The 20 winners La preuve par l'image (LPPI) 2021

The tongue is covered with taste buds that can perceive five tastes: sweet, salty, sour, bitter and umami. This organ remains poorly understood, both regarding its structure and the different cells that make it up. However, immunofluorescence provides a better view of it. The image shows the surface of an epithelium (a tissue that has a covering function) of a rodent’s tongue. The small spikes are filiform papillae (blue autofluorescence), which play a mechanical role in bringing food to the…

Zeolites, which are like tiny, hard, dense sponges, are made up of extremely porous crystals with unique properties: a single gram of zeolite contains billions of nanometre-sized pores and cavities, with an astounding internal surface area of up to 900m²! The image shows a rather pleasing arrangement of zeolite crystals placed on carbon tape. What scientists are trying to do here is explore and characterise the internal organisation of these crystals at the nanometre scale in order to elucidate…

In the village of Aghien-Télégraphe, near Abidjan, Côte d’Ivoire, a teacher is telling schoolchildren about their future role as sentinels for the protection of natural resources in the area, for the village is located at the edge of a lagoon that supplies more than 10 000 local inhabitants with freshwater. In order to meet the growing need, the Aghien lagoon is also likely to be used as an additional reserve of drinking water for the capital. Particularly vulnerable to human pressure, the…

Bryozoans are reef-building multicellular organisms less than a millimetre in size that have calcium carbonate skeletons. These tiny animals, which live in colonies at all latitudes, play a major role in regulating the climate by storing the CO2 dissolved in seawater in their mineral structure. This is the tip of the skeleton of a colony of bryozoans of the species Cellaria fistulosa. Each organism lives in a sort of calcium carbonate chamber with openings, the main one of which enables the…

Under the microscope, these strange little blue ice cubes mirror the fragility of the world around us. However, these tiny blocks of ice apparently adrift on the ocean are in fact crystals of metal-organic frameworks (MOF), nanostructured materials renowned for their exceptional porosity. Here, they are undergoing a process that is the exact opposite of an ice sheet breaking up: deposited on a silicon wafer, they will first grow and then combine with their neighbours to produce the smoothest,…

This is a small, remarkably well-preserved gastropod of the genus Cassiope. The beautiful turriculate shell was discovered in Edelbach, Austria, in a fossil site dated to around 90 million years ago. The colourful pattern it sported when alive is revealed under ultraviolet light. Almost undetectable to the naked eye, it is arranged in several rows of spots: the pale areas (white and light yellow) correspond to the parts that contained a high concentration of pigments, the composition of which…

Photographed in the Massif des Maures, in southeastern France, this voracious praying mantis is devouring its prey, a young common wall gecko (Tarentola mauritanica), a species of gecko well known in the Mediterranean region. Both intraguild predation (between predators exploiting the same resources) and superpredation (in which predators themselves are the prey of other predators) are commonplace. However, arthropod predation of vertebrates, made possible here by the similar sizes of both…

During the southern summer in Antarctica, the sun never sets. It simply sinks to the horizon, casting a golden-red glow over the frozen ocean. This photograph was taken aboard the South African research vessel, SA Agulhas II, where scientists were carrying out oceanographic sampling in the inhospitable and little-explored Weddell Sea. In the image, two of the icebreaker’s sailors can be seen deploying the Conductivity Temperature Depth (CTD) probe, which measures the ocean’s temperature and…

Introducing Euphysetta lucani, a star ballet dancer in the Rhizaria company! Normally found in the depths of the ocean, this specimen was seen floating near the surface in the North Atlantic. Although measuring a mere 250 micrometres, this single-celled planktonic animal may play a fundamental role in marine ecosystems. By extracting silicon from the oceans in the form of biogenic silica in order to build their tiny glass skeletons, these protists compete with microalgae called diatoms that…

Grabbing a pen, hammering in a nail, inserting a credit card, screwing in a light bulb: the former high-level Paralympic athlete and pilot of the French Smart ArM team, Christophe Huchet, is here seen training for the Cybathlon 2020. These unconventional Olympic Games have been organised every four years since 2016 for disabled people equipped with active, robotic technologies. The athlete is fitted with an arm prosthesis specially designed for him, one of the few in the competition to have a…

