The Experts below are selected from a list of 73923 Experts worldwide ranked by ideXlab platform
Sangho Kim - One of the best experts on this subject based on the ideXlab platform.
-
erythrocyte Aggregation may promote uneven spatial distribution of no o2 in the downstream vessel of arteriolar bifurcations
Journal of Biomechanics, 2016Co-Authors: Bumseok Namgung, Hwa Liang Leo, Sangho KimAbstract:This study examined the effect of red blood cell (RBC) Aggregation on nitric oxide (NO) and oxygen (O2) distributions in the downstream vessels of arteriolar bifurcations. Particular attention was paid to the inherent formation of asymmetric cell-free layer (CFL) widths in the downstream vessels and its consequential impact on the NO/O2 bioavailability after the bifurcations. A microscopic image-based two-dimensional transient model was used to predict the NO/O2 distribution by utilizing the in vivo CFL width data obtained under non-, normal- and hyper-aggregating conditions at the pseudoshear rate of 15.6±2.0s(-1). In vivo experimental result showed that the asymmetry of CFL widths was enhanced by the elevation in RBC Aggregation Level. The model demonstrated that NO bioavailability was regulated by the dynamic fluctuation of the local CFL widths, which is corollary to its modulation of wall shear stress. Accordingly, the uneven distribution of NO/O2 was prominent at opposite sides of the arterioles up to six vessel-diameter (6D) away from the bifurcating point, and this was further enhanced by increasing the Levels of RBC Aggregation. Our findings suggested that RBC Aggregation potentially augments both the formation of asymmetric CFL widths and its influence on the uneven distribution of NO/O2 in the downstream flow of an arteriolar bifurcation. The extended heterogeneity of NO/O2 downstream (2D-6D) also implied its potential propagation throughout the entire arteriolar microvasculature.
-
influence of erythrocyte Aggregation at pathological Levels on cell free marginal layer in a narrow circular tube
Clinical Hemorheology and Microcirculation, 2016Co-Authors: Bumseok Namgung, Hiromi Sakai, Sangho KimAbstract:Human red blood cells (RBCs) were perfused in a circular micro-tube (inner diameter of 25 μm) to examine the dynamic changes of cell-free marginal region at both physiological (normal) and pathophysiological (hyper) Levels of RBC Aggregation. The cell-free area (CFA) was measured to provide additional information on the cell-free layer (CFL) width changes in space and time domains. A prominent enhancement in the mean CFL width was found in hyper-aggregating conditions as compared to that in non-aggregating conditions (P < 0.001). The frequent contacts between RBC and the tube wall were observed and the contact frequency was greatly decreased when the Aggregation Level was increased from none to normal (P < 0.05) and to hyper (P < 0.001) Levels. In addition, the enhanced Aggregation from none to hyper Levels significantly enlarged the CFA (P < 0.01). We concluded that the RBC Aggregation at pathophysiological Levels could promote not only the CFL width (one-dimensional parameter) but also the spatiotemporal variation of CFA (two-dimensional parameter).
-
effect of erythrocyte Aggregation at pathological Levels on no o2 transport in small arterioles
Clinical Hemorheology and Microcirculation, 2015Co-Authors: Seungkwan Cho, Bumseok Namgung, Han Sung Kim, Hwa Liang Leo, Sangho KimAbstract:This study examined the effects of red blood cell (RBC) Aggregation at pathological Levels on NO/O2 transport in small arterioles. Transient gas diffusion simulations were performed with in vivo cell-free layer (CFL) widths data obtained from arteriolar flows in the rat cremaster muscle. The CFL data were measured at physiological and pathological Levels of Aggregation under reduced flow conditions (pseudoshear rate = 31.4 ± 10.5 s-1). Our results showed that the mean peak NO concentration significantly decreased with increasing the Aggregation Level from non-aggregating to normal-aggregating (P < 0.05) and to hyper-aggregating (P < 0.01) conditions. In contrast, the partial O2 pressure (PO2) in pathological aggregating conditions significantly increased from those under non-aggregating (P < 0.001) and normal-aggregating (P < 0.05) conditions. Although the NO scavenging by RBCs could be impaired with a thicker CFL at higher Levels of Aggregation, the overall decrease in NO production due to reduction of wall shear stress with the thicker CFL dominantly limited the NO availability in tissue. On the other hand, the O2 availability in tissue increased due to the relatively high core hematocrit in the blood lumen with the thicker CFL.
