Shell microstructure of the Late Carboniferous rostroconch molluscApotocardium lanterna(Branson, 1965)

2003 ◽  
Vol 77 (4) ◽  
pp. 655-673 ◽  
Author(s):  
Nicole S. Rogalla ◽  
Joseph G. Carter ◽  
John Pojeta
Keyword(s):  
Sensu Stricto ◽  
Outer Shell ◽  
Late Carboniferous ◽  
Shell Layer ◽  
Shell Microstructure

The Late Carboniferous bransoniid conocardioideanApotocardium lanterna(Branson, 1965) had an entirely aragonitic shell with a finely prismatic outer shell layer, a predominantly crossed lamellar to complex crossed lamellar middle shell layer, and an “inner” shell layer of finely textured porcelaneous and/or matted structure. This “inner” layer is probably homologous with the inner part of the middle shell layer and the inner layersensu strictoof bivalved molluscs. Shell morphological and microstructural convergences between conocardioids and living heart cockles suggest that at least some conocardioids may have farmed algal endosymbionts in their posterior mantle margins. This symbiosis may have helped conocardioids compete with the biomechanically more efficient bivalves during the latter part of the Paleozoic.

Taxonomy and phylogeny of the Triassic bivalve families Mysidiellidae Cox, 1964 and Healeyidae new family

2008 ◽  
Vol 82 (3) ◽  
pp. 555-564 ◽  
Author(s):  
M. Hautmann
Keyword(s):  
Outer Shell ◽  
Junior Synonym ◽  
Late Triassic ◽  
Late Paleozoic ◽  
Great Similarity ◽  
Shell Layer ◽  
Shell Microstructure ◽  
General Shape ◽  
New Family

The Mysidiellidae are morphologically isolated among Triassic bivalves but share important characters with Late Paleozoic Ambonychioidea. Apart from a great similarity in the general shape of the shell, the most primitive mysidiellid genus Promysidiella resembles ambonychioids in the presence of a duplivincular-opisthodetic ligament system. Within the Mysidiellidae, this ligament type evolved into the transitional ligament system that characterizes Late Triassic Mysidiella. The phyletic polarity indicates that this evolution probably took place by paedomorphosis. New examinations of the shell microstructure of Mysidiella demonstrate the presence of simple prismatic and possibly foliated structures in the calcitic outer shell layer, which further supports an ambonychioid affinity. Therefore, the Mysidiellidae are removed from the Mytiloidea and assigned to the Ambonychioidea. The poorly known genus Protopis, which was originally included in the Mysidiellidae, probably had a parivincular ligament system and was hence a member of the Heteroconchia. Joannina, which was previously considered a junior synonym of Protopis, is re-established. The hinge margin of Joannina carries a well developed nymph but lacks teeth. These characters as well as its modioliform shape, anterior shell lobe, and pronounced diagonal carina link Joannina with the Late Triassic genus Healeya (Modiomorphoidea). Both taxa are herein placed in the new family Healeyidae, which differs from the morphologically similar Kalenteridae in the absence of elaborated hinge teeth. Protopis, as well as the recently described genera Leidapoconcha, Waijiaoella, and Qingyaniola, are tentatively assigned to the Healeyidae.

Links between shell chemistry and microstructure – A case study using Arctica islandica

2020 ◽  
Author(s):  
Ellen Schnabel ◽  
Kotaro Shirai ◽  
Naoko Murakami-Sugihara ◽  
Klaus Peter Jochum ◽  
Nils Höche ◽  
...  
Keyword(s):  
Environmental Control ◽  
Formation Rate ◽  
Strong Relationship ◽  
Outer Shell ◽  
Ventral Margin ◽  
Shell Layer ◽  
Shell Microstructure ◽  
Arctica Islandica ◽  
Growth Increments ◽  
Strong Control

