scholarly journals Covarying Shell Growth Parameters and the Regulation of Shell Shape in Marine Bivalves: A Case Study on Tellinoidea

2014 ◽  
Vol 2014 ◽  
pp. 1-10
Author(s):  
Jean Béguinot
Keyword(s):  
Growth Parameters ◽  
Shell Growth ◽  
Shell Shape ◽  
Shape Parameters ◽  
Bivalve Molluscs ◽  
Severe Limitation ◽  
Interspecific Variability ◽  
Marine Bivalves ◽  
Shape Descriptions

Specific parameters characterising shell shape may arguably have a significant role in the adaptation of bivalve molluscs to their particular environments. Yet, suchfunctionally relevantshape parameters (shell outline elongation, dissymmetry, and ventral convexity) are not those parameters that the animal may directly control. Rather than shell shape, the animal regulates shell growth. Accordingly, an alternative,growth-baseddescription of shell-shape is best fitted to understand how the animal may control the achieved shell shape. The key point is, in practice, to bring out the link between those two alternative modes of shell-shape descriptions, that is, to derive the set of equations which connects thegrowth-basedshell-shape parameters to thefunctionally relevantshell-shape parameters. Thus, a preliminary object of this note is toderivethis set of equations as a tool for further investigations. A second object of this work is to provide an illustrative example of implementation of this tool. I report on an unexpected negative covariance between growth-based parameters and show how this covariance results in a severe limitation of the range of interspecific variability of the degree of ventral convexity of the shell outline within the superfamily Tellinoidea. Hypotheses are proposed regarding the constraints possibly at the origin of this limitation of interspecific variability.

scholarly journals Covariations between Shell-Growth Parameters and the Control of the Ranges of Variation of Functionally Relevant Shell-Shape Parameters in Bivalves: A Theoretical Approach

2014 ◽  
Vol 2014 ◽  
pp. 1-8
Author(s):  
Jean Béguinot
Keyword(s):  
Growth Parameters ◽  
Shell Growth ◽  
Practical Interest ◽  
Theoretical Background ◽  
Shell Shape ◽  
Shape Parameters ◽  
Functional Parameters ◽  
Intraspecific Variations ◽  
Adaptive Constraints ◽  
Geometrical Relationships

Major traits of shell shape in bivalves may alternatively be described in terms of (i) functionally relevant parameters, assumed to play a significant role in the adaptation of bivalves molluscs to their environments (such as the shell-outline elongation E, ventral convexity K, and dissymmetry D), or (ii) growth-based parameters, directly controlled by the animal. Due to the geometrical linkage between functionally-relevant and growth-based parameters, adaptive constraints that may either widen or narrow the respective ranges of variations of the functional parameters lead to the onset of specific covariations (either positive or negative) between the growth-based parameters. This has practical interest since adaptive constraints are often difficult to identify directly, while they can be conveniently inferred indirectly via the easily recorded patterns of covariances between growth-based parameters. Hereafter, I provide the theoretical background of this tool, including (1) establishing the geometrical relationships between growth-based and functionally relevant parameters and (2) then specifying the correspondences between the different patterns of adaptive constraints, widening or narrowing the variations of the functional parameters and the corresponding patterns of covariations between the growth-based parameters. Illustrative examples of the practical use of this tool are provided, considering both interspecific and intraspecific variations within marine and fresh-water clams.

scholarly journals Unexpected Covariances between Shell Growth Parameters are Controlling the Range of Interspecific Variations of Shell shape in the Deep-Sea Clams Genus Calyptogena (Bivalvia: Veneroida)

2018 ◽  
pp. 1-13
Author(s):  
Jean Béguinot
Keyword(s):  
Environmental Conditions ◽  
Deep Sea ◽  
Growth Parameters ◽  
Shell Growth ◽  
Niche Differentiation ◽  
Interspecific Variation ◽  
Shell Shape ◽  
Shallow Waters ◽  
Mechanical Resistance ◽  
Interspecific Variations

In Bivalves, shell shape descriptors (in particular, elongation E, dissymmetry D, ventral convexity K) are considered functionally-relevant parameters, each of them likely being exposed to specific selective pressures, according to environmental conditions. Indeed, previous investigations, have repeatedly confirmed that different types of constraints do apply to the respective ranges of interspecific variations of E, D, K: in particular, a trend for a substantially extended range of interspecific variation of shell-elongation E (likely attributed to niche differentiation) and, on the contrary, a trend for a severely restricted range of interspecific variation of ventral-convexity K (closely centered at an optimum for mechanical resistance of valves). In turn, due to rigid geometrical relationships linking shell-shape to shell-growth, this pattern of constraints on shell-shape variations implies, mathematically, the occurrence of specifically associated covariances between shell-growth parameters, the occurrence of which were, indeed, repeatedly observed within all groups of shallow-waters clams examined so far. Yet, the fairly different environmental conditions prevailing at bathyal / abyssal depths invite addressing comparatively some typically deep-sea clams; hereafter the genus Calyptogena. Contrary to expectation, the same types of covariances between shell-growth parameters are reported in deep-sea Calyptogena as those reported in shallow-waters clams, thus suggesting less dissimilar patterns of constraints than expected between shallow waters and deep-sea conditions.

