by Matthew Cobb

Well, not completely different. As some of you may know, every week during the academic year, I send out an electronic newsletter to Zoology students at Manchester University, past and present, and to another hundred or so interested people. I just sent out the latest issue of the Z-letter, and one of my readers – Jerry Coyne – replied from Guatemala, or wherever: “Post this WHOLE THING on my website! Including the stuck skunk!” So here you are… If any of you want to subscribe to the Z-letter, send a mail to: cobb at manchester dot ac dot uk

Hello everyone

Here’s the latest Z-letter, with everything from a stuck skunk video to ideas about how morality evolved, including rapping about natural selection… Don’t forget to send in your links! 288 subscribers now!

Matthew

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OPPOSING SLAVERY WITH DARWIN

James Moore, co-author of the recent book “Darwin’s Sacred Cause: Race, Slavery and the Quest for Human Origins”, will be giving a talk about his fascinating discoveries underlying Darwin’s motivations. Everyone is welcome – the talk will be in Roscoe B lecture Theatre, on Brunswick Street, at 5:30pm on Tuesday 20 October. Anyone with any interest in Darwin should go to what will be an excellent talk.

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RAPPING WITH DARWIN

When I first heard about this Darwin-themed event at the Manchester Museum, I was very doubtful – “evolution presented in the style of Eminem”. But Henry McGhie of the Museum, who’s been heavily involved with it, assures me that it really is fantastic. Baba Brinkman explores the history of Darwin’s theory combining hilarious remixes of popular rap songs with clever lyrical storytelling that covers Natural Selection, Sexual Selection, Evolutionary Psychology, and much more. Friday 23 October at 6pm in the Museum.

Baba Brinkman’s page:

http://www.babasword.com/

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THE END OF THE LINE

The new documentary about the fishing industry which was mentioned in the last Z-letter will be shown on More4 at 10:00pm on Tuesday October 20th.

The End of the Line trailer:

http://www.youtube.com/watch?v=bedirwk95Oc

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WHY SPONGES ARE ANIMALS

I had to address this issue in my second year lecture this morning. I was so amazed by some of the stuff I uncovered while researching the talk that I had to blog about it as Jerry Coyne’s guest blogger. See whether you’re equally convinced.

WhyEvolutionIsTrue.com blog:

http://tinyurl.com/yh99scs

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REMOTE CONTROLLED BEETLES

I had to check the date on this one, but no, it’s not date-stamped 1 April. US researchers at Berkeley are apparently able to radio control giant beetles (up to 20cm long) using electrodes implanted when the beetle was a grub. They can be “flown” round a room using a laptop. Although undoubtedly macabre, it isn’t quite so amazing as it sounds, as the electrodes are implanted into the muscles, not the brain. Stimulating the wing muscles on one side rather than the other would make the animal turn. Controlling the neuronal activity leading to that movement would be a lot more difficult, indeed impossible given our current knowledge. [EDIT – How wrong I was! Now I have been able to read the original article – see below, they did indeed plant electrodes into the beetle’s brain, which controlled flight initiation (wing flapping) and elevation (presumably a function of wing vibration speed). Amazing!] However, there are alarming implications of this work, which is being funded by the US military… Sheffield’s Professor Neil Starkey is particularly concerned by this. The work is allegedly reported in Frontiers in INTEGRATIVE Neuroscience (open access, includes movies!)  but I can’t find the original article…

BBC page:

http://news.bbc.co.uk/1/hi/technology/8302903.stm

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ALBATROSS-CAM!

From the EZNews produced by John Altrincham (Leeds): Cameras fitted to albatrosses show that they follow killer whales, perhaps to take advantage of fish flushed to the surface. They also appear to dive in the company of other albatrosses and dive surprisingly infrequently.

BBC page:

http://news.bbc.co.uk/1/hi/sci/tech/8291732.stm

Original Paper in PLoS ONE (open access):

http://tinyurl.com/ygruwwu

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STUCK SKUNK

Oklahoma skunk gets its head stuck in a jar of peanut butter. Will it spray its rescuers?

http://news.bbc.co.uk/1/hi/world/americas/8306488.stm

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THE EVOLUTION OF MORALITY

This is an issue that Darwin (again) was fascinated by, and which is growing in importance. There’s an excellent site by Douglas Allchin of the University of Minnesota which effectively functions as a textbook on the question. Essential reading.

