scholarly journals The energetic costs of living in the surf and impacts on zonation of shells occupied by hermit crabs

2020 ◽  
Vol 223 (16) ◽  
pp. jeb222703 ◽  
Author(s):  
Guillermina Alcaraz ◽  
Brenda Toledo ◽  
Luis M. Burciaga
Keyword(s):  
Water Flow ◽  
Wave Action ◽  
Hermit Crabs ◽  
Energetic Cost ◽  
Shell Shape ◽  
Energetic Costs ◽  
Shell Size ◽  
Conical Shells ◽  
Drag Forces ◽  
Submerged Body

ABSTRACTCrashing waves create a hydrodynamic gradient in which the most challenging effects occur at the wave breaking zone and decrease towards the upper protected tide pools. Hydrodynamic forces depend on the shape of the submerged body; streamlined shapes decrease drag forces compared with bluff or globose bodies. Unlike other animals, hermit crabs can choose their shell shape to cope with the effects of water flow. Hermit crabs occupy larger and heavier shells (conical shape) in wave-exposed sites than those used in protected areas (globose shape). First, we investigated whether a behavioral choice could explain the shells used in sites with different wave action. Then, we experimentally tested whether the shells most frequently used in sites with different wave action reduce the energetic cost of coping with water flow. Metabolic rate was measured using a respirometric system fitted with propellers in opposite walls to generate bidirectional water flow. The choice of shell size when a large array of sizes are available was consistent with the shell size used in different intertidal sites; hermit crabs chose heavier conical shells in water flow conditions than in still water, and the use of heavy conical shells reduced the energetic cost of coping with water motion. In contrast to conical shells, small globose shells imposed lower energy costs of withstanding water flow than large globose shells. The size and type of shells used in different zones of the rocky shore were consistent with an adaptive response to reduce the energetic costs of withstanding wave action.

Study of the Change of Performance of an Elastic Vertical Hydrofoil With Deformation

2014 ◽  
Author(s):  
Alexander Führing ◽  
Subha Kumpaty ◽  
Chris Stack
Keyword(s):  
Water Flow ◽  
Lift Coefficient ◽  
Flow Analysis ◽  
Turbulence Models ◽  
Flow Property ◽  
Performance Data ◽  
Cfd Analysis ◽  
Ansys Fluent ◽  
Drag Forces ◽  
Fluid Flow Analysis

In external and internal fluid flow analysis using numerical methods, most attention is paid to the properties of the flow assuming absolute rigidity of the solid bodies involved. However, this is often not the case for water flow or other fluids with high density. The pressure forces cause the geometry to deform which in turn changes the flow properties around it. Thus, a one-way and two-way Fluid-Structure Interaction (FSI) coupling is proposed and compared to a CFD analysis of a windsurfing fin in order to quantify the differences in performance data as well as the properties of the flow. This leads to information about the necessity of the use of FSI in comparison to regular CFD analysis and gives indication of the value of the enhanced results of the deformable analysis applied to water flow around an elastically deformable hydrofoil under different angles of attack. The performance data and flow property evaluation is done in ANSYS Fluent using the k-ω SST and k-ε model with a y+ of 1 and 35 respectively in order to be able to compare the behavior of both turbulence models. It is found that the overall lift coefficient in general is lower and that the flow is less turbulent because of softer transition due to the deformed geometry reducing drag forces. It is also found that the deformation of the tip of the hydrofoil leads to vertical lift forces. For the FSI analysis, one-way and two-way coupling were incorporated leading to the ability to compare results. It has been found that one-way coupling is sufficient as long as there is no stall present at any time.

Notodiscus (Charopidae) on South Georgia: some implications of shell size, shell shape, and site isolation in a singular sub-Antarctic land snail

2011 ◽  
Vol 23 (5) ◽  
pp. 442-448 ◽  
Author(s):  
P.J.A. Pugh ◽  
R.I. Lewis Smith
Keyword(s):  
East Coast ◽  
Land Snail ◽  
Shell Shape ◽  
Shell Size ◽  
Site Isolation ◽  
South Georgia ◽  
North East ◽  
Larus Dominicanus ◽  
Close Proximity ◽  
Georgia Population

AbstractMultivariate analysis shows that shells of Notodiscus sp. (Charopidae: Pulmonata) reported from South Georgia are smaller and proportionately taller than, but otherwise similar to, populations of Notodiscus hookeri (Reeve) from Iles Crozet and Iles Kerguelen. The origin of this solitary, and spatially limited, South Georgia population is enigmatic. It is confined to a remarkably small coastal lowland site which was glaciated at Last Glacial Maximum, precluding a Tertiary relict origin, and on the leeward north-east coast, ruling out post-glacial ocean rafting. The site is close to the King Edward Point settlement, yet the absence of any logistics connections with the Iles Crozet or Iles Kerguelen mitigates against anthropogenic introduction. The close proximity of the population to nests of blue-eyed shag (Phalacrocorax atriceps), Dominican gull (Larus dominicanus) and light-mantled sooty albatross (Phoebetria palpebrata) could imply the snail was originally introduced to South Georgia via these ocean transiting seabirds.

