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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)

 

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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.
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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.

Zero Waste: living without producing waste – Interview to Esther Peñarrubia

Esther Peñarrubia (Barcelona, December 10, 1980), known for being the translator of the book Zero Waste Home into Catalan and Spanish, by Bea Johnson, and ambassador of the Zero Waste philosophy in Catalonia and Spain, is a PhD in Agronomy Engineering from the University of Lleida (Catalonia), besides being fond of historic gardens and bicycle touring.

ZERO WASTE: LIVING WITHOUT PRODUCING WASTE – INTERVIEW TO ESTHER PEÑARRUBIA

Esther, thank you very much for accepting this interview to share with us and our readers your experience with the non-generation of waste. Being an agronomist, why did you translate the book Zero Waste Home?

Looking for a recipe in Google to make homemade toothpaste, I saw a video of Bea Johnson, the author of the book. Many of the examples she mentioned to reduce waste were already made at home, but we didn’t call it Zero Waste. Nevertheless, there were still some tips that we weren’t applying. I saw the book was not available neither in Catalan nor in Spanish, so I was encouraged to contact her to translate it.

zero waste home, bea johnson, residuo cero, esther peñarrubia
The book Zero Waste Home was translated into Catalan and Spanish by Esther Peñarrubia (Picture: Zero Waste Home).

I see you were practising the zero waste without knowing the concept itself. What did it lead you to live without generating waste?

It has been a passion since adolescence and now it has become a philosophy of life.

What changes did you make in your life?

We learned to reduce many things, we lost the shame at the time of asking for objects or tools that we need punctually to friends, we adopted the bicycle as a daily means of family transport, we try to share a vehicle on long trips…

The Zero Waste is a current issue. Is it really possible to live without generating any waste?

Of course not, we do not live isolated inside a cave! Absolute zero is almost impossible, we will always need a drug, for example, that goes in a container. But it is very easy to live without generating too much waste… For years we have tried and it is not difficult, you just have to want to change habits.

I imagine that at the beginning it is a bit complicated and that you have to be always alert and vigilant. Is it like that?

In a certain way yes, above all you have to learn to reject, like the small objects that you want to filter in your life and that should not go beyond the threshold of the entrance: advertising gifts or samples of new products…

Few weeks ago, the European Union approved the banning of several single-use plastic items in 2020. What do you think of this measure?

It’s perfect, I would like they had set it up from tomorrow! If people need to be prohibited from certain aspects of their lives to have to change their habits when these are not beneficial for them or for the environment, such as smoking in public places a few years ago or the current indiscriminate use of disposable plastics, law must be those that mark the guidelines.

Imagine for a moment that you have the power to make decisions of a political nature. What measures would you promote to avoid the generation of garbage?

I would encourage companies to invest in R & D, taking into account aspects of sustainability and the circular economy. I would also try to promote responsible and second-hand trade in various fields and the exchange of goods between people and groups, such as repair shops, tool libraries, free books…

Surely when you explain that you live without almost generating waste, people give you all kinds of excuses to avoiding start. It has happened to me.

One of the most recurrent is the lack of time and another the lack of legislation to prevent the generation of waste. They often tell me: “Until governments and big companies don’t act, I cannot do anything”. It’s not true! It is clear that as consumers we have a power that we sometimes forget, and buying equals voting, so individually we can do a lot! We all have the same time, what is needed is to learn to prioritise, although it is not an easy task and, above all, to value if our free time can be invested in interesting things that fill us and make us happy or we simply dedicate it to non-meaningful actions.

One of the excuses that I have found is that this way of living is more expensive. What does your own experience say?

It is true that there are products related to the Zero Waste that compared with the conventional ones from a common supermarket are more expensive, such as some that may come from Fair Trade, organic farming or available in bulk. But, on the whole, if we consume less, we share more, we buy in bulk, second hand and local and seasonal products we can save money, without taking into account other collateral benefits.

Now let’s go to the practical part. Someone who might consider living according to Zero Waste in a big city will find it easier to buy in stores that sell all kinds of bulk products. However, in smaller populations, how can it be carried out?