<p>Bivalves offer outstanding potential as environmental archives. However, vital effects exert a strong control on the incorporation of many trace and minor elements into the shell so that their use as environmental proxies is currently limited. Furthermore, Sr and Mg show a strong relationship to the micrometer-sized shell architecture (shell microstructure), i.e., near growth lines, which are typically dominated by irregular simple/spherulitic prismatic microstructures, the concentrations of these elements are significantly higher than in portions between growth lines (= growth increments, which are microstructurally more complex). In contrast, Ba is uncoupled from the prevailing shell microstructure. To shed more light on these issues, we conducted a combined element chemical (in-situ analysis by means of LA-ICP-MS) and microstructural analyses (using SEM) of shells of <em>Arctica islandica</em> collected alive in NE Iceland.</p><p>According to our findings, (1) contemporaneous shell portions in the hinge and ventral margin (both belonging to the outer shell layer) within individual specimens showed nearly identical Sr/Ca and Mg/Ca values, but Ba/Ca was 1.5 – 2.5 times higher in the ventral margin than in the hinge. (2) In agreement with previous studies, Sr and Mg were strongly elevated near annual growth lines. (3) Along an isochronous transect from the inner portion of the outer shell layer near the myostracum toward the outer shell surface (in the ventral margin), Si/Ca values increased, on average, by 75% ± 11%, whereas Na/Ca values decreased by 7% ± 1%. Along this transect, the shell microstructure gradually changed from crossed-acicular to homogeneous suggesting that Si and Na are linked to the prevailing nanometer-sized shell architecture or underlying physicochemical processes controlling their formation. (4) In the hinge, Ba/Ca, Sr/Ca, Mn/Ca and Mg/Ca attained highest values along the axis of maximum growth, but gradually decreased in slower growing (contemporaneous) shell portions away from that axis. (5) In contemporaneous shell portions (in either the hinge or the ventral margin), the concentration of some elements varied significantly among specimens, whereas others showed little variability. For example, in similar and contemporaneous shell portions of different specimens, Na/Ca values exhibited only little variation (17.4 – 23.7 mmol/mol), whereas Sr/Ca and B/Ca differed more severely (0.3 – 1.6 mmol/mol and 0.04 – 0.07 mmol/mol, respectively; both within growth increments). Despite these inter-specimen chemical differences, the shell microstructure remained largely invariant.</p><p>Our findings firstly suggest that the extrapallial fluid, if it exists at all, is chemically inhomogeneous. This could result from differences in the efficiency of transmembrane ion transport or to differences in shell formation rate along the growing margin (e.g., faster growth in the outer portion of the outer shell layer than in portions closer to the myostracum). Secondly, chemical differences among specimens may be attributed to physiological differences. Thirdly, some elements such as Ba are uncoupled to microstructural properties, but co-vary strongly among specimens suggesting an environmental control on the uptake and incorporation of this element into the shell.</p>

Evolution and phylogenetic significance of cardioidean shell microstructure (Mollusca, Bivalvia)

2001 ◽  
Vol 75 (3) ◽  
pp. 607-643 ◽  
Author(s):  
Jay A. Schneider ◽  
Joseph G. Carter
Keyword(s):  
Phylogenetic Relationships ◽  
Outer Shell ◽  
Data Sets ◽  
Shell Layer ◽  
Shell Microstructure ◽  
Data Set ◽  
Fracture Control ◽  
Selection For ◽  
Morphologic Data ◽  
Combined Data

