scholarly journals A 15-million-year-long record of phenotypic evolution in the heavily calcified coccolithophore <i>Helicosphaera</i> and its biogeochemical implications

2020 ◽  
Vol 17 (11) ◽  
pp. 2955-2969 ◽  
Author(s):  
Luka Šupraha ◽  
Jorijntje Henderiks
Keyword(s):  
Cell Size ◽  
Resource Limitation ◽  
Tropical Indian Ocean ◽  
Adaptive Strategies ◽  
Cellular Level ◽  
Phenotypic Evolution ◽  
Production Rates ◽  
Environmental Forcing ◽  
Modern Species ◽  
Mean Size

Abstract. The biogeochemical impact of coccolithophores is defined not only by their overall abundance in the oceans but also by wide ranges in physiological traits such as cell size, degree of calcification and carbon production rates between different species. Species' sensitivity to environmental forcing has been suggested to relate to their cellular PIC : POC (particulate inorganic carbon : particulate organic carbon) ratio and other physiological constraints. Understanding both the short-term and longer-term adaptive strategies of different coccolithophore lineages, and how these in turn shape the biogeochemical role of the group, is therefore crucial for modeling the ongoing changes in the global carbon cycle. Here we present data on the phenotypic evolution of a large and heavily calcified genus Helicosphaera (order Zygodiscales) over the past 15 million years (Myr), at two deep-sea drill sites in the tropical Indian Ocean and temperate South Atlantic. The modern species Helicosphaera carteri, which displays ecophysiological adaptations in modern strains, was used to benchmark the use of its coccolith morphology as a physiological proxy in the fossil record. Our results show that, on the single-genotype level, coccolith morphology has no correlation with growth rates, cell size or PIC and POC production rates in H. carteri. However, significant correlations of coccolith morphometric parameters with cell size and physiological rates do emerge once multiple genotypes or closely related lineages are pooled together. Using this insight, we interpret the phenotypic evolution in Helicosphaera as a global, resource-limitation-driven selection for smaller cells, which appears to be a common adaptive trait among different coccolithophore lineages, from the warm and high-CO2 world of the middle Miocene to the cooler and low-CO2 conditions of the Pleistocene. However, despite a significant decrease in mean coccolith size and cell size, Helicosphaera kept a relatively stable PIC : POC ratio (as inferred from the coccolith aspect ratio) and thus highly conservative biogeochemical output on the cellular level. We argue that this supports its status as an obligate calcifier, like other large and heavily calcified genera such as Calcidiscus and Coccolithus, and that other adaptive strategies, beyond size adaptation, must support the persistent, albeit less abundant, occurrence of these taxa. This is in stark contrast with the ancestral lineage of Emiliania and Gephyrocapsa, which not only decreased in mean size but also displayed much higher phenotypic plasticity in their degree of calcification while becoming globally more dominant in plankton communities.

scholarly journals A 15 million-year long record of phenotypic evolution in the heavily calcified coccolithophore <i>Helicosphaera</i> and its biogeochemical implications

2020 ◽  
Author(s):  
Luka Šupraha ◽  
Jorijntje Henderiks
Keyword(s):  
Cell Size ◽  
Resource Limitation ◽  
Tropical Indian Ocean ◽  
Adaptive Strategies ◽  
Cellular Level ◽  
Phenotypic Evolution ◽  
Environmental Forcing ◽  
Modern Species ◽  
Wide Range ◽  
Mean Size

Abstract. The biogeochemical performance of coccolithophores is defined by their overall abundance in the oceans, but also by a wide range in cell size, degree of calcification and carbon production rates between different species. Species’ sensitivity to environmental forcing has been suggested to relate to their cellular PIC : POC ratio and other physiological constraints. Understanding both the short and longer-term adaptive strategies of different coccolithophore lineages, and how these in turn shape the biogeochemical role of the group, is therefore crucial for modeling the ongoing changes in the global carbon cycle. Here we present data on the phenotypic evolution of a large and heavily-calcified genus Helicosphaera (order Zygodiscales) over the past 15 million years (Ma), at two deep-sea drill sites from the tropical Indian Ocean and temperate South Atlantic. The modern species Helicosphaera carteri, which displays eco-physiological adaptations in modern strains, was used to benchmark the use of its coccolith morphology as a physiological proxy in the fossil record. Our results show that, on the single-genotype level, coccolith morphology has no correlation with physiological traits in H. carteri. However, significant correlations of coccolith morphometric parameters with cell size and physiological rates do emerge once multiple genotypes or closely related lineages are pooled together. Using this insight, we interpret the phenotypic evolution in Helicosphaera as a global, resource limitation-driven selection for smaller cells, which appears to be a common adaptive trait among different coccolithophore lineages, from the warm and high-CO2 world of the middle Miocene to the cooler and low-CO2 conditions of the Pleistocene. However, despite a significant decrease in mean size, Helicosphaera kept relatively stable PIC : POC (as inferred from the coccolith aspect ratio) and thus highly conservative biogeochemical output on the cellular level. We argue that this supports its status as an obligate calcifier, like other large and heavily-calcified genera such as Calcidiscus and Coccolithus, and that other adaptive strategies, beyond size-adaptation, must support the persistent, albeit less abundant, occurrence of these taxa. This is in stark contrast with the ancestral lineage of Emiliania and Gephyrocapsa, which not only decreased in mean size but also displayed much higher phenotypic plasticity in degree of calcification while becoming globally more dominant in plankton communities.

