Delicious weeds and marine algal treasure

So after a risky dive I found these beauties growing close together on a big rock in the waters at the beach at Skopelos, one of the islands in the Sporades – the scattered islands in the Aegaen Sea. I think it is Acetabularia, but of course, since I am no algae expert and I don´t have an algal flora, I cannot be sure.

Acetabularia out of its habitat. Did not last long in the heat

Acetabularia out of its habitat. Did not last long in the heat

What I´m definitely sure of is that there are much better chances of growing lovely tomatoes in Greece than in Norway. Our neighbor Marina has a vegetable garden and I was introduced to a herb I have not seen before. It´s called Andrakla, and is considered a weed in North American, but here in Greece it is just another herb you put in your salad (according to Wikipedia and Marina). It´s a succulent, taste bitter and is delicious tossed with tomatoes, cucumbers, feta cheese and parsley.

The Greens

The Greens – zucchini flowers, parsley, mint and purslane from Marina’s garden

Picture from the blog Gastric Surgery Success

Common Purslane – Portulaca oleracea Picture from the blog Gastric Surgery Success

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Mermaid’s wineglass

There is a feeling of summer, although faint, it´s far from how the days during winter (can they even be called proper days?) make me feel more of a hibernating animal than anything else. It is still not warm enough, but at least the sun is up until late in the evening, here in the southern parts of Norway.

Summer means vacation and being lucky as I am, the 7 years old bathing nymph and I are going for a week to visit grandma and grandpa on a Greek island. Aside from the economic crisis, which we know affects so many of the local populace; it is a lovely place to spend some time. Speaking to my supervisor I found another reason for wanting to visit the beach this year. Growing on the rocks in the water of the Aegean Sea lives an amazing alga. It looks like a multicellular organism, but it is a single cell! I have many times dived down to pick it up, because, well because that´s what I do when I see something green and growing.

The genus Acetubularia, or Mermaid´s wineglass, can grow up to 10 cm. It has three parts; rhizoids (much like roots), a stalk and a top of branches that in some species grow together to form an umbrella-like cap. The nucleus is located at the base of the stalk.

Due to its complex size Acetabularia is great for studying gene expression and differentiation. I 1943 the Danish-German biologist Joachim Hämmerling used two species of Acetabularia, A. mediterranea and A. crenulata to demonstrate that the nucleus determines the cellular fate. The two different species have each a distinct cap-morphology. Hämmerling grafted the stalk of one species onto the rhizoid of the other species. The cap eventually changed to the morphology belonging to the rhizoid.

So, this was the usual “I-found-this-new-awesome-species-I-want-the-world-to-know-about”. A common situation around the lunch table. I love that.

The sentence I will never forget by Ernst Haeckel: "Ontogeny recapitulates phylogeny". Studied and learned during BIO 4280

Algae is a good excuse for including the work of biologist Ernst Haeckel in this post. The sentence I will never forget by Ernst Haeckel: “Ontogeny recapitulates phylogeny”. Studied and learned during BIO 4280 – take the course if you are interested in evolution and development at the University of Oslo. It´s great 🙂

Never let me go – multicellularity in a test tube

Spread across the eons of evolutionary time are the transitions that define the different groups of life on earth. One of these is the transition from unicellularity to multicellularity. Appearing more than 25 times; in bacteria; in amoeba, algae and fungi, as well as in the ancestors of plants and the ancestors of animals, this mode of life has proved a successful one. But as we have no means of travelling back in time, the first steps towards multicellularity are still elusive. A good thing it is, then, that Bakers yeast, the fungi that helps us with our daily bread also helps us shed light on the stepping-stones towards the complexity we observe in our natural world today.

William Ratcliff, an evolutionary biologist working at Georgia Institute of Technology, has spent the last five years studying the evolution of multicellularity in real time, alleviating the need for time travel. Together with scientists from Germany, England and Minnesota, Ratcliff designed experiments to select for traits in the unicellular fungi that would eventually lead to multicellularity. Centrifuging liquid containing yeast cells and discarding the ones still afloat after centrifugation, simply selected for heaviness. This way the fungi that clustered would be selected to survive and any mutation causing cells to stay together after cell division would be favoured. Repeating this procedure for seven months, the unicellular fungi evolved to a multicellular community named Snowflake yeast after its snow flake-like way of growing.