The shell microstructure of Carboniferous and Triassic permophorids; Triassic and Recent carditids; Devonian, Carboniferous, and Triassic crassatelloideans; and Jurassic through Recent cardioideans is examined in a phylogenetic context, using separate microstructural and morphologic data sets, as well as a combined data set. The microstructural and morphologic data sets are significantly incongruent, but the combined data set suggests that modiomorphoideans (modiomorphids and permophorids) are basal to crassatelloideans; crassatelloideans are basal to carditids (includingSeptocardia), and carditids are basal to cardiids. On the other hand, the possibility of direct permophorid ancestry for the carditid-cardiid clade cannot be excluded, as suggested by the retention of permophorid-like matted (transitional nacreous-porcelaneous) structure in some early carditids and cardiids. In the absence of stratigraphic data and other evidence for phylogenetic relationships, shell microstructure offers limited potential for assessing subfamily-level phylogenetic relationships within the Cardioidea. This is because of microstructural convergences reflecting biomechanical adaptations for fracture control and abrasion resistance, and possibly also selection for metabolic economy of secretion in tropical, oligotrophic habitats. General evolutionary trends in cardiid shell microstructure are nevertheless apparent: Cretaceous cardiids completely replaced an ancestral laminar, matted structure in their inner shell layer with non-laminar porcelaneous structures; evolved better defined CL structure, stronger reflection of the shell margins, and increased thickness or secondary loss of the ancestral prismatic outer shell layer; and, inProtocardia(Pachycardium)stantoni, added inductural deposition. Some Cenozoic cardiids then evolved wider first-order crossed lamellae, non-denticular composite prisms, composite fibrous prisms, ontogenetic submergence of a juvenile non-denticular composite prismatic outer shell layer into the CL middle shell layer, or ontogenetic submergence of the inner part of a juvenile fibrous prismatic outer shell layer into the CL middle shell layer.The shell microstructure ofHemidonax donaciformisis unusual for a cardioidean, and suggests closer affinities with the superfamily Tellinoidea than with the superfamily Cardioidea.Extensive inductural deposits inProtocardia(Pachycardium)stantoniraise the possibility that photosymbiosis evolved among some Mesozoic members of the Protocardiinae, thereby increasing the likelihood that this feature has evolved several times independently in the Cardiidae.Cemented, calcareous periostracal granules or spines are known to occur in modiolopsoideans, mytiloideans, modiomorphids, permophorids, trigonioids, astartids, cardiids, myoids, pholadomyoids, and septibranchoids. Consequently, the presence of these structures is not necessarily indicative of close anomalodesmatan affinities.

Condensing lenses and shell microstructure in Corculum (Mollusca: Bivalvia)

1997 ◽  
Vol 71 (1) ◽  
pp. 56-61 ◽  
Author(s):  
J. G. Carter ◽  
J. A. Schneider
Keyword(s):  
Light Transmission ◽  
Outer Shell ◽  
Shell Layer ◽  
Shell Microstructure ◽  
Microstructural Modification

The microstructure of the non-window portions of the shell of Corculum cardissa resembles other Fraginae, with predominantly fibrous prismatic outer, branching crossed lamellar middle, and complex crossed lamellar inner layers. Both the anterior and posterior windows in its shell reflect reduced pigmentation and incursion of the outer shell layer, but the posterior windows involve deeper incursion plus reduction of the outer and middle sublayers of the outer shell layer and microstructural modification of the middle shell layer to enhance light transmission. The planoconvex shape of the posterior windows has more likely evolved to direct and focus light toward the deeper, zooxanthellae-rich gills and anterior mantle, than to merely disperse light.

scholarly journals Molecular phylogeny and shell microstructure of Fungiacava eilatensis Goreau et al. 1968, boring into mushroom corals (Scleractinia: Fungiidae), in relation to other mussels (Bivalvia: Mytilidae)

2011 ◽  
Vol 80 (3) ◽  
pp. 169-178 ◽  
Author(s):  
Masato Owada ◽  
Bert W. Hoeksema
Keyword(s):  
Sister Group ◽  
Shell Shape ◽  
Phylogenetic Position ◽  
Shell Layer ◽  
Shell Microstructure ◽  
Phylogenetic Reconstructions ◽  
Molecular Phylogenetic ◽  
Coral Reef Ecosystems ◽  
Mushroom Coral ◽  
Rrna Sequences

