Aspidella on the move?

This is Aspidella:

(Peterson et al. [2003] via Palaeos)

The Internet tells me this is also Aspidella:

(Amy Campbell)

And so is this:

(Menon et al., 2013)

(How on earth did all of those things end up with the same name???)

Aspidella, you see, is one of those problematic Ediacaran fossils that may or may not belong to a single kind of organism, which may or may not be an animal. It’s an impression of something soft with a rather variable assortment of surface features, and hence it’s pretty hard to tell what made it, although the wide holdfast of some bottom-dwelling, filter-feeding animal is a popular opinion. This nice Charniodiscus specimen (Tina Negus via Wikipedia) explains why:

Seeing how fossils like these are one of our precious few sources of evidence on the early history of animals, any additional evidence to help us figure out what they were is awesome. It’s especially cool to find evidence of behaviour, because “behaviour” is something that only certain groups of organisms exhibit, and some of the candidates for Ediacaran thingies like this (e.g. fungi, lichens, microbial mats) specifically don’t.

In a short paper in Geology, Menon et al. (2013) argue that they have found such evidence in some Aspidella specimens from the mid-Ediacaran Fermeuse Formation of Newfoundland. There are two kinds of features they report on. First, there are shallow, short trails that look like whatever made the impressions slid or hopped along a soft sediment surface in short movements. Some of the trails show faint impressions of the radiating ridges some conventional Aspidella specimens possess (like the one below, taken from the paper):

They are fairly rare, the best bet for finding them being slabs of rock practically carpeted with Aspidellas. A couple of things indicate that they weren’t just made by some random current or mudslide sweeping hapless Aspidella creatures along. For one thing, even in a whole pile of Aspidella imprints, you’ll find only a few such trails. (Although that could be because most of the living creatures would have been firmly rooted to the sediment!) For another, neighbouring trails point in all kinds of random directions, so if it was a current, it must have been the most chaotic one in earth history.

The other kind of evidence is what looks like the “evolution” of vertical burrows, layers of sediment dipping downwards like there used to be something sitting on them that gradually relocated further up as more sand and mud accumulated around it. Of course, an animal sitting in the mud isn’t the only thing that can produce similar features, so the authors considered a few alternatives.

They didn’t find any signs of water or gas bubbles escaping. They also didn’t think the features looked like sediment slumping into a hole, which they actually experimented with by piling sand and mud on top of dissolving liquid capsules (laundry capsules?? :o). The dips produced by falling sediment get conspicuously shallower towards the top, which the fossil dips don’t seem to do, plus the latter also have round structures like small Aspidella on top. Personally, I find the photos of the fossil dips really hard to compare with the picture of the experimental dips, though. Here’s perhaps the best specimen they show alongside one of their experiments:

Yeah… I can kind of see where you’re coming from, but…

So the idea is that an animal lived with its rear end buried in the sediment and its feeding structures up in the water column. As the water brought in more sediment (the Fermeuse Formation is thought to be marine in origin), the unknown creature moved upwards to avoid complete burial. Eventually, it would die, leaving behind a stack of little dips indicating its previous seats, topped by a good old-fashioned Aspidella impression.

Interestingly, only small Aspidella are associated with these vertical traces. Did young and old Aspidella creatures live in different ways, or do larger specimens simply belong to a different organism?

The authors specifically think the Aspidella animal was cnidarian-like because other possible candidates such as sponges and giant moving protists haven’t been observed to move vertically through sediment. Only well-muscled creatures like sea anemones (and bilaterians, but there’s absolutely no reason to think this thing was a bilaterian) are known to do that.

Which is really pretty exciting – more Ediacarans directly associated with traces of movement! I maybe should have mentioned that the paper keeps going on about Retallack (2013), mainly to say that it was Wrong, but I thought it was interesting enough in its own right. The fact that it discusses signs of animal-like behaviour in a kind of fossil that’s also common in the Australian rocks reinterpreted by Retallack as terrestrial is kind of beside the point.