As opposed to aggregates of cells that come together when there is little food or when there is need for protection, a multicellular organism is a community with identical genetic composition. Each cell is a clone carrying a genome that must evolve ways of organizing the entire group of cells. Adhesion molecules on the surface of each cell connect them to each other, building the tissue of say, a heart or leaves on the branches of trees. For communication the cells secrete signalling molecules traveling short or long distances to convey messages important for cooperation. Neighbours even tell a cell to stay alive, reducing the risk of uncontrolled cell growth, known to us as cancer. Increasing in size, the multicellular organism is also faced with the threat of accumulating potentially harmful mutations at each cell division, a phenomenon called Müllers ratchet. Separating a germ cell line that gives rise to the reproductive egg and sperm from the cells that constitute the body of the organism, has been hypothesized as a way around this problem. During development a patterning program unfolds as signal molecules are spread across different areas of a zygote and later on the foetus, giving identity to every cell by switching on different parts of their shared genome. All of this, however, starts out when a unicellular cell divides only to remain attached to its daughter cell.

When comparing genes of snowflake yeast with ancestral unicellular yeast, disruption of a single gene, ACE2, was found in half of the colonies. ACE2 is responsible for controlling the production of proteins involved in separating the daughter from the mother cell after cell division. In each of the Snowflake communities, different parts of the gene were damaged. Suggested by the model, one can ask if a single mutation might be responsible for the watershed in the evolution of some, if not all, of the transitions from unicellularity to multicellularity occurring at different times in the tree of life. If so, it sides with one of the two explanations concerning how change in a species occurs. In the field of evolutionary developmental biology many scientists work with evolvability – the predisposition of an organism to evolve – trying to understand how genes and the physiological and morphological traits of a species either restrains or encourage the direction to which the species will evolve given a certain environment. The punctuating evolution hypothesis holds that if a single mutation can cause fundamental change in any of the traits of an organism evolution might happen fast, punctuating long periods of stasis in the history of the species. On the other hand, as organisms become more complex and the same genes are involved in a myriad of different processes separated by time and space in an organism, abrupt changes might be more damaging than beneficial, causing change to happen slowly and gradually in a species during long periods of time. The early appearance of the mutation in ACE2 of Snowflake yeast seems to favour the punctuating evolution model. Still, when working with multicellularity, one needs more than a single mutation to account for the drastic changes.

The transition from unicellularity to multicellularity happens according to multilevel selection theory in two stages; the first stage of the transition involves the reduction of genetic differences between individuals. Genetic similarity reduces the conflict between self-preserving cells that stops the group becoming an individual. The second stage is initiated when a cells chance of surviving and reproducing is higher when adapting as a part of a group rather than adapting as a solitary player within the group. The Snowflake yeast went through both of these stages; after reaching a minimum size branches of the structure broke of and thereby formed clones of independent daughter clusters, arising from the cell at the break point. During the experiment the colonies first evolved larger cells followed by a change in the overall structure of the cluster from elongated branches to a more hydrodynamic rounded shape. This reduced drag in the liquid, and spherical colonies were quicker to sink to the bottom compared to those with larges sized cells. Selection for size and shape resulted in selection at the community level and increases the fitness of the whole group of cells. Division of labour was also observed as cells underwent controlled cell death – quite unthinkable for a unicellular organism – to release new daughter clusters.

Studying the Snowflake yeast gives some clues of the first stages of the evolution of multicellularity. As with every model designed in a lab, we cannot know for sure if it really mimics the actual events in nature, but they are far better than knowing nothing. The swift appearance of multicellularity in a test tube and its frequent occurrence in nature tells us this: leaving the world of solitude might not be a difficult task after all.

Further reading:

Origins of multicellular evolvability in snowflake yeast. William Ratcliff et al. in Nature Communications, Vol. 6, pages 1-9; May 2014.
Experimental evolution of multicellularity. William Ratcliff et al. in Proceedings of the National Academy of Sciences, Vol. 109, No. 5, pages 1595-1600; 2012.