Rediscovered in the collections of the MNHN French national museum of natural history, this specimen of Aeger insignis comes from the Solnhofen Limestone, in Germany. This small crustacean lived in a lagoon in the Late Jurassic around 140 million years ago. At that time, what is now Europe was a vast archipelago with turquoise waters and a tropical climate. This prawn belonged to an extinct family whose main feature was that it had highly-developed jawfeet (also known as maxillipeds) endowed…

Particles of cosmic dust from comets or asteroids, known as micrometeorites, have always fallen on our planet. Some of these are spherules, micrometeorites that have totally or partially melted on entering the atmosphere. The spherule shown here has a diameter of 170 micrometres. Its surface reveals pale-coloured, dendritic (tree-like) crystals of magnetite that formed as a result of the interaction of the molten meteorite with oxygen in the atmosphere as it solidified. This cosmic dust grain…

When muscle precursor cells fuse, they happen to form the swirling patterns shown here, unmistakably reminiscent of Van Gogh’s painting, The Starry Night. In these microscopic whorls, their cell nuclei can be seen in cyan, the actin cytoskeleton in blue, and, in yellow, a protein indicating the formation of new muscle fibres. The cells are grown on an ultra-nutritious medium – Matrigel – that serves as a support for them. Their behaviour is subsequently studied with the aim of developing…

Listed as extinct until recently, the bone skipper (Thyreophora cynophila) hadn’t been spotted in France since 1836. However, in 2019, this elusive fly was rediscovered by a hunter-naturalist in the French Pyrenees. After such a long absence, many questions about this unusual insect remain unanswered. Researchers are now studying its range, life cycle and ecology with the help of citizen scientists. Unlike other flies, it is only present in winter, and on the corpses of large mammals, like the…

For PR2, an autonomous service robot, finding its way around an unfamiliar environment is certainly a complex task, yet by no means impossible! Using the 3D camera located on its “head” and its optical motion capture system, PR2 can sense its surroundings and learn to see what it can move, lift or press using its gripper. The screen displays the representation of the ongoing construction of its environment. The small objects that the robot has learned it can interact with are shown in yellow…

Foraminifera are single-celled marine organisms that have inhabited marine or brackish environments from the poles to the equator for more than 500 million years. When alive, they are remarkable bio- indicators of the state of our oceans since they are particularly sensitive to pollution. As fossils, their mineral shells enable palaeontologists to reconstruct past climates. Foraminifera make up one of the most abundant and diverse groups of fossils. This 2 mm-long alveolinid specimen was…

To invade other organs, tumour cells engage in a very sophisticated dialogue with the surrounding tissue and the extracellular matrix. In particular, they trigger the creation of new blood vessels (angiogenesis) to obtain food and proliferate. Here, it is precisely these reprogramming mechanisms that scientists are trying to identify using endothelial cells, which line the inside of vessels. In this complex microenvironment, their structure stands out, in grey, due to their actin cytoskeleton…

The image shows a bird’s eye view of one of the galleries of the Grotte de la Madeleine cave, located in the heart of the Gorges de l’Ardèche in southern France. This was entirely scanned using ground-based lidar, also known as 3D laser scanning, which makes it possible to “see” from the outside and thus identify features formed in the past. This technology provides an unprecedented overhead view (or nadir view) of the ceiling of the gallery and its astonishing formations, testifying to the…

Although this landscape has only just been created, there is nothing new about it. In fact, this is a numerical model of the ecosystem of the Bright Angel Trail, a hiking path located in Grand Canyon National Park, Arizona (US). Using the underlying terrain, as well as environmental and biological data, the system deployed here can reconstruct a landscape by automatically selecting various plant and animal species and placing them in the most suitable location. The different plants are grouped…

Throughout their use, materials are exposed to mechanical stress, which deforms and damages them. Such stress can be both mechanical, like an unforeseen impact, and thermal, such as a temperature change. This causes the formation and propagation of numerous defects within the material. However, the only way to understand, and therefore predict, their collective behaviour is to use numerical simulations. This micrometre-scale image, produced by digital modelling, shows a sample of copper that…