***

References:

Menon LR et al. (2013) Evidence of Cnidaria-like behavior in ca. 560 Ma Ediacaran Aspidella. Geology advance online publication 06/06/2013, doi: 10.1130/G34424.1

Peterson KJ et al. (2003) A fungal analog for Newfoundland Ediacaran fossils? Integrative and Comparative Biology 43:127-136

Retallack GJ (2013) Ediacaran life on land. Nature 493:89–92

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Living jellyfish =/= earliest stage in metazoan evolution…

So, admittedly, I wasn’t interested enough in Bielecki et al. (2013) to read the whole thing. But if the abstract is an accurate reflection of their reasoning, then “WTF” is an accurate reflection of my reaction.

The reason I went to have a look at this shiny new PLoS paper is that it was titled “Fixational Eye Movements in the Earliest Stage of Metazoan Evolution”. Anything to do with early metazoan evolution automatically interests me, plus my immediate reaction was to ask how the hell they discovered any kind of eye movement in the earliest animals (which have been, you know, dead for like 600 million years).

Turns out they didn’t. Turns out all they found was that the rhythmic contraction of a box jelly‘s bell keeps the image in its eyes changing so they don’t go blind from photoreceptor fatigue. We accomplish the same effect by constantly moving our eyes (though apparently that’s more for the brain getting bored than photoreceptors burning out?), but the jellies supposedly don’t have the same level of nervous and muscular control over their eyeballs.

Yes, box jellies have frickin’ amazing eyes, complete with lenses. In fact, they have 4 sets of 6 eyes, two of the six being proper camera eyes and the other four much simpler. They can use their eyes to navigate around obstacles and stuff. They are pretty cool creatures. Here’s a box jelly eye cluster (rhopalium) in its full glory from the UCMP:

(Was that just a little bit unsettling? :D)

But these complex, image-forming eyes are an innovation of box jellies. No other cnidarian – in fact, no other animal outside the Bilateria – has them. So complex eyes and good vision are examples of convergent (or should I say parallel?*) evolution, not inheritance from a common ancestor. Conversely, bilaterians don’t have bells like jellyfish, so anything they do to move their eyes has to be an independent invention from the get-go.

So, while box jellies are awesome and it’s always cool to learn more about them, I’m not sure what profound insight about animal evolution we are supposed to find here. That animals with eyes have ways of avoiding visual fatigue? Well, duh. Of course they would, it’s really useful. But I’m not even sure the pulsation of a jellyfish should be regarded as a vision-enhancing adaptation, never mind an adaptation with any relation to what we do. To me it seems like the default way a jelly moves just happens to be good at keeping its eyes entertained. Evolution doesn’t have to do anything special about it.

Of course, the whole thing is soaked with that grandmother of evolutionary misconceptions, exemplified by this quote from the introduction:

Cnidarians were the first of the extant metazoan phyla to develop a nervous system which is therefore considered close to the evolutionary origin of all nervous systems [9].

Nooooooo, for the love of hungry anomalocaridids, don’t do this to me.

Cnidarians and bilaterians shared a common ancestor with a nervous system. Never mind “phyla” – phyla are arbitrary lines humans drew around the branches of the phylogenetic tree. Our ancestors and theirs had nervous systems for the exact same length of time. Neither of us was “first”. Life is a tree, not a goddamned ladder.

Well, at least we got to look at some disembodied jellyfish eyes. Yay!

*goes away to growl quietly*

***

*The difference being that parallel evolution is convergence  from a common starting point. While complex eyes are clearly later inventions, the common ancestor of cnidarians and bilaterians might well have possessed simple eyespots of some sort, providing said common starting point. But we’re getting pedantic here.

***

Reference:

Bielecki J et al. (2013) Fixational eye movements in the earliest stage of metazoan evolution. PLoS ONE 8:e66442

In which I *don’t* blame journalists

Given the existence of this blog, you might have guessed that I’m interested in communicating science to a wider audience. Recently (well, in November) I went to one of Sense About Science‘s media workshops to learn more about science communication – specifically, about the representation of science in the media and issues surrounding same. When I’d digested the experience, I had some thoughts. Then I committed them to writing. Then the writing sat in a folder on my desk for half a year. I think it might just be time to publish it 😛

(Although this should go without saying, I don’t speak for all scientists. I have a personality and I have experiences, and both of those may distort my perspective. Read the following as my personal opinion.)

