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The mysterious Ediacaran fauna

During many years, it has been considered that the origin of metazoans (i.e. multicellular animals) took place in the Cambrian period (541-484 My ago) after the Cambrian Explosion. However, several scientists, including Darwin, already suspected that the true origin of metazoans must be even older.

Did metazoans exist in the ancient and understudied Precambrian supereon? We invite you to know the Ediacaran fauna, a paleontological puzzle and a clue link in the evolutive history of animals.

The mysterious Ediacaran fauna

Before start talking about the Ediacaran period and its odd fauna, we must set it into a geological time context.

Our planet Earth formed around 4600 My Ago. The span between Earth’s formation and the moment in time 543 My ago is known as Precambrian supereon, the first and largest period of history of Earth, as well as the less studied and comprehended. It is suggested that the first life forms appeared 3800-3500 My ago, not very after the beginning of the Precambrian.

The end of the Precambrian supereon lead to the beginning of the Phanerozoic eon, whose first geological period, the Cambrian, has been traditionally considered to set the origin of all phyla of metazoans (multicellular animals). All animal phyla were already represented shortly after the beginning of this period; that is, it took place a great diversification of living beings on a global scale in a short span, an evolutive radiation event. This massive evolutive event was named as Cambrian Explosion.

Geological time scale: end of the Precambrian supereon and beginning of the Phanerozoic eon (specifically, the Paleozoic era). The Ediacaran and the Cambrian are highlighted in red. Source: The Geological Society of America.

The idea of the Cambrian period as the cradle of most of animal groups was deduced from the study of fossil records and their age. However, is it true that the origin of every animal phyla took place entirely during this period? Some scientists, as the selfsame Darwin, suspected that the first metazoan lineages could have appeared even earlier.

Precambrian fossils

The Precambrian was an instable period at a geological level: tectonic movements, vulcanism… put many troubles in the preservation of any biological rest. On the other hand, the succession of several global glaciations during this supereon (‘Snowball Earth’), the last of which took place 650 My ago, put even more difficulties into the progression of life on Earth.

No wonder, so, that the Cambrian, a more stable period from both a geologic and climatic point of view, was long considered the origin of metazoans, since the geological instability during the Precambrian presumably made it impossible to preserve any fossil record. That is, supposedly there were not “clues” about the existence of metazoans before the Cambrian Explosion.

However, something happened. At the end of the 19th century, a Scottish scientist discovered what was later considered as the first Precambrian fossil ever known: Aspidella terranovica, a disk-shaped fossil of uncertain affinity. But as it was found in Precambrian strata, it was considered an artifact.

Aspidella fossils (also known as Cyclomedusa, currently a synonym). Its shape reminds of that of a jellyfish. Source: Verisimilus (CC 3.0) on Wikipedia.

This discovery was followed by others throughout the world, in which fossils from the Precambrian were also found (e. g., Namibia and Australia), but the strong belief that multicellular animals appeared during the Cambrian or even later eclipsed the true origin of these fossil records for many years. It was not until the 20th century and after the discovery of a second iconic fossil in Charnwood Forest (England), Charnia masoni, that the Precambrian origin of metazoans was not really considered, this fossil being the first to be recognized as Precambrian. So, Aspidella terranovica, Charnia and the rest of Precambrian fossil records would be, at last, connected.

Charnia masoni holotype. Despite its frond-like appearance, it is not considered a plant or an alga since the nature of the fossil beds where specimens have been found implies that it originally lived in deep water, well below the photic zone where photosynthesis can occur. Source: Smith609 (CC 2.5) on Wikipedia.

The Ediacaran period

At last, Precambrian fossil have been found all over the world. Most of them have been found in strata date from 575-541 My ago, marking the end of the Precambrian and the beginning of the Phanerozoic.

Nowadays, representatives of the Ediacaran fauna occur at 40 localities worldwide, with 4 particularly good localities:

  • Southeastern Newfoundland (Canada)
  • The Flinders Ranges (South of Australia)
  • White Sea region (Russia)
  • Namibia

In 1960, the term ‘Ediacaran’ was proposed to name the geological span which the Ediacaran fauna is date from. The term comes from the Ediacara Hills in Australia, where one of the most important Precambrian fossil sites is found. This name competed with others, but in 2004, the International Union of Geological Sciences stablished the Ediacaran as the period that started 635 My ago (after the Marinoan glaciation) and that ended 542 My ago (with the discover of the earliest widespread complex trace fossil).

The Ediacaran fauna

Once the Precambrian was finally accepted as the origin of metazoans, and assuming that complex animals appeared during a hypothetical explosion of diversity just after the great Precambrian glaciations and some million years before the Cambrian (Avalon Explosion), some questions were raised:

How did the Ediacaran fauna look like?

Most of fossil records of the Ediacaran fauna consist of macroscopic, morphologically diverse (mainly radial or circular shapes) and generally soft-bodied organisms, without hard elements that could last until our days. This can be deduced from the shape and typology of the fossils, since most of them are simply marks or trails they left after dying, preserved in a manner that is, in many cases, unique to the Ediacaran fauna.

Tribrachidium fossil. It is, in fact, a negative impression, that is, the trail that the animal left after dying. It is suggested that it could be an organism with triradial symmetry very close to nowadays Lophophorata. Source: Aleksey Nagovitsyn (CC 3.0) on Wikipedia.

Besides, they were probably sessile, aquatic, with feather-like structures and filter feeders. However, several researchers consider that a few of them could be free-living animals with a bilateral symmetry (that is, with an anteroposterior axis that splits the body into two symmetric halves), one of the most successful body plans after the Cambrian Explosion.

Dickinsonia costata fossil. According to its shape, it was probably a bilateral animal (with a ‘head’ and an ‘anus’), and for a long time it was suggested that it was related to some kind of flat worm, some of which could be up to 1 meter long. In 2018, cholesterol molecules found in Dickinsonia fossils confirmed that it was an animal. Source: Verisimilus (CC 3.0) on Wikipedia.

