Shell Damage Research Articles

Are Spine-Bearing Freshwater Gastropods Better Defended?

Freshwater snails usually possess thin unadorned shells lacking structural components such as spines. Exceptions can be found on the high, well-watered islands of the South Pacific. Streams on these islands support a rich freshwater molluscan fauna with several nerite taxa (Neritimorpha: Neritidae) exhibiting extremely long dorsal spines. We sought to assess the defensive capacity of these structures for several co-occurring nerite genera on the Island of Ovalau, Fiji. Our overarching hypothesis was that spines confer a defensive advantage. We tested four predictions for eight common taxa: (i) predator “rich” habitats (the creek entrance) would be dominated by spine-bearing nerites, (ii) spine-bearing species should be smaller in size, (iii) nerites with spines would exhibit lower levels of shell damage and (iv) nerites with spines should invest less in their shells (i.e., their shells should be thinner). Most of these predictions received support. Spine-bearing species dominated the entrance to the creek and were smaller in size. Levels of shell damage were low overall, with 2 of the 3 spinose taxa exhibiting no shell damage, as did many of the nonspinose taxa. Finally, shells of spinose species were 25% thicker, demonstrating increased rather than decreased investment. Taken together, these findings suggest that the elaborate spines of Clithon spp. play a defensive role.

Dynamic response and damage assessment of spherical robot GFRP spherical shell under low velocity impact

Abstract In the normal operation of a spherical robot, its spherical shell structure is often accompanied by low velocity impact. At the same time, the spherical shell structure should take into account its protective ability against high strength impact of small probability. Glass fiber reinforced polymer (GFRP), which has high specific strength, specific stiffness, corrosion resistance and an impact energy dissipation coefficient, can be used as the ideal spherical shell material for spherical robots. In this study, the low velocity impact damage of GFRP spherical shell is studied based on the background that a thin-walled shell structure of spherical robot may suffer from large deformation and dynamic load. This study is divided into three aspects: experiment, simulation and calculation. The dynamic response and residual bearing capacity of the GFRP spherical shell is obtained through experiments; the progressive damage model of the composite structure, which demonstrates expounded stress distribution, a structural deformation mode and an energy dissipation mechanism under impact, is established based on the Hashin criterion. Low velocity impact-penetrating failure of the elastic brittle thin-walled GFRP spherical shell is calculated according to the geometrical principle and energy method. In this paper, the material dynamic behavior and impact damage of a GFRP spherical shell are systematically studied. This is of great significance for the development of high-performance spherical robots and the realization of accurate control.

The Secret ‘After Life’ of Foraminifera: Big Things Out of Small

Calcareous and siliceous microorganisms are common components of mudrocks, and can be important in terms of stratigraphy and environmental interpretation. In addition, such microorganisms can have a significant ‘after life’, through post-mortem alteration, and represent a potential source of additional information about the diagenetic and deformation history of the rock unit. Some examples of the latter are illustrated in this study from foraminifera within a Cretaceous black shale of Colombia. This includes foraminifera tests acting as understudied repositories of authigenic calcite cement, and of elements such as Ba, Zn, Fe and S through the formation of baryte, sphalerite and iron sulphides (pyrite, marcasite). Such repositories, within the body chambers of foraminiferal tests, can provide important windows into the diagenetic processes within mudstones. If calcite cement is not recognised or separated from biogenic calcite, the depositional calcite budget can be easily overestimated, skewing the application of mudrock classification schemes, and affecting environmental interpretation including that of productivity. The elements Ba, Zn and Fe (often in ratio with Al) are commonly utilised as geochemical proxies of environmental parameters (productivity, bottom water redox conditions, etc.). Therefore, the presence of significant amounts of baryte, sphalerite and pyrite-marcasite (within foraminifera) should be noted and their origins (source and timing) investigated based on their spatial relationships before making environmental deductions based on geochemical analysis alone. Additionally, commonly observed marginal shell damage of many of the observed foraminifera is reported. We interpret this damage, for the first time, as an indicator of lateral dissolution, brought about by horizontal foreshortening during orogenesis. This is also supported by the occurrence of microscale anastomosing horizontal to inclined baryte-filled fractures within the mudstone matrix.