Searching and buying local producers, which there are for sure. Buying in a cooperative way, together with other families (forming part or not of a consumer cooperative) and taking advantage of trips for different reasons to other populations where they do have these products that you don’t find near your home. There are no excuses! Now we are in the information era and luckily webs and apps start coming out that can help us a lot to make our lives easier and more sustainable.

armario residuo cero, residuo cero, compra a granel, esther peñarrubia
A Zero Residue cabinet is made up of glass jars with all products bought in bulk (Picture: Esther Peñarrubia).

Buying food in bulk is easy if we think about it. Now, how do we do it with personal and household cleaning products?

To clean our house, we only need sodium bicarbonate, bought in bulk, and concentrated white vinegar, which can sometimes be found in bulk. In the book there is a chapter that talks about “The magic of vinegar”, with basic recipes to perform various cleaning tasks and other personal hygiene. At home we prefer to buy personal care products in bulk from local producers, such as deodorant, tonic, shampoo, toothpaste and body cream.

I try myself to reduce the waste that I generate by carrying out small actions, but this summer I went to Indonesia on holidays and it was really complicated for me. What can we do when we are travelling?

We can do many things! For example, in terms of personal hygiene, we can take our soaps, toothpastes, shampoos, etc. in small glass or metal jars, thus avoiding having to take the ones available in the hotels, which often are in a plastic container. You can also carry cloth bags, which weigh almost nothing, to buy everything we can in bulk and even carry bottles that can be refilled. On the other hand, we can use the glass jars that we have bought, like a jam, as a container to carry food, so that we don’t need to carry a lunch box from home.

materiales residuo cero, residuo cero, esther peñarrubia
There are many products that allow us to avoid the generation of waste and, some of them, can be useful while we travel (Photo: Esther Peñarrubia).

Any other advice for our readers?

They shouldn’t be afraid to reject what they don’t need, as long as they do it in an educated way. Also they can always carry a cloth bag with them.

Perhaps at a domestic level it is relatively easier to achieve the Zero Waste. But, at companies’ level, public administrations… what would you advise them to do?

Well, I would advise them to follow the same steps that we have taken at home: analyse what waste is generated and look for alternatives that generate less.

In the case of private companies, I would advise them to appoint a Zero Residue delegate, that is essential to be motivated, to manage any doubts that may arise in this regard and, above all, to encourage people to change their waste generating habits. As for public administrations, an entire department could be created in this respect, it is a sufficiently important subject to invest part of the budgets.

And with all this effort that you and your family do, have you found an improvement in your life?

On a personal level we are very satisfied with the alternatives that we have found to the products or ways of doing, although sometimes they have required some time. Another improvement is  that it allows us to enjoy more time to practise our passions.

Thinking a bit about the dates of consumerism that are approaching, such as Christmas, what gifts would you advise people to lead a Zero Waste life?

As a physical gift, a good bottle of water made of stainless steel or glass. Other gifts are the experiences, like a movie or theatre ticket, without printing it.

Any other advice for these Christmas days?

Think a little before consuming or buying. Giving local products and staples (a batch of local foods and bought in bulk is just as acceptable as the best jewel); give experiences; buy second-hand (without fear of saying it); wrap the gifts with a piece of cloth, following the steps of the Furoshiki technique, and without using paper or tape …

Esther, thank you very much for sharing your experience with us. I am sure that you have given more light on this path to the Zero Waste to many people who haven’t dared to take the first step so far.

Crown shyness: trees that don’t touch

When you walk through the forest or the city, do you usually look up? The usual thing is to look at where we are going or where we put our feet, but if you find yourself in the middle of nature, do not forget to observe the trees, perhaps you find yourself with an image as beautiful as the cover of this post: you are observing the crown shyness.

A BOTANICAL PHENOMENON

Less than 100 years ago, back in 1920, a botanical phenomenon that give us beautiful and impressive images of certain forests was observed for the first time. In 1955, the botanist Maxwell R. Jacobs, described this phenomenon as “crown shyness” after studying various populations of eucalyptus. The crown shyness is also known as canopy disengagement, canopy shyness or intercrown spacing.

