Science round-up: sawfish, exfoliation, extinction and evolution.

This week’s science highlights include:

  • understanding how sawfish use their seemingly ungainly and cumbersome saw;
  • spying on bears in the bath;
  • rates of climate change-induced extinction of tropical birds; and
  • the oldest fossil with a notochord.

It's a sawfish. (Image: ABC news)


These fish live in tropical marine environments and were previously thought to feed off the bottom. Researchers from the University of Western Australia have observed the feeding methods (linky) of these odd-looking fish and found that they do actually feed via attacking fish swimming above them with their saw, in addition to eating things off the bottom. Sawfish are endangered, so understanding their ecology is important. A quote from lead author Barbara Wueringer: ‘When the animals encountered prey in the water column, they lifted themself off the bottom and vigorously waved their saw around’. I know it’s a saw, not a sword, but that gives me a mental image of a sawfish shouting “on guard!” before running its saw through its prey.


A brown bear in Alaska has been observed using a rock to scratch itself, in the first recorded instance of a bear using a tool. The bear was sitting in shallow water and was seen using barnacle-covered rocks for the purpose of scratching its face, presumably to assist with removing fur being moulted.

Bear scratching using rock. (Image: New Scientist website)


New climate models predict that up to 900 species of tropical birds could be at risk of extinction by the end of the century. The models included at 3.5 deg C increase in average global temperature and found that this increase may mean curtains for many species. Only a small proportion of birds are migratory, and tropical birds are usually not migratory at all. This means that they will have to move up altitude gradients (higher altitudes = cooler temperatures), putting them on an ‘escalator to extinction’. Presumably, this escalator will have fewer guitar solos than a stairway to heaven. Seriously, however, this also means that other tropical organisms are also likely to be at the same high risk of extinction as the birds.


From the fossil awesomeness of the Burgess Shale we have the oldest known organism to have a notochord. Pikaia gracilens was an ell-like organism about 5cm long. And it while it was first discovered about a century ago, it is only now using new diagnostic techniques that researchers have identified that it did indeed have a notochord. But why is this important? The notochord a structure that runs down the back of all chordates (an ‘evolutionary forerunner’ to the vertebral column) and is the thing that all vertebrates have but that invertebrates do not. So, notionally, in simplistic terms P. gracilens could be our ancestor. In actual fact, it is probably not directly related to humans in the strict sense, but it does show that notochords have been in existence for longer than previously thought as these creatures are about 530 million years old.

Final rant:

I read the information about P. gracilens on the New Scientist website, then saw it again on a news website owned by media conglomerate News Ltd. This company, apart from phone hacking scandals in the UK, owns many of the tabloid newspapers in Australia and much of the content of the newspapers and their websites is in typical sensationalist tabloid style. But I’ve had my hackles raised a few times over the past couple of weeks by the way News Ltd articles have been written (and nearly got myself caught in a stoush on Facebook over one particular article). The P. gracilens news piece is an example of the typical inflammatory style of writing, designed to be divisive and controversial, that really pisses me off. The headline on the News Ltd story: “Humans ‘evolved from worm creature'”. The first sentence: “SCIENTISTS now believe humans evolved from a five-centimetre-long worm-like creature that wriggled in the sea more than 500 million years ago.” No, they don’t. The journal article, on which the media release and subsequent news items is based, makes absolutely no mention of anyone “believing” anything. I’m sick of this kind of crappy journalism, appealing to the lowest common denominator. aaarrrgghhhhh!





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