Small spatial scale effects of wave action exposure on morphological traits of the limpet Lottia subrugosa

2019 ◽  
Vol 99 (06) ◽  
pp. 1309-1315
Author(s):  
Edson A. Vieira ◽  
Marília Bueno
Keyword(s):  
Spatial Scale ◽  
Scale Effects ◽  
Spatial Scales ◽  
Wave Exposure ◽  
Wave Action ◽  
Shell Shape ◽  
Small Scale ◽  
Small Spatial Scale ◽  
Large Spatial Scale ◽  
Exposed Shore

AbstractMany studies have already assessed how wave action may affect morphology of intertidal species among sites that vary in wave exposure, but few attempted to look to this issue in smaller scales. Using the most common limpet of the Brazilian coast, Lottia subrugosa, and assuming position on rocky boulders as a proxy for wave action at small scale, we tested the hypothesis that waves may also influence limpet morphology at a smaller spatial scale by investigating how individual size, foot area and shell shape vary between sheltered and exposed boulder sides on three shores in the coast of Ubatuba, Brazil. Limpets consistently showed a proportionally larger foot on exposed boulder sides for all shores, indicating that stronger attachment is an important mechanism to deal with wave action dislodgement at a smaller scale. Shell shape also varied in the scale investigated here, with more conical (dissipative) shells occurring in exposed boulder sides in one exposed shore across time and in the other exposed shore in one year. Shell shape did not vary regarding boulder sides across time in the most sheltered shore. Although we did not assess large spatial scale effects of wave action in this study, variations of the effect of waves at small spatial scale observed for shell shape suggest that it may be modulated by the local wave exposure regime. Our work highlights the importance of wave action at small spatial scales, and may help to understand the ecological variability of limpets inhabiting rocky shores.

scholarly journals Intra-Specific Variability in Whorl Growth-Rate among Land Gastropods with Conispirally-Coiled Shells

2021 ◽  
pp. 59-69
Author(s):  
Jean Béguinot
Keyword(s):  
Growth Rate ◽  
Statistical Significance ◽  
Repeated Measurements ◽  
Species Level ◽  
Shell Shape ◽  
Snail Species ◽  
Strong Positive Correlation ◽  
Shell Size ◽  
Strong Negative Correlation ◽  
Species Specific

For most conispirally-coiled Gastropods with determinate growth, the geometry of spirally-winding whorls is usually constrained by a strong negative correlation between whorl growth rate and the number of whorls reached at adulthood, as originally reported by the late S.J. Gould. Yet, beyond the tight control of shell-shape at the species level – resulting from this constraint – what about the amplitude of the intra-specific variability of whorl growth-rate, partly contributing to the variability of the overall shell-size at the species level? I address the issue by designing and implementing a new, indirect method for routinely evaluating whorl growth-rate, thereby aiming at considerably saving measurement time, and making it possible to easily achieve repeated measurements across samples large enough to reach statistical significance. This approach was applied to a series of eight common land snail species. The amplitude of intra-specific variability in whorl growth, evaluated this way, proves: (i) being markedly different among the eight investigated species (by a factor that can exceed 2x); (ii) being, yet, high enough, in all cases, to require compensating variations in the adult number of whorls, so as to limit the resulting consequences on the amplitude of the intra-specific variability of adult shell-size. Despite those marked differences in the amplitudes of intra-specific variability of whorl growth-rate among species, no significant relationship was observed between intraspecific variability of whorl growth rate and species-specific shell-shape types (discoidal/globular/elongate) and only weak positive relationship was observed with species-specific typical shell sizes. However, a rather strong positive correlation was found, as expected, between the degree of intra-specific variability of the whorl growth-rate and the degree of intra-specific variability of the number of whorls reached at adulthood (with the yet unexplained exception of one among the eight investigated species).

