘stepping-stone’ habitats and/or ‘bridge species’ were involved in the dispersal and evolution of these cold-seep endemic chitons.The ZooBank Life Science Identifier (LSID) for this publication is: urn:lsid:zoobank.org:pub:AD93E4BC-2977-405E-B681-D956C5C66D83. And the ISID for Thermochiton xui sp. nov. is: urn:lsid:zoobank.org:act:0C75D2E3-F30E-4970-9BC2-3363B397720C.

The first step for animals to interact with external environment is to sense. Unlike vertebrate animals with flexibility, it is challenging for ancient animals that are less flexible especially for mollusca with heavy shells. Chiton, as an example, has eight overlapping shells covering almost the whole body, is known to incorporate sensory units called aesthetes inside the shell. We used micro-computed tomography combined with quantitative image analysis to reveal the optimized shell geometry to resist force and the aesthetes' global distribution at the whole animal levels to facilitate sense from diverse directions both in the seawater and air. Additionally, shell proteomics combined with transcriptome reveals shell matrix proteins responsible for shell construction and potentially sensory function, highlighting unique cadherin-related proteins among mollusca. Together, this multi-level evidence of sensory units in the chiton shell may shed light on the formation of chiton shells and inspire the design of hard armor with sensory function. [ABSTRACT FROM AUTHOR]

Major ecological disturbance events can provide opportunities to assess multispecies responses to upheaval. In particular, catastrophic disturbances that regionally extirpate habitat‐forming species can potentially influence the genetic diversity of large numbers of codistributed taxa. However, due to the rarity of such disturbance events over ecological timeframes, the genetic dynamics of multispecies recolonization processes have remained little understood. Here, we use single nucleotide polymorphism (SNP) data from multiple coastal species to track the dynamics of cocolonization events in response to ancient earthquake disturbance in southern New Zealand. Specifically, we use a comparative phylogeographic approach to understand the extent to which epifauna (with varying ecological associations with their macroalgal hosts) share comparable spatial and temporal recolonization patterns. Our study reveals concordant disturbance‐related phylogeographic breaks in two intertidal macroalgal species along with two associated epibiotic species (a chiton and an isopod). By contrast, two codistributed species, one of which is an epibiotic amphipod and the other a subtidal macroalga, show few, if any, genetic effects of palaeoseismic coastal uplift. Phylogeographic model selection reveals similar post‐uplift recolonization routes for the epibiotic chiton and isopod and their macroalgal hosts. Additionally, codemographic analyses support synchronous population expansions of these four phylogeographically similar taxa. Our findings indicate that coastal paleoseismic activity has driven concordant impacts on multiple codistributed species, with concerted recolonization events probably facilitated by macroalgal rafting. These results highlight that high‐resolution comparative genomic data can help reconstruct concerted multispecies responses to recent ecological disturbance. [ABSTRACT FROM AUTHOR]

The edible chiton C hiton articulatus is a commercially important mollusk found in the rocky intertidal zones of the Mexican tropical Pacific. Despite the intense harvesting in Acapulco Bay, Mexico, knowledge of its growth patterns is limited, hindering the development of effective management strategies. This study investigated the growth dynamics of C. articulatus using a multi-model inference approach based on size structure data collected in four sampling periods covering four decades. Results revealed continuous recruitment throughout the year, contributing to population resilience. The species exhibited growth plasticity, highlighting its adaptive potential. We found complex temporal patterns influenced mainly by climatic events. The El Niño event sowed higher growth rates and lower asymptotic length, while La Niña events showed the opposite pattern. This research provides insights into the growth dynamics of C. articulatus , highlighting the need for holistic management strategies for this commercially important species in the face of environmental change. [Display omitted] • Continuous recruitment of Chiton articulatus contributes to population resilience. • C. articulatus shows growth plasticity under varying environmental conditions. • El Niño: faster growth, lower asymptotic lengths in C. articulatus. • La Niña: slower growth, higher maximum lengths in C. articulatus. • Holistic approach vital for C. articulatus growth dynamics and management. [ABSTRACT FROM AUTHOR]