scholarly journals Chaos and the (un)predictability of evolution in a changing environment

2017 ◽  
Author(s):  
Artur Rego-Costa ◽  
Florence Débarre ◽  
Luis-Miguel Chevin
Keyword(s):  
Evolutionary Dynamics ◽  
Initial Conditions ◽  
Strong Dependence ◽  
Environmental Stochasticity ◽  
Phenotypic Evolution ◽  
Evolutionary System ◽  
Chaotic Oscillations ◽  
Changing Environment ◽  
Environmental Forcing ◽  
Evolutionary Trajectories

Among the factors that may reduce the predictability of evolution, chaos, characterized by a strong dependence on initial conditions, has received much less attention than randomness due to genetic drift or environmental stochasticity. It was recently shown that chaos in phenotypic evolution arises commonly under frequency-dependent selection caused by competitive interactions mediated by many traits. This result has been used to argue that chaos should often make evolutionary dynamics unpredictable. However, populations also evolve largely in response to external changing environments, and such environmental forcing is likely to influence the outcome of evolution in systems prone to chaos. We investigate how a changing environment causing oscillations of an optimal phenotype interacts with the internal dynamics of an eco-evolutionary system that would be chaotic in a constant environment. We show that strong environmental forcing can improve the predictability of evolution, by reducing the probability of chaos arising, and by dampening the magnitude of chaotic oscillations. In contrast, weak forcing can increase the probability of chaos, but it also causes evolutionary trajectories to track the environment more closely. Overall, our results indicate that, although chaos may occur in evolution, it does not necessarily undermine its predictability.

scholarly journals Hematological convergence between Mesozoic marine reptiles (Sauropterygia) and extant aquatic amniotes elucidates diving adaptations in plesiosaurs

PeerJ ◽  
2019 ◽  
Vol 7 ◽  
pp. e8022 ◽  
Author(s):  
Corinna V. Fleischle ◽  
P. Martin Sander ◽  
Tanja Wintrich ◽  
Kai R. Caspar
Keyword(s):  
Cell Size ◽  
Marine Mammals ◽  
Middle Triassic ◽  
Sensory Ecology ◽  
Cellular Level ◽  
Thin Sections ◽  
Marine Reptiles ◽  
Canal Diameter ◽  
Physiological Adaptations ◽  
Pelagic Habitat

Plesiosaurs are a prominent group of Mesozoic marine reptiles, belonging to the more inclusive clades Pistosauroidea and Sauropterygia. In the Middle Triassic, the early pistosauroid ancestors of plesiosaurs left their ancestral coastal habitats and increasingly adapted to a life in the open ocean. This ecological shift was accompanied by profound changes in locomotion, sensory ecology and metabolism. However, investigations of physiological adaptations on the cellular level related to the pelagic lifestyle are lacking so far. Using vascular canal diameter, derived from osteohistological thin-sections, we show that inferred red blood cell size significantly increases in pistosauroids compared to more basal sauropterygians. This change appears to have occurred in conjunction with the dispersal to open marine environments, with cell size remaining consistently large in plesiosaurs. Enlarged red blood cells likely represent an adaptation of plesiosaurs repeated deep dives in the pelagic habitat and mirror conditions found in extant marine mammals and birds. Our results emphasize physiological aspects of adaptive convergence among fossil and extant marine amniotes and add to our current understanding of plesiosaur evolution.

scholarly journals Scaling gene expression for cell size control and senescence in Saccharomyces cerevisiae

