A Squirmy Jellyfish

Scientists from Oxford University have discovered that a very rare, gutless, worm-like animal called Buddenbrockia is more closely related to jellyfish than to worms.

First described in 1851, Buddenbrockia is a bizarre animal because it is missing many features that true worms should have.












Lead scientist Prof. Peter Holland explained that:

"It has no mouth, no gut, no brain and no nerve cord. It doesn’t have a left or right side or a top or bottom – we can’t even tell which end is the front!"

Unlike true worms such as planarians, which I've blogged about before, Buddenbrockia doesn't have different specialized organs on different sides of its body.

Prof. Holland added that:

"Buddenbrockia is very unusual in not displaying this kind of body asymmetry. Seen in cross section it is completely symmetrical so no way is ‘up’ and no direction is ‘forward’."

So it IS made up of the same mushy meat throughout its body.

Based on DNA analysis, Prof. Holland's team discovered that Buddenbrockia is more closely related to jellyfish and sea anemone.

Which means that it is classified under the Phylum Cnidaria, a group of animals that are diploblastic - they have two embryonic germ layers: endoderm and ectoderm.

Other animals, such as true worms and vertebrates like us, are classified in a group called Bilateria. Such animals are triploblastic, containing three embryonic germ layers: endoderm, mesoderm and ectoderm.

So this is a particularly striking example of convergent evolution, where animals from different phyla can end up with the same body shape.

While Buddenbrockia is a diploblastic animal like the jellyfish, it doesn't appear to have an opening of any sort.

Perhaps it is tiny enough to absorb nutrients from the environment through its surface.

Jellyfish are not so lucky.

As Cervantes (from Stayin' Alive) describes in excruciating detail:

"You may have noticed that one thing that all of the triploblastic organisms have in common is a gut, a hollow tube running through the body. The food goes in one end, gets serially disassembled and the useful components absorbed, and the waste goes out the other end.

That is a major innovation, and for those contemplating possible options for reincarnation, it's a good reason to request not to come back as a diploblastic jellyfish. (Thanks to Jan Pechenik for this observation.) The food comes in, and the waste goes out, through the same opening. Life without an anus is clearly inferior. Not only is it impossible to take a meal until the last one has been discharged, but movement involves physical distortion of the digestive cavity and expulsion of much of what is in there. So, you can't digest and swim at the same time. Finally, you have to discharge your gametes and embryos through the same opening. Yuck.

So, let's hear it for one of our most important body parts, that gets very little respect."

Dammit I was eating.


Would you like to know more?

About other bizarre organisms
- Magnetic bacteria
- Planarian worm
- Vole

Tagged!

I've been tagged by the long beak of Hawks!

Although I'm not much into chain mail (except when Samantha Mumba is wearing it) , I'll let this one slip.


















1. We have to post these rules before we give you the facts.
2. Players start with eight random facts/habits about themselves.
3. People who are tagged need to write their own blog about their eight things and post these rules.
4. At the end of your blog, you need to choose eight people to get tagged and list their names.
5. Don't forget to leave them a comment telling them they're tagged, and to read your blog.

And here are 'em random facts!

1. Fresh Brainz was inspired by an insane British science show called Brainiac.

This entire blog is littered with references to British comedies (Brainiac, Blackadder, Monty Python, Whose Line Is It Anyway, Wallace and Gromit...) and American comedies (George Carlin, Saturday Night Live, Daily Show...).

2. I have conscious control over my left lower eyelid twitch muscle. I can pull my lower eyelid inwards at will. Nobody else I know has this ability.

If some people have doubts about evolutionary biology, I'll show them my eyelid and freak them out.

3. I was born a left-hander. My parents encouraged me to use my right hand more and I "switched over" as a little kid.

4. In 1990 I won my secondary school's Talentime competition. Even today I don't go to Karaoke much because other people really hate me when I sing.

By the way Karaoke is pronounced as "Ka La Okay", not "Carry Okie".

5. In 1994 I experienced "sidereal depth" when looking at the Moon and Venus. Celestial objects normally look like they are about the same distance away, "pasted" on the flat blue sky.

One morning, while taking a bus to school I looked at the Moon and Venus, and suddenly... WHOOOSH! Venus receded into the distance and I could feel how far away it is, compared to the Moon.

I haven't experienced that feeling again.

6. In July 1999 I saw a UFO above the skies of Singapore.

During the day, it lingered at around the same position in the sky and changed colour (towards red) in the evening. I asked the Meteorological Service if it was a weather balloon, but got no reply. When I pointed a binocular at it, I could faintly see a "U"-shaped silhouette and what looks like two green exhaust ports on the top of the "U". It disappeared after a few days.

I don't know if aliens exist, but if they do, they certainly have a stupid sense of humour.

7. I was once a Playstation horror game addict. I've played all the Silent Hill games, the Fatal Frame series, Forbidden Siren series, Echo Night series, Kuon and others. Earlier this year I played a new horror game called Rule of Rose, which appeared quite innocent in the beginning and became so frighteningly mad that I had nightmares for a week.

Rule of Rose is the only horror game I didn't finish.

8. I get lucid dreams a few times a year. In most of them, I am flying around breaking fragile things like neon signs and windows with my mind.

My favourite lucid dream involved two extremely beautiful and extremely naked women.

And a hot tub.

