Shell Morphology Research Articles

A new species of Petraeomastus Möllendorff, 1901 (Gastropoda: Stylommatophora: Enidae) with a varied shell from the Daduhe River Valley in southwest China

AbstractA new enid land snail, Petraeomastus liuzhengpingi Z.-G. Chen & Z.-Y. Chen, sp. n. is described from Danba County, Sichuan Province, China based on shell and genital morphology. The new species displays a varied shell morphology with some individuals exhibiting a completely detached last whorl, which is the first record of this phenomenon in the family Enidae. The discovery contributes to our understanding of the high species diversity of Enidae in the dry-hot river valleys in China.

Possible roles of Wnt in the shell growth of the pond snail Lymnaea stagnalis

Although the mechanisms of molluscan shell growth have been studied using mathematical models, little is known about the molecular basis underpinning shell morphogenesis. Here, we performed Wnt activation experiments to elucidate the potential roles of Wnt signaling in the shell growth of Lymnaea stagnalis. In general, we observed following three types of shell malformations in both dose- and developmental stage-dependent manners: (i) cap-shaped shell, (ii) cap-shaped shell with hydropic soft tissues, and (iii) compressed shell with a smaller number of coiling. We analyzed the morphologies of these malformed shells using the growing tube model, revealing that the compressed malformations show significantly larger values for T (torsion), with no significant changes in the values for the remaining parameters E (expansion) and C (curvature). We also found that cap-shaped malformations have significantly larger values for E, suggesting that the effects of BIO on shell formation may change during growth. Since the changes in T and/or E parameter values can greatly alter the shell morphologies from a planispiral or a cap-shaped one to various three-dimensional helices, changes in shell developmental processes possibly controlled by Wnt signaling may account for at least a part of the evolution of diverse shell forms in molluscs.

Molecular phylogeny reveals a new genus and species of freshwater mussel (Bivalvia, Unionidae, Gonideinae) from Jiangxi, China

Freshwater mussels of the tribe Gonideini (Bivalvia: Unionidae: Gonideinae) constitute one of the most taxonomically diverse groups and serve as keystone species in riverine and lacustrine ecosystems across East Asia. A new genus and species of Gonideini (Bivalvia: Unionidae) is described from Jiangxi, China, as Pseudopostolata angulagen. et sp. nov. based on an integrative analysis of shell morphology and molecular data. The validity of the new genus and species is supported by distinct conchological features: a short, rounded anterior; a long, wide posterior; a slightly downward-curved dorsal margin; and a distinctly obtuse angle at the center of the posterior margin. The multi-locus (COI + 16S rRNA + 28S rRNA) phylogeny showed that the species formed a monophyletic group in the tribe Gonideini of the subfamily Gonideinae. Pseudopostolata angulagen. et sp. nov. is identified as the sister group to a clade comprising the genera Postolata, Cosmopseudodon, Obovalis, Ptychorhynchus, Parvasolenaia, and Koreosolenaia. We emphasize the significant morphological convergence in freshwater mussels, particularly within Gonideini, highlighting the necessity of an integrated taxonomic approach for accurate generic classification of this group.

A preliminary key for the genera of sinistral Triphoridae

A preliminary key for the discrimination of sinistral Triphoridae genera, limited to those represented by living species, is presented. Some images are provided to display the characters used in the key. A series of notes highlights doubts and uncertainties, which would require more in-depth studies than those available today.

Plasmonic Nanocubes with a Controllable "Crescent Arc" Facet: Tunable Hotspot Engineering for Highly Reliable and Sensitive SERS Detection.

