Category Archive : Nature

This Ancient Fish Represents The Earliest Known Evolutionary Evidence of Fingers

The four-limbed animals of the world have several things in common. Spines. Bilateral symmetry. And most of us have (or, in the case of birds, had) five digits at the end of each of our four limbs.

 

When and how these digits emerged in animals has been something of a mystery. Palaeontologists have just found the earliest evidence of this anatomical feature, in the fin of a fish that lived 380 million years ago.

The rudimentary digit bones may not look like much, but they mark one of the most important transitions in vertebrate evolution.

“We have made a major breakthrough in the origin of how the hand was first formed for all vertebrates,” palaeontologist John Long of Flinders University in Australia told ScienceAlert.

“This is the first time that we have unequivocally discovered fingers locked in a fin with fin-rays in any known fish. The articulating digits in the fin are like the finger bones found in the hands of most animals,” he said in a statement.

The transition from aquatic fish to four-limbed creature (tetrapod) is one of the most important in evolutionary history, yet there are significant gaps in our knowledge. One of those gaps has been the point at which fish emerged from the depths and started foraging in shallower waters – what’s considered to be an intermediate step before crawling out onto land.

 

In order to complete that transition, animals would have needed something pretty vital for crawling – that is, hands and feet, digits and all.

This is where a specimen of an ancient lobe-finned fish called Elpistostege watsoni enters the picture. It’s a type of tetrapod-like fish belonging to an order called Elpistostegalia, on the ancestral line that leads to tetrapods; our understanding of the emergence of tetrapods largely relies on what we know about that order.

e watsoni(Cloutier et al., Nature, 2020)

But the elpistostegalian fossil record has been pretty scarce, with incomplete pectoral fin skeletal anatomy. Until 2010, when an almost complete 1.57-metre (5.15-foot) fossilised E. watsoni skeleton was found in the Escuminac Formation of Miguasha in Quebec, Canada.

Long and his colleague palaeontologist Richard Cloutier from Universite du Quebec a Rimouski in Canada have been carefully studying the fossilised bones to see what they can tell us about this mysterious animal. This paper is the first in a series, and it describes how the pair and their team used CT scanning to discover the skeletal anatomy of the fin.

 

“We focused on the discovery of digit bones in the fin as this was a really spectacular discovery – the first definite (not controversial) case of a fish with finger bones,” Long told ScienceAlert.

“Once we had compared our fin skeleton of Elpistostege with the arm and hand skeletons of terrestrial animals, it became clear that the rows of small digit bones were – in the evolutionary sense – the same as to phalange bones in the hands of land animals (like us).”

anatomy of the fish fingers chartComparison of early tetrapod limb anatomy. (Richard Cloutier and John Long)

The bones are not exactly true fingers, since they’re tucked inside the fin like a mitten, and can’t move freely. The fin still retains the outer fringe covered in fin-ray bones, called lepidotrichia; the fingers wouldn’t be able to move freely unless E. watsoni lost those.

But it does confirm the animal as an intermediate between fish and tetrapods. Although some have thought digits and carpals may be unique to tetrapods, we have had hints otherwise; for instance, the tetrapod-like arrangement of humerus, radius and ulna bones was discovered in lobe-finned fishes all the way back in 1892.

“The origin of digits relates to developing the capability for the fish to support its weight in shallow water or for short trips out on land. The increased number of small bones in the fin allows more planes of flexibility to spread out its weight through the fin,” Cloutier explained.

“The other features the study revealed concern the structure of the upper arm bone or humerus, which also shows features present that are shared with early amphibians. Elpistostege is not necessarily our ancestor, but it is the closest we can get to a true ‘transitional fossil’, an intermediate between fishes and tetrapods.”

The next part of the team’s work describing the fossil will focus on the head and parts of the skull, making comparisons with early tetrapods to further trace those evolutionary connections.

“It’s a truly amazing specimen indeed,” Long said.

The research has been published in Nature.

 

A Crucial Idea Darwin Had on Evolution Was Just Confirmed, 140 Years After His Death

Published in 1859, Charles Darwin’s On the Origin of Species made a number of bold claims about the nature of evolution – including the suggestion that an animal species with greater diversity in its line will produce more sub-species, too.

 

This assumption is not as obvious as you might think at first. Only a couple of years ago, this hypothesis was finally found to be true for birds. Now, researchers from the University of Cambridge in the UK have shown that Darwin was right on this point for mammals, too: Mammal subspecies are indeed important in evolutionary terms, and perhaps more so than previously thought.