The repaired durophagous scar in the shell of a lingulid brachiopod immediately after the end Ordovician mass extinction

Repaired shell injuries, widely reported mainly on mollusks, give first hand evidence of biological activity in fossil communities. Scars in fossil brachiopods from predation are rarely found, particularly after major biotic crises. A repair scar on a lingulid brachiopod Pseudolingula? sp. that lived immediately after the end Ordovician mass extinction is reported for the first time here. The specimen, cohabited with other components of Cathaysiorthis fauna, was collected from the basal Shiyang Formation (earliest Rhuddanian, Llandovery, Silurian), Jiangxi, southeast China. The scar’s near-margin position and its drape-like shape, together with the quiet middle to deeper shelf living environment and nearly infaunal lifestyle of the species, suggest that the shell damage was biotic-induced, from a failed predation, possibly by a nautiloid cephalopod. The successful repair supports previous studies showing that environmental conditions ameliorated quickly after the extinction. To analyze its repair mode, another repaired specimen of its living relative Lingula anatina collected from the Yellow Sea, China was examined here as well. Compared to the much more efficient repair for the living lingulids, the drape-like structure of the scar on the shell of Pseudolingula? sp. is more similar to the published repair specimens of Cambrian lingulate brachiopods, which may indicate the evolution of its repair mechanisms.Bing Huang [bhuang@nigpas.ac.cn], State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, 39 East Beijing Road, Nanjing 210008, China; Rongyu Li [lir@brandonu.ca] Department of Geology, Brandon University, 270-18th Street, Brandon, Manitoba R7A 6A9, Canada.

DUROPHAGOUS FISH PREDATION TRACES VERSUS TUMBLING-INDUCED SHELL DAMAGE—A PALEOBIOLOGICAL PERSPECTIVE

ABSTRACTDurophagous (shell-crushing) fish predation is considered to have been a major force of evolutionary change in the history of marine communities. However, because fish predators are very rarely preserved in the act of predation, fossil evidence of such interactions is commonly indirect. For instance, it has been argued that shell fragments with sharp margins constitute a good proxy for durophagy. However, drawing a distinction between predation- and abiotic-induced shell damage can be challenging. Notably, experimental data on shell fragmentation by marine durophagous fishes are almost lacking. In this study, we explore whether shell breakage caused by durophagous marine fishes versus physical factors can be distinguished. Aquarium experiments involving commercially available predatory fishes (Diodon) and thin-shelled invertebrate preys (gastropods Nassarius and brachiopods Frenulina) show that the predation by some fish produces shell fragments displaying extremely low roundness and varying degree of sphericity. Importantly, these fragments typically display sharp and jagged margins, and reveal distortion of individual crystal fibers. Tumbling experiments showed that the disintegration of brachiopod shells proceeds much more rapidly than that of gastropods, which may suggest that abiotic-induced fragmentation of brachiopods may be eventually confused with predation. However, the tumbling-induced fragmentation and damage in both groups are typically characterized by the presence of spherical or discoidal and rounded shell fragments displaying smooth edges (without any microstructural distortion), and numerous abrasive scratches and wear scars on the surface. These data underscore that the shell fragments produced by a durophagous fish, if not subsequently abraded by physical factors, can be recognized in the fossil record.

Impact damage of hemispherical shells formed by direct metal laser sintering

Abstract Cellular structures have excellent potential to become alternatives to composites with the advent of 3D printing due their environment robustness, ease of manufacturing, light weight and higher energy absorption capabilities. The behavior of the cellular structures at high impact energies remains largely unexplored. The current work consists of carrying out impact test on hemispherical shells. The hemispherical shells having hexagonal grid patterns are modeled and printed using Direct Metal Laser Sintering (DMLS) with IN718 material. The printed shell structures are then subjected to impact of steel ball using a gas gun for a range of impact velocities and locations on the shells. Tensile test specimen geometries are developed and printed using In718 material to study the material properties. The test results are presented and future scope of work is discussed

