Shell Thickening Research Articles

Fasciola hepatica: Updates on egg morphology, host range, and distribution

During a survey for helminths in reindeer (Rangifer tarandus) across the Palearctic region, eggs were found in zoo reindeer feces. These were identified as eggs of Fasciola hepatica based on their morphology, morphometrics, location, and analysis of their partial sequence of ITS rDNA region. Some of the eggs had an appendage, previously unreported. Additionally, adults of F. hepatica were studied. Eggs derived from their uteri were also appendaged. Diagnostic morphological traits of F. hepatica eggs (abopercular appendage, knob, egg shell thickening, and egg shape) are discussed in this article. Three dimensional models of F. hepatica eggs were created to demonstrate the eggs features as best as possible. Since fecal examination remains gold standard in diagnosing fasciolosis in humans and animals worldwide, our findings may contribute to improved diagnostics. This research has also shown that reindeer can be a final host for F. hepatica. We also discuss whether the Novaya Zemlya archipelago might be the northernmost site of fasciolosis.

Compensatory shell thickening in corrosive environments varies between related rocky-shore and estuarine gastropods

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.

Predator signaling of multiple prey on different trophic levels structures trophic cascades.

The capacity of an apex predator to produce nonconsumptive effects (NCEs) in multiple prey trophic levels can create considerable complexity in nonconsumptive cascading interactions, but these effects are poorly studied. We examined such effects in a model food web where the apex predator (blue crabs) releases chemical cues in urine that affect both the intermediate consumer (mud crabs seek shelter) and the basal prey (oysters are induced to grow stronger shells). Shelter availability and predator presence were manipulated in a laboratory experiment to identify patterns in species interactions. Then, experimentally induced and uninduced oysters were planted across high-quality and low-quality habitats with varying levels of shelter availability and habitat heterogeneity to determine the consistency of these patterns in the field. Oyster shell thickening in response to blue crab chemical cues generally protected oysters from mud crab predation in both the laboratory and in field environments that differed in predation intensity, structural complexity, habitat heterogeneity, and predator composition. However, NCEs on the intermediate predator (greater use of refugia) opposed the NCEs on oyster prey in the interior of oyster reefs while still providing survival advantages to basal prey on reef edges and bare substrates. Thus, the combined effects of changing movement patterns of intermediate predators and morphological defenses of basal prey create complex, but predictable, patterns of NCEs across landscapes and ecotones that vary in structural complexity. Generalist predators that feed on multiple trophic levels are ubiquitous, and their potential effects on NCEs propagating simultaneously to different trophic levels must be quantified to understand the role of NCEs in food webs.

Modelling the effect of lateral inertia on the dynamic response of aluminium square tube extrusions

Crashworthiness of automotives require the design of crush tubes installed as a frontal structure to absorb energy by deforming plastically during collision. The crushing behaviour of aluminium extrusions modelled as square tubes is investigated under quasi-static and dynamic loading conditions using the non-linear explicit finite element code LS DYNA. Previous works have attributed the dynamic increase of the peak and mean crushing load of aluminium thin-walled structures under axial compression, to inertia effects. Results of our investigation revealed that there is a considerable thickening of the shell side walls before and during progressive folding. This shell thickening is established as the cause of lateral inertia which consequently results in increased crush strength. In addition, a positive correlation was established between the shell thickening and crushing speeds. 

Platymerella—a cool-water virgianid brachiopod fauna in southern Laurentia during the earliest Silurian

AbstractPlatymerella from the lower Red Mountain Formation in Georgia and Tennessee, the Bowling Green Dolomite of west-central Illinois, and the Elwood Dolomite of northeastern Illinois represents a paleosubtropical, cool-water occurrence of virgianid brachiopods in Laurentia during the early Silurian (middle–late Rhuddanian). These occurrences were located in the southern Appalachian foreland basin and the distal end of the Sebree Trough, likely subjected to frequent cool-water current and upwelling from Gondwana. Compared with broadly coeval species of Virgiana from lower paleotropical to equatorial latitudes, Platymerella has significantly smaller, dorsoventrally flattened shells, with subequal ventral and dorsal umbones and beaks that extend only slightly above the hinge line. Relative to its shell size, however, Platymerella has more prominent thickening of the shell wall, median septum, spondylium, and hinge plates than Virgiana, resembling more closely the extravagant shell thickening of Tcherskidium and Proconchidium from the Late Ordovician (late Katian) equatorial regions. The thickening of hinge plates resulted in the formation of a pseudocruralium, which separates Platymerella from Virgiana. In latest Ordovician–earliest Silurian virgianids, there was a general morphological gradient toward a smaller shell, reduction in the ventral-valve convexity, and reduction in the size and height of the ventral umbo from paleoequatorial to southern subtropical regions, with Platymerella representing the most southerly forms.