With which current groups do they relate?

The fact is we still do not know. Most of them have shapes that reminds of some basal metazoans (like sponges and cnidarians) and a few, to annelids and arthropods. However, these are artificial relationships, as phylogenetic relationships between the Ediacaran fauna and the current fauna are still a mystery. Even some fossils cannot be related to any nowadays phyla, so they are considered as a part of an extinct Precambrian lineage.

However, not everything is lost. Similarities between some Ediacaran fossils and current metazoans shed some light on how animals could have evolved, and which was their origin.

Why Ediacaran fossils are not found beyond the Ediacaran period?

The fact is they are found in strata that date from after the Ediacaran period. Posterior studies demonstrated that some Ediacaran organisms were located in Cambrian strata together with fossils that resulted from the Cambrian Explosion, so it would be possible some representatives of the Ediacaran fauna gave place to certain current groups of animals. However, it is true that Ediacaran fauna representatives are found in a smaller proportion in Cambrian strata than other Cambrian organisms, and many living forms had already disappeared.

There exist some hypotheses that explain why most of the Ediacaran fauna did not survived beyond the Cambrian, for example:

  • Changes in atmospheric oxygen levels.
  • Competence with the Cambrian fauna, which probably had better adapted bodies or more successful body plans.
  • Changes in the sea level.

Are the Ediacaran organisms the true origin of metazoans?

Although this has been the general belief after their discovery, the truth is that even older metazoans have been recently found.

As we have explained above, most representatives of the Ediacaran fauna date from 575-541 My ago. Well, evidence of ancient sponges (Porifera) from 600 My ago has been found. The most recent discovery was that of Otavia antiqua in 2012 in Namibia, a sponge date from 760 My ago; that is, it is dated from before some of the great Precambrian glaciations.

Otavia antiqua. Source: National Geographic.

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Do you believe there are even older metazoan fossils out to be discovered? Leave your comments!

Main image by Ryan Somma, from the Smithsonian National Museum of Natural History (CC 2.0).

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Beyond red: the color of blood

There are people who remember with great impact the first time they saw their own blood. Even in adulthood and in controlled conditions (for example, during an extraction in a medical center) the vision of the red fluid is not always pleasant. Sometimes more intense, sometimes darker, but always red… or not? Do you know if there are animals with blue, green or maybe yellow blood? Keep reading to find out.

BEYOND RED: THE COLOR OF BLOOD

We are used to the color of blood being red, since it is the color of our blood and many vertebrates, like all mammals. The color of the blood is due to respiratory pigments, those responsible for transporting oxygen to cells throughout the body and carbon dioxide to the lungs. As you may remember, the human respiratory pigment is hemoglobin, which is found in red blood cells or erythrocytes.

But other animals have respiratory pigments other than hemoglobin, which endow their blood with colors as varied as green, blue, yellow and even purple.

glóbulos rojos, sangre, eritrocitos, hematíes
Human red blood cells (erythrocytes) seen under the electron microscope. Photo: John Kalekos

RED BLOOD

As mentioned, the respiratory pigment of mammals and many other vertebrates is hemoglobin, a protein. In its molecular structure, hemoglobin is formed by 4 subunits (called globins) linked to a heme group. The heme group has a central iron atom (iron II) that is responsible for the red color.

sangre color rojo hemoblogina molécula
Representation of the structure of hemoglobin. We can see the globins joined to their corresponding heme group, and an enlargement of the heme group with the iron (II) atom at its center. Picture: Buzzle

The hue of red may vary, depending on how oxygenated hemoglobin is. When it is attached to oxygen (O2), it is called oxyhemoglobin and its color is an intense light red (arterial blood). In contrast, deoxyhemoglobin is the name given to reduced hemoglobin, that is, when it has lost oxygen and has a darker color (venous blood). If hemoglobin is more oxygenated than normal it is called methemoglobin and has a red-brown hue. This is due to the intake of some medications or a congenital disease (methemoglobinemia).

sangre venosa, sangre arterial, rojo intenso, rojo oscuro, color
Color hue difference between venous blood (upper syringes) and arterial blood (lower syringes). Photo: Wesalius

As we have seen, deoxygenated blood is not blue. The blue tone that we see in our veins is due to an optical effect resulting from the interaction between the blood and the tissue that lines the veins.

BLUE BLOOD

Some animals, on the other hand, do have blue blood: decapod crustaceans, some spiders and scorpions, horsehoe crabs, cephalopods and other molluscs. When dealing with invertebrates, we must specify that instead of blood its internal liquid is called hemolymph, but in this post we will not distinguish hemolymph from blood for better understanding.

cangrejo herradura sangre azul xfosuro
Ventral view of a wounded horsehoe crab, in which its blue blood can be observed. Photo: Dan Century

The pigment responsible for the blue color of blood in these animals is hemocyanin. Its structure is quite different from that of hemoglobin, and instead of iron, it has a copper (I) atom at its center. When hemocyanin is oxygenated, it is blue, but when it is deoxygenated it is colorless.

molécula hemocianina
Chemical structure of oxygenated hemocyanin. Picture: Chemthulhu

GREEN BLOOD

There are some animals with green blood, such as some annellids (worms), some leeches and some marine worms. Its respiratory pigment, called chlorocruorine, gives its blood a light greenish color when it is deoxygenated, and a little darker when it is oxygenated. Structurally, it is very similar to hemoglobin, since it also has an iron atom at its center. Unlike hemoglobin, it is not found in any cell, but floats in the blood plasma.

molécula clorocruorina
Chemical structure of chlorocruorine. Public domain image

 

sangre color verde
Tube containing green blood from a New Guinea lizard. Photo: Christopher Austin