Apart from being an important contribution to our understanding of evolution in general, the findings could also be useful in ongoing conservation efforts – helping experts to figure out which species need to be protected in order to ensure their survival.

“My research investigating the relationship between species and the variety of subspecies proves that subspecies play a critical role in long-term evolutionary dynamics and in future evolution of species,” says biological anthropologist Laura van Holstein.

“And they always have, which is what Darwin suspected when he was defining what a species actually was.”

Darwin actually called them “varieties”, but the idea is the same – groups within a species with their own traits and breeding ranges. There are three subspecies of northern giraffe, for example, and 45 subspecies – the highest in the animal kingdom – of the red fox.

 

Human beings, on the other hand, don’t have any subspecies.

To test Darwin’s hypothesis, van Holstein looked at a huge database of animal classifications, analysing the collected knowledge we have about mammal species and subspecies to look for patterns.

The data showed that diversification between species and between subspecies was linked, as Darwin had suggested, but there was more – subspecies tend to form, diversify and increase differently depending on habitat (land versus sea, for example).

The findings show that the correlation between species diversity and subspecies diversity is strongest in non-terrestrial mammals – those living in the sea, or spending a lot of time in the air – and thus less affected by physical boundaries like mountains.

In animals like bats and dolphins, the researchers say, it might be better to consider subspecies more as the start of a new species rather than the evolution of an old one.

A further question posed by the researchers was whether there was any relationship between subspecies and the eventual creation of a whole new species.

“The answer was yes,” says van Holstein. “But evolution isn’t determined by the same factors in all groups and for the first time we know why because we’ve looked at the strength of the relationship between species richness and subspecies richness.”

 

The discoveries on subspecies habitat are particularly significant when it comes to conservation, because the habitats of so many animals are under threat from climate change and human activity -and these findings indicate that our actions really are having an impact on the process of evolution.

“Evolutionary models could now use these findings to anticipate how human activity like logging and deforestation will affect evolution in the future by disrupting the habitat of species,” says van Holstein.

“The impact on animals will vary depending on how their ability to roam, or range, is affected. Animal subspecies tend to be ignored, but they play a pivotal role in longer term future evolution dynamics.”

The research has been published in Proceedings of the Royal Society B.

 

This ‘Wonderchicken’ Could Be The Oldest Modern Bird Fossil, And a True Survivor

Back when fearsome dinosaurs roamed the land, an unimpressive avian, about the size of a very small duck, somehow survived alongside them – eking out a life along a prehistoric European seashore.

 

It had the long slender legs of a shorebird, and a face like a chicken, according to the Cambridge University researchers, who found its ancient traces hidden away in rocks dug up at a Belgium quarry 20 years ago.

“The moment I first saw what was beneath the rock was the most exciting moment of my scientific career,” said evolutionary palaeobiologist Daniel Field.

The skull and fragments of leg bones, revealed by CT scans, date as far back as 66.8 million years ago – the oldest evidence we have of a modern bird so far. The researchers have named this newly discovered species Asteriornis maastrichtensis, after the Titan goddess of falling stars, Asteria; the story goes that she turned herself into a quail to escape a threat.

By analysing the structures of the fossils, Field and colleagues found they had a combination of features now seen in modern waterfowl like ducks and landfowl like chickens and quails. This suggests A. maastrichtensis might be a common ancestor of both these groups.

Comparison between skulls. (Daniel Field/University of Cambridge)Comparison between skulls. (Daniel Field/University of Cambridge)

We’ve known for some time now that birds are descended from meat-eating dinosaurs called theropods, thanks to ‘missing link’ discoveries like 150 million-year-old Archaeopteryx – it had features such as teeth (like its dinosaur ancestors did), but also feathers and wrist bones shared by modern birds.

But so far there has been little evidence of exactly when modern birds arose.

 

“The origins of living bird diversity are shrouded in mystery – other than knowing that modern birds arose at some point towards the end of the age of dinosaurs, we have very little fossil evidence of them until after the asteroid hit,” explained palaeontologist Albert Chen.

When that rock fell from the sky, violently ending the Cretaceous period 66 million years ago, this slight ‘wonderchicken’, or some of its relatives, must have managed to live on to produce the amazing spectrum of birds we know and love today. Meanwhile, its more dinosaurian neighbours – like the teethed Icthyornis-like bird ancestors found in the same quarry – did not.