Evolution of Morality site:

http://www1.umn.edu/ships/evolutionofmorality/

Review by me of three books on the question:

http://tinyurl.com/yzclouu

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LIFE

The Big Moment of many people’s week will have been the new BBC natural history series, Life, narrated (but not filmed) by David Attenborough. I found the music incredibly irritating, overblown and unnecessary, but the images are absolutely stunning. (The flying fish were my favourite.) If you’re in the UK, you can still watch it again on line at:

http://tinyurl.com/yghljvv

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THE STRESS OF BEING A PREY

Much of the footage in the first episode of Life was devoted to predation, with scenes of prey animals being chased by hungry predators. What are the physiological effects of such stress on prey animals? An article in a recent issue of Journal of Animal Ecology looks at snowshoe hares.

Magazine article (Sub needed to get past abstract):

http://dx.doi.org/10.1111/j.1365-2656.2009.01602.x

Research article (Sub needed to get past abstract):

http://dx.doi.org/10.1111/j.1365-2656.2009.01552.x

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ATTENTION TENSION

More from John Altrincham: Spiders adjust thread tension to improve their ability to detect prey on the web.

BBC picture:

http://tinyurl.com/yjnbmgc

Proceedings of the Royal Society article (Sub needed to get beyond abstract):

http://dx.doi.org/10.1098/rspb.2009.1583

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THE VEGETARIAN SPIDER

Promised about a month ago by Geoff North, editor of Current Biology and assiduous Z-letter reader, this news of a salticid spider from Central America that is vegetarian. Or nearly. Its primary food are small tender shots of acacia leaves, which are guarded by ants as part of an ant-plant mutualism. The spider can jump over the ants and get the buds. Quite amazing.

WhyEvolutionIsTrue.com blog:

http://tinyurl.com/ylpbouo

BBC page, including video:

http://news.bbc.co.uk/1/hi/sci/tech/8302535.stm

Current Biology News & Views article:

http://dx.doi.org/10.1016/j.cub.2009.08.043

Current Biology research article:

http://dx.doi.org/10.1016/j.cub.2009.08.049

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MASSIVE DINO PRINTS FOUND IN FRANCE

A huge set of dino prints, covering several hectares, has been found in Eastern France. Some of the sauropod traces are over *two metres* wide. That doesn’t mean that the dino’s feet were that wide, of course. The way that prints are preserved in gloopy mud often means that they are much broader than the animal’s feet.

BBC page:

http://news.bbc.co.uk/1/hi/world/europe/8294425.stm

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NAME THAT ANIMAL

This sent in by PhD student Neil Buttery, who spotted it on PopBitch, which is obviously what he surfs when he’s not playing Scrabble on Facebook…

http://tinyurl.com/yjtf2kz

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by Matthew Cobb

Aristotle thought they were plants; for centuries, we have used them to scrub ourselves clean, while millions of kids round the planet think they wear square pants and play with stupid starfish. Nevertheless, sponges are in fact the oldest living animals, one of the most amazing success stories on the planet.

Argument rages over exactly how old the earliest sponge is. Some fossils that are claimed to be sponges have been dated back to around 710 MY ago, but not everyone accepts these. Everyone agrees, however, that they were around shortly before the Cambrian Explosion, around 560MY.

They now cover every part of the ocean, and can account for up to 75% of the biomass on the floor of the Antarctic ocean. 15,000 species have been identified, most of them marine, but there are around 150 freshwater species. There are three main extant groups, and – confusingly – three main body forms, which don’t overlap (i.e. the body forms don’t form distinct evolutionary lineages).

One group of sponges – the Archaeocyaths – flowered briefly (metaphorically speaking) during the Cambrian, but disappeared after around 15 MY. Most sponges are filter feeders, but a few deep sea sponges are carnivorous, spiking tiny crustaceans on their spicules and then absorbing their body contents.

Sponges have no neurons, no muscles, no cell-cell junctions, no gut, no front/back, no reproductive organs.

So what makes them animals?

Studies of DNA show that all the animals – “metazoa” – form what is called a monophyletic group. In other words, all us animals share a common ancestor which is not shared by any other life form. Animals evolved only once, and the earliest branch is the sponges, says the data.

But strictly speaking, that doesn’t make them an animal. They could be some multicellular non-animal, which branched off before the rest of us started on our animally way.

However, recent studies have revealed some amazing things about sponges that clearly place them with the animals – they share fundamental characters with us that no other life-form shares. We can see in the sponge the beginnings of our own way of organizing our bodies and behaving.

They have a simple immune system – a sponge will accept a graft of its own flesh, but will reject that of another sponge. This rejection can be stopped by using an immunosuppressant widely used in medicine. In other words, we share a biochemical pathway that the body uses to distinguish self and non-self.