Research on the evolution of the symbiosis between the boring mussel Fungiacava eilatensis (Bivalvia: Mytilidae) and its mushroom coral hosts (Scleractinia: Fungiidae), which requires phylogenetic reconstructions of both the Mytilidae and the Fungiidae, contributes to the understanding of the complexity of coral reef ecosystems. Previously, Fungiacava was regarded as a genus that had descended from Leiosolenus or as belonging to the subfamily Crenellinae, but no phylogenetic support has been obtained for this hypothesis. In the present study, the 18s rRNA sequences of ten mytilid species and the shell microstructures of 12 mytilids were investigated. The phylogenetic position of F. eilatensis is discussed in relation to its associations with its host species. The results of the molecular phylogenetic analysis indicate that F. eilatensis forms a sister group with Leiosolenus simplex, a livecoral- boring species within the Leiosolenus clade. Scanning electron microscope observations indicate that the shell of F. eilatensis is constructed of 3 layers: the outer shell layer with a homogeneous structure, the middle shell layer as a sheet nacreous structure, and the inner shell layer with an irregular simple prism structure. This shell microstructure of F. eilatensis is similar to that of Leiosolenus malaccanus and L. simplex. These findings show that F. eilatensis has descended from a coral-boring Leiosolenus species and that it would be adequate for Fungiacava to be treated as Leiosolenus. However, because of its extraordinary shell shape it has been kept as a separate genus.

Thermal potentiation and mineralogical evolution in the Bivalvia (Mollusca)

1998 ◽  
Vol 72 (6) ◽  
pp. 991-1010 ◽  
Author(s):  
Joseph G. Carter ◽  
Enriqueta Barrera ◽  
Michael J. S. Tevesz
Keyword(s):  
Natural Selection ◽  
Genetic Basis ◽  
Outer Part ◽  
Outer Shell ◽  
Shell Layer ◽  
Soft Bottom ◽  
Prismatic Shell ◽  
Calcite Deposition ◽  
Fracture Localization ◽  
Bivalve Shells

The most important factor controlling the timing of Phanerozoic mineralogical evolution in the Bivalvia appears to be thermal potentiation of calcite deposition in colder marine and estuarine environments. Cold temperature has promoted mineralogical evolution in the Bivalvia by kinetically facilitating (potentiating) initially weak biological controls for calcite, thereby exposing their genetic basis to natural selection. Calcite has evolved in bivalve shells for a variety of selective advantages, including resistance to dissolution; resistance to chemical boring by algae and gastropods; reduced shell density in swimming and soft-bottom reclining species; enhanced flexibility in simple prismatic shell layers; and fracture localization and economy of secretion in association with certain foliated structures.Endogenous calcite in bivalve shells varies from biologically induced to weakly and strongly biologically controlled. Biologically controlled calcite generally first appears in bivalve shells as an impersistent component of the outer shell layer, only later, in some groups, expanding to include the entire outer and then part or all of the middle and inner shell layers. The initial stages of mineralogical evolution are shown by certain modern Mytilidae, Veneridae and Petricolidae. In the latter two families, the calcite occurs as conellae in the outer part of the outer shell layer. Calcitic conellae in the inner shell layer of Pliocene Mercenaria are not barnacle plates, as previously indicated, but endogenous calcite comparable in origin to other venerid conellae. Their occurrence in Mercenaria may reflect thermal potentiation of weak biological controls for calcite, as well as local detachment of the secretory mantle epithelium near the pallial and adductor musculature.

The structure of the outer shell layer in radiolitid rudists, a morphoconstructional approach

Lethaia ◽  
2008 ◽  
Vol 41 (3) ◽  
pp. 219-234 ◽  
Author(s):  
JOSE MARIA PONS ◽  
ENRIC VICENS
Keyword(s):  
Outer Shell ◽  
Shell Layer

scholarly journals Fabrication of Double-Layered Alginate Capsules Using Coaxial Nozzle

2017 ◽  
Vol 5 (4) ◽  
Author(s):  
Yifei Jin ◽  
Danyang Zhao ◽  
Yong Huang
Keyword(s):  
Layer Thickness ◽  
Flow Rate ◽  
Outer Shell ◽  
Pharmaceutical Chemical ◽  
Shell Layer ◽  
Core Diameter ◽  
Model Liquid ◽  
The Core ◽  
Coaxial Nozzle ◽  
Alginate Capsules