The 6 hours race

Today I have tried the following; writing non stop from start to finish a popular science article. This is not, I repeat NOT, the way to a good article, as it usually needs some polishing and some criticism and some killing of precious babies. Nonetheless, when the going gets though, the though gets going, here is the result! 

Society! 

During the last stages of the neolithic era – the last part of the Stone age – the gradual transition from the hunter-gatherer way of living to the start of what we now call civilization slowly changed human condition. There was agriculture and domestication of animals and concomitant settlement. There was specialization of labor, urban development and social stratification. The fertile lands around Euphrates and Tigris nourished human society and gave rise to the cradle of western civilization – a complex society where we emphasise our freedom as human beings while at the same time remain dependent on the political stability in our home lands and world wide.
However, this is not a history lesson. This is a tale about how there seems to be a penchant for cooperation among the different groups of life. And we´re not talking social structures. There will be no wolf packs, bee societies nor any examples of tree-loving fungi . Before any of the afore mentioned cooperative species evolved, something more profound happened. Single-celled organisms evolved to become multicellular. This is no cake walk. Because it involves dependency. Becoming multicelluar means identifying yourself as a part of a whole – your individuality is now of lesser importance. In fact, it is not wanted, unless it can contribute to the survival of all the other cells that constitute the multi of the organism. Now, obviously there is no you or me when we talk about single celled organism, just as there are no decision-making involved in the emergence of multi-cellular organisms. But there are advantages; reduction of predation risk and division of labor, as well as a comptetitive advantage of increase in size. Multicellularity is the work  – as always – of natural selection. And time and time again, as we will see, multicellularity is selected for. As to the beginning of this text – there is a weak analogy connecting the evolution of multicellularity and the advent of civilization; cooperation and organization pays off.

Multicellularity in a broad sense simply means sticking together. Both bacteria and eukaryotes – cells with a nucleus and other cell organs in its interior – have evolved from unicellularity to multicellularity multiple times. In the eukaryote lineages there are slime molds, colony formation and of course, the plants, the fungi and us; the animals. In the bacterial lineages there are biofilms, filaments and fruiting bodies, some of which will be discussed later.

But let´s start where we all like to start; with ourselves. The animal version of multicellularity is by far the most complex. It is also multicellularity in it´s narrow sense. One cell gives rise to all of the cells in an animal body. A cell community must be able to stay together and also ensure that the right kind of cells remains next to each other. They also need to communicate so that they are all in tune with one another. If the cells loose these two important characteristics, they turn into something well known in our society today: cancer cells! Last, but not least, just as a society needs individuals with different jobs and roles, a multicellular community consists of many different cell types with specific functions. Some constitute the outer layers of a body, some make the hard structures like bone and cartilage or the carpace of crabs, lobsters and shrimps. Some build the blood vessels, other construct internal organs, some sense light, touch, sound and smell, and some make up the muscles and nervous system giving animals the ability to move. And some give rise to the egg cells and the sperm – ensuring that a new generation will develop.

The emergence of different cell types during the developmental stages of an organism is called differentiation and is a result of the genetic developmental program. Almost every cell the body of a multicellular species contain all the heritable information needed to make that organism. Differentiation is simply telling each cell which page in the cookbook, if you like, it should take it´s instructions from.

The animal lineage can trace it´s origin to the unicellular choanozoans. The ancestor of all animals, prior to the transition to a multicellular form must have looked something like a choanoflagellate, a chonozoan. At its rear end it has one flagella, a tail-like structure, surrounded by a collar made up of tiny sticky rods that makes a net used to catch nutrients. The beating flagella propel the choanoflagellate forward. Now, in one of the most basal animal groups, the sessile sponges, the cells that make nutrient-containing sea water flow into the internal canals and cavities of the sponge, have the exact shape and apperance as the choanoflagellates. These cells are appropriately called choanocytes. Their resemblance to the choanoflagellates were first described by James-Clark in 1866. With the computer programs we have today, we can also infer evolutionary relationship by looking at the genes of this species and compare it with the animal lineage. Most interestingly, the choanoflagellates form colonies. The common ancestor of both the choanoflagellates and the animal might have been a colony forming organism.