-
cell free layer formation in small arterioles at pathological Levels of erythrocyte Aggregation
Microcirculation, 2011Co-Authors: Peng Kai Ong, Bumseok Namgung, Swati Jain, Yeon I Woo, Sangho KimAbstract:Objective: To test our hypothesis that an elevation in the Aggregation Level of red blood cells found in human pathological conditions will significantly enhance cell-free layer formation in small arterioles. Methods: Visualization of arteriolar blood flow in rat cremaster muscle was carried out in both normal and reduced flow conditions before and after Dextran 500 infusion to simulate physiological and pathological Levels of red blood cell Aggregation in humans. Results: Both normalized mean ( p< 0.0001) and SD ( p< 0.002) of the layer width were significantly enhanced after hyperAggregation induction in reduced flow conditions (mean pseudoshear rate = 57.3 ± 7.2 ⁄sec). Normalized mean and SD of the layer width generally increased with decreasing vessel radius and this effect was most pronounced with hyper-Aggregation in reduced flow conditions. The threshold pseudoshear rate at which the layer formation became more pronounced when compared with non-aggregating condition was higher with hyper-Aggregation (217 ⁄sec) than normal-Aggregation induction (139 ⁄sec). Conclusion: Our findings confirmed the formation of a prominent cell-free layer in the arterioles under higher shear conditions at pathological Aggregation Levels and this effect became more pronounced in smaller arterioles in normalizing the layer to the vessel radius.
-
effect of cell free layer variation on arteriolar wall shear stress
Annals of Biomedical Engineering, 2011Co-Authors: Bumseok Namgung, Peng Kai Ong, Paul C Johnson, Sangho KimAbstract:Relationship between a cell-free layer and wall shear stress (WSS) in small arterioles has been of interest in microcirculatory research. However, influence of temporal variation in the cell-free layer width on the WSS in vivo has not been fully elucidated. In this study, we tested the hypothesis that the layer variation would increase the WSS, and this effect would be enhanced by red blood cell Aggregation. The cell-free layer width in arterioles (29.5–67.1 μm ID) in rat cremaster muscles were obtained with a high-speed video camera, and the layer width data were introduced into WSS estimation. Dextran 500 was administrated to elevate the Aggregation Level of red blood cells to those seen in normal human blood. The variation of the layer was quantified by the variability (coefficient of variation), and its effect on WSS was studied under normal and reduced flow conditions. We found that the dextran-induced red blood cell Aggregation significantly elevated the variability (p < 0.01) at low pseudoshear rates of 9.2 ± 0.6 s−1. The WSS estimated without taking account of the variability showed underestimation of its value than that of with consideration of the variability under all flow conditions, and this effect became more pronounced with increasing the variability. The variation of the cell-free layer should, therefore, be considered in the determination of the WSS particularly in the presence of red blood cell Aggregation under reduced flow condition.
Bumseok Namgung - One of the best experts on this subject based on the ideXlab platform.