In Situ Studies of Single-Nanoparticle-Level Nickel Thermal Oxidation: From Early Oxide Nucleation to Diffusion-Balanced Oxide Thickening.

High-temperature oxidation mechanisms of metallic nanoparticles have been extensively investigated; however, it is challenging to determine whether the kinetic modeling is applicable at the nanoscale and how the differences in nanoparticle size influence the oxidation mechanisms. In this work, we study thermal oxidation of pristine Ni nanoparticles ranging from 4 to 50 nm in 1 bar 1%O2/N2 at 600 °C using in situ gas-cell environmental transmission electron microscopy. Real-space in situ oxidation videos revealed an unexpected nanoparticle surface refacetting before oxidation and a strong Ni nanoparticle size dependence, leading to distinct structural development during the oxidation and different final NiO morphology. By quantifying the NiO thickness/volume change in real space, individual nanoparticle-level oxidation kinetics was established and directly correlated with nanoparticle microstructural evolution with specified fast and slow oxidation directions. Thus, for the size-dependent Ni nanoparticle oxidation, we propose a unified oxidation theory with a two-stage oxidation process: stage 1: dominated by the early NiO nucleation (Avrami-Erofeev model) and stage 2: the Wagner diffusion-balanced NiO shell thickening (Wanger model). In particular, to what extent the oxidation would proceed into stage 2 dictates the final NiO morphology, which depends on the Ni starting radius with respect to the critical thickness under given oxidation conditions. The overall oxidation duration is controlled by both the diffusivity of Ni2+ in NiO and the Ni in Ni self-diffusion. We also compare the single-particle kinetic curve with the collective one and discuss the effects of nanoparticle size differences on kinetic model analysis.

Context-dependent effects of ocean acidification on the interaction between a crab predator and its oyster prey

Ocean acidification affects the fitness of species in coastal and estuarine systems, although interactions among species may alleviate or elevate the responses. Acidification effects on predator-prey interactions were evaluated between the blue crab Callinectes sapidus and eastern oyster Crassostrea virginica. Animals were exposed to 5 pH treatments: (1) control (pH ~8.00), constant pH at (2) 7.10 and (3) 6.75, and cycling pH from (4) 7.10 and (5) 6.75 to ~8.00, respectively. Crab foraging behavior, oyster size, and their defensive response against crabs (i.e. shell thickening) were compared among pH treatments. Results showed that predation rates of crabs tended to decrease with pH and from cycling to constant conditions, though statistical differences were only found at the lowest pH value and when consuming the larger oysters offered. Also, crab interest in oysters decreased with decreasing pH. In contrast, prey handling times and foraging motivation triggered by an odor stimulus were not affected by pH. In oysters, size metrics decreased with pH and also from cycling to constant conditions. Additionally, shells were thicker in the presence of predators, although the defensive strategy of oysters was weakened at the lowest pH level examined. Results indicate that although impaired foraging behavior of blue crabs may compensate for the negative effects on oysters under extreme acidification conditions, net effects are difficult to predict depending on the conditions to which animals are exposed and the size and behavioral variables considered.

New three-way symbiosis: an eukaryotic alga, a blue mussel, and an endolithic cyanobacteria

In several parts of the world, mytilid mussels, Mytilus spp., are infected with pathogenic, single-celled, photosynthetic algae belonging to the genus Coccomyxa. The posterior shell edge of heavily infected mussels becomes considerably thickened with an extra shell material. Also, the external shell surface is usually eroded as a result of the microboring activity of endolithic cyanobacteria. We compared the number of bioeroded shells, the bioerosion degree, and the number of badly eroded shells, in uninfected and Coccomyxa-infected Mytilus spp. from the Lower St. Lawrence Estuary, Quebec, Canada. The thickness of prismatic and nacreous layers was measured. The epibionts (pink calcareous algae, crustose brown algae, and barnacles) which encrusted surface of studied shells, were counted. Epibionts did not occur frequently and their possible relationship with the partners of a three-way symbiosis, Coccomyxa sp. – Mytilus spp. – endolithic cyanobacteria, has been neglected. We suggest that the mussel provides the alga Coccomyxa a protected space and metabolic carbon for photosynthesis. The alga stimulates shell thickening, and this protects mussel against ocean acidification and predators. The endolithic cyanobacteria remove black-colored periostracum providing the mussel and alga with an increased ability to survive during sunny days when exposed at low tide. The eroded shells become more translucent which encourages alga photosynthesis. However, shell degradation caused by endolithic cyanobacteria is a possible reason for the death of the Coccomyxa-infected mussels at the studied sites.

