Factors Influencing Shell Shape in the Mussel Mytilus Edulis

1968 ◽  
Vol 48 (3) ◽  
pp. 561-584 ◽  
Author(s):  
R. Seed
Keyword(s):  
Mytilus Edulis ◽  
Slow Growth ◽  
Shell Height ◽  
Shell Morphology ◽  
Population Variation ◽  
Shell Shape ◽  
Factors Influencing ◽  
High Incidence ◽  
Local Variability ◽  
Transplantation Experiments

An attempt is made to explain the great variations in gross shell morphology noted in field populations of Mytilus edulis.In any one mussel population, variation in shell form can be attributed to differences in age, old mussels having proportionately heavier shells where width often exceeds shell height. This is invariably accompanied by down-turned, divergent umbones and varying degrees of incurvature of the ventral shell margin.Variations in the age structure of mussel populations from different habitats can also account for local variability in shell morphology. Localities where the life expectancy of mussels is increased due to absence of predators (especially in the upper shore) reveal a high incidence of old ‘ungulate’ individuals, whereas populations in which the mussel turnover is more rapid show a preponderance of relatively young mussels.Shell morphology is greatly influenced by growth rate and density. These probably exert their effect through physical compression which is maximum in localities of fast growth and high density and least in areas of slow growth and low density. High compression leads to an elongate form whereas low compression results in higher, more triangular shaped shells. Growth rates and densities, even within the same habitat, are, however, exceedingly variable.Since all environmental conditions vary in both time and space, wide variation in shell morphology is to be expected, even in animals from the same locality.Transplantation experiments indicate that variation in shell morphology is essentially phenotypic, older animals being more likely to exhibit a form which is characteristic of their particular habitat. Smaller mussels from widely different habitats show remarkable similarity in shell morphology.

Shell morphology of larval and post-larval mytilids from the north-western Atlantic

1989 ◽  
Vol 69 (1) ◽  
pp. 181-218 ◽  
Author(s):  
S. Cynthia Fuller ◽  
Richard A. Lutz
Keyword(s):  
Mytilus Edulis ◽  
Shell Height ◽  
Sympatric Species ◽  
Shell Morphology ◽  
Scanning Electron Micrographs ◽  
Geukensia Demissa ◽  
Western Atlantic ◽  
The North ◽  
Number Of Teeth ◽  
North Western

Comparison of early shell morphological features of six mytilids from the north-western Atlantic revealed differences useful for species identification and classification. Brachidontes exustus, lschadium recurvum, Geukensia demissa, Amygdalum papyrium, Mytilus edulis, and Modiolus modiolus larvae and post-larvae were cultured in the laboratory. Scanning electron micrographs of the shell and hinge during early ontogenetic stages showed that all species had a long provinculum with taxodont dentition. In addition, provinculum length and number of teeth increased during the larval period in the six species. The small, numerous provincular teeth of Mytilus edulis and the bold, comparatively few provincular teeth of Amygdalum papyrium clearly differentiated these two species. Most species had a low umbo, round posterior margin, and more pointed anterior margin, although Amygdalum papyrium was distinguished by a high, prominent umbo. Distinction of Geukensia demissa and lschadium recurvum larval shells was difficult due to similarity in their shapes and hinge dentition. However, discriminant analysis using larval shell length, shell height, provinculum length, and number of teeth aided in classification of these and other sympatric species.

Shell shape, dysodont tooth morphology, and hinge-ligament thickness in the bay mussel Mytilus trossulus correlate with wave exposure

2000 ◽  
Vol 78 (2) ◽  
pp. 240-253 ◽  
Author(s):  
Robert J Akester ◽  
André L Martel
Keyword(s):  
Shell Length ◽  
Shell Height ◽  
Wave Exposure ◽  
Shell Morphology ◽  
Shell Shape ◽  
Width Ratio ◽  
Mytilus Trossulus ◽  
Barkley Sound ◽  
High Wave Energy ◽  
Mussel Mytilus Trossulus

We examined the shell morphology of the bay mussel Mytilus trossulus (Gould) at six locations with various levels of wave exposure in Barkley Sound on the west coast of Vancouver Island, British Columbia, Canada. Young adult M. trossulus (29-35 mm shell length) collected from wave-exposed sites displayed striking differences in shell morphology from M. trossulus from sheltered sites. Mytilus trossulus from wave-exposed habitats had a lower shell height / shell width ratio and a thicker shell; they also had higher, more robust dysodont teeth, as well as a thicker hinge ligament. Examination of juveniles (12-14 mm shell length) collected from a wave-exposed shore and a sheltered shore separated by only a few hundred metres displayed similar differences in shell morphology and ligament thickness. These observations suggest that wave exposure is the cause of the observed differences in shell morphology and ligament thickness in M. trossulus. This is the first report of a correlation between wave exposure and morphology of the dysodont teeth and ligament in a bivalve. We discuss potential selective pressures that may favor characteristics of wave-exposed shells, including the probability of dislodgment and misalignment of valves in high wave energy areas.