Previous research, which Field also worked on, suggests that small, non-arboreal birds not unlike A. maastrichtensis had an edge in a post-impact world stripped of trees.

“This is an incredibly informative specimen,” Johns Hopkins University palaeontologist Amy Balanoff, who was not involved in the study, told Science Magazine.

“It gives us some clues about what characteristics were key in surviving that event.”

(Phillip Krzeminski)(Phillip Krzeminski)

Fossils of other early modern birds found in the Southern Hemisphere, like the partial skeleton of 66.5 million year old Vegavis iaai, had led some researchers to suggest modern birds may have originated from Gondwana.

But this Northern Hemisphere find now casts doubt on this idea.

Asteriornis now gives us a search image for future fossil discoveries,” said Field. “Hopefully it ushers in a new era of fossil finds that help clarify how, when and where modern birds first evolved.”

The study was published in Nature.

 

Worms in Raw Seafood Have Increased 280x, But It’s Not Sushi We Should Worry About

Since the 1970s, a parasitic worm that infects fish, squid, whales, dolphins and sometimes even us has increased globally by 283-fold, according to a new meta analysis.

That’s no small amount, and yet because this creature is so tiny and the oceans so vast, it’s somehow evaded our notice until now. Not even the researchers themselves can figure out why this parasite is “growing like gangbusters”, or what it could possibly mean in the long run.

 

Known as the “herring worm” or Anisakis simplex, this particular parasitic nematode can hide in raw seafood; if mistakenly eaten by humans, it can cause symptoms similar to a bad case of food poisoning.

Other mammals aren’t so lucky. While the fishing industry might be inconvenienced by a rising tide of Anisakis, this parasite poses a much bigger threat to cetaceans, such as whales and dolphins.

Unlike humans, these marine mammals can get stuck with Anisakis for years, and they don’t have seafood processors and sushi chefs around to carefully clean out their catch.

Aquatic and fishery scientist Chelsea Wood says consumers don’t need to be too worried; she herself continues to eat sushi regularly. Given that the fishing industry hasn’t even noticed this increase in the parasitic worm, any risk of us ingesting it probably remains quite low. But the same can’t be said for marine mammals.

“It’s not often considered that parasites might be the reason that some marine mammal populations are failing to bounce back,” says Wood.

“I hope this study encourages people to look at intestinal parasites as a potential cap on the population growth of endangered and threatened marine mammals.”

 

The impact of this rising parasite on marine mammals is currently unknown, but if the numbers are right, cetaceans are facing a much greater risk of contracting Anisakis than half a century ago.

Analysing a total of 123 papers, the researchers reveal an astonishing increase in Anisakis abundance over a 53 year period from 1962 to 2015. On average, they explain, this means we have gone from finding less than one worm in every 100 hosts to more than one worm in every single host caught.

The global scale of this analysis was too great to pin down any one factor driving this growth, but Wood has a strong suspicion she knows what’s going on.

“My gut is that this is about the improvements we’ve made in marine mammal conservation,” Wood told ScienceAlert.

“The time frame of our study directly overlaps with when a bunch of really important marine mammal legislation went into effect like the Marine Mammal Protection Act in 1972 and the international whaling commission moratorium on commercial whaling which came in the 1980s.”

Strangely enough, however, not all marine mammal parasites are increasing. The authors found another similar parasite, called Pseudoterranova, which infects fish, sea lions and other seals, remained relatively stable throughout the same time period.

 

Wood says they were expecting it to be the other way around, given how much seals and sea lions have thrived in recent years and how much whales have struggled. So maybe Anisakis is increasing because its life cycle has to pass through fewer hosts. Or perhaps it has something to do with the fitness of cetaceans versus seals.

The problem is, we have no baseline for what ‘natural’ looks like. The rising number of ocean worms could be a sign of the ecosystem thriving, or they could represent a growing threat to already endangered and vulnerable creatures like Hector’s dolphin (Cephalorhynchus hectori).

The only studies available for analysis come from near history, and by this time, humans had already changed the oceans in drastic ways.

This raises the question: is the abundance of Anisakis increasing in response to human impacts, like fishing, pollution, or climate change, or is it recovering alongside an exploited marine mammal host?

Right now, we just can’t say for sure. Wood thinks the most plausible explanation is that some marine mammals are doing well, leading to an increase in the parasite at the expense of more vulnerable creatures who now face an increased risk of infection. We simply need more research.