Engineering structures that bridge between elements with disparate mechanical properties are a significant challenge. Organisms reap synergy by creating complex shapes that are intricately graded. For instance, the wear-resistant cusp of the chiton radula tooth works in concert with progressively softer microarchitectural units as the mollusk grazes on and erodes rock. Herein, we focus on the stylus that connects the ultrahard and stiff tooth head to the flexible radula membrane. Using techniques that are especially suited to probe the rich chemistry of iron at high spatial resolution, in particular synchrotron Mössbauer and X-ray absorption spectroscopy, we find that the upper stylus of Cryptochiton stelleri is in fact a mineralized tissue. Remarkably, the inorganic phase is nano disperse santabarbaraite, an amorphous ferric hydroxyphosphate that has not been observed as a biomineral. The presence of two persistent polyamorphic phases, amorphous ferric phosphate and santabarbaraite, in close proximity, is a unique aspect that demonstrates the level of control over phase transformations in C. stelleri dentition. The stylus is a highly graded material in that its mineral content and mechanical properties vary by a factor of 3 to 8 over distances of a few hundred micrometers, seamlessly bridging between the soft radula and the hard tooth head. The use of amorphous phases that are low in iron and high in water content may be key to increasing the specific strength of the stylus. Finally, we show that we can distill these insights into design criteria for inks for additive manufacturing of highly tunable chitosan-based composites. [ABSTRACT FROM AUTHOR]

The Greek vocabulary of clothing and textile production is rich and varied. It contains hundreds of words that have survived in literary texts or in epigraphic resources. Ancient lexicographers attempted to compile these terms but the meaning of many of them has disappeared, only a few can be identified with certainty in visual representations. The clothing nomenclature used today was mainly established by German academics in the 19th century and has become widely adopted. However, modern studies show that some of these interpretations could be questioned. In this situation, what words should be used to designate Greek garments represented on artworks? There are different propositions: continue to use Greek terms conventionally or try to establish alternative nomenclature. In this paper it is argued that the use of modern generic terms could minimise problems of interpretation in the study of Greek clothing [ABSTRACT FROM AUTHOR]

Teratological specimens deviate from the conserved form of their species. In doing so, they serve as natural experiments that refine our knowledge of developmental mechanisms and the natural limits of phenotypes. Here, we describe a specimen of the West Indian Fuzzy Chiton Acanthopleura granulata (Gmelin, 1791) with a fifth valve split into two halves. Using micro‐CT to non‐invasively visualize the external and internal morphology of this specimen, we find that the half valves are symmetrical and independent from each other and from any of the other valves. The presence of girdle‐like tissue between the split valves suggests that this shell abnormality arose in early development and was not the product of damage to the adult animal. While the present specimen of A. granulata is clearly abnormal for its species, its split valve may provide some insights into the developmental pathways that would underlie macroevolutionary transitions to multi‐plated chiton forms known from the fossil record. [ABSTRACT FROM AUTHOR]

Iron is critical for life. Nature capitalizes on the physical attributes of iron biominerals for functional, structural, and sensory applications. Iron biomineralization is well exemplified by the magnetite‐bearing radula of chitons, the hardest known biomineral of any animal. Although magnetism is an integral property of iron biominerals, limited information exists on the magnetic state, structure, and orientation of these nanoscale materials during mineralization. The advent of quantum‐based magnetic microscopy provides a new avenue to probe these biological systems directly, providing detailed magnetic information of the iron oxide structures. Here two complementary quantum magnetic microscopy methods are applied, based on nitrogen‐vacancy centers in diamond, to spatially map the mineral phases ferrihydrite and magnetite in the developing teeth of the chiton Acanthopleura hirtosa. The images reveal previously undiscovered long‐range magnetic order, established at the onset of magnetite mineralization. This is in contrast to electron microscopy studies that show no strong common crystallographic orientation. The implications of these results are important, not just for the insights gained in biomineralization of the target organism, but also for the study of a broad range of iron minerals in the physical and biological sciences. [ABSTRACT FROM AUTHOR]

The hard shells of mollusks are products of biomineralization, a distinctive feature of the Cambrian explosion. Despite our understanding of shell structure and mechanical properties, their origin remains mysterious. In addition to their shell plates, most chitons have calcium deposits on their girdles. However, the similarity of these two mineralized structures still needs to be determined, limiting our comprehension of their origins. In our study, we analyzed the matrix proteins in the spicules of chiton (Acanthopleura loochooana) and compared them with the matrix proteins in the shells of the same species. Proteomics identified 96 unique matrix proteins in spicules. Comparison of biomineralization-related matrix proteins in shell plates and spicules revealed shared proteins, including carbonic anhydrases, tyrosinase-hemocyanin, von Willebrand factor type A, cadherin, and glycine-rich unknown proteins. Based on similarities in key matrix proteins, we propose that spicules and shell plates originated from a common mineralization system in their ancestral lineage, suggesting the existence of a common core or toolkit of matrix proteins among calcifying organisms. In this study, we try to understand the types and diversity of matrix proteins in the biomineralization of chiton shell plates and spicules. Through a comparative analysis, we seek insights into the core biomineralization toolkit of ancestral mollusks. To achieve this, we conducted LC-MS/MS and RT-qPCR analyses to identify the types and relative expression levels of matrix proteins in both shell plates and spicules. The analysis revealed 96 matrix proteins in the spicules. A comparison of biomineralization-related matrix proteins in shell plates and spicules from the same species revealed shared proteins including many unknown proteins unique to chitons. Blast searching reveals a universal conservation of these proteins among other chitons. Hence, we propose that spicules and shell plates originated from a common mineralization system in their ancestral lineage. Our work provides a molecular basis for studying biomineralization in polyplacophoran mollusks and understanding biomineralization evolution. In addition, it identifies potential matrix proteins that could be applied to control crystal growth. [Display omitted] • 96 distinct matrix proteins were identified in chiton (Acanthopleura loochooana) spicules. • Spicules and shell plates may originate from a common mineralization system in their ancestral lineage. • A shared origin for spicules and shell plates implies a universal matrix protein toolkit among mollusca. [ABSTRACT FROM AUTHOR]

