Exudate detection in color retinal images for mass screening of diabetic retinopathy

International audienceThe automatic detection of exudates in colour eye fundus images is an important task in applications such as diabetic retinopathy screening. The presented work has been undertaken in the framework of the TeleOphta project, whose main objective is to auto-matically detect normal exams in a tele-ophthalmology network, thus reducing the burden on the readers. A new clinical database, e-ophtha EX, containing precisely manually contoured exudates, is introduced. As opposed to previously available databases, e-ophtha EX is very heterogeneous. It contains images gathered within the OPHDIAT telemedicine network for diabetic retinopathy screening. Image definition, quality, as well as patients condition or the retinograph used for the acquisition, for example, are subject to important changes between different examinations. The proposed exudate detection method has been designed for this complex situation. We propose new preprocessing methods, which perform not only normalization and denoising tasks, but also de-tect reflections and artifacts in the image. A new candidates segmentation method, based on mathematical morphology, is proposed. These candidates are characterized using classical features, but also novel contextual features. Finally, a random forest algorithm is used to detect the exudates among the candidates. The method has been validated on the e-ophtha EX database, obtaining an AUC of 0.95. It has been also validated on other databases, obtaining an AUC between 0.93 and 0.95, outperforming state-of-the-art methods

Water-skel

International audienceThis paper introduces a distance-based skeleton approach. It starts from a set of prese-lected shape extremities. The extremities lead to the definition of markers on the objectboundary. These markers are then immersed on the inverse distance function. Finalya watershed provides a thin, homotopic and centered skeleton linking the provided ex-tremities. The main contribution of the paper is the interpretation of the skeleton as awatershed process from markers, a well known operator and for which efficient implemen-tations exist

Behavioural response to predation risks depends on experimental change in dehydration state in a lizard

Optimal regulation of body temperature and water balance is essential for the survival of terrestrial ectotherms in a changing world. A behavioural trade-off exists between these two constraints because maintaining a high body temperature usually increases evaporative water losses. In addition, the evaluation of predation risk is a key factor in behavioural decision for prey species, and predation threat can cause shift in individual behaviours due to the modification of the cost-benefit balance of thermo-hydroregulation. However, little is known on how prey integrate these different biotic and abiotic stressors when combined. Here, we performed an experimental study on the common lizard, a terrestrial ectotherm prey species, sensitive to water restriction and able to detect specialised predator scents in its environment. We analysed changes in thermo-hydroregulation behaviours, activity patterns and body temperature in response to a chronic water stress coupled with simulated punctual occurrences of predator scents. Water restriction and predator threat had mostly additive effects on lizard thermoregulation behaviour. They both reduced the time spent basking and thermoregulation precision. They also had opposite effects on the time spent active, water restriction reducing activity whereas the presence of predator scents increased it. Yet, we also found an interactive effect on hydroregulation behaviour, as water-restricted lizards showed a wet-shelter preference only in absence of predator odours. This study demonstrates the existence of some hydration state dependent behavioural responses to predator threat and suggests that fear of predators may compromise thermo-hydroregulation and thus prey performances

Density-dependent immunity and parasitism risk in experimental populations of lizards naturally infested by ixodid ticks

International audienceWhen effective immune defenses against parasites are costly and resources limited, individuals are expected to alter their investment in immunity in response to the risk of infection. As an ecological factor that can affect both food abundance and parasite exposure, host density can play an important role in host immunity and host-parasite interactions. High levels of intraspecific competition for food and social stress at high host density may diminish immune defenses and increase host susceptibility to parasites. At the same time, for contagious and environmentally transmitted parasites, parasite exposure often increases with host density, whereas in mobile parasites that actively search for hosts, parasite exposure can decrease with host density due to the encounter-dilution effect. To unravel these multiple and potentially opposing effects of host density on immunity, we manipulated density of the common lizard Zootoca vivipara and measured local inflammation in response to PHA injection and levels of infestation by the tick Ixodes ricinus, a mobile ectoparasite for which we expected an encounter-dilution effect to occur. Local inflammation strongly decreased with lizard density in adults, but not in yearlings. Tick infestation (abundance and prevalence) was negatively correlated with lizard density in both age classes. Using path analyses, we found independent, direct negative density feedbacks on immunity and parasite exposure in adults, supporting the hypothesis of energy constraints and/or physiological stress acting on immunity at high density. In contrast, for yearlings, the best path model showed that density diluted exposure to parasites, which themselves down-regulated immune defenses in lizards. These results highlight the importance of investigating the pathways among host density, host immunity, and parasite infestation, while accounting for relevant individual traits such as age