 

“This is the story of only two parasite species among millions that are extant, and we encourage others to use historical ecology approaches to track change across a diversity of marine parasite species,” the authors write

“Only then will we have the data to indicate whether contemporary oceans are facing a ‘rising tide’ of marine disease.”

In the Arctic, where Anisakis flourishes, we often lack long-term data, even for the best known parasites and their diseases. And if we don’t know where they’re going or where they’ve been, we can’t predict how diseases will change with the times.

In this case, we completely missed out on the rise of Anisakis, and while it might not matter to humans this time, some day it very well could.

“There are way bigger infectious disease threats that people have to worry about, particularly for now,” says Wood. The effects of Anisakis are pretty mild, she says, and while it’s certainly not fun to barf, we’ve got bigger fish to fry.

The study was published in Global Change Biology.

 

The Largest Mass Migration on The Planet Happens Every Single Day, And We Never See It

At night, they rise. As the Sun disappears over the horizon, a vast movement takes place in the world’s oceans, as countless sea creatures begin the long trek upwards towards the surface waters above.

 

They do not stay long. When the Sun rises, bringing light and the threat of watchful surface predators, they will retreat once more, down into the lower depths of the sea, sheltering in whatever protection the enveloping darkness can afford them.

This endless back-and-forth – called diel vertical migration (DVM) – is thought to be the largest mass migration on the planet in terms of the enormous amount of biomass involved, and it’s something that happens every single day and night, even though humans, for the most part, hardly even notice.

Some do, however. Scientists at the Monterey Bay Aquarium Research Institute in California have been watching closely, analysing thousands of hours of footage of this phenomenon, and publishing their findings in a new study.

In short, the migration is no picnic. For vertical migrators who are preyed upon, there really is no such thing as a truly safe harbour, as predators hunt them basically every step of the way on their up-down journey, which usually spans hundreds of metres each way.

010 mass migration 2A Gonatus onyx squid eating a lanternfish. (MBARI)

“Just as there is a second set of predators that occupy the migrators’ dark daytime depths, there is also a diverse suite of predators that comprise a gauntlet of threats during the migrations,” the authors write in their paper.

Drawing upon a huge amount of observations recorded between 1997 and 2015 in Monterey Bay – and taken by human-occupied vehicles (HOVs), remotely operated vehicles (ROVs), and autonomous underwater vehicles (AUVs) – the researchers sought to examine vertical migration “from the standpoint of the migrators”, to gauge the level and kind of threats they meet during daily movements.

 

“Nobody has ever looked at migration from that perspective,” says midwater ecologist Bruce H. Robison.

“People have always made predictions of predation on vertical migrators based on data from net tows or acoustic surveys. But we spent so much time in the water videotaping the animals that we realised we could look at the risks of migration directly, based on what they actually encounter.”

In addition to a particular focus in the study on encounters faced by two prey animals – krill (Euphausia pacifica and Thysanoessa spinifera) and lanternfish (also known as myctophids) – the researchers also developed a model, based on the encounter data, to calculate the “threat potentials” these animals face from predators during vertical migration.

“Threat potential is a measure of the latent risk of encountering a potential predator or obstacle during diel vertical migration,” the researchers explain.

“It does not equate to mortality nor is it a proxy for predation rate or predatory impact.”

Given the seemingly omnipresent predatory obstacles these vertical migrators face, the researchers acknowledge “the odds of successful migration seem very small” – and yet, somehow, high threat potentials don’t always spell high death rates.

 

The reason why depends on the defensive and evasion capabilities of particular prey, but can include tactics such as mimicry, bioluminescence, schooling and swarming behaviour, among others, the team says.

While they may have to run the gauntlet their entire lives – every day, and every night – prey populations tend to find a way to persist in the face of hungry dangers, whether swimming to the light, or swiftly in the opposite direction.

The findings are reported in Frontiers in Marine Science.

 

Les calmars peuvent modifier leur ARN d'une manière sans précédent, découvrent les scientifiques

 

En ce qui concerne les calmars, vous ne pouvez tout simplement pas les réduire.

Non seulement parce qu’ils sont glissants, mais aussi parce qu’ils ont une incroyable capacité d’édition génétique – cela leur permet de modifier leur propre ARN longtemps après qu’il ait quitté le noyau.

 

Voici ce que cela signifie. Les gènes, au moins chez l’homme, restent pour la plupart inchangés jusqu’à ce qu’ils soient recombinés et transmis à la génération suivante.