Convergent and Parallel Evolutionary Traits in Early Cretaceous Rudist Bivalves (Hippuritidina)

Early Cretaceous Hippuritida clades, requieniide (family Requieniidae) and hippuritide (families Radiolitidae, Polyconitidae,Caprinidae, “Caprinulidae” and Caprinuloideidae), show distinctive myophoral arrangements and shell structures. Nevertheless they share some characters, such as the transverse shell thickening of the myophores of the attached valve which are convergent traits in Lovetchenia (Requieniidae) and Homopleura (Monopleuridae). The bent posterior myophore of the right valve of Pseudotoucasia (Requieniidae) closely resemble the posterior myophore of the left valve of Horiopleura and Polyconites (Polyconitidae). The shell cellular structure is one of the key attributes of the family Radiolitidae (e.g.Eoradiolites) but this structure is also present in some advanced Requieniidae (“Toucasia-Apricardia “group). Canaliculate shell structures are convergent evolutionary traits which are common in the Caprinidae and Caprinuloideidae and also exist in the Polyconitidae and “Caprinulidae”. In most of the foregoing canaliculated groups, two trends are well expressed, reflecting parallel evolution: expansion of canals into the entire shell and increasing complexity of canal architecture. Convergent taxa took some advantages by using former innovations. An Albian peak of convergence coincided with the emergence of new clades, which suggests a reset following the mid-Aptian extinction event.

Foamy oysters: vesicular microstructure production in the Gryphaeidae via emulsification.

The vesicular microstructure is a very distinctive arrangement of calcite, consisting of hollow cavities (vesicles) of diverse sizes and shapes, usually elongated in the direction of shell thickening. It is uniquely found among living bivalves in a single oyster family, Gryphaeidae. The vesicles are distributed in lenses interleaved with compact foliated layers. We have studied the morphology and distribution of vesicles within the lenses using optical and electron microscopy, and micro-computed tomography. At a small scale, vesicles do not follow a classical von Neumann-Mullins route typical of ideal foams. At a larger scale, the initiation and evolution of a vesicular layer statistically proceed like a foam, with vesicles becoming more numerous, larger and more even in size. In summary, the vesicular material follows a foam-like coarsening to reduce the number of energetically costly interfaces. However, a steady state is never reached because the animal permanently introduces energy in the system by creating new vesicles. The fabrication of the vesicular material is mediated by the production of an emulsion between the extrapallial fluid and the precursor PILP of the calcitic walls within the thin extrapallial space. For this mechanism to proceed, the mantle cells must perform highly sophisticated behaviours of contact recognition and secretion. Accordingly, the vesicular material is under mixed physical-biological control.

An experimental and numerical investigation of compressive response of designed Schwarz Primitive triply periodic minimal surface with non-uniform shell thickness

Recently, Schwarz Primitive triply periodic minimal surface (P-TPMS) structures have emerged as high-value engineering structures for a wide range of applications. The elastic modulus and ultimate strength of P-TPMS architecture are tunable and superior. Herein, the influence of structural porosity and shell thickness on the compressive response of a P-TPMS lattice structure has been separately studied. Moreover, an enhanced design method, based on local shell thickening, is proposed to obtain a lightweight structure with superior mechanical properties. A comparison between primary and enhanced architectures is carried out by using experimental characterization and finite element analysis (FEA). It has been demonstrated that the enhanced structure renders higher relative elastic modulus and ultimate strength than primary P-TPMS structures. In addition, P-TPMS structural models are reconstructed from micro X-ray tomography (μ-CT) images and compared with as-designed models. The results reveal that selective laser sintering (SLS) is a promising fabrication route to achieve desired geometric accuracy. In addition, the comparison of experimental and FEA results indicates that the proposed enhanced design method is effective and reliable to obtain shell-based lattices with better mechanical properties.