Ontogeny in the steinmanellines (Bivalvia: Trigoniida): an intra- and interspecific appraisal using the Early Cretaceous faunas from the Neuquén Basin as a case study

Paleobiology ◽  
2021 ◽  
pp. 1-23
Author(s):  
Pablo S. Milla Carmona ◽  
Dario G. Lazo ◽  
Ignacio M. Soto
Keyword(s):  
Trajectory Analysis ◽  
Sedentary Lifestyle ◽  
Shape Change ◽  
Shell Shape ◽  
Shape Variation ◽  
Ontogenetic Changes ◽  
Ontogenetic Trajectories ◽  
Higher Genus ◽  
Gradual Decay

Abstract Despite the paleontological relevance and paleobiological interest of trigoniid bivalves, our knowledge of their ontogeny—an aspect of crucial evolutionary importance—remains limited. Here, we assess the intra- and interspecific ontogenetic variations exhibited by the genus Steinmanella Crickmay (Myophorellidae: Steinmanellinae) during the early Valanginian–late Hauterivian of Argentina and explore some of their implications. The (ontogenetic) allometric trajectories of seven species recognized for this interval were estimated from longitudinal data using 3D geometric morphometrics, segmented regressions, and model selection tools, and then compared using trajectory analysis and allometric spaces. Our results show that within-species shell shape variation describes biphasic ontogenetic trajectories, decoupled from ontogenetic changes shown by sculpture, with a gradual decay in magnitude as ontogeny progresses. The modes of change characterizing each phase (crescentic growth and anteroposterior elongation, respectively) are conserved across species, thus representing a feature of Steinmanella ontogeny; its evolutionary origin is inferred to be a consequence of the rate modification and allometric repatterning of the ancestral ontogeny. Among species, trajectories are more variable during early ontogenetic stages, becoming increasingly conservative at later stages. Trajectories’ general orientation allows recognition of two stratigraphically consecutive groups of species, hinting at a potentially higher genus-level diversity in the studied interval. In terms of functional morphology, juveniles had a morphology more suited for active burrowing than adults, whose features are associated with a sedentary lifestyle. The characteristic disparity of trigoniids could be related to the existence of an ontogenetic period of greater shell malleability betrayed by the presence of crescentic shape change.

What is gradualism? Cryptic speciation in globorotaliid foraminifera

Paleobiology ◽  
1996 ◽  
Vol 22 (3) ◽  
pp. 386-405 ◽  
Author(s):  
Richard D. Norris ◽  
Richard M. Corfield ◽  
Julie Cartlidge
Keyword(s):  
Reproductive Isolation ◽  
Morphological Changes ◽  
Morphological Evolution ◽  
Reproductive Ecology ◽  
Shell Growth ◽  
Shell Shape ◽  
Planktic Foraminifera ◽  
Near Surface ◽  
Surface Ocean ◽  
Speciation Event

Analysis of the evolution of the Globorotalia (Fohsella) lineage of planktic foraminifera suggests that reproductive ecology and shell shape have evolved independently in this group. The silhouette of fohsellid shells displays a nearly unbroken anagenetic trend, yet isotopic data show that the fohsellids changed their depth of reproduction during the anagenetic evolution of their skeletons. Remarkably, there are no correlations between anagenesis in skeletal shape and the establishment of reproductive isolation. Apparently, anagenesis masks at least one speciation event that is apparent only in the isotopic evidence for a change in reproductive ecology. Although anagenetic trends have been widely cited as evidence for gradual speciation in planktic foraminifera and other microfossil groups, our data suggest that they should not always be considered to record either the tempo or mode of speciation.Speciation was apparently uncoupled from morphological evolution in fohsellids because these evolutionary phenomena occurred in different phases of ontogeny. Gradual morphological changes were associated with the main phase of shell growth of both the ancestor and descendant species in the near-surface ocean. Reproductive isolation occurred when ancestral and descendant populations became established at different depths near the end of the life cycle. Morphological evolution may also be uncoupled from reproductive isolation in other organisms that experience very different selection pressures over the duration of their ontogenies, such as parasites with many hosts, species with multiple phases of metamorphosis, and organisms that broadcast their gametes.

scholarly journals Regeneration, growth of Hill Sal and plant diversity in Community Forest: A case study from Pragatisil Community Forest in Kaski District, Western Nepal

2016 ◽  
Vol 23 (2) ◽  
pp. 37-43 ◽  
Author(s):  
B. K. Paudyal
Keyword(s):  
Plant Species ◽  
Plant Diversity ◽  
Growth Parameters ◽  
Basal Area ◽  
Community Forest ◽  
Shorea Robusta ◽  
Plot Size ◽  
Regeneration Status ◽  
M 10