Sponges - Porifera Morphologies

Sponges – Porifera
Morphologies

The beating flagellum of the choanocytes produces a current that makes water flow into the sponge

The beating flagellum of the choanocytes produces a current that makes water flow into the sponge

Colony forming choanoflagellate: Sphaeroeca

Colony forming choanoflagellate: Sphaeroeca

With the introduction of the colony forming choanoflagellates we are entering into multicellularity in it´s broad sense. Now, independently arising cells aggragate to form a structure in which they arrange themselves in a cooperative manner. The eukaryote slime mold aggregate in response to diminished food supply. It can exist as a solitary cell on decaying logs, eating bacteria. When there is no food left, they aggregate and together becomes what is called a migrating slug. When this structure reach an illuminated area , the tens of thousands og slime molds create a fruiting body, containing differentiated slime mold cells. Some make up the spore cells and others, the stalk that elevates the fruiting body. The stalk cells die, but the spore cells disperse and give rise to new myxamoeba.

mycota.tumblr.com

The Fruiting body of Dictyostelium
from mycota.tumblr.com

Bacterias are usually thought of as the ultimate loners, but there have been a broader recognition of bacterial multicellularity in the microbiology and evolutionary biology communities. A widespread mode of bacterial multicellularity are biofilms: aggregated bacterial cells that together produce and secrete a substance in which they are embedded. Many bacterial species switch between independent life styles and sessile biofilm lifestyles depending on the resources available and other environmental factors. In streptomycetes multicellularity is initiated from a single cell; a spore. As the cell divides, the daughter cells stays connected forming network of threadlike structures called a hyphal network in the soil. A stress signal initiates differentiation and growth of aerial spore bearing fruiting bodies.

The evolution of cooperating lifeforms both in the bacterial and eukaryote lineages raises the question of what the prerequisites for a more advanced form of multicellularity are.  Knowledge about bacterial broad sense multicellularity relates the animals to the rest of the three of life and gives our lineage a context in which to understand early animal evolution. How deep is the root of the genes that enables multicellularity? Or have they arisen independently at many time point during evolution? Questions like this tie together the tree of life and awakens the quriosity about what, by many, are thought of as lesser life forms. Research that focuses on the evolution of the genetic programs that increases the complexity of living forms is exciting. Working out the similarities and differences between the animal lineage and it´s closest unicellular and colony forming relatives may give scientist an idea of how and why complex multicelluar organisms appeared.

Sources:
Gilbert, S. F. 2014. Developmental biology. Tenth edition.
Hickman et al. 2011. McGraw Hill’s Animal Diversity 6th Edition
van Wezel, G.P 2014. Bacterial solutions to multicellularity: a tale of biofilms, filaments and fruiting bodies. Nature Reviews Microbiology.

and some Wikipedia, as always…

Deep Phylogeny and Multicellularity

We can´t return
 We can only look
Back from where we came
And go ‘round and ‘round and ‘round in the Circle Game
- Joni Mitchell

Projects in the field of evolutionary developmental (evo-devo) biology try to look back from where we came. As the radiation of all known animal phyla most likely happened 700 million years ago it is quite a task to find answers to questions regarding the relationships among early branching animals; Sponges, Placozoans, Comb jellies and Cnidarians (Jelly fish, sea anemones). Their diversification is still debated, and there are even studies that place comb jellies as the earliest diverging animal group, even though they are more complex than both sponges and placozoans.

The question of deep metazoan phylogeny is only one of the interesting ones – a more fundamental one is the question of the origin of animal multicellularity. The transition from unicellularity to multicellularity has happened many times. Plants, Fungi, slime molds, some bacteria and algae have all evolved to become multicellular organisms, but it is in the animal lineage we found the highest degree of complexity.

The genetic toolkit associated with multicellularity consists of genes involved in adhesion, communication and differentiation. A cell community must be able to stay together and also ensure that the right kind of cells remains next to each other. They also need to communicate so that they are all in tune with one another. If the cells loose these two important characteristics, they turn into something well known in our society today: cancer cells! Last, but not least, just as a society needs individuals with different jobs and roles, a multicellular community consists of many different cell types with specific functions. The emergence of different cell types during the developmental stages of an organism is called differentiation and is a result of the genetic developmental program.