Multilayered encapsulation has been of great interest for various pharmaceutical, chemical, and food industries. Fabrication of well-defined capsules with more than one shell layer still poses a significant fabrication challenge. This study aims to investigate the feasibility of using a coaxial nozzle to fabricate double-layered (core–shell–shell) capsules during vibration-assisted dripping. A three-layered coaxial nozzle has been designed, manufactured, and tested for double-layered capsule fabrication when using sodium alginate solutions as the model liquid material for inner and outer shell layers and calcium chloride solution as the core fluid. To facilitate the droplet formation process, a vibrator has been integrated into the fabrication system to provide necessary perturbation for effective breakup of the fluid flow. It is demonstrated that double-layered alginate capsules can be successfully fabricated using the proposed three-layered coaxial nozzle fabrication system. During fabrication, increasing the core flow rate leads to an increase in capsule and core diameters while the inner and outer shell layer thicknesses decrease. Increasing annular flow rate results in an increase in capsule diameter and inner shell layer thickness while the outer shell layer thickness decreases. An increase in the sheath flow rate leads to an increase in capsule diameter and outer shell layer thickness but has no significant effect on the core diameter and inner shell layer thickness.

Quantitative digital x-ray imaging of the outer shell layer of mytilus edulis (Bivalvia)

1992 ◽  
Vol 50 (2) ◽  
pp. 1746-1747
Author(s):  
Donald L. Parker ◽  
Gary D. Rosenberg
Keyword(s):  
Mytilus Edulis ◽  
High Spatial Resolution ◽  
Imaging System ◽  
Image Data ◽  
Outer Shell ◽  
Shell Layer ◽  
X Ray ◽  
Growth Increments ◽  
X Ray Imaging ◽  
First Time

Compositional mapping using digital x-ray imaging has been applied to a variety of applications. The extension of these procedures permitting complete quantitation allows EPM application where detailed structures exist requiring higher resolution. We apply these techniques here for the first time to the study of the molluscan shell. The outer shell layer of the mussel, Mytilus edulis, consists of fibrous calcific prisms (1-3μm diameter) which are organized structurally as layers corresponding to growth increments (up to ca.100μm thick, deposited daily, normal to the direction of growth). Digital imaging is used here to precisely determine the composition of these layers with high spatial resolution.Digital images were obtained with a Cameca® three spectrometer EPM system interfaced to a Kevex 8000® analyzer/imaging system. Images are stored as WDS intensity pixels, with final extraction of image data for complete quantitation being performed offline. The extracted intensities were corrected for dead time, background and transformed into K-ratios for full matrix correction using the CITZAF routines.Shells were sectioned along selected growth axes and polished using alumina followed by ultrasonic cleaning. All specimens were coated with ∼50nm of aluminum (as opposed to carbon) to retard degradation of the carbonate during analysis.

Nacre in an early gryphaeid bivalve (Mollusca)

1994 ◽  
Vol 68 (6) ◽  
pp. 1405-1408 ◽  
Author(s):  
Christopher A. McRoberts ◽  
Joseph G. Carter
Keyword(s):  
Outer Layer ◽  
Outer Shell ◽  
Late Triassic ◽  
Left Valve ◽  
Shell Microstructure ◽  
Shell Surface ◽  
Prismatic Structure ◽  
Dark Material ◽  
Foliated Structure

McRoberts (1992, figs. 4.13, 4.14, 6.8) illustrated the shell microstructure of late Triassic Gryphaea (Gryphaea) arcuataeformis Kiparisova, 1936, and Gryphaea (Gryphaea) nevadensis McRoberts, 1992. McRoberts (1992, p. 33) described the left valve of G. arcuataeformis as showing “neomorphosed calcite with multiple laminae of ?prismatic structure perpendicular to [the] outer shell surface ….” He described the left valve of G. nevadensis as consisting of two distinct layers of neomorphosed calcite:“…an outer layer with ?prismatic structure occasionally with bands of dark material (?micritic matrix), and a much thinner inner layer with ?cross-foliated structure ….” Subsequent study has shown these microstructural diagnoses to be inaccurate. They are revised as follows.

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