Ecophenotypic plasticity in shell growth direction of asari clam Ruditapes philippinarum

2021 ◽  
pp. 1-6
Author(s):  
Takeshi Tomiyama
Keyword(s):  
Growth Rate ◽  
Shell Growth ◽  
Shell Height ◽  
Growth Direction ◽  
Ruditapes Philippinarum ◽  
Shell Morphology ◽  
Individual Growth ◽  
Shell Size ◽  
Internal Factors ◽  
Suitable Habitats

Abstract Asari clam (or Manila clam) Ruditapes philippinarum is an important bivalve for local fisheries. This species exhibits a large variation in shell morphology, and the shell roundness tends to be greater in more unsuitable habitats. To test whether the increments in shell size parameters (length, height and width) were affected solely by environmental conditions or by internal factors such as initial shell shapes or growth rate, a field caging experiment was conducted at two different sites of unsuitable and suitable habitats in Matsukawaura Lagoon, Japan, where shell shapes of wild clams were significantly different between the habitats. In the experiment, clams were released from the two sites to the same site or to the other site and were re-collected after 3, 6 and 12 months of caging. Caged clams originating from unsuitable habitats and released to suitable habitats showed a reduction in shell height relative to shell length, while clams from suitable habitats introduced to unsuitable habitats showed marked increases in both shell height and width. Generalized linear mixed models suggested that the increase in shell height was affected largely by the release habitat (environment) whereas the increase in shell width was affected largely by the individual growth rate. These results suggest that marginal growths in shell height and width respond differently to external and internal factors of clams, resulting in plasticity in their shell shapes according to the environments to which they are translocated.

A geometric analysis of growth in gastropod shells, with particular reference to turbinate forms

1983 ◽  
Vol 63 (4) ◽  
pp. 777-797 ◽  
Author(s):  
S. U. K. Ekaratne ◽  
D. J. Crisp
Keyword(s):  
Conversion Factor ◽  
Shell Height ◽  
Geometric Analysis ◽  
Logarithmic Spiral ◽  
Maximum Growth ◽  
Relative Magnitude ◽  
Shell Shape ◽  
Growth Band ◽  
Apical Angle ◽  
Image Position

Nucella lapillus and Littorina littorea afford examples of turbinately coiled shells with no space between the columella and the inner face of the whorls. Three constants are sufficient to determine the form of such shells: λ, the ratio between diameters of successive whorls; β, the semi-apical angle and ρ, the ratio of aperture length and breadth in the apertural plane passing through the axis. The variation of these three constants with size was examined and shown to be relatively small and insignificant in Nucella, but in Littorina it was significant.For Nucella and Littorina these shell characteristics were used to relate for the nth whorl, the length along the shell spiral (ln) to the shell height (Hn), the latter being the measure usually employed in growth studies. This relation was derived mathematically and confirmed empirically aswhere α is the angle of the logarithmic spiral given by α = tan−1 2π sin β/loge λ. The increased resolution of the micro-growth band increments, which are measured along the shell spiral was directly related to the ln:Hn ratios.Since the formula for the ln/Hn ratio (= shell conversion factor) includes λ, β and ρ, the three constants necessary to determine shell form in turbinately coiled shells of the type described, the shell conversion factor may be a better index of shell shape than indices based on a single constant. In species where the shell grows isometrically this ratio will remain constant, whereas changes in shell shape with size will influence this ratio. Such changes in shell shape during growth can be quantified in terms of the shell constants and when included in calculating the shell conversion factor, will show the relative magnitude of shell shape changes brought about by growth. The shell conversion factor may also be used to study the effects of ecological variations on the geometry of the shell.The conical shell of the limpet, Patella vulgata, is geometrically a much simpler system in which direct shell measurements were used to relate length along the direction of maximum growth to the antero-posterior diameter of aperture.

scholarly journals Incidence Of Diarrheal Infections In Ukraine: Epidemiological Peculiarities

2019 ◽  
Author(s):  
Nina Malysh ◽  
Oksana Chemych ◽  
Roman Rodyna ◽  
Inna Chorna ◽  
Svitlana Doan
Keyword(s):  
Drinking Water ◽  
Food Item ◽  
Analytical Study ◽  
Incidence Rates ◽  
Epidemiological Surveillance ◽  
Statistical Research ◽  
Factors Influencing ◽  
High Incidence ◽  
The World ◽  
Low Incidence