Sub-lethal predatory shell damage does not affect physiology under high CO2 in the intertidal gastropod Tritia reticulata

Ocean acidification (OA) poses a major threat to marine animals, especially marine shelled invertebrates such as molluscs. Although many organisms are capable of compensating for the effects of OA, this can impose physiological costs and impact performance (e.g. through increased metabolism and decreased growth). Sublethal injuries on shells may provoke changes in energy allocation. Under acidified conditions, organisms would spend less energy on reproduction and somatic growth to repair the damage. Therefore, we analysed the physiological responses of the intertidal gastropod Tritia reticulata during shell regeneration under OA conditions. We simulated a sub-lethal predation event (a notch in the outer lip of the shell) and individuals were exposed to control (pH 8.08) and low pH scenarios (pH 7.88 and 7.65). After two months exposure, all individuals showed shell repair, with a full repair rate observed in 75% of individuals. Contrary to expectations, shell repair following sub-lethal damage and OA had no apparent impact on physiological state in terms of energy reserves (as measured by whole-animal Carbon/Nitrogen) or growth potential (as measured by whole-animal RNA:Protein and RNA:DNA ratios). As an intertidal organism, T. reticulata could be resilient to future global environmental change because of compensatory mechanisms that are inherent in intertidal animals, and may represent a robust species with which to study future scenarios of OA in temperate coastal ecosystems. However, unrestricted food availability during experiment could have played a role in the results and therefore food limitation should be considered in future studies regarding shell repair and metabolism under the effects of OA.

Stability-based damage assessment and rapid post-disaster quantification of a latticed shell subjected to earthquake loading

Abstract Damage of latticed shells due to the earthquake has been observed and the damage can affect the critical load for global instability. In the present study, an investigation of the critical load factor of a spherical latticed dome after sustaining seismic excitation is carried out. The evaluation of the damage factor is presented based on the initial and remaining critical load factors for global instability before and after the structure sustained an earthquake. The statistics and the probabilistic model of the damage factor of the latticed shell are presented by considering the record-to-record variability and the use of the uni- and bi-directional seismic excitation. The results show the importance of considering bidirectional ground motions to assess the damage factor. Fragility curves are estimated and are used as a basis to develop an approach for practical and rapid post-disaster quantification of a latticed shell for temporary emergency use. The qualification can be carried out using the observed ground motion record at the structural site. If the record of the sustained seismic event is unavailable, a practical chart for qualifying the structure for temporary emergency use is recommended based on the magnitude and epicentral distance of the seismic event.

A Nano-BODIPY Encapsulated Zeolitic Imidazolate Framework As Photoresponsive Integrating Antibacterial Agent.

Drug-resistant bacteria challenge the antimicrobial agents and antibacterial strategy. To develop environmental friendly smart technology for treating pathogens, we report a kind of photoactivated nano-BODIPY (BCNBA@ZIF). First BODIPY compound (BC) was synthesized by coupling phenethyl caffeate (CAPE) with brominated BODIPY through B-O bonds. Next, BC was encapsulated in ZIF-8 together with 2-nitrobenzaldehyde (o-NBA) to form photoactivated BCNBA@ZIF nanoparticles. TEM confirm the structural change of BCNBA@ZIF after illumination. BCNBA@ZIF is less toxic to cells without illumination. Under illumination of blue LED light, the BCNBA@ZIF worked as a photoacid generator initiating the damage of ZIF shell with the release of BC, metal ions, and the production of singlet oxygen for achieving multifunctional antibacterial uses. Therefore, BCNBA@ZIF is a kind of photodriven smart "Domino" agent for bacterial inhibition.