Most molluscs have mineralized shells to protect themselves. Although the remarkable mechanical properties of shells have been well-studied, the origin of shells is still elusive. Chitons are unique in molluscs because they are shelly Aculifera which diverged from Conchifera (comprising all the shell-bearing classes of molluscs) in the early pre-Cambrian. We developed a method to extract shell proteins from chiton shell plates (removing embedded soft tissues) and then compared the shell proteome to that of Conchifera groups. Sixteen shell matrix proteins from Acanthopleura loochooana were identified by proteomics, in which Nacrein-like, Pif-like proteins, and protocadherin were found. Additional evidences from shell proteome in another species Chiton densiliratus and comparative sequence alignment in five chitons supported a conserved biomineralization toolkit in chitons. Our findings shed light on the evolution of mineralization in chitons and pose a hypothesis that ancestral molluscs have already evolved biomineralization toolkits, which may facilitate the formation of mineralized shells. [Display omitted] • Sixteen shell matrix proteins from chiton Acanthopleura loochooana were identified by proteomics. • Nacrein-like, Pif-like proteins, and protocadherin were found to be conserved in chitons. • The formation mechanism of chiton shell biomineralization is deduced based on proteomics. [ABSTRACT FROM AUTHOR]

A new deep-sea chiton of the genus Placiphorella Dall, 1879, Placiporella laurae n. sp. is described from the Pacific coast of North America. It is compared with its congener Placiphorella pacifica Berry, 1919, from which it differs primarily by having granular valves, lacking false beaks, a papillose girdle, and the characteristics of its girdle spicules. [ABSTRACT FROM AUTHOR]

According to importance of Chabahar Bay as one of the marine strategic areas and need to learn about pollution of this area, in this study, Cu, Ni and Zn concentration was investigated in the soft tissue of chiton Acanthopleura vaillantii from 5 stations in the coast of Chabahar Bay at autumn of 1394. For this purpose, samples were collected and transferred to the laboratory, then after preparation and chemical digestion process, concentration of heavy metal was measured in soft tissue of Chiton by Atomic Absorption spectrophotometer. The results showed that the mean of concentration of heavy metals in soft tissue of Chiton had a pattern just Zn> Ni> Cu. Statistical analysis showed that all stations had significant differences (P

Things without names are difficult to rationalise, and so species that go without names are difficult to conserve or protect. This is a case study in resolving conflicts in historical taxonomy and ‘real’ species (identifiable and evolutionarily relevant groupings) using an approach including population genetics, natural history, and pragmatism. We report the observation that populations of a shallow-water chiton species from Washington and British Columbia demonstrate extremely high site fidelity and patchy distribution. Their limited dispersal potential and isolation could be explained by a brooding life history. This stands in direct contrast with the supposedly wide distribution of this “species”, Leptochiton rugatus (Carpenter in Pilsbry, 1892) sensu lato, from the Sea of Japan to Baja California. But this lineage has previously been suggested to comprise several cryptic species. Indeed, a haplotype network analysis using 61 individual sequences of the cytochrome oxidase c subunit I gene for L. rugatus s.l. revealed four discrete clusters which correspond to different parts of the geographic range. We infer these to represent four distinct species, at least two of which are likely novel. Leptochiton rugatus sensu stricto is herein reinterpreted as restricted to California and Baja California, and the new name L. cascadiensis sp. nov. is established for the lineage with a distribution in the Cascadia coastal bioregion from the panhandle of Alaska to Oregon. There are minor morphological differences among these species in the L. rugatus species complex, but genetic data or morphological observations alone would not have been sufficient to definitively recognise these groups as species-level lineages. The observation that different species within the complex may have different life history strategies provides important support for interpreting different populations as genuinely separate species. [ABSTRACT FROM AUTHOR]