Abstract Background : Diarrheal infections remain relevant for many countries of the world. The processes of globalization, fundamental changes in nutrition and water consumption contributed to the fact that the significance of individual infection sources, etiological structure of diarrheal infections changed. Purpose of the study: on the background of the analytical study of the incidence of diarrheal infections in Ukraine under the current conditions, to determine the factors influencing epidemic situation. Methods: The reports of the Ministry of Health of Ukraine, Main Administrations of Statistics in Kharkiv, Odesa, Zaporizhia oblasts for 2011-2018 are used in the paper. Epidemiological and statistical research methods are applied. Results: The epidemic situation with diarrheal infections in Ukraine is characterized by a low incidence of typhoid fever (from 0.012 to 0.14 per 100 thousand people), shigellosis (from 1.97-6.13 per 100 thousand people), stable incidence rates without the downward trend, salmonellosis (from 17.35 till 24.1 per 100 thousand people), high incidence of diahrreal infections of specified etiology (from 115.5 to141.9 per 100 thousand people) and diahrreal infections of unspecified etiology (from 69.76 to 107.02 per 100 thousand people). The most complicated epidemic situation is observed in economically most developed regions of the country. Most diarrheal infectionsoutbreaks are connected with catering establishments 36.5 % and with children educational establishments 26.1 %. In the region with the highest shigellosis and salmonellosis incidence direct strong correlation relationships are established between the incidence and population, density, natural population movement. The oblasts with the highest diahrreal infections of specified etiology, rotaviral enteritis, diahrreal infections of unspecified etiology incidence are at least provided with water resources and have problems with provision of high-quality drinking water. There is a need to improve the system of epidemiological surveillance over diarrheal infections by extension of the indicators of microbiological study of drinking water quality in the regions of Ukraine, where high diahrreal infections of specified etiology, rotaviral enteritis, diahrreal infections of unspecified etiology incidence is registered; by increasing frequency of food item inspections in the oblasts, where mediana shigellosis and salmonellosis incidence exceeds the average one in Ukraine. Keywords: diarrheal infections, shigellosis, salmonellosis, rotaviral enteritis.

scholarly journals Some Morphological Variations in The Land Snail Monacha cantiana (Montagu,1803) within Baghdad Province

2013 ◽  
Vol 10 (1) ◽  
pp. 1-12
Author(s):  
Baghdad Science Journal
Keyword(s):  
Population Density ◽  
Shell Height ◽  
Calcium Content ◽  
Land Snail ◽  
Shell Morphology ◽  
Shell Size ◽  
Aperture Diameter ◽  
Morphological Variations ◽  
Shell Diameter ◽  
Soil Calcium

The present work includes investigation of some features of shell morphology; shell size, shell thickness, shell colour of the land snail Monacha cantiana, in addition to the correlation between height and diameter of shell and between shell aperture diameter and shell diameter at four sites within Baghdad Province, Iraq. Also, measurements of three environmental variables were made; soil temperature, soil moisture and soil calcium content in adition to population density. Shell Aperture Index (Ia) and Shell Index (SI) for individuals from size class ranged between (9-12)mm were measured. The results showed that the deference in shell size by using (Ia) within population related to temperature, moisture and population density but, the value of Shell Index decreased in AL-Kadhimiya site (0.81-0.97) due to increase in population density. The species was characterized by shell colour variation (creamy white, white ,creamy). Also, The results showed strong and positive correlation between shell height and diameter and between shell aperture diameter and shell diameter for all size classes.

Limits to optimization: fluid dynamics, adhesive strength and the evolution of shape in limpet shells

2000 ◽  
Vol 203 (17) ◽  
pp. 2603-2622 ◽  
Author(s):  
M.W. Denny
Keyword(s):  
Fluid Dynamics ◽  
Shell Height ◽  
Adhesive System ◽  
Hydrodynamic Forces ◽  
Optimal Shape ◽  
Shell Morphology ◽  
Rocky Shores ◽  
Adhesion System ◽  
Selection For ◽  
Lift And Drag

Limpets are commonly found on wave-swept rocky shores, where they may be subjected to water velocities in excess of 20 m s(−1). These extreme flows can impose large forces (lift and drag), challenging the animal's ability to adhere to the substratum. It is commonly thought that the conical shape of limpet shells has evolved in part to reduce these hydrodynamic forces while providing a large aperture for adhesion. This study documents how lift and drag actually vary with the shape of limpet-like models and uses these data to explore the potential of hydrodynamic forces to serve as a selective factor in the evolution of limpet shell morphology. At a low ratio of shell height to shell radius, lift is the dominant force, while at high ratios of height to radius drag is dominant. The risk of dislodgment is minimized when the ratio of height to radius is 1.06 and the apex is in the center of the shell. Real limpets are seldom optimally shaped, however, with a typical height-to-radius ratio of 0.68 and an apex well anterior of the shell's center. The disparity between the actual and the hydrodynamically optimal shape of shells may be due to the high tenacity of limpets' adhesive system. Most limpets adhere to the substratum so strongly that they are unlikely to be dislodged by lift or drag regardless of the shape of their shell. The evolution of a tenacious adhesion system (perhaps in response to predation) has thus preempted selection for a hydrodynamically optimal shell, allowing the shell to respond to alternative selective factors.