So far, data from genomes of unicellular relatives of animals show that some components of the genetic toolkit was present in the shared common ancestor of the unicellular relatives and what was to become animals. The preexisting components must have diversified in numbers and in function in the multicellular lineage. Some components of the toolkit are also absent from the unicellular relatives and are likely innovations in the multicelluar lineage.

Antonis Rokas in his review “ The Origins of Multicellularity and the Early History of the Genetic Toolkit For Animal Development” poses two intriguing questions that I hope will be answered. Was the genetic toolkit casual in the evolution of animal multicellularity or simply its product? What was the relative contribution of ecological and environmental, and genetic factors in the origion of animal diversity?

Leucothea multicornis | ©Marinko Babic (Adriatic Sea, Croatia)

A comb jelly (Ctenophore) – an early branching animal

The take home message

What sort of dawns on you during the new introductory course for master students at the institute of biosciences, UiO, is that no matter how much you love biology/molecular biology, there are many tools for analyzing data that is not thought on a sufficient level during the three years leading up to a master project. The need for statistics, more math and bioinformatics becomes quite clear, even though it has loomed in the distance from the time one began reading research articles. I, for one, even find the basic physics course  relevant as the evolution of life is constrained by and based upon the natural laws of the universe. What is this we percieve as color? How does thermodynamics explain the sun-powered order on this planet? And what about electricity and the development of a nerve system? 

That said, being one of those who occasionally focus more on what I lack of knowledge rather than being happy about what I know ( Three years does fill your head up, if you use your time well), there might come a time in two years where I actually master, to some extent, the brilliant tools available to biologists made possible by advances in other fields of science.

 

This was the late night musings before bed time. And it´s way past bed time. At least for early birds. 

 

kurle

 

I can´t help myself: this is a picture of a Frog Orchid/Grønnkurle (Dactylorhiza viridian)
I spotted it during our walk in the Pyrenees this summer.
So gorgeous…

Why you should do a roadtrip to Messel and Holzmaden

Two summers ago I went on a road trip with two friends from the university of Oslo. Destination: Messel and Holzmaden in Germany. Now why not visit Berlin, Dresden or the Bavarian Alps? The answer is not obvious, although a simple one: fossils. Messel and Holzmaden are Lagerstätten – fossil localities which are highly remarkable for either their diversity or quality of preservation.

The field of paleontology, which is much more than just dinosaurs, is super interesting. Fossils can tell us something of life, the evolution of different species and it can say something about the biodiversity that existed many hundreds of millions of years ago.

Although we today have moved beyond the way Linné did his systematics, that is, we have tools that correct and supplement the old way of builiding a genealogy based on morphology, palaentology gives ut tangible evidence of evolution that sometimes have information on the environment the species lived in, maybe it`s habitat, and even it`s niche! Take the ichtyosaur; this marine reptile looks much like a dolphin but where doplhin “gallops” through the water with movement derived from its land living mammal relatives, the ichtysaur caudal fin beats from one side to the other, a bit like a lizard running. Now to the point; fossils of ichtysaur have large eye sockets in their skull. One have hypothesized that this may be because they ate ammonites (looks a lot like the exctant nautilus) living in deep water. Preying on ammonites would need good vision and ability to catch every photon of light available.

But rather than having a continous fossil record what we have are snapshots into the past. Becoming a fossil is like winning a big lottery. After death, decay starts and to be preserved, a body must be buried in anoxic conditions. This is why the fossil record is full of marine animals. This is also why Messel is extraordinary.

messel

Messel

Messel is located close to Frankfurt and used to be a quarry where oil shale was mined from the second part of the 19th century. The oil shale were formed during the Eocene (~47 mya) by deposit of  mud and dead vegetation on the lake bed. The oil shales contains amazing fossils where sometimes hair on the dead animal and even the colour of beetle-wings have been preserved. And most important; this is where Ida (Darwinius massilae) was found. The Natural History Museum in Oslo bought the fossil after the norwegian paleontologist Jørn Hurum discovered it on a fossil fair in Germany (actually he did`nt find it exhibited on the fair, but he was contacted and offered it). The fossil is the oldest one we have, this well preserved by a primate. There it is.

meg                          bat

(Left: self wanna-be paleontologist, Right: the bat!)