-
erythrocyte Aggregation may promote uneven spatial distribution of no o2 in the downstream vessel of arteriolar bifurcations
Journal of Biomechanics, 2016Co-Authors: Bumseok Namgung, Hwa Liang Leo, Sangho KimAbstract:This study examined the effect of red blood cell (RBC) Aggregation on nitric oxide (NO) and oxygen (O2) distributions in the downstream vessels of arteriolar bifurcations. Particular attention was paid to the inherent formation of asymmetric cell-free layer (CFL) widths in the downstream vessels and its consequential impact on the NO/O2 bioavailability after the bifurcations. A microscopic image-based two-dimensional transient model was used to predict the NO/O2 distribution by utilizing the in vivo CFL width data obtained under non-, normal- and hyper-aggregating conditions at the pseudoshear rate of 15.6±2.0s(-1). In vivo experimental result showed that the asymmetry of CFL widths was enhanced by the elevation in RBC Aggregation Level. The model demonstrated that NO bioavailability was regulated by the dynamic fluctuation of the local CFL widths, which is corollary to its modulation of wall shear stress. Accordingly, the uneven distribution of NO/O2 was prominent at opposite sides of the arterioles up to six vessel-diameter (6D) away from the bifurcating point, and this was further enhanced by increasing the Levels of RBC Aggregation. Our findings suggested that RBC Aggregation potentially augments both the formation of asymmetric CFL widths and its influence on the uneven distribution of NO/O2 in the downstream flow of an arteriolar bifurcation. The extended heterogeneity of NO/O2 downstream (2D-6D) also implied its potential propagation throughout the entire arteriolar microvasculature.
-
influence of erythrocyte Aggregation at pathological Levels on cell free marginal layer in a narrow circular tube
Clinical Hemorheology and Microcirculation, 2016Co-Authors: Bumseok Namgung, Hiromi Sakai, Sangho KimAbstract:Human red blood cells (RBCs) were perfused in a circular micro-tube (inner diameter of 25 μm) to examine the dynamic changes of cell-free marginal region at both physiological (normal) and pathophysiological (hyper) Levels of RBC Aggregation. The cell-free area (CFA) was measured to provide additional information on the cell-free layer (CFL) width changes in space and time domains. A prominent enhancement in the mean CFL width was found in hyper-aggregating conditions as compared to that in non-aggregating conditions (P < 0.001). The frequent contacts between RBC and the tube wall were observed and the contact frequency was greatly decreased when the Aggregation Level was increased from none to normal (P < 0.05) and to hyper (P < 0.001) Levels. In addition, the enhanced Aggregation from none to hyper Levels significantly enlarged the CFA (P < 0.01). We concluded that the RBC Aggregation at pathophysiological Levels could promote not only the CFL width (one-dimensional parameter) but also the spatiotemporal variation of CFA (two-dimensional parameter).
-
effect of erythrocyte Aggregation at pathological Levels on no o2 transport in small arterioles
Clinical Hemorheology and Microcirculation, 2015Co-Authors: Seungkwan Cho, Bumseok Namgung, Han Sung Kim, Hwa Liang Leo, Sangho KimAbstract:This study examined the effects of red blood cell (RBC) Aggregation at pathological Levels on NO/O2 transport in small arterioles. Transient gas diffusion simulations were performed with in vivo cell-free layer (CFL) widths data obtained from arteriolar flows in the rat cremaster muscle. The CFL data were measured at physiological and pathological Levels of Aggregation under reduced flow conditions (pseudoshear rate = 31.4 ± 10.5 s-1). Our results showed that the mean peak NO concentration significantly decreased with increasing the Aggregation Level from non-aggregating to normal-aggregating (P < 0.05) and to hyper-aggregating (P < 0.01) conditions. In contrast, the partial O2 pressure (PO2) in pathological aggregating conditions significantly increased from those under non-aggregating (P < 0.001) and normal-aggregating (P < 0.05) conditions. Although the NO scavenging by RBCs could be impaired with a thicker CFL at higher Levels of Aggregation, the overall decrease in NO production due to reduction of wall shear stress with the thicker CFL dominantly limited the NO availability in tissue. On the other hand, the O2 availability in tissue increased due to the relatively high core hematocrit in the blood lumen with the thicker CFL.