The next eight hapless victims are:

Anders Rasmussen Blog

Bayblab

Globalizati

Orbital Teapot

The Empire of the Odd

The Ethical Palaeontologist

The Lord Geekington

The Other 95%

*cough*

What Doesn't Kill You Lets You Live

Sometimes I sit in the lab and think to myself:

"What am I doing here? I'm panning for specks of gold in an abandoned gold mine! There is nothing important left to discover; I'm wasting my time on picky details that nobody will care about!"

Then suddenly, like a huge rubber anvil, a bizarre new scientific discovery fell out of the sky and twacked me on the head.

*BOP!*

Oww!

Last month, the Encyclopedia of DNA Elements (ENCODE) Project Consortium published their findings on 1% of the human genome (about 30 million base pairs).

They were focusing on the regions of the genome that do not encode for proteins, and used a barrage of high-throughput genomics technologies to identify and catalogue functional DNA sequences.

They expected to discover new transcription start sites and non-protein coding transcripts. They also expected that the presence and activity of transcription start sites will be related to chromatin accessibility and histone modifications.

And they were right.

In the evolutionary aspect of their project, they compared the DNA sequences of 14 mammal species with 14 non-mammal vertebrates. They found that 5% of the human genome was highly similar in all mammals (evolutionary constraint). Within these constrained regions, only about 60% of the sequence had evidence of biological function.

Which is rather odd, since highly conserved sequences are expected to be functional. Why would a good 40% of the sequence be conserved if they had no function?

Stranger still, they then discovered that approximately 50% of functionally important non-coding DNA sequences were NOT constrained.

Mammals are using vastly different sequences for essentially the same functions.

In other words: functional conservation without sequence conservation.

Now that is weird.

The researchers noted that (italicized by me):

Surprisingly, many functional elements are seemingly unconstrained across mammalian evolution. This suggests the possibility of a large pool of neutral elements that are biochemically active but provide no specific benefit to the organism. This pool may serve as a ‘warehouse’ for natural selection, potentially acting as the source of lineage-specific elements and functionally conserved but nonorthologous elements between species.

I knew it!

Heh.

Mainstream evolutionary theory would have you believe that many (if not all) features of a living organism were "fine-tuned" by natural selection to be well-adapted to its environment.

You get the feeling that the organism is under such massive selection pressure that natural selection would efficiently prune away useless DNA sequences and preserve only the sequences that helped the organism to survive. This is true for protein-coding sequences, which tends to be highly conserved from fish to human beings.

We are all built from roughly the same building blocks.

So it was generally assumed that all conserved DNA sequences ought to be functionally important. However, the wide variation in total genome size is a clue that non-coding sequences do not play by the same rules.

To take two extreme examples: the grasshopper Podisma pedestris has about six times (18 Gbp) the total genome size of a human, while the tiny shrimp-like Ampelisca macrocephala has nearly 20 times (63 Gbp) our genome size!

In fact there is a 3 300-fold difference between the largest and smallest animal genomes.

There is no correlation between genome size and the number of protein-coding genes (which is much less variable, around 10-fold) in animals.

Our building blocks are arranged and used in different ways.

And because animals are complex systems with redundant genes and many organizational levels, it's hard to pin biological function all the way down to the DNA sequence level.

So I don't find it surprising that there are many neutral elements in the human genome. Considering the robustness of even a single cell, the reality is that Nature tolerates many variations at the sequence level, and natural selection won't remove even huge chunks of DNA if they don't kill the organism fast enough to stop it from reproducing.

To oversimplify:

What doesn't kill you, lets you live.

It usually doesn't make any difference and it rarely makes you stronger.

As for functional conservation without sequence conservation - structural biologists are already aware of this at the protein level. Some amino acid sequences are highly conserved, but changes in a few key positions can drastically affect the fold of the protein, so sequence conservation is not enough to guarantee the same function.

The converse is also true - drastically different amino acid sequences can end up having a similar 3D fold and serve similar functions. The EMBL Dali tool is an online resource that allows biologists to submit a protein crystal structure and search for other proteins with a similar 3D shape, no matter what the amino acid sequence is.

With the discovery that so much functionally important DNA has no evolutionary constraint, just knowing the DNA sequence itself is no longer sufficient.

Data from ENCODE and other related research projects may help create a Dali-like tool for non-coding DNA sequences one day.

This could prove quite difficult since the function of non-coding DNA is not just a matter of 3D shape - confounding variables such as the chromatin configuration and the expression timing of specific transcription factors will have to be accounted for.

So there are still some big mysteries left to be solved!

Oh well.

*goes back to panning for gold*


Would you like to know more?

- More about ENCODE

Fresh Science 8 July 2007

At Fresh Brainz, we do the hard work of teasing the globe for the munchiest science articles - so you don't have to.

The spotted hyena puts you to shame (Bayblab - Canada)

Virus linked to temporal lobe epilepsy (Mind Hacks - USA)

Now this is how to critique Ken Ham's creation "museum" (Pharyngula- USA)

Remember Roswell? (The Empire of the Odd - USA)

James Randi explains homeopathy (Alex Feldstein - USA)

Fresh Science 6 July 2007

Here at Fresh Brainz, we do the hard work of screening the globe for the choiciest science articles - so you don't have to.

Penises of the animal kingdom (Bayblab - Canada)

The soul exists but it's made up of billions of tiny robots... (Orbital Teapot - USA)

New example of the problem solving skills of orangutans (Pro-science - Denmark)

They're over here (The Ethical Palaeontologist - UK)

The last common ancestor between squid and octopus? (The Other 95% - USA)