Il en va de même pour notre ARN messager (ARNm). Des molécules utiles lisent notre ADN, créent de petits messages d’ARN courts et les envoient à l’extérieur du noyau pour dire au reste de la cellule quelles protéines doivent être construites.

Une fois que l’ARNm a quitté le noyau, on pense que les informations génétiques qu’il transporte ne peuvent pas être gâchées – mais de nouvelles recherches ont montré que dans les nerfs de calmar, ce n’est pas le cas.

“Nous montrons que le calmar peut modifier les ARN à la périphérie de la cellule”, déclare le généticien du laboratoire de biologie marine (MBL), Woods Hole Joshua Rosenthal.

“Il fonctionne par ce réglage massif de son système nerveux”, Rosenthal a dit Filaire . “Ce qui est une façon vraiment originale de vivre sa vie.”

L’équipe a prélevé des nerfs sur des spécimens de calamars côtiers mâles adultes ( Doryteuthis pealeii ), et a analysé l’expression des protéines, ainsi que le transcriptome des calmars , qui est similaire à un génome, mais pour l’ARNm.

Ils ont découvert que dans les nerfs de calmar (ou neurones), l’ARNm était édité à l’extérieur du noyau, dans une partie de la cellule appelée axone.

Cette édition d’ARNm permet aux calmars de régler finement les protéines qu’ils produisent sur des sites locaux (voir schéma ci-dessous). Avec cette découverte, les calmars sont devenus les seules créatures que nous connaissons qui peuvent le faire.

Squid RNA Editing Graphical Abstract ver. 3 (Vallecillo-Viejo et al., Nucleic Acids Research, 2020)

Ce n’est pas la première fois que des calmars ont montré leurs prouesses d’édition génétique, cependant. En 2015, une équipe similaire de MBL a découvert que les calmars modifient leur ARNm à l’intérieur de leur noyau à un degré incroyablement élevé – des ordres de grandeur de plus que ce qui se passe chez l’homme.

“Nous pensions que tout le montage d’ARN s’est produit dans le noyau, puis les ARN messagers modifiés sont exportés vers la cellule”, explique Rosenthal.

Mais l’équipe a montré que bien que l’édition se produise dans les deux, elle se produit beaucoup plus à l’extérieur du noyau dans l’axone, plutôt qu’à l’intérieur du noyau.

Alors, pourquoi les calmars dérangent-ils? Pourquoi ont-ils tellement besoin de changer leur ARNm? Eh bien, nous ne savons pas encore, mais l’équipe de recherche a quelques idées.

Les poulpes, les seiches et les calmars utilisent tous l’édition d’ARNm pour diversifier les protéines produites dans le système nerveux. Cela pourrait être l’une des raisons pour lesquelles ces créatures sont tellement plus intelligentes que les autres invertébrés.

“L’idée selon laquelle les informations génétiques peuvent être modifiées de manière différentielle au sein d’une cellule est nouvelle et étend nos idées sur la façon dont un plan unique d’informations génétiques peut donner lieu à une complexité spatiale”, écrit l’équipe dans leur nouveau document.

“Un tel processus pourrait affiner la fonction des protéines pour aider à répondre aux exigences physiologiques spécifiques des différentes régions cellulaires.”

Bien qu’il ne s’agisse pour l’instant que d’une étude génétique intéressante sur les calmars, les chercheurs pensent que ce type de système pourrait éventuellement aider à traiter les troubles neurologiques qui incluent la dysfonction axonale.

CRISPR a complètement changé le jeu quand il s’agit de modifier l’ADN à l’intérieur de nos cellules, et l’ARN est nettement moins permanent et donc le modifier pourrait être moins dangereux.

“L’édition d’ARN est beaucoup plus sûre que l’édition d’ADN”, Rosenthal a dit Wired .

“Si vous faites une erreur, l’ARN se retourne et s’en va.”

La recherche a été publiée dans Nucleic Acids Research .

Giant Freshwater Reserve Discovered Deep Under The Seabed Off New Zealand

 

Une réserve d’eau douce rare a été découverte sous la mer au large des côtes de l’île du Sud de la Nouvelle-Zélande, ce qui pourrait aider à prévenir les futures sécheresses et à atténuer l’impact du changement climatique dans les années à venir.

 

L’eau souterraine rafraîchie au large (OFG) a été découverte grâce à une combinaison de techniques de sismologie et de balayage des ondes électromagnétiques, qui ont été utilisées pour construire une carte 3D de l’aquifère sous la mer .