scholarly journals Defining the Energetic Costs of Cellular Structures

2019 ◽  
Author(s):  
Gita Mahmoudabadi ◽  
Rob Phillips ◽  
Michael Lynch ◽  
Ron Milo
Keyword(s):  
Opportunity Cost ◽  
Building Blocks ◽  
Fitness Cost ◽  
Cellular Structures ◽  
Energetic Cost ◽  
Energetic Costs ◽  
Evolutionary Trajectory ◽  
Essential Step ◽  
Molecular Building Blocks ◽  
Biomass Components

All cellular structures are assembled from molecular building blocks, and molecular building blocks incur energetic costs to the cell. In an energy-limited environment, the energetic cost of a cellular structure imposes a fitness cost and impacts a cell’s evolutionary trajectory. While the importance of energetic considerations was realized for decades, the distinction between direct energetic costs expended by the cell and potential energy that the cell diverts into cellular biomass components, which we define as the opportunity cost, was not explicitly made, leading to large differences in values for energetic costs of molecular building blocks used in the literature. We describe a framework that defines and separates various components relevant for estimating the energetic costs of molecular building blocks and the resulting cellular structures. This distinction among energetic costs is an essential step towards discussing the conversion of an energetic cost to a corresponding fitness cost.

scholarly journals Anthropogenic load іs a leading factor in the morphological variability of Chondrula tridens (Gastropoda, Enidae) in the northwestern Azov Sea region

2021 ◽  
Vol 29 (2) ◽  
pp. 102-110
Author(s):  
O. I. Koshelev ◽  
M. V. Gensytskyi ◽  
V. O. Koshelev ◽  
N. V. Yorkina ◽  
O. M. Kunakh
Keyword(s):  
Anthropogenic Impact ◽  
Vegetation Type ◽  
Morphological Variability ◽  
Morphological Characteristics ◽  
Load Level ◽  
Moisture Level ◽  
Anthropogenic Load ◽  
Shell Shape ◽  
Moisture Regime ◽  
Shell Size

Morphometric data are widely used in biology to assess intraspecific and inter-population variability and for bioindication and environmental condition assessment. The following hypotheses have been experimentally tested in the paper: 1) the vegetation type affects the change in the shell shape of Chondrula tridens martynovi Gural-Sverlova & Gural, 2010; 2) the change in the shell shape of this species is influenced by the biotope moisture regime; 3) the shell shape changes depending on the anthropogenic load level. The material in the form of empty, fully formed Ch. tridens shells was collected in 2019 in the north-western Azov region within the basin of the Molochna River. The collection points were located in settlements and outside them and differed in vegetation, moisture regime and level of anthropogenic load. The vegetation has been expertly attributed to two alternative types: herbaceous vegetation and tree plantations. By moisture level, the locations have been assessed as xerophytic and mesoxerophytic. The anthropogenic load levels have been assessed as low, medium and high. The study revealed that the morphological characteristics of Ch. tridens demonstrate a significant component of variability, which is due to the shell size. The shell size depends on the anthropogenic impact level. Under conditions of high anthropogenic impact, the shell size increases. Mollusks from locations with low and medium anthropogenic impact levels did not differ in shell size. After extraction of the size component, morphological properties develop three main trends of variability. The mouth apparatus development of mollusks does not depend on the vegetation type, but depends on the biotope moisture level and the anthropogenic transformation level. The mollusk shell elongation was observed to have the opposite dynamics of the height parameters in relation to the width and depended on the level of anthropogenic load. Rearrangement in the mouth apparatus depended on the biotope moisture level and the anthropogenic load level. There were distinguished four clusters, the quantitative morphological features of which allowed us to identify them as morphotypes. Each location was characterized by a combination of different morphotypes, according to which the sampling points may be classified. Morphotype 1 corresponds to biotopes with low level of anthropogenic load, morphotype 4 corresponded to biotopes with high anthropogenic load. Morphotypes 2 and 3 corresponded to moderate level of anthropogenic load. Vegetation type is not an important factor in determining the morphotypic diversity of populations. Under xerophytic conditions, morphotypes 2 and 3 are more common, and under mesoxerophytic conditions, morphotypes 1 and 4 are more common. The range of molluscs in different habitats needs to be expanded in the future to clarify climatic and other patterns.

Drag forces and energetic costs in Daphnia filter-feeding

1988 ◽  
Vol 23 (4) ◽  
pp. 2061-2061
Author(s):  
Walter Geller ◽  
Charles Knisely
Keyword(s):  
Filter Feeding ◽  
Energetic Costs ◽  
Drag Forces
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