Response of triceratops to impact forces: numerical investigations

Triceratops is one of the new generations of offshore compliant platforms suitable for ultra-deepwater applications. Apart from environmental loads, the offshore structures are also susceptible to accidental loads. Due to the increase in the risk of collision between ships and offshore platforms, the accurate prediction of structural response under impact loads becomes necessary. This paper presents the numerical investigations of the impact response of the buoyant leg of triceratops usually designed as an orthogonally stiffened cylindrical shell with stringers and ring frames. The impact analysis of buoyant leg with a rectangularly shaped indenter is carried out using ANSYS explicit analysis solver under different impact load cases. The results show that the shell deformation increases with the increase in impact load, and the ring stiffeners hinder the shell damage from spreading in the longitudinal direction. The response of triceratops is then obtained through hydrodynamic response analysis carried out using ANSYS AQWA. From the results, it is observed that the impact load on single buoyant leg causes periodic vibration in the deck in the surge and pitch degrees of freedom. Since the impact response of the structure is highly affected by the geometric and material properties, numerical studies are also carried out by varying the strain rate, and the location of the indenter and the results are discussed.

Morphological and damage growth characteristics of shell-type damage of fused silica optics induced by ultraviolet laser pulses.

Under the radiation of a nanosecond pulse laser, the types of damage and damage profile of fused silica optics are closely related to the surface and subsurface defects of the component. Using the raster-scanning mode to measure the laser-induced damage threshold of fused silica optics, three different types and sizes of damage patterns are found, of which shell damage is the intermediate state and is a bridge connecting submicrometer-size damage and catastrophic damage. This paper mainly studies the mechanism and damage growth law of shell damage, analyzes the model of laser-induced shell damage, and discusses the probability and cause of shell-damage growth.

Pathological changes by Eosinophilic Rickettsia-like organism in Japanese oyster, Crassostrea gigas

Rickettsia infection in adult Japanese oysters (Crassostrea gigas) was observed in 2015 at San Ignacio Lagoon, Baja California Sur, Mexico and characterized using molecular tools. In the present study, the degree of infection by Eosinophilic Rickettsia-Like Organism (E-RLO), characterized by intracellular inclusions in gill, mantle, labial palps, digestive tract and gonadal ducts, was evaluated using histological methods and was associated with visible injuries on body surface, such as blisters, shell damage and necrosis. Most of the oysters (92.2%) had some type of observable symptoms; 90.2% of all oysters had blisters in the mantle, and all oysters presented with E-RLO in the epithelia of at least one of the analyzed tissues (gills, labial palps, mantle, gonadal ducts and digestive tract). The highest intensity of infection (percent of E-RLO coverage) was observed in the labial palps (18.6%) and the lowest in digestive tract (2.6% of the examined tissue). Oysters with external injuries had higher infection intensities than the oysters without external injuries. Considering the clinical signs (observable symptoms and histological findings), we propose three infective stages of E-RLO disease development, a scale that could be used for early detection.

ANALYSIS OF MONI SIS OF MONITORING OF THE A ORING OF THE AT-3 AUTOTRANSFORM TRANSFORMATOR IN T OR IN TashTES MODE

The article considers the results of the analysis of autotransformers operation mode monitoring. The time diagram of active load current and oil temperature of autotransformer TashTES AT-3 is established and during one year changes of these variables and basic parameters of autotransformer were observed. Technical faults of the power transformer and high power autotransformer are established and methods of their elimination are determined. Damage of transformers and autotransformers with voltage of 110-500 kV of about 30% of the total number of outages which were accompanied by internal short-circuits and two main causes of damage were determined. The main causes of technological failures, which were not accompanied by internal short-circuits, are as follows: 20% of failures in operation of the onload tap-changer, 16% of oil leaks from the bushings, 13% of oil leaks and lowering of oil from the transformer due to violation of welded joints and rubber seals, 4% of engine damage to oil pumps of the cooling system, 3% of pressure increase in high-voltage hermetic bushings, 2% of film protection shell damage. The main reasons of technological violations accompanied by internal short-circuit in the transformer are as follows: breakdown of internal insulation of highvoltage bushings, insufficient short-circuit resistance, wear and tear of winding insulation, breakdown of insulation.