scholarly journals Adaptive divergence in shell morphology in an ongoing gastropod radiation from Lake Malawi

2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Bert Van Bocxlaer ◽  
Claudia M. Ortiz-Sepulveda ◽  
Pieter R. Gurdebeke ◽  
Xavier Vekemans
Keyword(s):  
Common Garden ◽  
Shell Morphology ◽  
Model Systems ◽  
Shell Shape ◽  
Adaptive Divergence ◽  
Nominal Species ◽  
Shape Variation ◽  
In The Wild ◽  
Evolutionary Radiations ◽  
Contrasting Habitats

Abstract Background Ecological speciation is a prominent mechanism of diversification but in many evolutionary radiations, particularly in invertebrates, it remains unclear whether supposedly critical ecological traits drove or facilitated diversification. As a result, we lack accurate knowledge on the drivers of diversification for most evolutionary radiations along the tree of life. Freshwater mollusks present an enigmatic example: Putatively adaptive radiations are being described in various families, typically from long-lived lakes, whereas other taxa represent celebrated model systems in the study of ecophenotypic plasticity. Here we examine determinants of shell-shape variation in three nominal species of an ongoing ampullariid radiation in the Malawi Basin (Lanistes nyassanus, L. solidus and Lanistes sp. (ovum-like)) with a common garden experiment and semi-landmark morphometrics. Results We found significant differences in survival and fecundity among these species in contrasting habitats. Morphological differences observed in the wild persisted in our experiments for L. nyassanus versus L. solidus and L. sp. (ovum-like), but differences between L. solidus and L. sp. (ovum-like) disappeared and re-emerged in the F1 and F2 generations, respectively. These results indicate that plasticity occurred, but that it is not solely responsible for the observed differences. Our experiments provide the first unambiguous evidence for genetic divergence in shell morphology in an ongoing freshwater gastropod radiation in association with marked fitness differences among species under controlled habitat conditions. Conclusions Our results indicate that differences in shell morphology among Lanistes species occupying different habitats have an adaptive value. These results also facilitate an accurate reinterpretation of morphological variation in fossil Lanistes radiations, and thus macroevolutionary dynamics. Finally, our work testifies that the shells of freshwater gastropods may retain signatures of adaptation at low taxonomic levels, beyond representing an evolutionary novelty responsible for much of the diversity and disparity in mollusks altogether.

scholarly journals To Double-Brood or not? Individual Variation in the Reproductive Effort in Black-Throated Blue Warblers (Dendroica Caerulescens)

The Auk ◽  
2005 ◽  
Vol 122 (3) ◽  
pp. 902-914 ◽  
Author(s):  
Laura R. Nagy ◽  
Richard T. Holmes
Keyword(s):  
Food Availability ◽  
Individual Variation ◽  
Substantial Effect ◽  
Population Variation ◽  
Key Factors ◽  
Dendroica Caerulescens ◽  
Factors Influencing ◽  
First Clutch ◽  
Breeding Attempt ◽  
Second Clutch

AbstractIndividuals within a population vary in important fitness components, such as reproductive success. In general, females can maximize the number of young they produce by altering either the number of young per breeding attempt or the number of breeding attempts per season. In short-lived species, and especially in small passerine birds, number of breeding attempts per season varies markedly among individuals. Here, we evaluated factors influencing whether female Blackthroated Blue Warblers (Dendroica caerulescens) initiated additional nests after a successful breeding attempt (i.e. double-brooded). The percentage of females that laid a second clutch after successfully fledging a first brood ranged from 0 to 87% and averaged 53% (n = 7 years). Multiple logistic regression and AICc model selection indicated that double-brooded females bred in territories with greater food availability and produced heavier nestlings than single-brooded females. Female age, male age, date of first breeding attempt, and number of young in the first clutch were not included in the best-fit model. Older females, however, produced heavier fledglings, and females mated to older males occurred on territories with greater food availability, indicating that age contributed to individual variation in reproductive output. Because the proportion of females that produce multiple broods within a season can have a substantial effect on the annual fecundity of a population, variation among females and among the territories they occupy (i.e. habitat quality) are key factors influencing population dynamics in this and other multibrooded, shortlived species.Poner Nidadas Dobles o No? Variación Individual en el Esfuerzo Reproductivo en Dendroica caerulescens

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