The furrows of sky that makes the crown shyness. Photo: Tom Cowey

This phenomenon consists in a limited growth of the canopy of the trees, in such a way that the leaves and branches of adjacent trees do not touch each other. This produces figures and patterns with the sky in the background when the trees are observed from the ground.

The canopy disengagement, among other themes, is explored in the documentary Once Upon a Forest.

WHY CROWN SHYNESS OCCURS?

The scientific community has not yet reached a consensus that explains the mechanism that gives rise to this phenomenon. A total of three hypotheses have tried to explain the crown shyness:

1. Friction hypothesis

The initial hypothesis of Maxwell R. Jacobs (currently barely accepted by the scientific community) explains that the friction of some branches with others, when the wind hits them, would limit the growth of the branches to avoid touching the neighboring trees, due to the damages produced by the abrasion.

2. Allelopathy hypothesis

The most supported hypothesis currently indicates that crown up  has an allelopathic origin.

In botany, allelopathy is any effect that one plant transmits to another through the production of different chemical compounds, either causing a positive or negative effect on the other plant. These compounds are the so-called allelochemicals. In other words, plants and trees communicate with each other by chemical signals. This relationship occurs more frequently between trees and plants of the same species, although it also occurs between different species. To know in depth the process of allelopathy, we invite you to read the post Communication among plants: allelopathy.

Photo: airwii

3. Photoreceptors hypothesis

In addition to chemical signals, phytochrome photoreceptors (sensors of light capable of detecting the area of distant red light) possessed by trees and plants allow them to perceive the proximity of other individuals. Another type of photoreceptor detects blue light, which produces in plants and trees the avoidance of shadows produced by other individuals.

Plant photoreceptors and photoresponses. Credit: Christian Fleck

As a whole, the signals captured by these photoreceptors would provoke the response of the tree to move away from the adjacent one, which would allow it to obtain a greater quantity of light, which is essential for photosynthesis.

ARE ALL TREES “SHY“?

Crown shyness has been observed in certain European oak and pine species and tropical and subtropical species, such as some eucalyptus, species of the Dryobalanops genus, Pinus contorta, Avicennia germinans, Didymopanax pittieri, Clusia alata, Celtis spinosa, Pterocymbium beccarii, Picea sitchensis and Larix kaempferi.

Arboreal canopy of Dryobalanops aromatica in Kuala Lumpur. Photo: Patrice78500

In other species, the tops of the trees come to touch and even cross their branches, although the canopy (habitat that includes the tops of the trees) does not usually mix completely.

HYPOTHESIS ON THE ADVANTAGES OF THE CANOPY SHYNESS

The evolutionary sense of the timidity of the glass remains unknown, although botany has launched several hypotheses:

  • It allows a greater penetration of light in the forest to perform photosynthesis more efficiently.
  • It avoids damaging the branches and leaves when hit against each other in case of storm or gusts of wind.
  • It prevent diseases, larvae and insects that feed on leaves from spreading easily from one tree to another.
File:Weaver Ants - Oecophylla smaragdina.jpg
Ants build structures with their own bodies to move from one leaf to another. Photo: Rose Thumboor

For now, it seems that crown shyness is due to a relationship of collaboration between species for survival, rather than a competition (the popularly known as the “survival of thje fittest”). We will have to wait for future studies to shed a little more light on this still unknown phenomenon.

From lab to big screen (II)

As I told you in the previous article on genetics and cinema, there is a wide variety of films that talk about genetics. In the next article we will talk about science fiction, with two well-known films. Beware: spoilers!