-
cell free layer formation in small arterioles at pathological Levels of erythrocyte Aggregation
Microcirculation, 2011Co-Authors: Peng Kai Ong, Bumseok Namgung, Swati Jain, Yeon I Woo, Sangho KimAbstract:Objective: To test our hypothesis that an elevation in the Aggregation Level of red blood cells found in human pathological conditions will significantly enhance cell-free layer formation in small arterioles. Methods: Visualization of arteriolar blood flow in rat cremaster muscle was carried out in both normal and reduced flow conditions before and after Dextran 500 infusion to simulate physiological and pathological Levels of red blood cell Aggregation in humans. Results: Both normalized mean ( p< 0.0001) and SD ( p< 0.002) of the layer width were significantly enhanced after hyperAggregation induction in reduced flow conditions (mean pseudoshear rate = 57.3 ± 7.2 ⁄sec). Normalized mean and SD of the layer width generally increased with decreasing vessel radius and this effect was most pronounced with hyper-Aggregation in reduced flow conditions. The threshold pseudoshear rate at which the layer formation became more pronounced when compared with non-aggregating condition was higher with hyper-Aggregation (217 ⁄sec) than normal-Aggregation induction (139 ⁄sec). Conclusion: Our findings confirmed the formation of a prominent cell-free layer in the arterioles under higher shear conditions at pathological Aggregation Levels and this effect became more pronounced in smaller arterioles in normalizing the layer to the vessel radius.
-
effect of cell free layer variation on arteriolar wall shear stress
Annals of Biomedical Engineering, 2011Co-Authors: Bumseok Namgung, Peng Kai Ong, Paul C Johnson, Sangho KimAbstract:Relationship between a cell-free layer and wall shear stress (WSS) in small arterioles has been of interest in microcirculatory research. However, influence of temporal variation in the cell-free layer width on the WSS in vivo has not been fully elucidated. In this study, we tested the hypothesis that the layer variation would increase the WSS, and this effect would be enhanced by red blood cell Aggregation. The cell-free layer width in arterioles (29.5–67.1 μm ID) in rat cremaster muscles were obtained with a high-speed video camera, and the layer width data were introduced into WSS estimation. Dextran 500 was administrated to elevate the Aggregation Level of red blood cells to those seen in normal human blood. The variation of the layer was quantified by the variability (coefficient of variation), and its effect on WSS was studied under normal and reduced flow conditions. We found that the dextran-induced red blood cell Aggregation significantly elevated the variability (p < 0.01) at low pseudoshear rates of 9.2 ± 0.6 s−1. The WSS estimated without taking account of the variability showed underestimation of its value than that of with consideration of the variability under all flow conditions, and this effect became more pronounced with increasing the variability. The variation of the cell-free layer should, therefore, be considered in the determination of the WSS particularly in the presence of red blood cell Aggregation under reduced flow condition.
Guy Cloutier - One of the best experts on this subject based on the ideXlab platform.
-
pilot clinical study of quantitative ultrasound spectroscopy measurements of erythrocyte Aggregation within superficial veins
Clinical Hemorheology and Microcirculation, 2020Co-Authors: Boris Chayer, Jean-françois Cailhier, Louise Allard, Zhao Qin, Julian Garciaduitama, Laurence Roger, Francois Destrempes, Andre Y Denault, Guy CloutierAbstract:BACKGROUND An enhanced inflammatory response is a trigger to the production of blood macromolecules involved in abnormally high Levels of erythrocyte Aggregation. OBJECTIVE This study aimed at demonstrating for the first time the clinical feasibility of a non-invasive ultrasound-based erythrocyte Aggregation quantitative measurement method for potential application in critical care medicine. METHODS Erythrocyte Aggregation was evaluated using modeling of the backscatter coefficient with the Structure Factor Size and Attenuation Estimator (SFSAE). SFSAE spectral parameters W (packing factor) and D (mean aggregate diameter) were measured within the antebrachial vein of the forearm and tibial vein of the leg in 50 healthy participants at natural flow and reduced flow controlled by a pressurized bracelet. Blood samples were also collected to measure erythrocyte Aggregation ex vivo with an erythroaggregometer (parameter S10). RESULTS W and Din vivo measurements were positively correlated with the ex vivoS10 index for both measurement sites and shear rates (correlations between 0.35-0.81, p < 0.05). Measurement at low shear rate was found to increase the sensitivity and reliability of this non-invasive measurement method. CONCLUSIONS We behold that the SFSAE method presents systemic measures of the erythrocyte Aggregation Level, since results on upper and lower limbs were highly correlated.