Bien que la capacité en eau précise n’ait pas encore été calculée, les chercheurs pensent que le système pourrait contenir jusqu’à 2 000 kilomètres cubes (ou près de 480 miles cubes) d’eau douce – soit 800 millions de piscines olympiques, ou plus de Lac Ontario .

tir aquifer 2 Comment s’est formée la réserve d’eau douce. (Marcan)

Ces aquifères au large, enfermés dans la roche, peuvent être trouvés à divers endroits dans le monde, bien qu’ils ne soient pas très courants. Dans ce cas, une grande partie de l’eau est susceptible d’avoir été laissée pour compte par les trois dernières périodes glaciaires, selon les scientifiques.

“L’un des aspects les plus importants de cette étude est la meilleure compréhension qu’elle offre à la gestion de l’eau”, , explique le géologue marin Joshu Mountjoy , de l’Institut national de recherche sur l’eau et l’atmosphère (NIWA). ) en Nouvelle-Zélande.

“Pour le moment, nous avons utilisé des techniques, de la modélisation et de la géophysique à distance. Nous avons vraiment besoin d’aller sur le terrain et de vérifier nos découvertes et nous étudions des options pour cela.”

Le premier indice qu’un tel système OFG était caché au large de la ville portuaire de Timaru était de l’eau saumâtre (un mélange d’eau salée et d’eau douce) découverte après un forage scientifique projet en 2012.

Une enquête plus approfondie a été lancée à bord d’un navire de recherche en 2017. L’aquifère est inhabituellement peu profond, à seulement 20 mètres (moins de 66 pieds) sous le fond marin. On pense qu’il s’étend à environ 60 kilomètres (37 miles) de la côte.

Son emplacement est particulièrement privilégié, la région plus large Canterbury faisant face à une pression accrue d’une population croissante et à des périodes de sécheresse prolongées. Le vaste réservoir d’eau douce pourrait représenter la moitié des eaux souterraines de Canterbury, selon les chercheurs.

Alors que des cartes détaillées de la salinité de l’eau et de la forme de l’aquifère ont maintenant été établies, de nombreuses inconnues demeurent. Ensuite, l’équipe veut réellement prélever des échantillons du système d’eau douce et les comparer aux modèles jusqu’à présent.

Selon les chercheurs, les mêmes techniques appliquées dans cette étude pourraient également être utilisées pour réévaluer des aquifères similaires à travers le monde. .

“En ce qui concerne la résilience à long terme pour nos communautés et notre économie, le district de Timaru étudie actuellement des options pour la sécurité de l’eau à long terme”, a déclaré le maire de Timaru, Nigel Bowen, à Lee Kenny lors de Stuff [19459004 ].

“L’eau est notre priorité numéro un pour aller droit aux générations futures.”

La recherche a été publiée dans Nature Communications .

There Are Striking Similarities in The Way Bacteria And Humans Settle Into Colonies

 

La façon dont les bactéries buccales s’installent dans nos bouches n’est pas sans rappeler comment nous, les humains, nous installons dans nos villes, selon une nouvelle étude.

Il y a une raison pour laquelle les bactéries vivraient en «colonies», et plus nous en apprenons sur la façon dont ces minuscules architectes construisent leurs communautés, plus leur comportement nous semble familier.

 

Une nouvelle étude suivant la façon dont plusieurs colons individuels se développent en microcolonies a trouvé des schémas de croissance et des dynamiques qui reflètent nos propres inclinations urbaines.

“Nous adoptons cette vue” au niveau du satellite “, à la suite de centaines de bactéries distribuées sur une surface depuis leur colonisation initiale jusqu’à la formation de biofilms”, dit Hyun Koo de l’Université de Pennsylvanie.

“Et ce que nous voyons, c’est que, remarquablement, les caractéristiques spatiales et structurelles de leur croissance sont analogues à ce que nous voyons dans l’urbanisation.”

Tout comme dans la nature, les bactéries dans votre bouche vivent dans des structures complexes appelées biofilms. En fait, 99,9% des procaryotes vivent entassés avec des millions d’autres voisins dans l’une de ces colonies.

Les biofilms sont partout, mais s’ils sont sur vos dents, nous les appelons plaque. Ce dépôt dense et collant est difficile à éliminer, protégeant ainsi les microbes résidents des agressions environnementales, comme le dentifrice, la soie dentaire ou même les antibiotiques.

Il s’accumule lorsque plusieurs colons se transforment en microcolonies, mais la manière exacte dont cela se produit reste sous-explorée.