In the case of vertebrates with green blood (like some New Guinea lizards), the color is due to biliverdin, which results from the degradation of hemoglobin. Biliverdin is toxic, but these lizards are able to withstand high levels in their body. In the rest of vertebrates, if biliverdin levels are high because the liver can not degrade it to bilirubin, they cause jaundice, a disease that gives a yellowish color to the skin and corneas of the eyes. But in species of lizards like Prasinohaema prehensicauda, the high presence of biliverdin could protect them against malaria, according to some research.

lagarto nueva guinea sangre verde
Species of New Guinea lizard with green blood. Photo: Christopher Austin

YELLOW BLOOD

Tunicates (fixed ascidians) are a type of animals with yellow/yellow-green blood. The pigment responsible for this color is hemovanabine, a vanadium-containing protein, although it not transport oxygen, so its function remains unknown. Similarly, the yellowish, yellow-green and even orange color of the blood (hemolymph) of some insects is not due to the presence of a respiratory pigment, but to other dissolved substances that do not carry oxygen.

tunicado
Tunicate (Didemnum molle) in Sulawesi, Indonesia. Photo: Bernard Dupont

PURPLE BLOOD

Some marine invertebrates have violet blood (hemolymph), such as priapulids, sipunculides, brachiopods and some annelids.

priapulida hemeritrina
Priapulus caudatus, a priapulid. Photo: Shunkina Ksenia

The responsible respiratory pigment is hemeritrin, which turns violet-rosacea when it is oxygenated. In its deoxygenated form it is colorless. Like the rest of the respiratory pigments we have seen, hemeritrin is less efficient than hemoglobin when transporting oxygen.

hemeritrina color sangre violeta
Chemical structure of hemeritrin in its oxygenated form. Like hemoglobin, the central element is iron II

TRANSPARENT BLOOD

Finally, there is a family of fish called crocodile icefish whose blood is transparent. Actually, these are the only vertebrates that have lost hemoglobin. Similarly, erythrocytes are usually absent or dysfunctional. This strange anatomy is because they live in very oxygenated waters and their metabolism is very slow. In order for oxygen to reach all cells, it dissolves in the blood plasma, which distributes it throughout the body.

pez de hielo draco sangre color transparente
Crocodile Icefish (Chionodraco hamatus). Photo: Marrabbio2

CONCLUSION

To conclude, we have seen that in animals that require a respiratory pigment to deliver oxygen to all tissues, the color of blood (or hemolymph) will depend on the type of pigment that is present. In contrast, other animals that do not require respiratory pigments, have transparent blood or their color is due to other dissolved substances that have nothing to do with breathing.

infografía colores de la sangre
Infographic-summary of the chemistry of the main blood or hemolymphatic respiratory pigments (click to enlarge). Image: compound interest

 

Cover photo: John Kalekos

The importance of biological collections

Biological collections are cornerstones for the study of biodiversity and an almost endless source of scientific information. Many are those within the social networks who demand scientists to stop using ‘classical’ biological collections as they are seen as primitive tools that promote animals and plants extinctions.

We explain you why this statement is incorrect, which types of collections do exist and which are their most relevant functions.

The importance of biological collections

It is more than probably that the first thing it comes to mind when you hear someone talking about biological collections are hundreds of animals or plants dried, pinned and placed inside boxes by a fanatical collector. Yes, this type of collections exists. However, and without demonizing them (since these collectors can be very useful for science), this is not the type of collections we want to talk about and, of course, not the only one that exists.

Biological collections are systematized repositories (well identified, classified and ordered) of a combination of any biological material. Most of these repositories are deposited in natural history or science museums, but also in universities, research centers or even totally or partially in private collections.

ICM’s (Institute of Marine Sciences) Biological Reference Collections, in Barcelona. Picture by Alícia Duró on ICM’s web.
Some drawers of the Australian National Insect Collection. Picture by the Australian National Insect Collection.

Types of collections

Even though the concept of biological collection is something quite new, the collection and classification of biological material started some centuries ago with the first animals and plants collected by zoologists and botanists.

Nowadays, the term of biological collection has acquired a broader meaning:

  • Cryogenic collections

Storage of living biological material in frozen state under the assumption that it will retain its viability and normal functioning when being thawed after a long period of time. Cryogenic collections are typically used to store cells, tissues and genetic material. And even though science fiction has given us many fantastic ideas, the truth is that this method is very rarely used for preserving entire organisms.

  • ‘Classical’ biological collections

They essentially include collections of zoological museums (entire specimens or some of their parts) and herbaria (plants), among others. Some of these collections go back over more than two centuries, so ‘classical’ biological collections are considered the oldest within all types of collections. And also, one of the most valuable.

Collection of inquiline cynipids or gall wasps . Source: Irene Lobato Vila.

Most of these collections are deposited in museums or research centers and, excepting some particular cases, able to be required and examined by the scientific community as it pleases. A lot of private collectors collaborate with these institutions by transfering their specimens, which is quite common among insect collectors.

Drawers from the National Museum of Natural History, Washington D.C., Smithsonian Institution, containing thousands of insect specimens. Source: Irene Lobato Vila.

It is worthwhile remembering that transferring is subjected to an exhaustive revision and done only under contract, so institutions do not accept specimens obtained directly by the collector from illegal methods (e. g., poaching or wild animal trading).

  • Collections of biological information online

Repositories of biological information online. This type of collections has gained a lot of importance during the last years since it allows to share biological information of interest to science and technology immediately around the world. The most consulted online databases are those containing molecular data (proteins, DNA, RNA, etc.), which are necessary for phylogenetic studies and to make ‘trees of life’. Some of these databases are:

Other types of very consulted webs are the online databases of museum collections (which are of very importance to preserve massive amounts of data deposited in this institutions; remember the case of the Brazil National Museum fire) and webs of citizen science projects and collaborations, where either experts and amateurs provide information of their observations (like Biodiversidad Virtual).