-
modeling of the acoustic signal backscattered by a biphasic suspension application to the characterization of red blood cell Aggregation
2002Co-Authors: David Savery, Guy CloutierAbstract:The model explained experimental observations on the power backscattered by flowing blood, namely the increase in power at low frequencies and the decrease of the spectral slope at higher frequencies both due to the growing size of scatterers. The angular dependence of BSC for anisotropic particles could also be reproduced by the simulations. However, some improvements would be necessary to get more insight into the understanding of ultrasound backscattering by blood. Firstly, the model is valid for diluted suspensions but cannot be easily generalized for a dense medium, where the packing of particles plays an important role. Another limitation is the hypothesis that all scatterers are identical and have Gaussian shapes. Polydispersity and variations in orientation are not currently taken into account. It remains yet that blood characterization by the backscattering method has a good potential to provide accurate information about the RBC Aggregation Level.
-
Differences in the erythrocyte Aggregation Level between veins and arteries of normolipidemic and hyperlipidemic individuals
Ultrasound in Medicine and Biology, 1997Co-Authors: Guy Cloutier, Louis Allard, Xiaoduan Weng, Ghislaine O. Roederer, Francine Tardif, Raymond BeaulieuAbstract:Abstract The objectives of this study were to detect differences in the Doppler power backscattered by blood in vivo , and to identify factors affecting the backscattered power. The main hypothesis was that variations in the erythrocyte Aggregation Level between veins and arteries of normolipidemic and hyperlipidemic individuals can be detected with power Doppler ultrasound. Doppler measurements were performed at 5 MHz, with an Acuson 128 XP10 system, over the carotid artery and jugular vein, external iliac artery and vein, common femoral artery and vein and popliteal artery and vein. Doppler signals were recorded at the center of each vessel to optimize the detection of erythrocyte Aggregation, and processed off-line to obtain the backscattered power. The power of each recording was compensated for Doppler gain differences, tissue attenuation with depth and transmitted power variations occurring with pulse-repetition interval modifications. Results showed statistically stronger backscattered power in veins compared to arteries for the iliac, femoral and popliteal sites. In comparison with healthy subjects, stronger powers were observed in hyperlipidemic patients for the femoral and popliteal sites. Power differences were also found between peripheral measurements. On the other hand, no difference was observed between the power measured in the carotid artery and jugular vein for both groups of individuals. Multiple linear regression analyses were performed to identify factors affecting the backscattered power. Results showed a correlation ( r ) of 71.2% between the Doppler power in the femoral vein and the linear combination of two parameters: an erythrocyte Aggregation index S 10 measured with a laser scattering method, and the diameter of the vessel measured on B-mode images. Statistically significant linear correlation Levels were also found between S 10 and the Doppler power in various vessels. In conclusion, this study showed that power Doppler differences exist in vivo in large vessels between veins and arteries of normolipidemic and hyperlipidemic individuals. The Doppler power variations were also shown to be related to erythrocyte Aggregation.
Peng Kai Ong - One of the best experts on this subject based on the ideXlab platform.