*

Once upon a time, I was a regular reader of ScienceDaily. It’s one of those places where science news gather, and I was interested in science news. I’d never been a big reader of other news, so it suited me perfectly.

Except I’m a pedantic nerd, and reading press releases can be… trying for my kind. I eventually got to the point of asking my supervisor how much scientists had to do with press releases of their papers, because so many of the ones I’d read on SD seemed to have been written by people who either wanted to blow everything out of proportion or simply had no clue.

The boss answered that the researchers would provide source material, but the press office write the actual release, and poor scientists can’t do a whole lot about its final incarnation. He made no secret of his dismissal of the press office, and opinionated little crusader that I am, I felt vindicated.

For a good long while, then, I felt completely justified in griping about journalists. They were, after all, churning out overblown claims and garbling perfectly good science to turn it into news. Was it a wonder, then, that so many people were becoming jaded and mistrustful of science? If you read articles touting miracle cures for cancer and marvelling at the biggest, oldest, most awesomest something ever, if every week decades-old paradigms seem to be turning on their heads, it isn’t at all surprising that you’d end up as some of my online discussion partners did. I saw these people, dismissive of science, firmly convinced that since science changes like the wind, it isn’t worth believing. Today’s knowledge will just become tomorrow’s outdated theory anyway. It infuriated me.

Sometimes, the scientists themselves seemed to be part of the problem. Remember “Ida,” the beautiful Eocene primate fossil? The sensational claims of her being a “missing link” in our own ancestry came from her describers, not their press offices. Likewise, the press release in which palaeontologist John Ruben was quoted as saying (to any vaguely well-informed dinosaur nerd) hugely outlandish things that weren’t even implied, never mind discussed or demonstrated, in the corresponding paper (Quick and Ruben, 2009), could hardly have been all the journalists’ fault.

I was (and still am) angry at such scientists. In my perception, we were at war with anti-science sentiments, and they were playing into the enemy’s hand. Still, it appeared, most of the problem was journalism. Well, this media workshop provided me with a few reality checks. It changed my perspective in some ways, and reinforced my convictions in others. Let me count the ways.

The opening panel in the workshop featured scientists. My first surprise was learning that one of them had absolutely no issue with journalists. He loved making headlines, even if said headlines would make my hair stand on end. He’d found that journalists were generally decent people who want to Get It Right as much as you do.

Then, of course, we got the journalists’ perspective. Their insane work schedules, their pressure to sell stories, their attempt to do so while still retaining accuracy. All in all, they did seem like decent people who wanted to get it right.

But here’s the first problem: given the demands of the job, that can be very difficult to achieve. If, as one of them explained, you might have to report on something even before you’ve had time to actually read the sources, you can very easily make mistakes with the best of intentions.

This is a problem we can help journalists with. Make sure the press office has clear and accurate information so the press release isn’t complete nonsense. When you write a paper, make sure your key points are made clearly and concisely right in the abstract, not in a long and complicated paragraph on page fifteen, where the people writing the news will never see it. If a journalist requests your help, be there to explain and clarify and provide non-wtf quotes. That’s one thing the panellists were very clear about: they need scientists’ cooperation, and they often need it at short notice.

The second problem, I think, is a more fundamental one: scientists and journalists mean something different by “getting it right”. (At least in my idealised world where all scientists think like me. :)) A journalist primarily wants to sell a story, where a scientist primarily wants to increase human knowledge. Of course, scientists also want to sell their stories – no one wants to publish papers that are never cited, and no one wants their career to wither without funding. The crucial difference is, I think, in what each group means by a good news story, and what compromises they are willing to make in order to write one.