The fine control of the nanogap and morphology of metal nanoparticles (NPs) has always been an obstacle, hindering the development and application of surface-enhanced Raman scattering (SERS) quantitative detection. Here, Au/4-mercaptobenzoic acid@Ag@Au-Ag bimetal core-shell nanocubes (NCs) with a "crescent arc" facet (C-Au/4MBA@Ag NCs) as a highly reliable and sensitive surface-enhanced Raman scattering SERS substrate is proposed for the first time. The bifunctional internal standard (IS) molecules (4MBA) govern the morphology of metal shells to maintain cubic configuration and provide calibration for SERS signals' flotation. In parallel, the controllable curvature of the C-Au/4MBA@Ag NCs is directly modulated by adjusting the relative rates of the galvanic replacement and co-reduction reaction, which generates a controllable interparticle nanogap to offer large depositing spaces for analytes and improve authoritative SERS signals' enhancement. The proposed C-Au/4MBA@Ag NCs exhibit an enhancement factor of up to 4.8 × 1010 and contribute to the ultralow RSD (7.9%). These C-Au/4MBA@Ag NCs also enable the detection of hazardous pesticide residues such as methamidophos and thiram in herbal plants with a complex matrix, with an average detection accuracy of up to 96%. In summary, this study achieves a fine control strategy of the "crescent arc" surface for improving SERS performance and explores the practical application potential for accurate and sensitive Raman detection of hazardous substances.

Aesthete Pattern Diversity in Chiton Clades (Mollusca: Polyplacophora): Balancing Sensory Structures and Strength in Valve Architecture.

Chitons possess the most elaborate system of shell pores found in any hard-shelled invertebrate. Although chitons possess some anteriorly located sense organs, they lack true cephalization, as their major sensory systems are not concentrated in a distinct head region. Instead, the aesthete system within their shells forms a dense sensory network that overcomes the barrier of their hard dorsal armour. The basic arrangement of neural structures embedded within a solid, opaque matrix, has confounded understanding of the overall network. In this study, we use synchrotron X-ray μCT to visualise the aesthete canal networks inside chiton valves. We selected representatives from all three major chiton clades: Lepidopleurida, the basal branching clade, and Callochitonida and Chitonida, which both havemore complex shell morphology, to compare internal structure. Lepidopleurida aesthete canals are oriented vertically and pass directly through the shell to connect with the body. By contrast, aesthetes canals in Callochitonida and Chitonida have complex internal structures with extended horizontal passages, coalescing at the shell diagonal that corresponds to the valve insertion slits. This represents a stepwise evolution of chiton shell form, where thicker and more complex valves require a diverting and rewiring of the entire sensorynetwork. Aspects of the aesthete system, such as the microscopic arrangement of surface pores, have long been used in chiton taxonomy for species diagnoses; insertion slits should also be understood as a secondary feature of the aesthete system. Chiton shell structures that are used for morphological systematics are driven by sensory adaptations.

Assessing shell morphology in freshwater mussels (Mollusca: Bivalvia: Unionidae) from the Maâden River, Tunisia: Insights from geometric morphometrics and shape descriptors

Identifying freshwater mussel species within the Unionidae family can be challenging due to systematic confusion. This study investigates shell shapes to identify four sympatric species of freshwater mussels (Potamida littoralis, Unio durieui, U. gibbus, and U. ravoisieri) in the Maâden river (northern Tunisia) using two morphological approaches: global shape descriptors and geometric morphometrics of shell contours. The results revealed significant differences in global shape descriptors among the species. More in-depth analyses showed distinct shape variations, with P. littoralis and U. gibbus significantly differing from U. durieui and U. ravoisieri across most descriptors. Notably, U. durieui and U. ravoisieri exhibited similar shape traits, differing primarily in roundness, characterized by low circularity and high ellipticity. Principal Component Analyses depicted substantial morphological variance, with Procrustes data requiring the first two components to fully elucidate dispersion. Linear Discriminant Analysis revealed effective discrimination among species, with an accuracy rate of over 74 % in classifying individuals into their respective populations across both approaches. Geospatial analyses indicated varying influences of latitude, longitude, and altitude on shell morphology among species. Latitude had noteworthy impacts on P. littoralis, approaching significance for shape descriptors and Procrustes data. Conversely, U. durieui and U. gibbus displayed minimal geographic influence on shell morphology, while U. ravoisieri showed significant variations across these parameters. This study highlights the distinct morphological differences among sympatric mussel species in northern Tunisia, providing valuable insights for conservation efforts, especially for species vulnerable to climate change.