GATTACA (1997)

Director: Andrew Niccol

Cast: Ethan Hawke, Uma Thurman, Jude Law

Genre: Science fiction

Story line: Vincent is one of the last “natural” babies born into a sterile, genetically-enhanced world, where life expectancy and disease likelihood are ascertained at birth. Myopic and due to die at 30, he has no chance of a career in a society that now discriminates against your genes, instead of your gender, race or religion. Going underground, he assumes the identity of Jerome, crippled in an accident, and achieves prominence in the Gattaca Corporation, where he is selected for his lifelong desire: a manned mission to Saturn’s 14th moon (titan). Constantly passing gene tests by diligently using samples of Jerome’s hair, skin, blood and urine, his now-perfect world is thrown into increasing desperation, his dream within reach, when the mission director is killed – and he carelessly loses an eyelash at the scene! Certain that they know the murderer’s ID, but unable to track down the former Vincent, the police start to close in, with extra searches, and new gene tests. With the once-in-a-lifetime launch only days away, Vincent must avoid arousing suspicion, while passing the tests, evading the police, and not knowing whom he can trust.

Relation with genetics: GATTACA is the “genetic” film par excellence. Starting with the title, this is formed by the initials of the four nitrogenous bases that make up DNA (guanine, adenine, thymine and cytosine). In addition, the helical shape of the DNA is repeated in several moments of the film, as in the stairs of Vincent’s house.

The main issue is about genetic selection, all children born have been genetically selected, closely linked to bioethics. The idea of ​​this selection is to reach eugenics, that is, to improve the population by selecting the “best” humans. This concept can be related to the Hitler’s Germany, who believed that Germans belonged to a superior group of races called “Aryan”. Hitler said that German Aryan race had been better endowed than the others and that this biological superiority destined Germans to oversee an empire in Eastern Europe.

Although nowadays genetic selection is valid and is used to avoid diseases, it is not applied with the same purposes as those of the film. At present, it is decided to carry out genetic selection after having studied the family and carried out the appropriate genetic counselling. It aims to help patients and their families avoid the pain and suffering caused by a genetic disease and should not be confused with the eugenic objective of reducing the incidence of genetic diseases or the frequency of alleles considered to be deleterious in the population.

This is very related to the genetic discrimination, case also exposed in the film. Gattaca is situated in a possible future in which genetics, trying to improve the quality of life of society, causes a movement of discrimination.

When we talk about discrimination, we tend to think about racial discrimination. This is defined as the different or exclusive treatment of a person for reasons of racial or ethnic origin, which constitutes a violation of the fundamental rights of individuals, as well as an attack on their dignity. Racism has been present throughout the history of mankind, especially in the twentieth century with racial discrimination in the United States and apartheid in South Africa.

For some time now, genetic discrimination has been gaining weight. It happens when people are treated differently by their company or insurance company because they have a genetic mutation that causes or increases the risk of a hereditary disorder. Fear of discrimination is a common concern among people who undergo genetic testing, and is a current problem that concerns the population because your own genome does not have to be a curriculum vitae that opens or closes doors as happens in the film. Vincent goes to work in Gattaca after performing a urine test and a blood test, since in Gattaca they do not choose workers for their ability or ability but for their DNA.

However, the film ends with the sentence “There is no gene for the human spirit”. This means that, although the society in which Gattaca is located is based on genetic modification, it does not affect the morality and final character of people because there is no way to genetically relate to the spirit, only the body has the genetic information.

Video 1. Trailer Gattaca (Source: YouTube)

JURASSIC PARK (1993)

Director: Steven Spielberg

Cast: Sam Neill, Laura Dern, Jeff Goldblum

Genre: Science fiction

Story line: Huge advancements in scientific technology have enabled a mogul to create an island full of living dinosaurs. John Hammond has invited four individuals, along with his two grandchildren, to join him at Jurassic Park. But will everything go according to plan? A park employee attempts to steal dinosaur embryos, critical security systems are shut down and it now becomes a race for survival with dinosaurs roaming freely over the island.

Relation with genetics: In the first film of this saga, from dinosaur’s fossils scientists extract DNA to be able to clone dinosaurs. The cloned dinosaurs will be part of the Jurassic park on which the film is based.

It is true that DNA can be extracted from bones, widely used in forensic genetics. Same as the issue of cloning, which was known by the Dolly sheep, the first large animal cloned from an adult cell in July 1996. But the film goes further and raises the possibility of reintroducing, in today’s world, extinct species and challenge natural selection.