Biological collections can be also classified according to their function: scientific collections (research), commercial collections (cell cultures for medicine, pharmacy, etc.) and ‘state’ collections (those created and managed for the sake of the state, like botanical garden, in order to preserve the biodiversity of a region and to promote its study and outreach).

The term of biological collections also embraces the biobanks, that is, collections exclusively containing human samples for biomedical studies. However, we will not go farer with this term.

Why are classical biological collections so necessary?

Biological collections and, especially, classical biological collections, are essential for biodiversity conservation. And no, they are not a direct cause of species extinction: the number of collected specimens is derisory compared with those lost as a consequence of pollution and habitats loss, and collections are carried out following several rules, always making sure to not disturb populations and their habitats.

Although it is true that pictures and biodiversity webs are a very useful tool for the study of worldwide biodiversity, unfortunately they are just a completement of physical collections.

So, why are these classical and physical collections so important?

  • They are a very valuable source of genetic material that can be obtained from stored samples and used in molecular studies. Thanks to these studies, we can approach to the origins and relationships of living beings (phylogeny), know their genetical diversity and the speciation mechanisms that lay behind species differentiation, or even to improve strategies to conserve them (e. g., in reintroduction and conservations plans).
  • They are a perpetual reference for future scientists. One of the basic pillars of zoological and botanical collections are the type specimens or type series: those organisms that a scientist originally used to describe a species. Types must be correctly labelled and stored because they are the most valuable specimens within a collection. The type or types should be able to be examined and studied by all scientists and used by them as a reference for new species descriptions or for comparative studies, since original descriptions can sometimes be insufficient to characterize the species.
Paratype insect (specimen from the type series) properly labelled and deposited in the entomological collection of the National Museum of Natural History of the Smithsonian Institution, in Washington D.C. Source: Irene Lobato Vila.
  • Regarding the previous point, classical collections allow to study the inter and intraspecific morphology (external and internal), which is sometimes impossible to assess only with pictures.
  • Classical collections contain specimens collected from different periods of time and habitats, including extinct species (both from a long time ago and recently due to the impact of human activity) and organisms from endangered ecosystems.  As habitat destruction continues to accelerate, we will never have access to many species and the genetic, biochemical, and environmental information they contain unless they are represented in museum collections. The information these samples provide is essential to investigate how to slow or mitigate the negative pressure on still extant species and ecosystems.
  • They provide us past and present information about geographic distribution of different organisms, since each of them is usually stored together with data about its locality and biology. This kind of information is very useful both for ecological and evolutive studies, as well as for resource management, conservation planning and monitoring, and studies of global change.
  • They are an important tool for teaching purposes and popular science, since people get directly in touch with samples. Pictures and books are undoubtfully essential for outreaching, but insufficient when they are not complemented with direct observations. Both visits to museums and field trips are basic tools for a complete environmental education.
At the end of the course each year,  thousands of students visit the collections of the National Museum of Natural History in Washington D.C. Some of them may even visit the scientific collections. Source: Irene Lobato Vila.

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Do you still think biological collections are unnecessary after reading this post? You can leave your comments!

This is the state of the planet: Living Planet Index 2018 (WWF)

Even though nature provides us with everything our modern society needs, our relationship with her is rather destructive. All the impact that our society has inflicted on Earth has led to a new geological era, which experts have baptised as Anthropocene. The Living Planet Report shows us what is the state of the planet. Do not miss it!

THIS IS THE STATE OF THE PLANET: LIVING PLANET INDEX 2018 (WWF)

This is not the first time that we make a summary of the Living Planet Report, carried out by the WWF and, with this latest edition, turns 20 years and has the participation of more than 50 experts. Previous reports stressed the remarkable deterioration of Earth’s natural systems: both nature and biodiversity are disappearing at an alarming rate. In addition, it is estimated that on a global scale nature provides services valued at around 110 billion euros per year.

WHAT IS THREATENING BIODIVERSITY?

According to a recent study, the main threats to biodiversity are two: overexploitation and agriculture. In fact, 3 out of 4 species of plants, amphibians, reptiles, birds and mammals extinct since 1500 disappeared due to these two reasons. This is due to the huge growth of consumption worldwide, which explains that the ecological footprint has increased by 190% in the last 50 years.

sobreexplotacion, agricultura, amenazas biodiversidad, informe planeta vivo 2018, wwf
Overexploitation and agriculture are the main threats for biodiversity (Picture: Ininsa, Creative Commons).

The demand for products derived from ecosystems, linked to their lower capacity to replace them, explains that only 25% of the earth’s surface is completely free of the impacts of human activities. This fraction is expected to be only 10% by 2050.

Soil degradation includes the loss of forest, with the highest rate of deforestation in tropical forests, which harbour the highest levels of biodiversity. Soil degradation has diverse impacts on the species, the quality of the habitats and the functioning of the ecosystems:

  • Biodiversity loss.
  • Alteration of the biological functions of biodiversity.
  • Alteration of habitats and their functions.
  • Alteration of the wealth and abundance of the species.

Invasive species are also a common threat, the dispersion of which is associated with trade. Pollution, dams, fires and mining are additional pressures, in addition to the increasing role of global change.

LIVING PLANET INDEX 2018

The Living Planet Index (LPI) is an indicator of the state of global biodiversity and the health of the planet. It is established by calculating the average abundance of about 22,000 populations of more than 4,000 different species of fish, amphibians, reptiles, birds and mammals from around the world.

The global LPI shows that the size of vertebrate populations has decreased by 60% in just over 40 years (between 1970 and 2014).

indice planta vivo, tortuga marina, wwf, marc arenas camps, flores island, komodo national park, indonesia
Vertebrate populations has been reduced a 60% in just over 40 years (Picture: Marc Arenas Camps ©).

