The visual ecology of bees - Tales of diverse eyes and behaviours

The buzzing flight of bees is a popular summer hit. Yet, outside of a few familiar species of honeybees and bumblebees, these fantastic little creatures are still mostly unknown. With about twenty-five thousand species, bees are a very diverse group. They can be found in drastically different habitats. For example, some kinds of bumblebees endure the freezing temperatures and windswept tundra of Greenland, while others only thrive in the heat and humidity of the Amazonian forest. Some bees live in huge colonies with tens of thousands of members, while others live solitary lives. Some are narrower than a sesame seed, while others can reach the size of a human thumb. Despite these differences, bees all have in common the urge to visit flowers where they find their food. This habit makes them very important for the pollination of plants across the world. To go about their laborious life, bees make extensive use of their vision. They possess two types of eyes – ocelli and compound eyes – that they use to control their flight, find their way through the world, discover flowers and spot possible mates. To understand how bees interact with the environment, we thus need to explore the diversity of their eyes and of how they use them.The first chapter of my thesis is about landing, which is a fundamental behaviour in flying insects. However, in bees it is poorly known whether different species land in different ways. During an expedition to Brazil, I came across a species of bee with the most peculiar landing style. Rather than slowing down to land, as most animals do, these bees accelerate just before touchdown on the entrance to their hive. Why do these bees speed up when they land? Using a computer simulation, I found that this weird strategy may help the bees to avoid mid-air collisions with nestmates and reduce bee ‘traffic jams’ in front of the hive. In turn, this would make food collection more efficient for the colony and it would be easier for hive members to defend against intruders. With this chapter, I showed that the lifestyle of bees – where they live, how many there are and if they are exposed to intruders – can strongly influence their behaviour.In chapter two, I then asked if and how the bees from chapter one use vision to control their peculiar landing. I found that they did indeed rely on vision to control their landing and that they did so in a simple manner. Essentially, when the image of the entrance of the hive reaches a given size on their eyes, these bees start to speed up. When the image of the entrance reaches a second set size on the eyes of landing bees, they extend their landing gear – which is, for bees, their legs – in preparation for touchdown. This chapter reveals that bees can use simple rules to achieve complex behaviours such as landing safely.To explore the diversity of eyes in a large number of bees, we use X-ray images taken from a sample as it rotates (an approach known as computed tomography or CT, commonly used in a medical setting) to produce 3D images of the eyes. However, powerful tools are needed to analyse the large amounts of data that this approach generates. As I want to better understand how bee eyes work, I needed an efficient method for analysing 3D eye images created by CT, so I developed an automatic tool for distinguishing essential optical structures in the eyes of insects and other arthropods. In chapter three, I describe this method, provide a guide to use it, and give examples of its application to a few insect eyes.In the last chapter, I used CT to look into the diversity of the eyes across a range of bumblebees from different habitats around the world. Even though different species are genetically close to each other, I found that their eyes were far from ‘all the same’. For example, bumblebees that live in forests have eyes that may enable them to see less sharp but better in dim light than bumblebees living in open landscapes. I also found that cuckoo bumblebees – bees that lay their eggs in another bumblebee hive like cuckoo birds do – had peculiar eyes in comparison to other bumblebees. This indicates that the eyes of each species of bumblebees may be specialised for a specific combination of lifestyle and habitat. These results are important for the conservation of bumblebees because they suggest that the eyes of some species may make them more sensitive than others to changes in the environment. For example, farming practices that create large open fields may particularly disadvantage bumblebees with eyes adapted to forests.These four chapters only scratch the surface of the tight links between the eyes of bees, the ways they behave, and the worlds they live in. I hope that efforts to look into their diverse eyes will continue and will help to protect these crucial but endangered animals

Informative and misinformative interactions in a school of fish

It is generally accepted that, when moving in groups, animals process information to coordinate their motion. Recent studies have begun to apply rigorous methods based on Information Theory to quantify such distributed computation. Following this perspective, we use transfer entropy to quantify dynamic information flows locally in space and time across a school of fish during directional changes around a circular tank, i.e. U-turns. This analysis reveals peaks in information flows during collective U-turns and identifies two different flows: an informative flow (positive transfer entropy) based on fish that have already turned about fish that are turning, and a misinformative flow (negative transfer entropy) based on fish that have not turned yet about fish that are turning. We also reveal that the information flows are related to relative position and alignment between fish, and identify spatial patterns of information and misinformation cascades. This study offers several methodological contributions and we expect further application of these methodologies to reveal intricacies of self-organisation in other animal groups and active matter in general

Streptococcus agalactiae clones infecting humans were selected and fixed through the extensive use of tetracycline

Streptococcus agalactiae (Group B Streptococcus, GBS) is a commensal of the digestive and genitourinary tracts of humans that emerged as the leading cause of bacterial neonatal infections in Europe and North America during the 1960s. Due to the lack of epidemiological and genomic data, the reasons for this emergence are unknown. Here we show by comparative genome analysis and phylogenetic reconstruction of 229 isolates that the rise of human GBS infections corresponds to the selection and worldwide dissemination of only a few clones. The parallel expansion of the clones is preceded by the insertion of integrative and conjugative elements conferring tetracycline resistance (TcR). Thus, we propose that the use of tetracycline from 1948 onwards led in humans to the complete replacement of a diverse GBS population by only few TcR clones particularly well adapted to their host, causing the observed emergence of GBS diseases in neonates. \ua9 2014 Macmillan Publishers Limited. All rights reserved