2020 ◽  
Author(s):  
Yuping Chen ◽  
Bruce Futcher
Keyword(s):  
Gene Expression ◽  
Cell Size ◽  
Size Control ◽  
Gene Expression Program ◽  
Set Point ◽  
Size Dependent ◽  
Large Size ◽  
Mean Size ◽  
Almost All ◽  
Expression Program

Abstract Cells divide with appropriate frequency by coupling division to growth—that is, cells divide only when they have grown sufficiently large. This process is poorly understood, but has been studied using cell size mutants. In principle, mutations affecting cell size could affect the mean size (“set-point” mutants), or they could affect the variability of sizes (“homeostasis” mutants). In practice, almost all known size mutants affect set-point, with little effect on size homeostasis. One model for size-dependent division depends on a size-dependent gene expression program: Activators of cell division are over-expressed at larger and larger sizes, while inhibitors are under-expressed. At sufficiently large size, activators overcome inhibitors, and the cell divides. Amounts of activators and inhibitors determine the set-point, but the gene expression program (the rate at which expression changes with cell size) determines the breadth of the size distribution (homeostasis). In this model, set-point mutants identify cell cycle activators and inhibitors, while homeostasis mutants identify regulators that couple expression of activators and inhibitors to size. We consider recent results suggesting that increased cell size causes senescence, and suggest that at very large sizes, an excess of DNA binding proteins leads to size induced senescence.

A STUDY OF SIZE DIFFERENCES IN TWO STRAINS OF CUCURBITA PEPO L.: II. HISTOLOGICAL AND CELLULAR SIZE DIFFERENCES

1957 ◽  
Vol 35 (6) ◽  
pp. 831-843 ◽  
Author(s):  
K. E. von Maltzahn
Keyword(s):  
Cell Division ◽  
Cell Size ◽  
Cucurbita Pepo ◽  
Small Strain ◽  
Cell Types ◽  
Cambial Activity ◽  
Cellular Level ◽  
Organ Size ◽  
Cell Enlargement ◽  
Internode Growth

Size differences were studied on the cellular level in vegetative organs of two purebred strains of Cucurbita pepo L. which differ greatly in inherited size.Mature organ size has been analyzed for the two strains on the histological and cellular levels with particular emphasis on mature internode size. Differences between the strains in tissue and cell size were observed for the main tissue and cell types. Differences in internode length were determined both by differences in cell size and cell numbers. Cambial activity as expressed in numbers of radial immature derivatives and in number of divisions in the interfascicular regions was found to be much greater in CF than in SRC.No important differences were found between the large and small strain in the size of the meristematic and submeristematic regions. Early internode growth in terms of cell division and cell enlargement was also found to be similar in the two strains. It is concluded that the cellular differences found in the mature organ must be due to a longer duration of growth mainly in terms of cell enlargement but also in terms of cell, division. This conclusion is supported by the results obtained on internode growth described in a previous paper.Grafting experiments with apical buds of the two strains did not show any influence of the stock on the scion; mature organ size was determined only by the scion.

scholarly journals Disentangling strictly self-serving mutations from win-win mutations in a mutualistic microbial community

2019 ◽  
Author(s):  
Samuel F. M. Hart ◽  
Jose Mario Bello Pineda ◽  
Chi-Chun Chen ◽  
Robin Green ◽  
Wenying Shou
Keyword(s):  
Microbial Community ◽  
Cell Size ◽  
Release Rate ◽  
Alternative Measure ◽  
Production Rates ◽  
Supply Rate ◽  
Fixed Amount ◽  
Chromosome Duplication ◽  
Yeast Strains ◽  
Engineered Yeast

AbstractMutualisms can be promoted by win-win mutations which directly benefit self (self-serving) and partner (partner-serving). Intuitively, partner-serving phenotype could be quantified as the benefit supply rate to partner by an individual. Here, we demonstrate the inadequacy of this thinking, and propose an alternative measure. Specifically, we evolved well-mixed mutualistic communities where two engineered yeast strains exchanged essential metabolites lysine and hypoxanthine. Among cells that consumed lysine and released hypoxanthine, a chromosome duplication mutation seemed win-win: it improved cell’s affinity for lysine, and increased hypoxanthine release rate per cell. However, increased release rate was due to increased cell size accompanied by increased lysine consumption per birth. Consequently this mutation is solely self-serving, since a fixed amount of intake lysine leads to an identical total hypoxanthine release rate - either by more numerous lower-releasing ancestors or fewer higher-releasing mutants. By extension, individuals with reduced benefit production rates may not be cheaters.

scholarly journals Size and dielectric properties of skeletal stem cells change critically after enrichment and expansion from human bone marrow: consequences for microfluidic cell sorting

