Phenotypic variability predicts decision accuracy in unicellular organisms

When deciding between different options, animals including humans face the dilemma that fast decisions tend to be erroneous, whereas accurate decisions tend to be relatively slow. Recently, it has been suggested that differences in the efficacy with which animals make a decision relate closely to individual behavioural differences. In this paper, we tested this hypothesis in a unique unicellular organism, the slime mould Physarum polycephalum . We first confirmed that slime moulds differed consistently in their exploratory behaviour from ‘fast’ to ‘slow’ explorers. Second, we showed that slow explorers made more accurate decisions than fast explorers. Third, we demonstrated that slime moulds integrated food cues in time and achieved higher accuracy when sampling time was longer. Lastly, we showed that in a competition context, fast explorers excelled when a single food source was offered, while slow explorers excelled when two food sources varying in quality were offered. Our results revealed that individual differences in accuracy were partly driven by differences in exploratory behaviour. These findings support the hypothesis that decision-making abilities are associated with behavioural types, even in unicellular organisms.

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Phenotypic variability in unicellular organisms: from calcium signalling to social behaviour

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2015.2322 ◽

2015 ◽

Vol 282 (1819) ◽

pp. 20152322 ◽

Cited By ~ 17

Author(s):

David Vogel ◽

Stamatios C. Nicolis ◽

Alfonso Perez-Escudero ◽

Vidyanand Nanjundiah ◽

David J. T. Sumpter ◽

...

Keyword(s):

Social Interactions ◽

Phenotypic Variability ◽

Cell Signalling ◽

Calcium Signalling ◽

Social Strategies ◽

Unicellular Organism ◽

Unicellular Organisms ◽

Behavioural Phenotypes ◽

The Mean ◽

Living Organisms

Historically, research has focused on the mean and often neglected the variance. However, variability in nature is observable at all scales: among cells within an individual, among individuals within a population and among populations within a species. A fundamental quest in biology now is to find the mechanisms that underlie variability. Here, we investigated behavioural variability in a unique unicellular organism, Physarum polycephalum . We combined experiments and models to show that variability in cell signalling contributes to major differences in behaviour underpinning some aspects of social interactions. First, following thousands of cells under various contexts, we identified distinct behavioural phenotypes: ‘slow–regular–social’, ‘fast–regular–social’ and ‘fast–irregular–asocial’. Second, coupling chemical analysis and behavioural assays we found that calcium signalling is responsible for these behavioural phenotypes. Finally, we show that differences in signalling and behaviour led to alternative social strategies. Our results have considerable implications for our understanding of the emergence of variability in living organisms.

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Chemotactic network responses to live bacteria show independence of phagocytosis from chemoreceptor sensing

eLife ◽

10.7554/elife.24627 ◽

2017 ◽

Vol 6 ◽

Cited By ~ 10

Author(s):

Netra Pal Meena ◽

Alan R Kimmel

Keyword(s):

Intracellular Signaling ◽

Molecular Model ◽

High Sensitivity ◽

Signal Propagation ◽

Model Systems ◽

Food Sources ◽

Signaling Networks ◽

Live Bacteria ◽

Unicellular Organisms ◽

Multiple Ligands

Aspects of innate immunity derive from characteristics inherent to phagocytes, including chemotaxis toward and engulfment of unicellular organisms or cell debris. Ligand chemotaxis has been biochemically investigated using mammalian and model systems, but precision of chemotaxis towards ligands being actively secreted by live bacteria is not well studied, nor has there been systematic analyses of interrelationships between chemotaxis and phagocytosis. The genetic/molecular model Dictyostelium and mammalian phagocytes share mechanistic pathways for chemotaxis and phagocytosis; Dictyostelium chemotax toward bacteria and phagocytose them as food sources. We quantified Dictyostelium chemotaxis towards live gram positive and gram negative bacteria and demonstrate high sensitivity to multiple bacterially-secreted chemoattractants. Additive/competitive assays indicate that intracellular signaling-networks for multiple ligands utilize independent upstream adaptive mechanisms, but common downstream targets, thus amplifying detection at low signal propagation, but strengthening discrimination of multiple inputs. Finally, analyses of signaling-networks for chemotaxis and phagocytosis indicate that chemoattractant receptor-signaling is not essential for bacterial phagocytosis.

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Convergent polymorphism between stream and lake habitats: the case of brook char

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/cjfas-2015-0116 ◽

2015 ◽

Vol 72 (9) ◽

pp. 1406-1414 ◽

Cited By ~ 8

Author(s):

Kurt M. Samways ◽

Peter R. Leavitt ◽

Pierre Magnan ◽

Marco A. Rodríguez ◽

Pedro R. Peres-Neto

Keyword(s):

Trophic Position ◽

Swimming Performance ◽

Phenotypic Variability ◽

Isotope Analysis ◽

Morphological Plasticity ◽

Trophic Relationships ◽

Food Sources ◽

Individual Species ◽

Body Morphology ◽

Brook Char

Phenotypic variability represents an important factor allowing species to adapt to local environmental conditions, but mechanisms underlying such variation are incompletely understood. This study investigated whether habitat-specific demands on swimming performance or difference in trophic relationships in lakes (pelagic, littoral) and streams (riffle, pool) were significant predictors of phenotypic variation exhibited by brook char (Salvelinus fontinalis), the only fish in the study habitats. Specifically, we hypothesized that pelagic and riffle habitats would impose greater selective pressures associated with swimming, resulting in body morphologies that were dorsoventrally compressed, anterior–posteriorly elongated, and that exhibited a long, narrow caudal peduncle. Geometric morphometrics was applied in a quantitative analysis of body morphology among habitats, whereas stable isotope analysis was used to differentiate between food sources. Analyses revealed that while body morphology differed between lake and stream habitats, there was convergence between the pelagic and riffle habitats, as well as among littoral and riffle and pool environments. The littoral and pool habitats were thought to be more structurally complex, thereby selecting for increased maneuverability but lower sustained swimming and correspondingly deeper bodies with shorter, dorsoventrally expanded caudal peduncles. Carbon source and trophic position did not differ among habitats with a system, suggesting that feeding was not the main influence on morphological plasticity; however, fish in the stream were feeding at a higher trophic position than fish in the lake. These findings suggest that individual species may take advantage of morphological variation to better adapt local surroundings.