The study was conducted in the Pragatisil Community Forest, Kaski District, Nepal in 2012 to assess the regeneration status of Sal (Shorea robusta) seedlings, its growth and plant diversity. A plot size of 25 m × 20 m was employed for trees, 10 m ×10 m for poles and 5 m × 5 m for regeneration. The growth parameters measured were dbh and height. A factorial arrangement of treatments was employed; the treatments being slope and aspect. The results showed that there was significant (p<0.05) effect of slope on dbh and basal area whereas there was no effect of aspect on growth parameters measured in the Pragatisil Community Forest. The regeneration of Sal was satisfactory (6,126 seedlings/ha), and there were 32 plant species in this forest. As there was higher basal area per ha in the Pragatisil Community Forest, it is recommended to have thinning of 40% of basal area for enhancing growth of remaining stems.Banko Janakari, Vol. 23, No. 2, 2013

scholarly journals Fully quantum calculations of the line-shape parameters for the Hartmann-Tran profile: A CO-Ar case study

2020 ◽  
Vol 243 ◽  
pp. 106803 ◽  
Author(s):  
Grzegorz Kowzan ◽  
Piotr Wcisło ◽  
Michał Słowiński ◽  
Piotr Masłowski ◽  
Alexandra Viel ◽  
...  
Keyword(s):  
Line Shape ◽  
Quantum Calculations ◽  
Shape Parameters

scholarly journals Age and growth variability of the yellow clam (Mesodesma mactroides) in two populations from Argentina: implications under climate change

2020 ◽  
Vol 98 (7) ◽  
pp. 481-494
Author(s):  
M.C. Risoli ◽  
A. Baldoni ◽  
J. Giménez ◽  
B.J. Lomovasky
Keyword(s):  
Climate Change ◽  
Cross Sections ◽  
Growth Rates ◽  
Growth Parameters ◽  
Shell Growth ◽  
Condition Index ◽  
Age And Growth ◽  
Shell Mass ◽  
Growth Variability ◽  
Two Populations

Morphometric relationships and age and growth rates of the yellow clam (Mesodesma mactroides Reeve, 1854 = Amarilladesma mactroides (Reeve, 1854)) were compared in two populations from Argentina: Santa Teresita (36°32′00″S) and Mar del Plata (37°57′52″S). The Santa Teresita clams were heavier (shell, soft parts) than the Mar del Plata clams. Cross sections stained with Mutvei’s solution and acetate peels revealed an internal shell growth pattern of well-defined slow-growing translucent bands and alternating fast-growing opaque bands. Translucent bands (clusters) representing external rings were formed mostly during October in both sites, coinciding with gonadal maturation processes and spawning. Data confirm the annual formation of translucent bands in this species. Comparison of growth parameters showed a higher growth rate k and lower maximum age in Mar del Plata (8 years) than in Santa Teresita (9 years), which could be triggered by differences in salinity between localities due to the influence of the Rio de la Plata estuary, which is strongly linked to climate variability. Shell mass condition index and Oceanic Niño Index were negatively correlated, showing the influence of El Niño in shell properties of the species. Considering that events are becoming more intense and frequent, changes in growth rates and shell properties of Santa Teresita’s population could be expected to be more vulnerable under climate change.

scholarly journals New Records of Two Non-native Clam Species (Bivalvia: Cardiidae) from the Coastal Waters of Bangladesh

2019 ◽  
pp. 1-8
Author(s):  
Md. Royhanur Islam ◽  
Sadman Sakin Nirob ◽  
Md. Habibur Rahman Molla ◽  
Kauser Rahman ◽  
Md. Mozammal Haque ◽  
...  
Keyword(s):  
Marine Invertebrates ◽  
Marine Bivalve ◽  
Bivalve Molluscs ◽  
Potential Biomarker ◽  
Marine Bivalves ◽  
The Family ◽  
The Tropics ◽  
Increasing Trends ◽  
Brackish Water Species ◽  
Water Species

Benthic suspension feeders, such as many marine bivalve molluscs, influence the nutrient and organic cycles of benthic and pelagic systems through their ability to filter a wide size range of particles and deposit organic matters that sink to the bottom. They also play important roles in coastal and marine ecosystems by filtering the water and serving as habitat and prey for a variety of sea life. Due to the increasing trends of environmental contaminations in recent years, many bivalves have been using as a potential biomarker for assessing the worse environment. Moreover, the shell of a bivalve is comprised of calcium carbonate, which may support thousands of calciferous organisms into the water body. Mostly, bivalves inhabit the tropics, as well as temperate and boreal waters, and they can survive and even flourish in extreme environmental conditions like Bangladesh. Nowadays, many bivalve molluscs have been identified as a superior source of bioactive compounds and are using for pharmaceutical and nutraceutical purposes as well as other applications. However, until now, few systematic studies on marine bivalve molluscs have been conducted through which a total of 437 marine and brackish water species were identified and recorded in Bangladesh. But still, our knowledge of taxonomy and systematic on marine molluscs are primitive in the context of the country. Here we report two new species of bivalve molluscs, Parvicardium exiguum and Trachycardium procerum belonging to the family Cardiidae, from the Kutubdia Island of Bangladesh. The study added these two bivalve species, which has not been recorded from the coastal zone of Kutubdia Island during the previous studies. To sum up, studies and survey on taxonomy and systematics in marine bivalves will provide new dimensions for further research about these important marine invertebrates.

Sign in / Sign up

Export Citation Format

Share Document