Scaredy-Oysters: In Situ Documentation of an Oyster Behavioral Response to Predators

Non-consumptive effects of predators on prey populations have received increased interest in recent years. For Crassostrea virginica (Eastern Oyster), much of the focus has been on induced morphological defenses (e.g., shell thickening). Here, we provide in situ documentation of a behavioral response of Eastern Oysters (valve closure) to the threat of predation on a natural reef. This behavioral response, while intuitive, has been largely ignored in the literature despite potential impacts on individual oyster health by affecting feeding and subsequently energy assimilation, reproductive condition, and growth. In situ photographs revealed that, under natural conditions, Eastern Oysters closed during the passive presence of a crab mate-guarding pair and took ∼5 minutes to reopen to pre-predator gapes. Given that multiple oysters in our photos reacted similarly, this behavioral response may scale up to have effects on the population and the ecosystem services that Eastern Oysters provide. Ultimately, our observations open the door to a number of testable hypotheses regarding a predator's non-consumptive effects on oyster reefs.

Long-term physical evolution of an elastomeric ultrasound contrast microbubble

HypothesisOne of the main assets of crosslinked polymer-shelled microbubbles (MBs) as ultrasound-active theranostic agents is the robustness of the shells, combined with the chemical versatility in modifying the surface with ligands and/or drugs. Despite the long shelf-life, subtle modifications occur in the MB shells involving shifts in acoustic, mechanical and structural properties. ExperimentsWe carried out a long-term morphological and acoustic evolution analysis on elastomeric polyvinyl-alcohol (PVA)-shelled MBs, a novel platform accomplishing good acoustic and surface performances in one agent. Confocal laser scanning microscopy, acoustic spectroscopy and AFM nanomechanics were integrated to understand the mechanism of PVA MBs ageing. The changes in the MB acoustic properties were framed in terms of shell thickness and viscoelasticity using a linearised oscillation theory, and compared to MB morphology and to nanomechanical analysis. FindingsWe enlightened a novel, intriguing ageing time evolution of the PVA MBs with double behaviour with respect to a crossover time of ∼50 days. Before, significant changes occur in MB stiffness and shell thickness, mainly due to a massive release of entangled PVA chains. Then, the MB resonance frequency increases together with shell thickening and softening. Our benchmark study is of general interest for emerging viscoelastomeric bubbles towards personalised medicine.

Compaction and Melt Transport in Ammonia‐Rich Ice Shells: Implications for the Evolution of Triton

AbstractAmmonia, if present in the ice shells of icy satellites, could lower the temperature for the onset of melting to 176 K and create a large temperature range where partial melt is thermally stable. The evolution of regions of ammonia‐rich partial melt could strongly influence the geological and thermal evolution of icy bodies. For melt to be extracted from partially molten regions, the surrounding solid matrix must deform and compact. Whether ammonia‐rich melts sink to the subsurface ocean or become frozen into the ice shell depends on the compaction rate and thermal evolution. Here we construct a model for the compaction and thermal evolution of a partially molten, ammonia‐rich ice shell in a one‐dimensional geometry. We model the thickening of an initially thin ice shell above an ocean with 10% ammonia. We find that ammonia‐rich melts can freeze into the upper 5 to 10 km of the ice shell, when ice shell thickening is rapid compared to the compaction rate. The trapping of near‐surface volatiles suggests that, upon reheating of the ice shell, eutectic melting events are possible. However, as the ice shell thickening rate decreases, ammonia‐rich melt is efficiently excluded from the ice shell and the bulk of the ice shell is pure water ice. We apply our results to the thermal evolution of Neptune's moon Triton. As Triton's ice shell thickens, the gradual increase of ammonia concentration in Triton's subsurface ocean helps to prevent freezing and increases the predicted final ocean thickness by up to 50 km.

Evolution kinetics of microgravity facilitated spherical macrosegregation within immiscible alloys

The evolution kinetics of microgravity facilitated spherical macrosegregation within model Fe-Cu immiscible alloys has been systematically investigated by drop tube experiments and 3D phase-field simulations. In microgravity environment, liquid phase separation of Fe-Cu alloys induced the appearance of spherical macrosegregation patterns with various core-shell structures. The formation probability and evolution characteristics of these phase-separated core-shell morphologies depended on the volume fraction of surface active Cu-rich liquid together with the cooling rate. As the cooling rate decreased, the duration time of phase separation extended and the formed dispersed structures showed a tendency to form as core-shell structures influenced by the effects of Marangoni convection and surface segregation. Meanwhile, core grew larger while the shell became thinner. The occurrence probability of spherical macrosegregation firstly increased and then decreased with the rise in the copper concentration, and core-shell morphologies changed from three-layer to two-layer which was accompanied by core shrinkage and shell thickening.