For example. To me, direct fossil evidence of how an ancient fish reproduced (Long et al., 2009) is fascinating in itself. I was pretty miffed with the press release accompanying this publication, which turned a relatively mundane finding about the oldest evidence of live birth in vertebrates into a sensational story about the oldest evidence of sex in animals.

If it wasn’t a gigantic digression, I could rant long and hard about all the ways in which this press release mangles science to make it more newsworthy, but the real question is this: does it matter? (To people other than me, I mean.) Is this distortion of facts necessary or even beneficial for getting non-science junkies even a little bit interested? Must we, the scientists, lower our standards of rigour to engage the general public?

Here’s another one. In early 2009, New Scientist ran a controversial feature article about the limitations of the tree of life concept. This article included a discussion of marine ecologist Donald Williamson’s unorthodox hypothesis that the larvae of many animals – which often look very different from their adults and discard most of their baby bodies during metamorphosis – originated from ancient hybridisation events between distantly related critters.

To most people knowledgeable about evolution, genomics or developmental biology, his claims don’t stand up to scrutiny. In our eyes, Williamson is promoting a very implausible hypothesis on weak and superficial evidence. I would only ever bring up his ideas as an example of a “loony theory,” most likely wrong but perhaps interesting from a sociological point of view. But here is a high-profile science magazine, presenting it as an exciting, “different,” and above all, credible alternative to the mainstream view(s) of animal evolution. (In the section on Williamson’s hypothesis, there is no indication of how “fringe” this idea is considered in the scientific community.) The writers at New Scientist were interested in cool stories, and not necessarily in critically examining them.

I see these issues as a fundamental difference between the two professions. I think it’s very difficult to reconcile our demand for accuracy and sound evidence with the journalist’s job. Unlike some audience members at the workshop, I don’t think a formal education in science is necessary to be a good science journalist. Like anything else, a “feel” for science can be picked up by being exposed to lots of it, and scientists are (or should be) there to help out with unfamiliar issues.

However, I do think that we as scientists can’t expect journalists to tell the stories we want them to tell. We can’t expect them not to “dumb things down”, we can’t expect them to respect technical distinctions they don’t see the importance of, and we can’t expect them not to sensationalise a discovery whose true importance is subtle and requires a lot of background knowledge and perhaps a good deal of pre-existing science nerdery to appreciate.

And who knows, maybe the masses reached by sensational news stories are worth a few disillusionments. The angry are always the loudest, and they may not be the majority. I don’t know. But if you are dissatisfied with the way science is represented in the media, griping about journalists to your colleagues isn’t going to solve the problem. This is the age of communication. Anyone can talk to the public. So if you want to change what they hear, why would you wait for others to say the things you want said? Go forth, scientist, and make your voice heard!

***

References:

Quick DE & Ruben JA (2009) Cardio-pulmonary anatomy in theropod dinosaurs: Implications from extant archosaurs. Journal of Morphology 270:1232-1246

Long JA et al. (2009) Devonian arthrodire embryos and the origin of internal fertilization in vertebrates. Nature 457:1124-1127

I has new addiction?

Eduroam is finally letting me play Phylo, a game about aligning DNA sequences. (Woo-hoo! The things that make me happy…) In the game, they are made of coloured blocks, not letters, and there’s an annoying background music you could theoretically turn off but it’s kind of part of the experience. And I can’t. Stop. Playing.

It’s quite interesting, though, in a way.

Things I’ve learnt so far:

1. I have no patience for this shit.

2. Consequently, I suck at DNA sequence alignment.

3. But I’m still better than a computer.

4. Rodents are weird.

It’s a little scary how often and how easily I can beat the computer’s score when I’m not even seriously trying. And there’s not enough excess human brainpower in the world to do all the aligning that needs doing. I suppose the problem is that there isn’t enough computer power either, which is why programmers have to settle for such shitty algorithms in the first place.

I wonder how the same game would look with protein sequences. I guess colour-coding 20 different amino acids would be a little tougher than four bases…

(Hey, idea. Someone should make a game out of Hox gene classification. Wonder if that would solve the problem I spent my undergrad project trying and failing to solve…)