Data from: Quantification of correlational selection on thermal physiology, thermoregulatory behavior and energy metabolism in lizards

Phenotypic selection is widely accepted as the primary cause of adaptive evolution in natural populations, but selection on complex functional properties linking physiology, behavior, and morphology has been rarely quantified. In ectotherms, correlational selection on thermal physiology, thermoregulatory behavior, and energy metabolism is of special interest because of their potential coadaptation. We quantified phenotypic selection on thermal sensitivity of locomotor performance (sprint speed), thermal preferences, and resting metabolic rate in captive populations of an ectothermic vertebrate, the common lizard, Zootoca vivipara. No correlational selection between thermal sensitivity of performance, thermoregulatory behavior, and energy metabolism was found. A combination of high body mass and resting metabolic rate was positively correlated with survival and negatively correlated with fecundity. Thus, different mechanisms underlie selection on metabolism in lizards with small body mass than in lizards with high body mass. In addition, lizards that selected the near average preferred body temperature grew faster that their congeners. This is one of the few studies that quantifies significant correlational selection on a proxy of energy expenditure and stabilizing selection on thermoregulatory behavior

Segmentation of elongated objects using attribute profiles and area stability: application to melanocyte segmentation.

International audienceIn this paper, a method to segment elongated objects is proposed. It is based on attribute profiles and area stability. Images are represented as component trees using a threshold decomposition. Then, some attributes are computed on each node of the tree. Finally, the attribute profile is analyzed to identify important events useful for segmentation tasks. In this work, a new attribute, combining geodesic elongation and area stability is defined. This methodol-ogy is successfully applied to the segmentation of cells in multiphoton fluores-cence microscopy images of engineered skin. Quantitative results are provided, demonstrating the performance and robustness of the new attribute. A compar-ison with MSER is also given

Chronic elevation of glucorticoids late in life generates long lasting changes in physiological state without a life history switch

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Do personalities co-vary with metabolic expenditure and glucocorticoid stress response in adult lizards?

International audienceStable differences in physiology among individuals may facilitate the evolution of consistent individual differences in behavior. In particular, according to the pace-of-life syndrome (POLS) hypothesis, individual variation in metabolic expenditure and stress physiology should be linked with exploration, aggression, or risk taking behaviors. Previous studies have uncovered stable individual differences in metabolic expenditure and circulating glucorticoids in common lizards (Zootoca vivipara). We tested for correlations between standard metabolic rates (SMR), glucorticoid stress response and behavioral traits (activity, aggressiveness, risk taking and sociability) in males. In ectotherms, the thermal dependence of SMR should be included in the POLS hypothesis; we therefore measured SMR at three temperatures from rest to preferred body temperature. Activity, aggressiveness and risk taking, but not sociability, exhibited significant, short term repeatability, and little correlation was found between behavioral traits. The SMR of lizards with a low metabolism at rest increased faster with body temperature. The SMR at rest was negatively correlated with behavioral variation in sociability and activity but not with risk taking behavior. In addition, the plasma corticosterone level after an acute, handling stress increased slightly but not significantly with aggressiveness. We discuss alternative interpretations for these relationships and conclude that the link between inter-individual variation in physiology and behavior is trait-dependent in the common lizard

Water restriction in viviparous lizards causes transgenerational effects on behavioral anxiety and immediate effects on exploration behavior

International audienc

On power Jaccard losses for semantic segmentation

International audienceIn this work, a new generalized loss function is proposed called power Jaccard to perform semantic segmentation tasks. It is compared with classical loss functions in different scenarios, including gray level and color image segmentation, as well as 3D point cloud segmentation. The results show improved performance, stability and convergence. We made available the code with our proposal with a demonstrative example