When domes are spandrels: on septation in turritellids (Cerithioidea) and other gastropods

AbstractAlthough generally considered rare in gastropods, septation has long been noted in turritellids, but functional hypotheses do not survive strong scrutiny. Here we outline a methodology for testing spandrel hypotheses and apply it to the problem of turritellid septa. We follow Gould in using “spandrel” as a term for all features that are nonadaptive sequelae of adaptive features of organisms, including those that are structurally necessary, those that are developmentally correlated, and nondeterministic by-products that are correlated to features under selection.In turritellids, septa are constructed in microstructural continuity with secondary internal thickening of the shell, are highly variable features infraspecifically, and are strongly associated with degree of shell thickening. We therefore conclude that rather than being themselves adaptive, turritellid septa are spandrels of shell thickening. Turritellid septa are composed of crossed lamellar aragonite, which appears to be constructed by mantle epithelium over the visceral mass. Septation was also found in 22 of 24 gastropod families examined from a broad phylogenetic distribution. Septa thus appear to be a widespread feature of caenogastropods, in strong contrast to previous assertions that septa are less common in modern or high-spired shells.

Predator-induced shell plasticity in mussels hinders predation by drilling snails

Sessile invertebrate prey that detect waterborne predator cues often respond by strengthening their structural defenses. Experimental evidence of the functional significance of such modifications using field-raised organisms is lacking. This study addresses that gap using intertidal mussels and predatory dogwhelks from Atlantic Canada. During the spring and summer of 2016, we ran a field experiment that manipulated dogwhelk presence to test their nonconsumptive effects on mussel traits. Dogwhelk cues elicited thickening at the lip, centre, and base of mussel shells, although simultaneously limiting shell growth in length. As shell mass was unaffected by dogwhelk presence, a trade-off between shell thickening and elongation was revealed. Thickening was strongest at the thinnest parts of the shell. Using the field-raised organisms, a lab experiment found that dogwhelks took, on average, 55 % longer to drill and consume mussels previously exposed to dogwhelk cues than mussels grown without such a cue exposure. Dogwhelks drilled at the thinnest parts of the shell but, nonetheless, the consumed cue-exposed mussels had thicker shells at the borehole than the consumed mussels not exposed to cues, which likely explains the observed difference in handling time. As handling time normally decreases predation success, this study indicates that the plastic structural modifications in mussels triggered by dogwhelk cues in the field hinder predation by these drilling predators.

Preparation and Optical Property of ZnS:Mn/XO<sub>2</sub> (X=Ti, Si) Nanoparticles with Core/Shell Structure

In this paper, Mn2+ doped ZnS (ZnS:Mn) nanoparticles were prepared by co-precipitation method. And then different thickness of TiO2 and SiO2 inorganic shell were coated on prepared ZnS:Mn through the hydrolysis reaction of tetrabutyl titanate (TBOT) and tetraethyl orthosilicate (TEOS). ZnS:Mn crystal and core/shell structure were described by X-ray diffraction (XRD) and scanning electron microscope (SEM). Optical property of all ZnS:Mn/XO2 (X=Ti, Si) nanoparticles were investigated by photoluminescence (PL) spectrometer. The effect of Mn2+ concentration and XO2 (X=Ti, Si) shell thickness on luminescence intensity of ZnS:Mn/XO2 was studied. The results showed that with TiO2 and SiO2 shell thickening, Mn2+ emission of ZnS:Mn/XO2 samples increased first and then decreased. When the thickness of inorganic shell (molar ratio of shell and core amount) reached to 0.5 (TiO2) and 1.0 (SiO2), the optimal luminescence intensity was obtained. The emission of ZnS:Mn/TiO2 and ZnS:Mn/SiO2 was 2.0 and 1.5 times more in intensity than that of uncoated ZnS: Mn, respectively.