Two chiton specimens were collected from sedimentary habitat by China’s manned Jiaolong submersible diving to a depth of 6 754 m in the north of the Yap Trench. This is a new locality record for chiton. Both morphological and molecular data support that the two specimens are the same species belonging to the genus Leptochiton. Morphologically, this species strongly resembles L. vanbellei and L. deforgesi. Phylogenetically, it has a close evolutionary relationship with L. vanbellei, L. deforgesi and L. boucheti. This is the third deepest record for deepsea chitons so far. [ABSTRACT FROM AUTHOR]

The present study provides new documented cases of abnormalities on chitons (hypomerism and coalescence of shell plates), in addition to four new cases on keyhole limpets (closed apical opening), and one new teratologic case on internal organs in octopuses (missing gill). We assess the frequency of these abnormalities and discuss about its possible environmental, mechanic and genetic causes. Several of these findings represent the first of these cases reported in South Pacific Ocean. [ABSTRACT FROM AUTHOR]

Compared to stable reef habitats, dynamic boulder-reefs (commonly called boulder-fields when intertidal) host many habitat specialist species. Most occur underneath boulders where they are largely hidden from view; only limited research has assessed their life-histories despite their widespread importance for biological diversity. But some abundant under-boulder species likely structuring this system are habitat generalists widely researched elsewhere. Here we review this research, focusing on three widespread under-boulder sessile taxa: spirorbids, serpulids (tubeworms) and nongeniculate coralline algae, and three mobile taxa: sea urchins, chitons and crabs. Spirorbids have extensive reproductive/colonization capabilities but are readily out-competed. We thus characterize spirorbids as mostly early-successional, while serpulids often have greater competitiveness. Nongeniculate corallines occur underneath boulders where light reaches, although they can withstand low levels of that and most other resources. Such traits characterize nongeniculate corallines as late-successional. Thus, succession underneath boulders may shift deterministically from early tubeworms to late nongeniculate corallines. Habitat generalist sea urchin and chiton species often have strong inter-specific interactions in exposed habitats. Future experiments may find that under-boulder aggregations of these taxa, and also crabs, are impacting algal and invertebrate assemblages. These experiments will be required if dynamic boulder-reefs are to be as thoroughly understood as other benthic systems. [ABSTRACT FROM AUTHOR]

Chiton (Ischnochiton hakodadensis) is one of marine mollusks well known for its eight separate shell plates. I. hakodadensis is important, which plays a vital role in the ecosystems it inhabits. So far, the genetic studies on the chiton are scarce due in part to insufficient genomic resources available for this species. In this study, we investigated the transcriptome of the chiton foot using Illumina sequencing technology. The reads were assembled and clustered into 256461 unigenes, of which 42247 were divided into diverse functional categories by Gene Ontology (GO) annotation terms, and 17256 mapped onto 365 pathways by KEGG pathway mapping. Meanwhile, a set of differentially expressed genes (DEGs) between distal and proximal muscles were identified as the foot adhesive locomotion associated, thus were useful for our future studies. Moreover, up to 679384 high-quality single nucleotide polymorphisms (SNPs) and 19814 simple sequence repeats (SSRs) were identified in this study, which are valuable for subsequent studies on genetic diversity and variation. The transcriptomic resource obtained in this study should aid to future genetic and genomic studies of chiton. [ABSTRACT FROM AUTHOR]

Variations of the radula and shell microstructures in 33 species of Japanese chiton were investigated along with molecular phylogenetic trees. The molecular phylogenetic trees indicated that Chitonida was composed of four clades, of which two clades formed Acanthochitonina and corresponded to Mopalioidea and Cryptoplacoidea, respectively, and the other clades formed Chitonina. In the radula, the shapes of the central and centro-lateral teeth and the petaloid process varied greatly among species or genera and were useful for the identification of particular species or genera. The presence of accessory and petaloid processes and the cusp shape were relatively conserved and useful for recognizing particular genera or even suborders. In the valves, four to six shell layers were found at the section, but the ventral mesostracum was not observed in Acanthochitonina. The shell microstructures in the ventral sublayer of the tegmentum varied at suborder, but those in the other layers were almost constant. The megalaesthete chamber type varied at superfamily and was helpful to identify particular families or superfamilies. The characteristics of the shell layers and shell microstructures appear to be a synapomorphy shared by the members of Acanthochitonina. The classification within Chitonina needs to be reexamined because the variations of the cusp shape and megalaesthete chamber type were relatively large and did not correspond to the current classification. Callochiton formed a sister group with Chitonida and would be equally closely related to Chitonina and Acanthochitonina because of possessing a mosaic of characteristics from both.