So, Aubrey Roberts, the one driving the car on the autobahn in Germany, happened to be the a master student in paleontology and Jørn Hurum was her supervisor. She was to deliver a painting of Ida by Esther van Hulsen (check her out!) to a scientist who helped Jørn in getting the Ida fossil to Norway. The painting was delivered and we was taken on a tour in the Messel pit. During our stay there, some of the scientists digging in the pit discovered a bat. They opened the oil shale, and there it was! Amazing.

As if a fossilized bat was`nt enough we got in the car and drove to Holzmaden where the ground is full of fossils from the Jurassic period. Here we got our digging gear ( the hard part of it was already done, though, we just had to bind some small rocks) and started to split them. I now have a small collections of ammonites and belemnites and something that I have no idea what is.

holzmaden

(Self in the sun with chisel and hammer – Holzmaden)

I won`t be working on fossils myself (in my next life I will), but the great thing about being at a university is that you get to meet people from so many different fields of science and also from within your own field doing something else than yourself. Some will take you on a roadtrip to visit fossil locations in Germany!

(If you are a biology student from the university of Oslo interested in paleontology, you should take the course GEO3710- Evolution of Life. It is really good, not so hard and you get to practise you writing skills).

(Aubreys master thesis is published: A New Upper Jurassic Ophthalmosaurid Ichthyosaur from the Slottsmøya Member, Agardhfjellet Formation of Central Spitsbergen).

finally autumn!

From where I sit – second floor, office, at a desk with a windom infront of me – I can see the first signs of autumn. The mornings is not bright with sunlight anymore, everything that grows have a baroque feeling to them, and most of the flowering plants have lost their petals and what`s left is the seed-filled fruits of many different kinds. Soon, the leaves will change color, and the air will become colder, but I really don`t mind. I love the autumn. Everything about is. For me, new years eve should be in the end of august. This is when I feel we start anew. 

I am writing this in the morning. I am soon off to the university. The third day of my master`s degree and we have`nt done anything but sit by the computer, because we are being introduced to R. A programming tool for analysis of biological data. This first course is a introduction to many topics; science commiunication, ethics and research, bioinformatics, critical reading of published papers (we are to read a paper on wolf ecology and diet) and of course R. I don`t really know how useful it really is – the course runs for two weeks – but I guess it is a ok way to start off. 

What I am looking forward to is a meeting with my supervisor later this week. We haven`t decided on everything I am to work with yet, so I am anxious to find out about that. 

Getting started

What I look forward to the most, leaving for the Pyrenees, is walking. For hours we will have the mountains on every side, the sky and the mountain dwellers, be it plant or animal. But it really comes down to walking. The feeling of being in transit is probably why I love running, riding shot gun in a car or taking the train to the university every day.

This is my first blogpost. The blog will be a way to process what I will be working with during the next two years. I´m so lucky to be studying a field of science that makes me want to jump out of bed every morning and do the forty minutes trip to the university of Oslo. I will start working on my master´s degree in molecular biology come august. But what´s even better is that I am to apply the techniques and everything else I have learned so far on the study of evolution.

There is much talk about the importance of science communication. I find that there is really no reason not to spread the word about what we´re working on. Trying to piece together this great puzzle which ultimately constitutes the universe is a formidable task, and as far as I can see, a never ending story. But, as everything else, writing not merely a walk in the park. Not for me, that is. That´s why I will start writing now and in english. My mother tongue is norwegian, but I want to work on my english as well.

As a sidekick, the wonders of the world of plants will frequently take up some space. I just love plants, and especially boreal orchids and the species of grass, rush and sedge.

IMG_6888

A posy of grasses from the forest nearby my home

First things first, though. I am leaving for the Pyrenees in less then two days and I am super excited. Five days of walking in the Midi-Pyrenees, on the french side of the mountain range.  The weather forecast is so far good, I´ve got everything I need (mind you, I have spent a lot of time in the norwegian mountains, so this should not be so hard), and I am traveling with one of my favorites.

Let the games begin!