Video 2. Trailer Jurassic Park (Source: YouTube)

REFERENCES

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War against plastic

The fact plastics cause problems in ecosystems, biodiversity and human health is well known. In fact, being aware of this, the European Union win ban in 2021, some single-use plastic objects and has established some measures for others. Let’s see what we can do to fight this war against plastic!

WAR AGAINST PLASTIC

REASONS TO FIGHT PLASTIC USE

According to a study published in 2015, it is estimated that there are 5.25 trillion plastic particles in the world’s oceans, equivalent to a weight of 268,940 tons. If we focus only at the Mediterranean Sea, there are about 2,000 tons of plastic particles. It is also known that 80% of marine plastic comes from land. Another study points, in addition, that by 2050 there will be more plastics than fish in the seas and oceans of the planet not to stop the current trend.

pantai pede, labuan bajo, indonesia, plasticos, basura marina, plastico marino, guerra plastico, residuo zero
In a beach of Labuan Bajo, Indonesia, it was strange not to find waste or plastic in every single step (Picture: Marc Arenas).

As we already talked in this other article, marine litter, of which 75-85% are plastics, causes serious problems in biodiversity, its habitats and the economy. In fact, it is known that every year one million birds and 100,000 marine mammals die from plastic.

The problem of plastic also affects our health. According to a study published in the recent weeks, microplastics have been detected in the excrements of all people who participated in the study. The presence of plastics in the body can be dangerous for the immune system and cause diseases due to their toxins.

HOW CAN WE LIFE WITHOUT PLASTIC?

We must recognise that, nowadays, living without plastic is quite complicated. The reason is that it is infinitely easier to find a product in a plastic container than in a glass one, or even without it, that is, in bulk. Does this mean that we cannot beat the plastic battle? Obviously, not, but we’ll have to make a little effort.

FORBIDDEN PLASTICS FOR THE EUROPEAN UNION

We have already said that the European Union will ban some plastic items in 2021. These objects are plates, glasses and cutlery, drinking straws and cotton buds. Considering that in two years we will not find them in the stores, go ahead to the prohibition and implement these alternatives.

Using plastic cutlery, plates and cups at a party with many people is comfortable, and if they are colourful it is even fun, but it is totally unsustainable. Alternatives:

  • In the market you can find these objects made with alternative materials. In particular, they are usually made of corn, so that when you finish your party or picnic you can throw them into the organic fraction, since they are compostable. You can also find them in paper, although they are less resistant and less sustainable.
  • Another alternative is to use your metal cutlery, your ceramic dishes and your crystal glasses. Simpler, smarter and more sustainable!

Plastic straws are a problem for the environment, since many of them end up in the sea.

In the United States alone, 500 million straws are consumed every day. Maybe you are going to think that this is why it is a very populated country. Well, in Spain every day 13 million are consumed and it is the European country in which they consume the most. If you are one of those who need (need!) to drink a soft drink or cocktail with a straw, we have an alternative for you.

  • At home, we can use reusable bamboo or metal straws. They are equally effective and you will be collaborating to avoid images like the ones in the video being repeated.
  • Do you really need to drink with a straw? If you only find plastic straws in a bar, pub, club or restaurant, reject it (but before they bring you the drink!). Surely you will survive!

The ear buds are another of the prohibited objects from 2021 since it is one of the most found among marine debris.

bastoncillos oidos, basura marina, caballito de mar, plastico, plastico marino, residuo zero, justin hofman
Cotton buds will be forbidden from 2021 (Picture: Justin Hofman)

Apart from the fact that the health authorities only advise its use for the external ear, if you cannot avoid its use, you should opt for alternatives to the plastic ones:

  • Use cotton buds made with bamboo or other woods which, in addition, are sold in recycled cardboard boxes.
  • If you want to be even more sustainable and reduce your garbage production, there is another better alternative: buy a metal stick as we recommend in this article and put a piece of clean cloth on a tip to absorb the water from the shower.