Surcharges en fer chez les patients ayant bénéficié de greffes de cellules hématopoïétiques

L'amélioration de la prise en charge des patients bénéficiant de transplantations de cellules souches hématopoïétiques a permis d'obtenir des guérisons ainsi que des survies de plus en plus prolongées. Cette évolution a fait apparaître de nouvelles séquelles à long terme dont la surcharge en fer qui peut être responsable de multiples complications (fibrose, ou cirrhose hépatique, hépatocarcinome, cardiotoxicité).Cette étude, rétrospective, portant sur 169 patients ayant bénéficié de greffe de cellules souches hématopoïétiques cherche à déterminer les facteurs influençant cette surcharge en fer et l'efficacité des moyens thérapeutiques. Avant la greffe, on constate une prévalence importante de cette surcharge puisque 80 % des patients en présentent déjà une. Les facteurs augmentant cette surcharge sont le sexe féminin, l'âge, plus de 20 transfusions sanguines avant la greffe, le diagnostic (leucémies aiguës, tumeurs solides, syndromes myélodysplasiques, lymphomes, hémoglobinopathies). Certains patients (patients thalassémiques, drépanocytaires, porteurs d'hépatite chronique C ou B, patient cancéreux risquent plus de développer des complications pouvant devenir rapidement irréversibles. Il est donc important d'introduire précocement un traitement par saignées, EPO, ou traitement chélateur du fer.NANCY1-SCD Medecine (545472101) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Bee Compound Eyes and Labels

Raw volumes and label volumes for eyes and heads. These data are archived at MorphoSource project ID 646. They are required as input for the computational code at: https://github.com/gavinscode/compound-eye-plotting-elife.gi

The neuroecology of bee flight behaviours

By combining functional, ecological and evolutionary perspectives, neuroecology can provide key insights into understanding how behaviour and the underlying sensory and neural processes are shaped by ecology and evolutionary history. Bees are an ideal system for neuroecological studies because they represent a numerous and diverse insect group that inhabit a broad range of environments. Flight is central to the evolutionary success of bees and is the key to their survival and fitness but this review of recent work on fundamental flight behaviours in different species – landing, collision avoidance and speed control – reveals striking differences. We discuss the potential ecological and evolutionary drivers behind this variation but argue that to understand their adaptive value future work should include multidisciplinary approaches that integrate neuroscience, ecology, phylogeny and behaviour

Accelerated landings in stingless bees are triggered by visual threshold cues

Most flying animals rely primarily on visual cues to coordinate and control their trajectory when landing. Studies of visually guided landing typically involve animals that decrease their speed before touchdown. Here, we investigate the control strategy of the stingless bee Scaptotrigona depilis, which instead accelerates when landing on its narrow hive entrance. By presenting artificial targets that resemble the entrance at different locations on the hive, we show that these accelerated landings are triggered by visual cues. We also found that S. depilis initiated landing and extended their legs when the angular size of the target reached a given threshold. Regardless of target size, the magnitude of acceleration was the same and the bees aimed for the same relative position on the target suggesting that S. depilis use a computationally simple but elegant 'stereotyped' landing strategy that requires few visual cues

New mixed lanthanum- and alkaline-earth cation-containing basic catalysts obtained by an alginate route

International audienceA new route using mixed ionotropic gels of the natural block copolymer alginate as precursor has been used for the preparation of basic catalysts. Gelification of the alginate has been performed with lanthanum which has been then exchanged by a second alkaline-earth cation. The amount of both type of cations was controlled by the pre-determined relative affinity of the lanthanum containing hydrogels for the alkaline-earth cations which trend is as follows: Ba2+ > Sr2+ > Ca2+ > Mg2+. The surface areas of the materials obtained after thermal decomposition of the ex-alginate samples dried under supercritical CO2 conditions are greatly improved compared to samples with similar composition obtained by coprecipitation. The catalytic test reaction of 2-Methylbut-3-yn-2-ol decomposition reveals the basic properties of the ex-alginate samples. They range as follows in function of the alkaline-earth cation: Mg > Ba > Sr > Ca. This emphasizes the very attractive properties of the Mg-containing catalysts obtained through the alginate route due to their high basic strength and surface areas

Accelerated landing in a stingless bee and its unexpected benefits for traffic congestion

To land, flying animals must simultaneously reduce speed and control their path to the target. While the control of approach speed has been studied in many different animals, little is known about the effect of target size on landing, particularly for small targets that require precise trajectory control. To begin to explore this, we recorded the stingless bees Scaptotrigona depilis landing on their natural hive entrance-a narrow wax tube built by the bees themselves. Rather than decelerating before touchdown as most animals do, S. depilis accelerates in preparation for its high precision landings on the narrow tube of wax. A simulation of traffic at the hive suggests that this counterintuitive landing strategy could confer a collective advantage to the colony by minimizing the risk of mid-air collisions and thus of traffic congestion. If the simulated size of the hive entrance increases and if traffic intensity decreases relative to the measured real-world values, 'accelerated landing' ceases to provide a clear benefit, suggesting that it is only a useful strategy when target cross-section is small and landing traffic is high. We discuss this strategy in the context of S. depilis' ecology and propose that it is an adaptive behaviour that benefits foraging and nest defence