-
cell free layer formation in small arterioles at pathological Levels of erythrocyte Aggregation
Microcirculation, 2011Co-Authors: Peng Kai Ong, Bumseok Namgung, Swati Jain, Yeon I Woo, Sangho KimAbstract:Objective: To test our hypothesis that an elevation in the Aggregation Level of red blood cells found in human pathological conditions will significantly enhance cell-free layer formation in small arterioles. Methods: Visualization of arteriolar blood flow in rat cremaster muscle was carried out in both normal and reduced flow conditions before and after Dextran 500 infusion to simulate physiological and pathological Levels of red blood cell Aggregation in humans. Results: Both normalized mean ( p< 0.0001) and SD ( p< 0.002) of the layer width were significantly enhanced after hyperAggregation induction in reduced flow conditions (mean pseudoshear rate = 57.3 ± 7.2 ⁄sec). Normalized mean and SD of the layer width generally increased with decreasing vessel radius and this effect was most pronounced with hyper-Aggregation in reduced flow conditions. The threshold pseudoshear rate at which the layer formation became more pronounced when compared with non-aggregating condition was higher with hyper-Aggregation (217 ⁄sec) than normal-Aggregation induction (139 ⁄sec). Conclusion: Our findings confirmed the formation of a prominent cell-free layer in the arterioles under higher shear conditions at pathological Aggregation Levels and this effect became more pronounced in smaller arterioles in normalizing the layer to the vessel radius.
-
effect of cell free layer variation on arteriolar wall shear stress
Annals of Biomedical Engineering, 2011Co-Authors: Bumseok Namgung, Peng Kai Ong, Paul C Johnson, Sangho KimAbstract:Relationship between a cell-free layer and wall shear stress (WSS) in small arterioles has been of interest in microcirculatory research. However, influence of temporal variation in the cell-free layer width on the WSS in vivo has not been fully elucidated. In this study, we tested the hypothesis that the layer variation would increase the WSS, and this effect would be enhanced by red blood cell Aggregation. The cell-free layer width in arterioles (29.5–67.1 μm ID) in rat cremaster muscles were obtained with a high-speed video camera, and the layer width data were introduced into WSS estimation. Dextran 500 was administrated to elevate the Aggregation Level of red blood cells to those seen in normal human blood. The variation of the layer was quantified by the variability (coefficient of variation), and its effect on WSS was studied under normal and reduced flow conditions. We found that the dextran-induced red blood cell Aggregation significantly elevated the variability (p < 0.01) at low pseudoshear rates of 9.2 ± 0.6 s−1. The WSS estimated without taking account of the variability showed underestimation of its value than that of with consideration of the variability under all flow conditions, and this effect became more pronounced with increasing the variability. The variation of the cell-free layer should, therefore, be considered in the determination of the WSS particularly in the presence of red blood cell Aggregation under reduced flow condition.
Jean-louis Deneubourg - One of the best experts on this subject based on the ideXlab platform.
-
Alteration of the Aggregation and spatial organization of the vector of Chagas disease, Triatoma infestans, by the parasite Trypanosoma cruzi
Scientific Reports, 2019Co-Authors: Stéphanie Depickère, Gonzalo Marcelo Ramírez-Ávila, Jean-louis DeneubourgAbstract:Triatominae insects are vectors of the parasite Trypanosoma cruzi , the etiological agent of Chagas disease affecting millions of people in Latin America. Some species, such as Triatoma infestans , live in the human neighborhood, aggregating in walls or roof cracks during the day and going out to feed blood at night. The comprehension of how sex and T. cruzi infection affect their Aggregation and geotaxis is essential for understanding their spatial organization and the parasite dispersion. Experiments in laboratory-controlled conditions were carried out with groups of ten adults of T. infestans able to explore and aggregate on a vertical surface. The influence of the sex (male vs. female) and the proportion of infected insects in the group were tested (100% of infected insects vs. a small proportion of infected insects, named infected and potentially weakly infected groups, respectively). Therefore, four distinct groups of insects were tested: infected males, infected females, potentially weakly infected males, and potentially weakly infected females, with 12, 9, 15, and 16 replicates, respectively. The insects presented a high negative geotaxis and a strong Aggregation behavior whatever the sex or their infection. After an exploration phase, these behaviors were stable in time. The insects exhibited a preferential vertical position, head toward the top of the setup. Males had a higher negative geotaxis and a higher Aggregation Level than females. Both behaviors were enhanced in groups of 100% infected insects, the difference between sexes being maintained. According to a comparison between experimental and theoretical results, geotaxis favors the Aggregation that mainly results from the inter-attraction between individuals.