En utilisant la bactérie orale Streptococcus mutans , les chercheurs ont montré que les cellules microbiennes se déposent au hasard et quel que soit le type de surface. Néanmoins, seul un sous-ensemble de colonisateurs commence réellement à se regrouper, élargissant leur portée “en fusionnant les bactéries voisines en microcolonies densément peuplées”.

“Nous pensions que la majorité des bactéries individuelles finiraient par croître”, dit Koo. “Mais le nombre réel était inférieur à 40%, le reste mourant ou étant englouti par la croissance d’autres microcolonies.”

Une fois que les clusters apparaissent, quelque chose de vraiment curieux se produit: ils commencent à interagir les uns avec les autres, se développant et s’organisant en des microcolonies à échelle micrométrique densément peuplées ” superstructure de biofilm.

Ce type de coopération est intéressant, car des études antérieures ont signalé une compétition bactérienne chez d’autres espèces, en particulier en cas de pénurie de nutriments.

Dans ce cas, les nutriments ont seulement eu un impact sur la formation réelle des colonies. Après cela, “les microcolonies individuelles (éloignées ou proches) ont continué de croître sans interruption jusqu’à ce qu’elles fusionnent les unes avec les autres, et les structures fusionnées se sont comportées et se sont développées comme une nouvelle communauté harmonisée”, écrivent les chercheurs .

Ce n’est que lorsque des espèces étrangères plus antagonistes ont été introduites que cela a affecté cette unité apparemment paisible, et la croissance des microcolonies a été réduite.

“Ces communautés (microcolonies) peuvent s’étendre et fusionner entre elles de manière collaborative, sans concurrence entre les communautés adjacentes”, concluent les auteurs .

bacteriaform (Paula et al., Nature Communications, 2020)

C’est le type de croissance qui indique un “comportement commun entre micro-organismes” “, et cela ressemble à l’urbanisation humaine, où certains colons restent statiques, tandis que d’autres se développent en villages qui se développent davantage en microcolonies ou villes densément peuplées, qui fusionnent ensuite en mégapoles microbiennes.

Bien sûr, il y a des limites à cette idée d’urbanisation bactérienne. Les auteurs ne disent pas que les microbes construisent des panneaux de signalisation, des routes et des conduites d’alimentation, mais l’idée générale est la même et elle peut non seulement nous aider à mieux lutter contre les infections, mais elle pourrait également nous aider à construire de manière plus durable .

“C’est une analogie utile, mais elle doit être prise avec un grain de sel”, dit Koo . “Nous ne disons pas que ces bactéries sont anthropomorphes. Mais adopter cette perspective de la croissance du biofilm nous donne une image multidimensionnelle et multidimensionnelle de leur croissance que nous n’avons jamais vue auparavant.”

L’étude a été publiée dans Nature Communications .

Butterfly Wings Have a Hidden Structure That Rivals Vantablack in Its Darkness

Butterflies have taken the colour black to an entirely new level. The scales that shingle this insect’s dark wings are nearly on par with the blackest of black coatings made by humans – except they’re only a fifth of the thickness.

 

At just a few microns wide, these natural nanostructures absorb 99.94 percent of the light that hits them, allowing only a tiny amount to be reflected. 

To put that in perspective, Vantablack, which used to be the blackest material known to science, absorbs 99.96 percent of light. And the material that surpassed its blackness has vertically aligned carbon nanotubes (CNTs) that can absorb more than 99.995 percent.

Even for the natural world, however, ultra-black butterflies are, well, ultra-black. Examining 10 species from around the world, which were either ultra-black, regular black or dark brown, researchers at Duke University found these creatures were between 10 to 100 times darker than charcoal, fresh asphalt and velvet. 

It’s the widest sample of black butterflies studied to date, with species coming from Central and South America, as well as Asia.

“Why be so black?” wonders biologist Alex Davis. “We think it’s likely some sort of signal to mates or maybe a predator. But there’s a host of other possibilities, and we’re hoping to clear that up.”

Under an electron microscope, the scales on a butterfly wing look kind of spongy or mesh-like, with ridges and holes held up by pillar-like beams of tissue (see image above).

 

Previously, it was the holes between these pillars that were thought to influence the level of blackness, but biologist Sönke Johnsen now thinks the shape and size of these hollowed-out spaces “doesn’t matter” as much.

The ultra-black butterflies studied showed a variety of holes, shaped like honeycomb, rectangles and chevron patterns. But there was something else they all had in common. 