Effects of ocean acidification and elevated temperature on shell plasticity and its energetic basis in an intertidal gastropod

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 472:155-168 (2013) - DOI: https://doi.org/10.3354/meps10046 Effects of ocean acidification and elevated temperature on shell plasticity and its energetic basis in an intertidal gastropod Sedercor Melatunan1,4,*, Piero Calosi1, Simon D. Rundle1, Stephen Widdicombe3, A. John Moody2 1Marine Biology and Ecology Research Centre and 2Ecotoxicology Research and Innovation Centre University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK 3Plymouth Marine Laboratory, Prospect Place, Plymouth PL1 3DH, UK 4Faculty of Fisheries and Marine Science, University of Pattimura, Poka Ambon 97123, Indonesia *Email: sedercor.melatunan@plymouth.ac.uk ABSTRACT: Phenotypic plasticity is a mechanism by which organisms can alter their morphology, life history or behaviour in response to environmental change. Here, we investigate shell plasticity in the intertidal gastropod Littorina littorea in response to the ocean acidification and elevated temperature values predicted for 2100, focusing on shell traits known to relate to protection from predators (size, shape and thickness) and resistance to desiccation (aperture shape). We also measured and desiccation rates (measured as percentage water loss). Ocean acidification was simulated by bubbling carbon dioxide into closed-circuit tanks at concentrations of 380 and 1000 ppm, giving respective pH levels of 8.0 and 7.7; temperatures were set at 15 or 20°C. Both low pH and elevated temperature disrupted the overall investment in shell material; snails in acidified seawater and elevated temperature in isolation or in combination had lower shell growth rates than control individuals. The percentage increase in shell length was also lower for individuals kept under combined acidified seawater and elevated temperature, and the percentage of shell thickness increase at the growing edge was lower under acidified and combined conditions. Shells were also more globular (i.e. had lower aspect ratios) under elevated temperature and lower pH. Desiccation rates were lower at low pH and high temperature. Counter to predictions, water loss did not relate to shell biometric measures but was negatively correlated with adenosine triphosphate (ATP) concentrations. Finally, ATP concentration was positively correlated with shell thickening and weight, confirming the idea that negative effects of exposure to elevated pCO2/low pH and elevated temperature on shell morphology may occur (at least in part) through metabolic disruption. KEY WORDS: Climate change · Ocean acidification · Phenotypic plasticity · Morphology · Growth · Shell thickness · Aspect ratio · Water loss · Littorina littorea Full text in pdf format PreviousNextCite this article as: Melatunan S, Calosi P, Rundle SD, Widdicombe S, Moody AJ (2013) Effects of ocean acidification and elevated temperature on shell plasticity and its energetic basis in an intertidal gastropod. Mar Ecol Prog Ser 472:155-168. https://doi.org/10.3354/meps10046 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 472. Online publication date: January 09, 2013 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2013 Inter-Research.

Plastic and Heritable Variation in Shell Thickness of the Intertidal Gastropod Nucella lapillus Associated with Risks of Crab Predation and Wave Action, and Sexual Maturation

The intertidal snail Nucella lapillus generally has thicker shells at sites sheltered from wave action, where crabs are abundant and pose a high risk of predation, than at exposed sites where crabs are rare. We studied two populations showing the opposite trend. We reciprocally transplanted snails between field sites and measured shell length, width and lip thickness of those recaptured 12 months later. Snails transplanted to the sheltered site grew larger than sheltered-site residents, which in turn grew larger than transplants to the exposed site. Relative shell-lip thickness was greater in residents at the exposed site than at the sheltered site. Transplants from shelter to exposure developed relatively thicker shells than their controls and relatively thinner shells from exposure to shelter. Progeny of the two populations were reared for 12 months in a common garden experiment presenting effluent from crabs feeding on broken conspecifics as the treatment and fresh sea-water as the control. The crab-effluent treatment decreased foraging activity, concomitantly reducing cumulative somatic growth and reproductive output. Juveniles receiving crab-effluent grew slower in shell length while developing relatively thicker shell lips than controls, the level of response being similar between lineages. F2 progeny of the exposed-site lineage showed similar trends to the F1s; sheltered-site F2s were too few for statistical analysis. At sexual maturity, shell-lip thickness was greater in snails receiving crab-effluent than in controls, indicating plasticity, but was also greater in the exposed-site than in the sheltered-site lineage, indicating heritable variation, probably in degree of sexual thickening of the shell lip. Results corroborate hypotheses that ‘defensive’ shell thickening is a passive consequence of starvation and that heritable and plastic control of defensive shell morphology act synergistically. Shell thickening of juveniles was similar between lineages, contrary to hypotheses predicting differential strengths of plasticity in populations from low- or high-risk habitats.