Predicting rapid adaptation in time from adaptation in space: A 30-year field experiment in marine snails

Predicting the outcomes of adaptation is a major goal of evolutionary biology. When temporal changes in the environment mirror spatial gradients, it opens up the potential for predicting the course of adaptive evolution over time based on patterns of spatial genetic and phenotypic variation. We assessed this approach in a 30-year transplant experiment in the intertidal snail Littorina saxatilis . In 1992, snails were transplanted from a predation-dominated environment to one dominated by wave action. On the basis of spatial patterns, we predicted transitions in shell size and morphology, allele frequencies at positions throughout the genome, and chromosomal rearrangement frequencies. Observed changes closely agreed with predictions and transformation was both dramatic and rapid. Hence, adaptation can be predicted from knowledge of the phenotypic and genetic variation among populations.

Shell morphology and reproductive anatomy of Levantina mardinensis (Gastropoda, Helicidae) from a new locality of Mardin, Türkiye

ABSTRACT The genus Levantina Kobelt, 1871, comprises 25 taxa inhabiting rocky environments across the Middle East. This study focuses on documenting a new location of L. mardinensis Kobelt, 1900, and provides a detailed analysis of its shell morphology and reproductive anatomy, contributing to the knowledge and conservation of this land snail from Mardin, southeastern Türkiye. The distribution of L. mardinensis is widespread in Mardin Province and extends into northern Syria and Iraq. The study provides measurements for previously unreported shell characteristics of specimens from Eskikale (Mardin), including aperture height, aperture width, spire height, and body whorl height, with high-resolution images for visual reference.

Three new species of Camaena Albers, 1850 (Gastropoda, Stylommatophora, Camaenidae) from Guizhou and Guangxi, China

AbstractThree new species of camaenid land snail, Camaena qiannanensis Chen, Dai, Wu & Ouyang sp. n., Camaena feichenyui Chen, Dai, Wu & Ouyang sp. n. and Camaena qinghuai Chen, Dai, Wu & Ouyang sp. n. are described from Guizhou and Guangxi of southern China based on shell and genital morphology, and molecular phylogeny. The phylogenetic result shows that the genus Camaena is not a monophyletic group, with Camaenella located within it. The discovery enhances the species diversity of Camaena in Southern China and fills the gap between distribution areas of known species.

A new genus and species of Nassariidae (Gastropoda: Neogastropoda) from the Red Sea

ABSTRACT Based on specimens collected from the Yemeni shore of the Red Sea, Yemeninassoides inusitatus gen. & sp. nov. is here described and figured. The shell morphology suggests that this species belongs to the family Nassariidae Iredale, 1916. The new taxon is characterised by light shell, base finely spirally lyrate, open umbilicus and multispiral non-keeled protoconch sculptured by spiral cords and arcuate axial riblets. The combination of these morphological features is so far unique and makes the new taxon easily distinguishable from all other known species and genera in the family Nassariidae. https://zoobank.org/References/0E009334-D9C7-4CC7-9A06-466582E1F263

Assessing the spatial variability of cage movement and velocity attenuation of an off-bottom oyster farm and its influence on eastern oyster (Crassostrea virginica) growth performance

The global shellfish aquaculture industry has expanded over the last seven decades. Similarly, the size of individual shellfish farming operations has grown in some states. Circulation processes in natural water bodies are dynamic and vary across multiple temporal and spatial scales. How gear installation affects the circulation of currents and waves, and subsequent phytoplankton delivery to crops within farms, is largely unknown. Documenting and understanding variability in wave and current energy within an individual farm could help optimize production. Our study sought to understand the variability in oyster growth attributable to hydrodynamic and atmospheric forcing across an active commercial shellfish aquaculture lease in the Patuxent River, Maryland. We observed a 17 % reduction in water flow downstream of the farm (rho = −0.673, p = 0.002, Spearman rank test), suggesting the bottom cages attenuated downstream current velocity during flood tides. Differences in flow speed and the movement of cages and oysters throughout the farm correlated with variances in oyster shell morphology and oyster survival while in bottom cages. Our results demonstrate the occurrence of variability in production within an individual farm location. Further, our findings suggest that insight into the spatial growth patterns across a lease can be practical for forecasting growth and quality of cultured oysters and may enable growers to strategically place oysters within their farm to improve yield and product consistency.