If we distribute the analysed species into biogeographic realms, as the lower image shows, we can observe differences in the LPI. The most pronounced population declines occur in the tropics. The Neotropical realm has suffered the most drastic decline: 89% loss respect the year 1970. On the other hand, in the Nearctic and Palearctic the reductions have been much lower: 23 and 31% respectively. The other two realms have intermediate declines, although important: in tropical Africa it is 56% and in the Indo-Pacific 64%. In all the realms, the main threat is the degradation and loss of habitats, but variations are observed.

reinos biogeograficos, indice planeta vivo 2018, wwf
Biogeographic realms of the LPI (Image: Modified de WWF).

Unlike recent reports, in which the index was separated according to whether the populations were terrestrial, marine or freshwater, in this edition only the freshwater LPI has been calculated. These are the most threatened ecosystems since they are affected by the modification, fragmentation and destruction of habitats; the invasive species; excessive fishing; pollution; forestry practices; diseases and climate change. Analysing 3,358 populations of 880 different species it has been calculated that the freshwater LPI has decreased by 83% since 1970, specially the Neotropical (94% decrease), the Indo-Pacific (82%) and tropical Africa (75%) realms.

AIMING HIGHER: REVERSING THE BIODIVERSITY LOSS CURVE

Despite political agreements for the conservation and sustainable use of biodiversity (Convention on Biological Diversity, COP6, Aichi Targets…), global biodiversity trends continue to decline.

As indicated in the Living Planet Report, “between today and the end of 2020 there is a window of opportunity without equal to shape a positive vision for nature and people.” This is because the Convention on Biological Diversity is in the process of establishing new goals and objectives for the future, adding the Sustainable Development Goals (SDGs). In the case of the SDGs, these refer to:

  • SDG 14: Conserve and sustainably use oceans, seas and marine resources for sustainable development.
  • SDG 15: Protect, restore and promote sustainable use of terrestrial ecosystems, sustainably manage forests, combat desertification, and halt and reverse land degradation and halt biodiversity loss.

The authors consider that what is needed are well-defined goals and a set of credible actions to restore the abundance of nature until 2050. To achieve this, the authors recommend following three steps:

  1. Specify clearly the objective of biodiversity recovery.
  2. Develop a set of measurable and relevant indicators of progress.
  3. Agree on a package of actions that together achieve the objective within the required time frame.

CONCLUSION

Looking at the data from the Living Planet Report 2018, it is evident that nature is in retreat: we have lost 60% of the vertebrate populations of the planet, despite the differences between the different areas. In addition, environmental policies are not enough to stop this trend. Therefore, more ambitious policies are needed to stop and recover the nature of the planet in which we live. We have an obligation to live with nature, not against nature. If we do not have more sustainable and respectful habits with the environment, the benefits that nature brings us will be lost and will affect our own survival.

You can read the full report at WWF.

Jane Goodall’s journeys: conferences and discoveries

Jane Goodall, one of today’s most important scientists, visited the cities of Madrid and Barcelona last December to tell her story and convey her message of hope and care for the environment. All You Need Is Biology  was at her conference in Barcelona to bring her words to you and contribute to the spreading of her message.

JANE GOODALL’S JOURNEYS: CONFERENCES AND DISCOVERIES

In her eighties, Jane Goodall travels 300 days a year to publicize her work and raise awareness about the environment. In his lectures she reviews her biography, her discoveries and spreads her message about sustainability and environmental conservation.

VERY SHORT BIOGRAPHY OF JANE GOODALL

Jane Goodall needs no instroduction. She has a PhD in Ethology from the University of Cambridge and honorary degrees from more than 45 universities around the world. She has also received more than 100 international awards and degrees, including Dame Commander of the Most Excellent Order of the British Empire and United Nations Messenger of Peace.

Jane Goodall nowadays. Photo: Michelle Valberg

Scientific studies on the chimpanzees of Gombe (Tanzania) that began in 1960, continue at the hands of her disciples more than 58 years later. Her investigations revolutionized the way in which animals in general and human beings in particular were seen at that moment. In fact, the opportunity to fulfill his dream of traveling to Africa, in addition to his mother and Jane’s own effort, was possible thanks to Louis Leakey, renowned paleoanthropologist. Louis wanted to study chimpanzees searching common behavior between them and current humans, which would mean that our common ancestor also had this behavior. Use of tools, cannibalism, altruism, wars between groups, personality, emotions, are just some of the examples of what Jane discovered by observing chimpanzees in their natural habitat.

Chimpanzee eating meat. Photo: Cristina M.Gomes, Max Planck Institute.

Jane has written 26 books, several scientific papers and has participated in 20 film and television productions. Among them we highlight Jane’s Journey  (2012) and Jane  (2018), available on platforms such as Filmin or Netflix .

JANE GOODALL’S CONFERENCES

Although her lectures are similar year after year, it is always a pleasure to hear Jane’s calm but strong voice spreading her message of hope in the future. In her story, she says phrases of great value to promote scientific vocations and remark the importance of education. We have divided her conference into three parts.

FIRST PART: FROM BABY JANE TO JANE IN AFRICA

Jane begins her speech explaining her scientific curiosity and how she learned a multitude of things by observing the animals at home (especially her dog). A mother who does not scold a girl for hiding worms under her pillow or being disappeared for hours hiding in the chicken coop to discover where the eggs come from, is undoubtedly worth mentioning: Jane always emphasizes that without her mother’s understanding, the little scientist who lived in Jane would have been crushed. Children are scientists in an innate way: they are curious, they ask questions, they make mistakes, they observe, they want to learn.