2017 ◽  
Vol 14 (133) ◽  
pp. 20170233 ◽  
Author(s):  
Miguel Xavier ◽  
María C. de Andrés ◽  
Daniel Spencer ◽  
Richard O. C. Oreffo ◽  
Hywel Morgan
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Dielectric Properties ◽  
Electrical Properties ◽  
Cell Size ◽  
Membrane Capacitance ◽  
Label Free ◽  
Biophysical Parameter ◽  
Mean Size

The capacity of bone and cartilage to regenerate can be attributed to skeletal stem cells (SSCs) that reside within the bone marrow (BM). Given SSCs are rare and lack specific surface markers, antibody-based sorting has failed to deliver the cell purity required for clinical translation. Microfluidics offers new methods of isolating cells based on biophysical features including, but not limited to, size, electrical properties and stiffness. Here we report the characterization of the dielectric properties of unexpanded SSCs using single-cell microfluidic impedance cytometry (MIC). Unexpanded SSCs had a mean size of 9.0 µm; larger than the majority of BM cells. During expansion, often used to purify and increase the number of SSCs, cell size and membrane capacitance increased significantly, highlighting the importance of characterizing unaltered SSCs. In addition, MIC was used to track the osteogenic differentiation of SSCs and showed an increased membrane capacitance with differentiation. The electrical properties of primary SSCs were indistinct from other BM cells precluding its use as an isolation method. However, the current studies indicate that cell size in combination with another biophysical parameter, such as stiffness, could be used to design label-free devices for sorting SSCs with significant clinical impact.

scholarly journals Density dependence in marine protected populations: a review

2000 ◽  
Vol 27 (2) ◽  
pp. 144-158 ◽  
Author(s):  
J.L. SÁNCHEZ LIZASO ◽  
R. GOÑI ◽  
O. REÑONES ◽  
J.A. GARCÍA CHARTON ◽  
R. GALZIN ◽  
...  
Keyword(s):  
Life History ◽  
Marine Protected Areas ◽  
Resource Limitation ◽  
Management Tools ◽  
Density Dependent ◽  
Mobile Species ◽  
Biological Variables ◽  
Resource Limited ◽  
Mean Size ◽  
Suitable Habitats

The cessation or reduction of fishing in marine protected areas (MPAs) should promote an increase in abundance and mean size and age of previously exploited populations. Thus density-dependent changes in life-history characteristics should occur when populations are allowed to recover in MPAs. In this review, we synthesize the existing information on resource limitation in marine ecosystems, density-dependent changes in life-history traits of exploited populations and evidence for biomass export from MPAs. Most evidence for compensatory changes in biological variables has been derived from observations on populations depleted by high fishing mortality or on strong year classes, but these changes are more evident in juveniles than in adults and in freshwater rather than in marine systems. It is unclear if adults of exploited marine populations are resource limited. This may suggest that exploited populations are controlled mainly by density-independent processes, which could be a consequence of the depleted state of most exploited populations. MPAs could be a useful tool for testing these hypotheses. If we assume that resources become limiting inside MPAs, it is plausible that, if suitable habitats exist, mobile species will search for resources outside of the MPAs, leading to export of biomass to areas which are fished. However, it is not possible to establish from the available data whether this export will be a response to resource limitation inside the MPAs, the result of random movements across MPA boundaries or both. We discuss the implications of this process for the use of MPAs as fisheries management tools.

scholarly journals Environmental effects on body size variation in Drosophila melanogaster and its cellular basis

1997 ◽  
Vol 70 (1) ◽  
pp. 35-43 ◽  
Author(s):  
G. H. DE MOED ◽  
G. DE JONG ◽  
W. SCHARLOO
Keyword(s):  
Drosophila Melanogaster ◽  
Genetic Variation ◽  
Body Size ◽  
Cell Size ◽  
Wing Length ◽  
Size Variation ◽  
Cell Number ◽  
Food Level ◽  
Mean Size ◽  
Food Conditions

Eight isofemale lines of Drosophila melanogaster were raised at four temperatures and at four yeast concentrations in their food. Temperature and food show a significant interaction in determining wing length and thorax length, affecting mean size per line and genetic variation between lines. The combination of low temperature and poor food conditions leads to a sharp increase in the genetic variation over lines of both body size characters. The increase in genetic variation in wing length under less favourable conditions is due to an increase in genetic variation of both cell size and cell number. Changes in wing area in response to both temperature and food level follow a common cell size/cell number trajectory. Changes in wing size are obtained by line-specific changes in the cellular composition of the wing, rather than by changes specific for the environmental factor.

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