The Potential Impact of Underwater Exhausted CO2 from Innovative Ships on Invertebrate Communities

Liquefied natural gas (LNG) powered ships equipped with an underwater exhaust system to reduce the ship’s water resistance could form a future generation of energy-efficient ships. The potential consequences of the underwater exhaust gas to the local ecosystems are still unknown. Especially, the CO2 levels may locally exceed estimated future global levels. The present study exposes marine communities to a wide range of CO2 dosages, resulting in pH 8.6–5.8 that was remained for 49 days. We found that the zooplankton and benthic community were adversely affected by high CO2 exposure levels. In detail, (1) between pH 6.6 and 7.1 polychaete worms became the dominating group of the benthic community and their larvae dominated the zooplankton group. (2) Due to the reduced grazing pressure and the flux of nutrients from decaying organic material planktonic microalgae (phytoplankton) stared blooming at the highest exposure level. The periphyton (fouling microalgae) community was not able to take advantage under these conditions. (3) Marine snails’ (periwinkle) shell damage and high mortality were observed at pH < 6.6. However, the growth of the surviving periwinkles was not directly related to pH, but was positively correlated with the availability of periphyton and negatively correlated with the polychaete worm density that most likely also used the periphyton as food source. Our result indicates that the impact of underwater exhaust gasses depends on various factors including local biological and abiotic conditions, which will be included in future research.

How do gastropods grow synchronized shell sculpture? Effect of experimental varix manipulations on shell growth byCeratostoma foliatum(Muricidae: Ocenebrinae)

AbstractGastropod shells display striking patterns in both color and sculpture, but rather little is known about the developmental mechanisms that produce those patterns. Here, we tested a physical feedback hypothesis for how snails control spatial patterning of shell sculpture. Varices—a form of synchronized, blade‐like axial sculpture—are produced at regular intervals around the shell and often aligned closely between adjacent whorls. Older varices were believed to provide a spatial cue about where to position a new varix. To test this hypothesis, we manipulated physical cues by cutting off varices or attaching new ones to the body whorl of individuals ofCeratostoma foliatum, and then allowing snails to grow a new varix. We found that previous varices on the shell were neither necessary nor sufficient to induce a new varix at a particular location. However, the position of older varices did appear to affect the fine tuning of subsequent varix placement. The results of our experiments therefore suggest that varix synchrony arises mainly from some internal mechanism that yields a standardized amount of spiral growth per growth spurt. We also found that shell damage can induce varix production in unusual or aberrant locations during subsequent shell growth.

Similarity in predator-specific anti-predator behavior in ecologically distinct limpet species, Scurria viridula (Lottiidae) and Fissurella latimarginata (Fissurellidae)

Many marine gastropods show species-specific behavioral responses to different predators, but less is known about the mechanisms influencing differences or similarities in specific responses. Herein, we examined whether two limpet species, Scurria viridula (Lamarck, 1819) and Fissurella latimarginata (Sowerby, 1835), show species- and size-specific similarities or differences in their reaction to predatory seastars and crabs. Both S. viridula and F. latimarginata reacted to their main seastar predators with escape responses. In contrast, both limpets did not flee from common crab predators, but, instead, fastened to the rock. All tested size classes of both limpet species reacted in a similar way, escaping from seastars, but clamping onto the rock in response to crabs. Limpets could reach velocities sufficient to outrun their specific seastar predators, but they were not fast enough to escape crabs. Experiments with limpets of different shell conditions (with and without shell damage) indicated that F. latimarginata with a damaged shell showed “accommodation movements” (slow movements away from stimulus) in response to predatory crabs. In contrast, intact F. latimarginata and all S. viridula (intact and damaged) clamped the shell down to the substratum. The response details suggest that the keyhole limpet F. latimarginata is more sensitive to predators (faster reaction time, longer escape distances, and higher proportion of reacting individuals) than S. viridula, possibly because the morphology of F. latimarginata (the relationship of its shell size and structure to its total body size) makes this species more vulnerable to predation. Our study suggests that chemically mediated effects of seastar and crab predators result in contrasting behavioral responses of both limpet species, independent of their habitat and morphology. Despite the different characteristics of the limpet species and the identity of predators, the limpets react in comparable ways to similar predator types.