They show coordinated movement – Ephydatia muelleri, a small sponge, “sneezes” (rather slowly!) when it is agitated or has inedible ink poured over it. This movement can be induced by pouring known animal neurotransmitters over the sponge, showing the sponge cells are sensitive to stuff that we use to activate our neurons.

They may not have neurons, but they have the tiny ion channels that are required to make a neuron work. Express these genes in another organism, and they work.

They have a simple form of the genes required to make neurons. Express these genes in a toad or fly and they start to make neurons there.

This is exactly what we would expect would have happened at the earliest stages of animal multicellularity. Animals didn’t suddenly appear as running, flying, swimming things. Our earliest, multicellular ancestors would have been perfectly adapted to their environment, but would also have used simple forms of cell-cell communication to build their bodies, and to respond to that environment.

Over the vast depths of evolutionary time, those methods were honed and shaped by natural selection, eventually leading to the stupendous array of animal life that the planet has carried, including me, typing these words to you.

But that doesn’t make sponges “primitive”, or in any way lesser beings. They have been on our planet for longer than any other animal – around 10,000 times longer than our species. They have survived repeated mass extinction events, and that suggests they will probably be around for at least another 600 MY. Not bad for an animal that Aristotle took for a plant.

[Added later: Current Biology has this “Quick Guide” to sponges [should be free], while the excellent Tree of Life website has this page on sponges.]

by Matthew Cobb

The “laws” of biology aren’t like the laws of physics, because they deal with stuff that’s alive, which doesn’t always obey the mathematical rigour of a “law”. And when we think we’ve found something that’s hard and fast, there’s generally an exception. So, for example, over 40,000 species of spider have been described, and they are all carnivorous (even if some occasionally sip nectar or eat pollen). “Spiders are carnivorous” would seem to be an appropriate generalization. But it isn’t a law.

Today’s issue of Current Biology [subscription needed] shows why. It features an amazing discovery – a largely herbivorous jumping spider (Salticid) going by the charming name of Bagheera kiplingi (if you don’t know why that’s charming, then you need to either watch or better still read The Jungle Book). This tiny spider has been found in Mexico and Costa Rica.

The spider eats the juicy orange tips (“Beltian bodies”) of the leaves of the acacia tree, which are protected by ants in a classic mutualist relationship (see picture below). First discovered in 2001 by Eric Olsen (Brandeis), and then – independently – in 2007 by a student, Christopher Meehan (Villanova, the spider uses its acute vision and jumping ability to avoid the ant protectors. Both behavioral observations and chemical analysis show that the spider eats the Beltian bodies. However, it is not strictly herbivorous – it will also nibble the odd ant larva.

The article – with Robert Curry (Villanova) as senior author – describes the biology of B. kiplingi and concludes that, paradoxically, the spider was able to make the shift to herbivory only because there was the previously-existing mutualism between the acacia tree and its Pseudomyrmex ant protectors. The ants protect the Beltian bodies very effectively, and only an agile herbivore – like the spider – could get past their protection (download a video here or watch it at the BBC here). Without the ants, more bovine herbivores would easily out-compete the spider.

by Matthew Cobb

There’s an interesting report in Science magazine today [subscription needed] about a meeting held in Gibraltar earlier this month about human evolution. Most of the debate seems to have revolved around the classification of around 28 >500,000 year old fossil hominins from Sima in Spain. Some people argue they were Homo heidelbergensis, generally viewed as an ancestor of the Neandertals.

Science reports that Ian Tattersall, from the American Museum of Natural History, argued that “two or more hominin lineages must have existed side by side in Europe for several hundred thousand years before H. sapiens arrived from Africa. One line led to the Neandertals and may have included the Sima fossils; another, rightly called H. heidelbergensis, went extinct while the Neandertals lived on until at least 30,000 years ago.”

Equally fascinating was the discussion about *how* we came out of Africa, and how many times. We seem to have originated in Africa around about 200,000 years ago, and to have left to colonize the world about 50,000 years ago. But in the “Levant” there are clear signs of co-habitation between humans and neanderthals from 75-130,000 years ago. Some people call this “the failed dispersal”. At the Gibraltar meeting, paleontologist Mike Petraglia (Oxford) summarized archeological evidence – stone tools and so on – that suggests the “failed” dispersal was not such a failure as that.

He argued that human populations may have gone on from the Levant into India and thence to Australia, where we turned up about 40,000 years ago. The archeological evidence suggests we crept along the sea-shore, at about 1km a year… If we didn’t leave the stone tools, who did? Some people at the meeting were skeptical, pointing out that archeology was not biology – without human fossils, you can’t tie the tools to us. As always with scientific arguments, evidence will decide who’s right and who’s wrong.

(Source: Michael Petraglia)