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Physical Non-Contact Communication between Microscopic Aquatic Species: Novel Experimental Evidences for an Interspecies Information Exchange

Journal of Biophysics ◽

10.1155/2016/7406356 ◽

2016 ◽

Vol 2016 ◽

pp. 1-5 ◽

Cited By ~ 2

Author(s):

Daniel Fels

Keyword(s):

Electromagnetic Fields ◽

Information Exchange ◽

Optical Spectrum ◽

Proliferation Rate ◽

Aquatic Species ◽

Paramecium Caudatum ◽

Unicellular Organism ◽

Unicellular Organisms

Previous experiments on physical non-contact communication within same species gave rise to test for this type of communication also across the species border, which was the aim of the present study. It was found that autotrophic unicellular organisms (Euglena viridis), separated by cuvettes, affected the proliferation rate of heterotrophic unicellular organisms (Paramecium caudatum). Further, the heterotrophic unicellular organism affected also the proliferation rate of a multicellular heterotrophic organism (Rotatoria sp.) and vice versa. In the case when populations (of Euglena viridis and Paramecium caudatum) were shielded against electromagnetic fields in the optical spectrum from each other, no effects were measured. The results may support the notion that the organisation of ecosystems relies also on the exchange of electromagnetic fields from their constituting biosystems.

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Octopamine mediates starvation-induced hyperactivity in adult Drosophila

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1417838112 ◽

2015 ◽

Vol 112 (16) ◽

pp. 5219-5224 ◽

Cited By ~ 93

Author(s):

Zhe Yang ◽

Yue Yu ◽

Vivian Zhang ◽

Yinjun Tian ◽

Wei Qi ◽

...

Keyword(s):

Energy Intake ◽

Energy Homeostasis ◽

Neural Mechanism ◽

Nutrient Sensing ◽

Food Sources ◽

Food Cues ◽

Feeding Behaviors ◽

Behavioral Paradigm ◽

Necessary And Sufficient ◽

Induced Changes

Starved animals often exhibit elevated locomotion, which has been speculated to partly resemble foraging behavior and facilitate food acquisition and energy intake. Despite its importance, the neural mechanism underlying this behavior remains unknown in any species. In this study we confirmed and extended previous findings that starvation induced locomotor activity in adult fruit flies Drosophila melanogaster. We also showed that starvation-induced hyperactivity was directed toward the localization and acquisition of food sources, because it could be suppressed upon the detection of food cues via both central nutrient-sensing and peripheral sweet-sensing mechanisms, via induction of food ingestion. We further found that octopamine, the insect counterpart of vertebrate norepinephrine, as well as the neurons expressing octopamine, were both necessary and sufficient for starvation-induced hyperactivity. Octopamine was not required for starvation-induced changes in feeding behaviors, suggesting independent regulations of energy intake behaviors upon starvation. Taken together, our results establish a quantitative behavioral paradigm to investigate the regulation of energy homeostasis by the CNS and identify a conserved neural substrate that links organismal metabolic state to a specific behavioral output.

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Stress signalling in acellular slime moulds and its detection by conspecifics

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2019.0470 ◽

2020 ◽

Vol 375 (1802) ◽

pp. 20190470 ◽

Cited By ~ 1

Author(s):

L. Briard ◽

C. Goujarde ◽

C. Bousquet ◽

A. Dussutour

Keyword(s):

Stress Responses ◽

Experimental Tests ◽

Slime Moulds ◽

Rapid Changes ◽

Unicellular Organisms ◽

Recognition Systems ◽

Physiological Reactions ◽

Evolving Models ◽

Homogeneous Environment ◽

Stress Signalling

Unicellular organisms live in unpredictable environments. Therefore, they need to continuously assess environmental conditions and respond appropriately to survive and thrive. When subjected to rapid changes in their environment or to cellular damages, unicellular organisms such as bacteria exhibit strong physiological reactions called stress responses that can be sensed by conspecifics. The ability to detect and use stress-related cues released by conspecifics to acquire information about the environment constitutes an adaptive survival response by prompting the organism to avoid potential dangers. Here, we investigate stress signalling and its detection by conspecifics in a unicellular organism, Physarum polycephalum . Slime moulds were subjected to either biotic (i.e. nutritional) or abiotic (i.e. chemical and light) stressors or left undisturbed while they were exploring a homogeneous environment. Then, we observed the responses of slime moulds facing a choice between cues released by stressed clone mates and cues released by undisturbed ones. We found that slime moulds actively avoided environments previously explored by stressed clone mates. These results suggest that slime moulds, like bacteria or social amoeba, exhibit physiological responses to biotic and abiotic stresses that can be sensed by conspecifics. Our results establish slime moulds as a promising new model to investigate the use of social information in unicellular organisms. This article is part of the theme issue ‘Signal detection theory in recognition systems: from evolving models to experimental tests’.

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