Jane Goodall in her conference in Barcelona, 2018. Photo: Mireia Querol

Feeding Jane’s passion, her mother gave her books about animals and nature. “Tarzan of the apes” was her favourite and when she was 10 years old she decided that she would go to Africa (although in the end Tarzan married the wrong Jane, -she jokes-). A difficult dream, considering her condition as a young woman without scientific studies and a family with little income. Jane gives us the advice her mother gave her: take advantage of any small thing, it can always be useful for you in the future. After jumping from one job to another, her secretarial studies allowed her to work with Leakey and fulfill his dream of going to Africa to work with animals.

JANE IN AFRICA

Because the British government did not take responsibility for a single woman in the jungle, Jane’s mother backs her up and establishes herself in the campsite with her. After weeks of observations and many frustrations, Jane makes important discoveries and to be able to publish them, she obtains the PhD without having studied a previous universitary degree. In the university, they tell her that everything she has done is wrong: she had given names to the individuals instead of assigning them a number, she spoke of emotions of the chimpanzees when the entire scientific community said that emotions were unique to humans… until that moment. Jane revolutionized the vision we had of animals and humans and established a method of observation of her own.

Jane Goodall pant-hooting whith a chimp, 1996. Photo: unknown

SECOND PART: JANE AROUND THE WORLD

In 1986, Jane talked in a conference about the destruction of the jungle, the diseases suffered by chimpanzees, how they are affected by human wars… Jane had known for some time long that each species has a role to play in the biodiversity network and that had to be conserved, but also realized that while people were suffering war and poverty, little could be done to conserve nature. The Jane activist was born, who would create the Jane Goodall Institute, which has a lot of research programs and projects. The most important project on education is Roots and Shoots. It is a program for schools around the world in which young people carry out projects for the respect of all living beings, cultures and the environment. If you are a teacher, you may want to implement it in your school.

Jane Goodall with boys and girls of a Roots and Shoots project. Photo: Jane Goodall Institute

THIRD PART: THE MESSAGE OF HOPE

Jane believes that there is a disconnection between the heart and the human brain, which leads us to destroy the only planet we have to live. We have lost the connection with nature and we have thought that we have inherited the world of our parents, when in fact we are stealing it from our children and the rest of the species.

We tend to focus on what we can not do, so we do not usually take action because we believe there is nothing to do to change the delicate situation the Earth is passin through. We must set our attention at what we can do: we have the power to decide the impact we have and the change we make.

DO WE HAVE TIME TO RESTORE THE ENVIRONMENT?

A recurring question that Jane and some of us face is how to preserve hope and optimism, although being aware of the serious situation our planet is going through.

Jane keeps hope based on 4 points:

  1. Young people: children have great enthusiasm and determination as soon as they know the problem and take action to carry out their projects to help others. They participate in the change and check the positive results of their actions.
  2. The human brain: it is undeniable that the technology developed by our brain is becoming more respectful with the environment. Only requires more government involvement and funding for research.
  3. Resilience of nature: many places that have been destroyed recover over time, if we give them a chance.
  4. The indomitable human spirit: despite the difficulties we face (for example, people with disabilities) there is always a way to reach the goal, either by following one path or another.

In this video you can see a whole talk of what Jane does:

Jane ends by saying that we live in dark times, but that she believes there is an open window if we all work together.

She finishes the conference with the emotional release of Wounda, a video that you should not miss:

(Cover photo: Morten Bjarnhof GANT)

Model organisms in genetics

For scientists it is basic to work with models to discover what happens in a complete organism, which is more complex than the sum of its parts. It is for this reason that there are certain organisms, that by their characteristics, it is easy to use them as model in science. Below I present the 7 most commonly used species as model organisms in genetics.

WHAT IS A MODEL ORGANISM?

Model organisms are easily studied organisms, which thanks to them we can study important phenomena and extrapolate them to the organism that interests us. As Jacques Monod, Nobel Prize in Medicine in 1965, said, “What is true for bacteria is for elephants“.

These are characterized by:

  • Easy maintenance: it is not a big cost to have them in the laboratory.
  • Rapid biological cycle: in a few hours or days your biological cycle is completed.
  • High number of descendants: they have a high number of children in a short time.
  • Simple genome: they have few genes.

Model organisms are used to obtain information about other species that are more difficult to study directly. These are widely studied because they are easy to maintain and reproduce in a laboratory environment and have particular experimental advantages (Video 1).

Video 1. What is model organism? What does model organism mean? Model organism meaning & explanation (Source: YouTube)

The most commonly used are: Drosophila melanogaster (fruit fly), Mus musculus (mouse), Escherichia coli (colon bacteria), Arabidopsis thaliana (meadowsweet), Caenorhabditis elegans (worm), Sacharomyces cerevisiae (yeast) i Danio rerio (fish).

DROSOPHILA MELANOGASTER

Drosophila melanogaster (Figure 1) is better known as the fruit fly or vinegar. Surely you have seen in your kitchens, flying over ripe fruit or initial decomposition, and sweetened or alcoholic liquids.

It is one of the best-known animals, each of its body parts and the different stages of its life cycle is known up to the formation of an adult animal. It can live 30 days and the process from egg to adult lasts 7 days. In addition, its genome was sequenced in 2000.

In research it has a prominent role in biomedicine because it is used to study aspects related to cancer, neurodegenerative diseases or drug addiction.

drosophila melanogaster
Figure 1. Drosophila melanogaster (Source: YourGenome)

MUS MUSCULUS

Mus musculus (Figure 2) is the scientific name of the common mouse, the most commonly used mammal in the laboratory. The adult mice gets to measure (from the nose to the tail) between 7.5 and 10 cm long and weighs between 10 and 25 grams. Its gestation period is 19-21 days and it has between 3 and 14 offspring.

Its genome was completely sequenced in 2002. This phenomenon generated a great expectation for being a mammal that has a great scientific relevance for the human species.