Speciation in the desert: A new endemic Iberus land snail restricted to the southeastern Iberian Peninsula

Arid habitats constitute harsh environments for hydrophilic animals such as land snails. Still, several land snail species appear to inhabit arid environments and such species present an array of adaptations needed to minimise water loss in dry habitats. However, different species may have found different solutions for the same problem. Here, we describe Iberus xerophilus sp. nov., a new species of arid-dwelling land snail from southeastern Spain, on the basis of phylogenetic analyses. Moreover, we show a detailed morphological description as well as a characterization of its habitat. A comparison with the shell morphology of other aridity resistant Iberus land snails casts the question of how this snail can succeed in such harsh arid environments. Southeastern Spain constitutes a hotspot for Iberus arid-dwelling species, displaying a plethora of shell morphologies. The description of this new species might contribute to our understanding of the evolution and diversification of land snails specifically adapted to drought and arid conditions.

Characterization and Optimization of Crustacean Shell-derived Activated Carbon for Wastewater Treatment Applications

Comparative studies of the Surface Chemistry, morphology, and physicochemical properties of crustacean shells activated chemically using acid (H2SO4) and base (KOH) were investigated. Following the activation, samples of acid and base activated Periwinkle shells (PSAAC and PSBAC), Clam shells (CSAAC and CSBAC), whelk shells (WSAAC and WSBAC), and a 1:1 Clam/Whelk composite Shells (CWSAAC and CWSBAC) were obtained. The properties investigated were moisture content, specific gravity, surface area, porosity, ash content, carbon yield, fixed carbon, FTIR, and SEM-EDX. The findings demonstrate the good physicochemical qualities of activated carbons made from Periwinkle, Clams, Whelks, and a Clam/Whelk composite by acid and base activation for the treatment of wastewater. Among them, the Clam acid-activated carbon (CSAAC) demonstrated exceptional physicochemical qualities with a surface area of 1277 m2/g, moisture content of 1.4%, ash content of 8.3%, carbon yield of 87%, and fixed carbon of 63.7%. On the other hand, the Clam Shell Base-Activated Carbon (CSBAC) exhibited a greater porosity of 0.88, indicating that it could be a more efficient option for adsorption in wastewater treatment. Both base- and acid-activated carbons generally showed modest ash contents; however, at 12.3%, Whelk Shell Base-Activated Carbon (WSBAC) had the highest ash concentration. The bulk densities of acid- and base-activated carbons were almost identical. The bulk densities, from highest to lowest, were CSBAC > CSAAC > CWSBAC > CWSAAC > PSBAC > PSAAC > WSBAC > WSAAC, with values ranging from 0.687 g/cm³ to 0.454 g/cm³. The porosity of the samples, ranked in descending order, was CSBAC > PSBAC > CSAAC > CWSAAC > PSAAC = CWSBAC > WSAAC > WSBAC, with values from 0.88 to 0.59. FTIR and SEM-EDX indicated that all samples were successfully converted to activated carbon. The results of this study demonstrate that it is possible to chemically activate crustacean shells using either an acid or a base without sacrificing the effectiveness of the activated sample that is produced, which can be used to remove adsorbates from wastewater samples. As a result, the selection of activation is widened since the natural abundance of precursors exists.