SUSTAINABLE ALTERNATIVES TO OTHER PLASTIC ITEMS

Plastic bottles also harm the environment. Did you know that it takes up to 1,000 years to degrade one bottle? In addition, to make each plastic bottle it is needed 100 mL of oil. For sure, many of you will be thinking about water, but the truth is that this also applies to soaps, detergents, softeners… Seeing how these bottles are accumulating, we give you some tips:

  • Buy larger bottles. It is needed less plastic for a bottle of 1L than for 4 of 250 mL.
  • For the specific case of water, use canteens to avoid the use of plastic. You can drink tap water if in your town has the right quality, but if it is not the case you can install an osmosis or buy water jugs (remember what we said in the previous point).
  • Observe what products you consume at home in plastic bottles and look for a store in your area that sells them in bulk.

Plastic bags, although their use is being reduced, are another problem. In Spain, according to Cicloplast, each year 97,000 tons of plastic bags are consumed, of which only 10% are recycled.

  • How easy and comfortable it is to go shopping with cloth bags, a trolley or a shopping basket!

Finally, we will now focus on polystyrene trays and plastic film. These two elements are increasingly common in supermarkets and homes, since supermarkets sell their fresh product packed in them. Some advises:

  • If your supermarket only sells meat, fish… in these containers, opt for a local store, which will sell it in bulk and you can also buy just the amount you need.
  • Go shopping in bulk stores and take your tupperware (best glass) from home to avoid plasticized paper (which goes to landfills) or the aforementioned objects.

We are aware that we have forgot many things to comment due to plastic is very present in our lives, but the best thing is to become aware of the plastics we generate every day to find an alternative to each of them.

What do you do to avoid the use of plastic? Leave us your advice in the comments for others to join this war against plastic.

(Cover picture: El Observador Crítico)

Insects are becoming smaller: miniaturization

According to different studies, multicellular organisms tend to become smaller and smaller through time. This phenomenon is called miniaturization and is considered one of the most significative evolutionary trends among insects. Miniaturization is a driving force for diversity and evolutionary novelties, even though it must deal with some limitations.

Learn more about this phenomenon and met some of the most extreme cases of miniaturization among insects through this post.

Why are animals becoming smaller?

For some years now, multiple studies suggest there is a widely extended trend to miniaturization among multicellular animals (i. e. organisms composed by more than one cell).

Miniaturization is a remarkable natural phenomenon headed to the evolution of extremely small bodies. This process has been observed in different non-related groups of animals:

  • Shrews (Soricomorpha: Soricidae), mammals.
  • Hummingbirds (Apodiformes: Trochilidae), birds.
  • Diverse groups of insects and arachnids.

To know more about giant insects, you can read Size matters (for insects)!

Diversification and speciation processes have given place to lots of new species through time, all of them constantly competing for limited space and food sources. This scenario turns even more drastic in tropical regions, where diversification rates are extremely high.

Learn about the ecological niche concept by reading “The living space of organisms“.

Facing the increasing demands of space and resources, evolution has given place to numerous curious phenomena such as miniaturization to solve these problems: by becoming smaller, organisms (either free-living or parasites) gain access to new ecological niches, get new food sources and avoid predation.

Despite many animals tend to miniaturization, this phenomenon is more frequently observed among arthropods, being one of their most remarkable evolutionary trends. Moreover, arthropods hold the record of the smallest multicellular organisms known to date, some of which are even smaller than an amoeba!

Guinness World Record of the smallest insects

The smallest arthropods are crustaceans belonging to the subclass Tantulocarida, which are ectoparasites of other groups of crustaceans, such as copepods or amphipodes. The species Tantulacus dieteri is still considered the smallest species of arthropods worldwide, which barely measures 85 micrometers (0,085 millimeters), thus being smaller than many unicellular life beings.

However, insects do not lag far behind.

Mymaridae

Mymaridae (or fairyflies) are a family of wasps inside the superfamily Chalcidoidea from temperate and tropical regions. Adults, ranging from 0.5 to 1 millimeter, develop as parasites of other insects’ eggs (e. g. bugs, Heteroptera). For this reason, fairyflies are very valuable as biological control agents of some harmful pests. Also, they are amongst the smallest insects worldwide.