Laboratory mice are not within the general laws of animal protection, but bioethical protocols and standards are followed.

It is used as a model in many fields, such as in the investigation of cardiovascular diseases, diabetes, neurological disorders, cancer … and in genetic engineering.

mus musculus
Figure 2. Mus muculus (Source: eLife)

ESCHERICHIA COLI

Escherichia coli (Figure 3) is the best known organism in the scientific field. It is a bacterium that lives in the lower part of the intestines of warm-blooded animals, including birds and mammals, and is necessary for the proper digestion of food. Its genome was sequenced in 1997 and it could be observed that the number of genes that comprise it is one seventh of the number of genes in humans.

In recent decades, this bacterium has become an instrument in the laboratory, especially in the field of molecular biology. Thanks to this, it has reached the knowledge of the foundations of modern biology and has earned the recognition of different Nobel prizes, such as the processes of genetic recombination of bacteria, RNA transcription, DNA replication and gene regulation.

ecoli
Figure 3. Escherichia coli (Source: Public Health England)

ARABIDOPSIS THALIANA

It is an annual plant (Figure 4) that was introduced into laboratories about 40 years ago. You can complete your entire life cycle in six weeks. The central floriferous stem grows in about three weeks from germination and the flowers naturally self-pollinate. In the laboratory, it can grow inside plates or sherds under fluorescent light or in greenhouses.

Like Drosophila melanogaster, its genome was sequenced in 2000 and it was the first sequenced genome.

Currently, researchers try to discover the secrets behind their development, growth or flowering.

arabidopsis
Figure 4. Arabidopsis thaliana (Source: Biology pages)

CAENORHABDITIS ELEGANS

It is a 1 mm long earthworm (Figure 5) that lives in temperate environments. Although more than 40 years ago we can find it in the laboratory, in the last decades it has achieved the prestige of more traditional organisms, such as Drosophila melanogaster or Mus musculus. The sequence of its genome as the first multicellular organism was published in 1998 and is considered complete today.

In research it has helped in the knowledge of the causes of aging, cell death and the structure of the genome.

C.-elegans
Figure 5. Caenorhabditis elegans (Source: Society for mucosal immunology)

SACHAROMYCES CEREVISIAE

Sacharomyces cerevisiae is a yeast (Figure 6), the yeast of bread, wine and beer. Its sequencing, specifically of strain S288C, was completed in 1996, after four years of a project led by the European Union and the participation of more than 100 laboratories from around the world. It was the first eukaryotic organism to be sequenced and it is currently the most known eukaryotic genome. This has made it gain weight and has become a powerful biological model of eukaryotic organisms.

It is used above all in biotechnological research, improving and innovating the processes of baking and production of alcoholic beverages.

yeast
Figure 6. Sacharomyces cerevisiae (Source: Fratelli Pasini)

DANIO RERIO

It is a zebrafish (Figure 7), a tropical freshwater fish that is surely known to lovers of aquariums. Genetically speaking, it is more similar to the human species than the Drosophila melanogaster or Caenorhabditis elegans and it is easier to manipulate, maintain and breed than Mus musculus. It is capable of producing between 300 and 500 eggs per laying and it can live up to 5 years. The draft of the sequencing of its genome was published in 2002.

A little more than 30 years ago, it was introduced as a model species for research in the field of development biology and genetics. It is widely used for the study of human biology.

danio-rerio
Figure 7. Danio rerio (Source: NCBI)

(Main picture: eLife)

 

Animals walking on walls: challenging gravity

How do insects, spiders or lizards for walking on smooth vertical surfaces or upside down? Why would not be possible for Spiderman to stick on walls the way some animals do?

Scientist from several areas are still in search of the exact mechanisms that allow some animals to walk on smooth surfaces without falling or sliding. Here we bring you the latest discoveries about this topic.

Animals walking on walls: challenging gravity

Competition for space and resources (ecological niche) has led to a lot of amazing adaptations throughout the evolution of life on Earth, like miniaturization.

When nails, claws or friction forces are insufficient to climb up vertical smooth surfaces, dynamic adhesion mechanisms come into play. Dynamic adhesion mechanisms are defined as those that allow some animals to climb steep or overhanging smooth surfaces, or even to walk upside down (e.g. on ceilings), by attaching and detaching easily from them. The rising of adhesive structures like adhesive pads as an evolutionary novelty has allowed some animals to take advantage of unexplored habitats and resources, foraging and hiding from predators where others could not.

Gecko stuck on a glass surface. Picture by Shutterstock/Papa Bravo.

Adhesive pads are found in insects and spiders, some reptiles like geckos and lizards, and some amphibians like tree frogs. More rarely they can be also found in small mammals, like bats and possums, arboreal marsupials native to Australia and some regions from the Southeast Asia.

The appearance of adhesive pads among these very different groups of animals is the result of a convergent evolution process: evolution gives room to equal or very similar solutions (adhesive pads) to face the same problem (competence for space and resources, high predation pressure, etc.).

Adaptation limits (or why Spiderman could not climb up walls)

Studying the underlying processes of the climbing ability of these animals is a key point in the development of stronger adhesive substances. So, a lot of research regarding this topic has been carried out to date.

Will humans be able to climb up walls like Spiderman some day? Labonte et al. (2016) explain us why Spiderman could not be real. Or, at least, how he should be to be able to stick on walls and do whatever a spider can.

Will humans be able to climb up walls like Spiderman some day? For now, we will have to settle for this sculpture. Public domain image.

Apart from the specific mechanisms of each organism (of which we will talk in depth later), the main principle that leads the ability for walking on vertical smooth surfaces is the surface/volume ratio: the smaller the animal, the larger is the total surface of the body with respect its volume and smaller is the amount of adhesive surface needed to avoid falling due to the body weight. According to this, geckos are the bigger known animals (i.e. those with the smallest surface/volume ratio) able to walk on vertical smooth surfaces or upside down without undergoing deep anatomical modifications.