The genus Kelliella (Bivalvia) in the Atlantic Ocean

ABSTRACT Kelliella M. Sars, 1870 is a genus of small epibenthic bivalves inhabiting muddy bottoms of the outer shelf and slope worldwide, commonly in habitats that are oxygen-poor or enriched in organic carbon. Currently, there are five accepted species of Kelliella with an Atlantic type locality, and six more Atlantic species, including Vesicomya atlantica (Smith, 1885), the type species of Vesicomya Dall, 1886, were at some time placed in Kelliella. In this work, we revise the genus Kelliella from the North Atlantic waters, based on large amounts of new material from both sides, and describe a new species from Martinique (Kelliella madininae n. sp.). We here propose, after revision of the shell morphology, the synonymy of K. biscayensis Allen, 2001 with K. miliaris (Philippi, 1844), and consider a single West European and Mediterranean species of Kelliella. The fossil “Kelliella” barbara is also excluded from the genus Kelliella and reallocated as Coralliophaga barbara (Studencka, 1987) n. comb. In the Atlantic margin of America, we consider that Diplodonta pilula Dall, 1881 remains a nomen dubium. The type material of K. concentrica Allen, 2001 is figured, and this species considered a member of the Vesicomyinae. The new Caribbean species, K. madininae, resemble K. brasuca Passos, Machado & Fantinatti, 2017 from southeastern Brazil. We recorded new localities for Kelliella goesi Odhner, 1960, so far known only from its original description. Diagnostic characters discriminating Vesicomya from Kelliella, stated by Krylova et al. (2018), Journal of Molluscan Studies, 84: 69–91, are discussed, and we consider the hinge architecture as the most robust.

Using two- and three-dimensional landmark data to examine the shape variation of Elliptio complanata from two heavily impounded rivers in northern New York (USA)

ABSTRACT Despite vast improvements in the quantification of shape variation with geometric morphometric methods, evaluating morphological variation in unionids has remained difficult due to the lack of measurable landmarks on shells and their overall morphological plasticity. In this study, we supplement traditional two-dimensional landmark data with three-dimensional landmark data. Using photogrammetry, we generate three-dimensional models that are landmarked. This approach adds a new, third dimension to capture shape changes, providing a more detailed understanding of the shell topography. With this method, we explore the differences in shell shape along river stretches of two heavily impounded rivers in northern New York (USA). We ask whether isolation by distance, presence of dams and/or difference in land use around sampling localities impact the shell morphologies of Elliptio complanata populations. Our data suggest that, although separated for almost a century, these unionid populations do not show a pattern of increased morphological difference with distance. But we find that broad, rounded morphs that are posteriorly extended occur more frequently in reservoir environments while unaltered river habitats have a higher number of slim and more elongated variants.

A symbiotic oyster in a shrimp burrow: phylogenetic position of Anomiostrea within the Ostreidae (Bivalvia)

ABSTRACT The ostreid genus Anomiostrea Habe & Kosuge, 1966, is monotypic for A. coralliophila Habe, 1975, which is known as a symbiont inhabiting the burrow of the ghost shrimp Neocallichirus jousseaumei (Nobili, 1904), but despite this unusual habit among oysters its phylogenetic position within the Ostreidae remained unknown. Using specimens collected from two distant localities of the Indo-Pacific, Oman and Japan, we compared shell morphology of these specimens with the holotype and assessed their phylogenetic relationships based on DNA sequence data from two mitochondrial and two nuclear genes. The genetic distance in cytochrome c oxidase subunit I between the specimens from Japan and Oman was 5.5%, indicating substantial geographic differentiation. Our molecular phylogenetic results suggest that A. coralliophila is sister to Ostrea algoensis G. B. Sowerby II, 1871, an oyster from rocky shores in South Africa, and both are closely related to other Ostrea species. This confirms assignment of Anomiostrea to Ostreinae and suggests that this burrow-wall symbiont evolved from typical rocky-shore oysters. Moreover, A. coralliophila was not monophyletic with another symbiotic ostreid Ostrea permollis G. B. Sowerby II, 1871, nor with other symbiotic oysters, indicating that the symbiotic habit evolved multiple times in the Ostreinae.