Calcium carbonate unit realignment under acidification: A potential compensatory mechanism in an edible estuarine oyster

Ocean acidification (OA) is well-known for impairing marine calcification; however, the end response of several essential species to this perturbation remains unknown. Decreased pH and saturation levels (Ω) of minerals under OA is projected to alter shell crystallography and thus to reduce shell mechanical properties. This study examined this hypothesis using a commercially important estuarine oyster Magallana hongkongensis. Although shell damage occurred on the outmost prismatic layer and the undying myostracum at decreased pH 7.6 and 7.3, the major foliated layer was relatively unharmed. Oysters maintained their shell hardness and stiffness through altered crystal unit orientation under pH 7.6 conditions. However, under the undersaturated conditions (ΩCal ~ 0.8) at pH 7.3, the realigned crystal units in foliated layer ultimately resulted in less stiff shells which indicated although estuarine oysters are mechanically resistant to unfavorable calcification conditions, extremely low pH condition is still a threat to this essential species.

Shell damage leads to enhanced memory formation in Lymnaea.

Ecologically relevant stressors alter the ability of the pond snail, Lymnaea stagnalis, to form long-term memory (LTM). Here, we show that an environmentally relevant stressor, shell damage, has a dramatic effect on the enhancement of LTM formation. Damage in the form of a shell clip 24 h before operant conditioning training resulted in long-term memory (LTM) formation following a single 0.5 h training session (TS). Typically, in these snails, two 0.5 h TSs with a 1 h interval between the sessions are required to cause LTM formation. We show here that even with a 72 h interval between shell clip and training, memory enhancement still occurred. The stress associated with shell clip could be mitigated by an ongoing high-Ca2+ pond water environment, an injection of propranolol and a DNA methylation blocker. However, use of an anaesthetic (MgCl2) during the clip or intermittent exposure to the high-Ca2+ pond water environment did not mitigate the stress associated with the shell clip. Shell clip was also sufficient to cause juvenile snails, which neither learn nor form memory, to gain the capacity to form LTM. Together, the experiments demonstrate that shell clipping is an environmentally relevant stressor that can cause enhancement of LTM formation.

Dredging-induced shell damages to hard clam (Meretrix meretrix): a Malaysian case study

The hard clam (Meretrix meretrix) is a popular edible shellfish in South and Southeast Asia, being heavily exploited by hand dredging in Marudu Bay, Malaysia. The current study was performed to evaluate the shell damages caused by this artisanal dredging gear. Samplings were conducted in triplicates at two sites using both hand dredging and hand collecting (control) sampling methods. The shell length and total weight, damage areas and breakage patterns of each clam were recorded. A questionnaire survey was conducted with local bivalve harvesters to gather information on the fishing pressure in Marudu Bay. Results revealed that the efficiency (fishing yield) of hand dredging gear was three times higher than hand collecting. However, hand dredging gear causes lethal shell damages to small hard clams (&lt;3cm in shell length). Hard clam harvesting is the main occupation of most fishermen in Kg. Popok, but most of them do not comply with the minimum harvesting size established by the fishery department. Moreover, most of the stakeholders are not aware of the negative impacts of hand dredging to the sustainability of the hard clam fishery in Marudu Bay. Therefore, organizing more awareness programs combined with introducing community-based fishery management are highly recommended to promote the sustainability of this artisanal fishery.

Study of morphological feature and mechanism of potassium dihydrogen phosphate surface damage under a 351 nm nanosecond laser.

The surface damage morphology of potassium dihydrogen phosphate (KDP) crystal under 351nm nanosecond laser irradiation is studied, and the formation mechanisms of each damage type are discussed. There are three unique types of KDP surface damage, namely, crack, shell, and crater, under the fluence between 5 and 15 J/cm2. The fracture feature of crack type damage indicates the pure mechanic process during laser exposure. Some cracks result in the upwarp of the material with a height of 0.1-0.5μm. The shell is a most typical damage morphology with a proportion as large as about 80%. The transverse size of shell ranges from 5 to 82μm, related to the fluence. The crater has a distinguished core structure related to the high-temperature process. The evidence of dehydration reaction is found in the core by energy dispersive spectrometer semiquantitative analysis. Internal morphology analysis with a focused ion beam suggests that the crack and shell damage originate from the surface or subsurface machining defects, while the crater damage is mainly due to material bulk defects.