Currently, the one holding the record as the smallest known adult insect is the apterous (wingless) male of the species Dicopomorpha echmepterygis from Costa Rica, with a registered minimum size of 0.139 millimeters. They neither have eyes nor mouthparts, and their legs endings are deeply modified to get attached to the females (somewhat bigger and winged) time enough to fertilize them. They are even smaller than a paramecium, a unicellular organism!

You can read “Basic microbiology (I): invisible world” to know more about unicellular organisms.

Male of D. echmepterygis. Link.

Fairyflies also include the smallest winged insects worldwide: the species Kikiki huna from Hawaii, with and approximate size of 0.15 millimeters.

Trichogrammatidae

Like fairyflies, trichogrammatids are tiny wasps of the superfamily Chalcidoidea that parasite eggs of other insects, especially lepidopterans (butterflies and moths). Adults of almost all the species measure less than 1 millimeter and are distributed worldwide. Adult males of some species are wingless and mate with their own sisters within the host egg, dying shortly after without even leaving it.

The genus Megaphragma contains two of the smallest insects worldwide after fairyflies: Megaphragma caribea (0.17 millimeters) and Megaphragma mymaripenne (0.2 millimeters), from Hawaii.

A) M. mymaripenne; B) Paramecium caudatum. Link.

Trichogrammatids also have one of the smallest known nervous systems, and that of the species M. mymaripenne is one of the most reduced and specials worldwide, as it is composed by only 7400 neurons without nucleus. During the pupae stage, this insect develops neurons with functional nuclei which are able to synthetize enough proteins for the entire adulthood. Once adulthood is reached, neurons lose their nuclei and become smaller, thus saving space.

Ptiliidae

Ptiliidae is a cosmopolitan family of tiny beetles known for including the smallest non-parasitic insects worldwide: the genera Nanosella and Scydosella.

Ptiliidae eggs are very large in comparison with the adult female size, so they can develop a single egg at a time. Other species undergo parthenogenesis.

Learn some more about parthenogensis by reading “Immaculate Conception…in reptiles and insects“.

Currently, the smallest Ptiliidae species known and so the smallest non-parasitic (free living) insect worldwide is Scydosella musawasensis (0.3 millimeters), from Nicaragua and Colombia.

Scydosella musawasensis. Link (original picture: Polilov, A (2015) How small is the smallest? New record and remeasuring of Scydosella musawasensis Hall, 1999 (Coleoptera, Ptiliidae), the smallest known free-living insect).

Consequences of miniaturization

Miniaturization gives rise to many anatomical and physiological changes, generally aimed at the simplification of structures. According to Gorodkov (1984), the limit size of miniaturization is 1 millimeter; under this critical value, the body would suffer from deep simplifications that would hinder multicellular life.

While this simplification process takes places within some groups of invertebrates, insects have demonstrated that they can overcome this limit without too many signs of simplification (conserving a large number of cells and having a greater anatomical complexity than other organisms with a similar size) and also giving rise to evolutionary novelties (e. g. neurons without nucleus as M. mymaripenne).

However, getting so small usually entails some consequences:

  • Simplification or loss of certain physiological functions: loss of wings (and, consequently, flight capacity), legs (or extreme modifications), mouthparts, sensory organs.
  • Considerable changes in the effects associated with certain physical forces or environmental parameters: capillary forces, air viscosity or diffusion rate, all of them associated with the extreme reduction of circulatory and tracheal (or respiratory) systems. That is, being smaller alters the internal movements of gases and liquids.

So, does miniaturization have a limit?

The answer is yes, although insects seem to resist to it.

There are several hypotheses about the organ that limits miniaturization. Both the nervous and the reproductive systems, as well as the sensory organs, are very intolerant to miniaturization: they must be large enough to be functional, since their functions would be endangered by a limited size; and so, the multicellular life.

.             .            .

Multicellular life reduction seems to have no limits. Will we find an even smaller insect? Time will tell.

Main picture: link.