-
polymorphism a weak influence on worker Aggregation Level in ants
Ecological Entomology, 2008Co-Authors: Stéphanie Depickère, Dominique Fresneau, Marcelo Ramirez G Avila, Jean-louis DeneubourgAbstract:1. Aggregation of individuals, a basic behaviour in social species, plays an essential role in many aspects of animal life (reproduction, defence, and alimentation). Understanding how this phenomenon is modulated is important to comprehend the social organisation of the group. 2. In social insects, Aggregation is influenced by environmental (e.g. the light Level) and social (e.g. polyethism in monomorphic ants) factors. Ants display a great variation of biological characteristics (e.g. queen number, polymorphism, division of labour, etc.) that are likely to influence the Level of inter-attraction and so the Aggregation. 3. The present research focused on one biological characteristic: the morphological castes (minors, majors), testing the hypothesis that minors will aggregate more than majors due to their greater need to fight against the loss of heat and to increase their self-protection. 4. Aggregation experiments were conducted on two highly polymorphic species, Atta sexdens rubropilosa and Solenopsis interrupta, using the two extreme morphological castes (majors and minors). 5. All castes exhibited a low Level of Aggregation: 40–50% of workers assembled for both species, the biggest cluster involving 20% of the total population. The lack of difference between morphological castes in the Aggregation shows the weak influence of polymorphism on the interactions between ants. 6. It is concluded that the main factor modulating the Aggregation behaviour is polyethism, i.e. the division of labour associated with the presence of an outside-the-nest experience: workers that only take care of the brood, without outside world experience (brood-tenders) assembling more than foraging workers (foragers).
-
marking as a decision factor in the choice of a new resting site in lasius niger
Insectes Sociaux, 2004Co-Authors: Stéphanie Depickère, Dominique Fresneau, Claire Detrain, Jean-louis DeneubourgAbstract:In ants, Aggregation is mainly based on the attraction between individuals. We confirmed the existence of ground marking in Lasius niger and demonstrated its influence on the aggregative behaviour of ants: the place of the gathering is leading by the existence of a ground marking which favours clustering by increasing the rate of the process but does not change the Aggregation Level. This factor could play a role in the choice of a new nest site and in the spatial distribution of ants inside the nest. This marking, presuming to have a long duration, could represent an external memory which could play an important role in various situations such as the choice of new nest or the reorganisation of ants after a disturbance.
-
Dynamics of Aggregation in Lasius niger (Formicidae): influence of polyethism
Insectes Sociaux, 2004Co-Authors: Stéphanie Depickère, Dominique Fresneau, Jean-louis DeneubourgAbstract:Polyethism is a well-known phenomenon in social insects. How this phenomenon influences interactions among individuals, the spatial distribution in the nest is, on the other hand, very rarely documented. Therefore, we conducted experiments on the ant Lasius niger to observe the influence of polyethism on Aggregation, by distinguishing two groups of ants: the brood-tenders and the foragers. We show a great difference in their self Aggregation Level. Brood-tenders are characterized by a rapid and dense gathering in one main stable cluster while foragers gather in several small unstable clusters. We show experimentally and verify with a model that this difference in behaviour is based on a smaller probability of leaving a cluster for the brood-tenders. Aggregation in the mixed case (groups composed of brood-tenders and foragers) is very close to that of the pure forager case, showing a decrease in the Level of Aggregation of the brood-tenders respecting to the pure group of brood-tenders. Nevertheless, experimental results supported by the results of the model, show that ants do not change their own behaviour when the two groups are together. Therefore, the decrease of the Aggregation of brood-tenders in the mixed case can be explained by a difference in the dynamics between brood-tenders and foragers.