And what does ‘without undergoing deep anatomical modifications’ mean? The same authors say that the larger the animal, the bigger is the adhesive pad surface needed for walking without falling to the ground. The growth of the adhesive pad surface with respect the size of the animal shows an extreme positive allometry pattern: by a small increase of the animal size, a bigger increase of the adhesive pad surface takes place. According to this study, a 200-fold increase of relative pad area from mites to geckos has been observed.

Picture by David Labonte

However, allometry is led by anatomical constraints. Therefore, if there was an animal larger than a gecko able to climb up smooth surfaces, it should have, for example, extremely large paws covered by an extremely large sticky surface. While this would be possible from a physical point of view, anatomical constraints would prevent the existence of animals with such traits.

Now we are in condition to answer the question ‘Why Spiderman could not stick to walls?’. According to Labonte et al., to support a human’s body weight, an unrealistic 40% of the body surface would have to be covered with adhesive pads (80% if we only consider the front of the body) or ridiculously large arms and legs should be developed. Both solutions are unfeasible from an anatomical point of view.

Great diversity of strategies

Dynamic adhesion must be strong enough to avoid falling as well as weak enough to enable the animal to move.

A great diversity of dynamic adhesion strategies has been studied. Let’s see some of the most well-known:

Diversity of adhesive pads. Picture by David Labonte.

1) Wet adhesion

A liquid substance comes into play.

Insects

Insects develop two main mechanisms of wet adhesion:

Smooth adhesive pads: this mechanism is found in ants, bees, cockroaches and grasshoppers, for example. The last segment of their legs (pretarsus), their claws or their tibiae present one or several soft and extremely deformable pads (like the arolia located in the pretarsus). No surface is completely smooth at microscale, so these pads conform to the shape of surface irregularities thanks to their softness.

Cockroach tarsus. Adapted picture from the original by Clemente & Federle, 2008.

Hairy adhesive pads: these structures are found in beetles and flies, among others. These pads are covered by a dense layer of hair-like structures, the setae, which increase the surface of the leg in contact with the surface.

Chrysomelidae beetle paw. Picture by Stanislav Gorb et al.

A thin layer of fluid consisting of a hydrophilic and a hydrophobic phase located between the pad and substrate comes into play in both strategies. Studies carried out with ants show that the ends of their legs secrete a thin layer of liquid that increases the contact between the pretarsus and the surface, filling the remaining gaps and acting as an adhesive under both capillarity (surface tension) and viscosity principles.

Want to learn more about this mechanism in insects? Then do not miss the following video about ants!

Tree frogs

Arboreal or tree frog smooth toe pads are made of columnar epithelial cells separated from each other at their apices. Mucous glands open between them and secrete a mucous substance that fill the intercellular spaces. Having the cells separated enable the pad to conform to the shape of the surface and channels that surround each epithelial cell allow to spread mucus over the pad surface to guarantee the adhesion. These channels also allow to remove surplus water under wet conditions that could make frogs to slide (most tree frogs live in rainforests).

Red-eyed tree frog (Agalychnis callidryas), distributed from Southern Mexico to Northeastern Colombia. Public domain image.

In the next video, you can see in detail the legs of one of the most popular tree frogs:

Smooth toe pads of tree frogs are similar to those found in insects. In fact, crickets have a hexagonal microstructure reminiscent of the toe pads of tree frogs. This led Barnes (2007) to consider the wet adhesion mechanism as one of the most successful adhesion strategies.

Different species of tree frogs (a, b, c) and their respective epithelia (d, e, f). Figure g corresponds to the surface of a cricket’s smooth toe pad. Picture by Barnes (2007).

Possums

The most detailed studies on possums have been carried out about the feathertail glider (Acrobates pygmaeus), a mouse-sized marsupial capable to climb up sheets of glass using their large toe pads. These pads are conformed by multiple layers of squamous epithelium with alternated ridges and grooves that allow them to conform to the shape of the surface and that are filled with sweat, the liquid this small mammal use to adhere to surfaces.

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Acrobates pygmaeus. Picture by Roland Seitre.
pygmffoot
Frontal toe pads of Acrobates pygmaeus. Picture by Simon Hinkley and Ken Walker.

2) Dry adhesion

Liquid substances do not come into play.

Spiders and geckos

The adhesion of both spiders and geckos depends on the same principle: the Van der Waals forces. Unlike insects, tree frogs and possums, these organisms do not secrete sticky substances.

Van der Waals forces are distance-dependent interactions between atoms or molecules that are not a result of any chemical electronic bond. These interactions show up between setae from footpads of geckos (which are covered by folds, the lamellae) and setae from spider paws (which are covered with dense tufts of hair, the scopulae), and the surface they walk on.

Spider paw covered with setae. Picture by Michael Pankratz.
Diversity of footpads of geckos. Picture by Kellar Autumn.

However, recent studies suggest dry adhesion in geckos is not mainly lead by Van der Waals forces, but by electrostatic interactions (different polarity between setae and surface), after confirming that their sticking capacity decreased when trying to climb a sheet of low energetic material, like teflon.

Anyway, the ability of geckos to climb is impressive. Check this video of the great David Attenborough:

3) Suction

Bats

Disk-winged bats (family Thyropteridae), native to Central America and northern South America, have disk-shaped suction pads located at the base of their thumbs and on the sole of their feet that allow them to climb smooth surfaces. Inside these disks, the internal pressure is reduced, and the bat stick to the surface by suction. In fact, a single disk can support the weight of the bat’s body.

Thyropteridae bat. Picture by Christian Ziegler/ Minden Pictures.

Now that you know about all these animals’ ability for climbing smooth walls, do you still think Spiderman is up to the task?

Main picture by unknown author. Source: link.