Comparative shell morphology of the rare land snails Levantina ninivita and Levantina escheriana (Gastropoda: Helicidae) in south-eastern Türkiye

Comparative shell morphology of the rare land snails Levantina ninivita and Levantina escheriana (Gastropoda: Helicidae) in south-eastern Türkiye

A new superfamily of freshwater mussels Deccanoidea nov. (Mollusca: Unionida) from an intertrappean deposit of Saurashtra province (Gujarat state, western India): An example of disjunct distribution

The Cretaceous-Palaeogene intertrappean deposits of the Deccan Volcanic Province of India comprise vertebrate, invertebrate and plant fossils of the dominantly continental realm. A 3–4 m thick shaly-sandstone lacustrine intertrappean sequence of Early Palaeogene (Palaeocene-Early Eocene) Bamanbor Formation, Chotila Basin (Saurashtra province, Gujarat State, western India) has yielded a collection of molluscans (bivalve and few gastropods) fauna. High-resolution digital photography and radiography of the recovered bivalves allowed us to gain detailed inferences on shell morphology. In a taxonomical context, we herein propose a new unionid molluscan superfamily Deccanoidea nov. represented by a single new family Deccanoidae nov. that includes two new subfamilies, that is, Deccanoinae nov. (represented by two new genera Deccanoida gen. nov. [including four new species: D. conrugis sp. nov., D. aleta sp. nov., and D. costaria sp. nov.] and Bamanboria gen. nov. [including one new species Bamanboria oblongis gen. et sp. nov.] and Chotiloinae nov. [represented by one new genus Chotilia gen. nov. and three new species: Chotilia trappeansis sp. nov., C. tuberculata sp. nov. and C. deccanensis sp. nov.]). Inorganic geochemistry of host (unionid-yielding) lithologies reveals oxic-freshwater conditions, humid-climate and moderate rainfall. The data on historical biogeography reveals that the Indian subcontinent hosted unionids during the late Cretaceous; however, the presence of new (at family/generic level) unionid fauna during the Early Palaeogene (Palaeocene-Early Eocene) in India indicates changes in the geographic position and ecologic condition linked to northward drift and lava outpouring, respectively. A disjunct distribution of unionid fauna in the erstwhile Gondwanan continents and insular India during the Cretaceous-Palaeogene interval can be explained in terms of both vicariance and dispersal.

Trifunctional Graphene-Sandwiched Heterojunction-Embedded Layered Lattice Electrocatalyst for High Performance in Zn-Air Battery-Driven Water Splitting.

Zn-air battery (ZAB)-driven water splitting holds great promise as a next-generation energy conversion technology, but its large overpotential, low activity, and poor stability for oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) remain obstacles. Here, a trifunctional graphene-sandwiched, heterojunction-embedded layered lattice (G-SHELL) electrocatalyst offering a solution to these challenges are reported. Its hollow core-layered shell morphology promotes ion transport to Co3S4 for OER and graphene-sandwiched MoS2 for ORR/HER, while its heterojunction-induced internal electric fields facilitate electron migration. The structural characteristics of G-SHELL are thoroughly investigated using X-ray absorption spectroscopy. Additionally, atomic-resolution transmission electron microscopy (TEM) images align well with the DFT-relaxed structures and simulated TEM images, further confirming its structure. It exhibits an approximately threefold smaller ORR charge transfer resistance than Pt/C, a lower OER overpotential and Tafel slope than RuO₂, and excellent HER overpotential and Tafel slope, while outlasting noble metals in terms of durability. Ex situ X-ray photoelectron spectroscopy analysis under varying potentials by examining the peak shifts and ratios (Co2+/Co3+ and Mo4+/Mo6+) elucidates electrocatalytic reaction mechanisms. Furthermore, the ZAB with G-SHELL outperforms Pt/C+RuO2 in terms of energy density (797Wh kg-1) and peak power density (275.8mW cm-2), realizing the ZAB-driven water splitting.