1 tomakeultrab(DirkHeumannK1966/Barnard Dupont)

Compared to regular black scales, ultra-black scales showed steep ridges on the surface as well as deeper and thicker pillars underneath.

Running these two features through computer simulations, the researchers illustrate that scales lacking in either ridged surfaces or interior pillars reflected up to 16 times more light. That’s essentially like going from ultra-black to dark brown.

Along with an added contrast from white borders or nearby bright patches, those dark colours on the wings of a butterfly appear even darker.

“Given that these structural changes increase the surface area for absorption,” the authors write, “we conclude that butterflies operate under the same design principles as synthetic ultra-black materials – high surface roughness and a large area for absorption.”

 

But because these scales are several times thinner than stacked carbon nanotubes, engineers and biologists alike are interested in learning how they can trap so much light without weighing themselves down.

The answer could possibly help us design better solar panels and telescopes. It could maybe even camouflage an aircraft so it can’t be detected at night or by radar.

The possibilities are huge for such a nanoscopic mechanism.

The study was published in Nature Communications.

 

The Fragment of an Ancient Lost Continent Has Been Discovered Off The Coast of Canada

Scientists have uncovered a splintered remnant of Earth’s continental crust from millions of years ago, embedded in the isolated wilderness of northern Canada.

Baffin Island, located in between the Canadian mainland and Greenland, is a vast Arctic expanse covering over 500,000 square kilometres (almost 200,000 square miles), making it the fifth largest island in the world.

 

While the island comprises part of the newest recognised territory in Canada – Nunavut, formally established in 1999 – a new discovery shows this ancient landmass has undisclosed ties that stretch backwards in time so far, they actually emanate from a distant geologic eon.

While analysing igneous rock samples recovered from diamond exploration drilling in the Chidliak Kimberlite Province at the southern stretches of Baffin Island, researchers identified a mineral signature in the rock they had never expected to find.

“Kimberlites are subterranean rockets that pick up passengers on their way to the surface,” explains geologist Maya Kopylova from the University of British Columbia.

“The passengers are solid chunks of wall rocks that carry a wealth of details on conditions far beneath the surface of our planet over time.”

In this case, those passengers had completed a very long journey. The team says kimberlite rocks like this, formed at depths below 150 kilometres (93 miles), are driven to the surface by both geological and chemical forces.

In terms of the geological component, their emergence underneath modern-day Baffin Island represents the end of a colossal dispersal that occurred approximately 150 million years ago, during rifting of the continental plate of the North Atlantic Craton (NAC).

 

This NAC refers to chunks of lithospheric rock that date back billions of years ago to the Archean Eon, representing some of the best exposures of Earth’s earliest continental crust.

Rifted into fragments millions of years ago, NAC has been exposed in Scotland, Labrador, and Greenland, but researchers weren’t expecting to find it in Baffin Island’s Hall Peninsula.

“The mineral composition of other portions of the North Atlantic Craton is so unique there was no mistaking it,” says Kopylova.

“It was easy to tie the pieces together. Adjacent ancient cratons in Northern Canada – in Northern Quebec, Northern Ontario and in Nunavut – have completely different mineralogies.”

To reach their findings, the team used a number of analytical techniques – including petrography, mineralogy, and thermobarometry – to study 120 rock samples, called xenoliths, taken from the kimberlite province.

The results showed the Chidliak mantle “strikingly resembles” the NAC rocks from West Greenland in terms of their bulk composition and mineral chemistry, while showing numerous contrasts with markers from other cratons.

“We conclude that the Chidliak mantle demonstrates an affinity with only one adjacent block of cratonic mantle, the NAC,” the authors explain in their paper.

 

“We interpret this similarity as indicating the former structural coherence of the cratonic lithosphere of the Hall Peninsula Block and the NAC craton prior to subsequent rifting into separate continental fragments.”

The new findings mean we’ve discovered about 10 percent more of the known expanse of the NAC – a pretty sizeable chunk of this incredibly ancient crust. And thanks to newer mantle modelling techniques, we can also envisage the shape of some of Earth’s earliest known rock formations at much greater depths than ever before.

“With these samples we’re able to reconstruct the shapes of ancient continents based on deeper, mantle rocks,” says Kopylova.

“We can now understand and map not only the uppermost skinny layer of Earth that makes up one percent of the planet’s volume, but our knowledge is literally and symbolically deeper.”

The findings are reported in Journal of Petrology.