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400 million years ago jawless vertebrates filled the oceans but today they are limited to only a few species: boneless, parasitic creatures such as lampreys and hagfishes.

So what happened to this ‘lost tribe’ of ancient mariners? Were they the victims of environmental change or thrust aside by jawed newcomers? And how did fish evolve jaws anyway?

Research reported in this week's Nature, by a team including Oxford University scientists, investigates the rise of jawed fish and gives us an ideal jumping off point to imagine what a dive through the ancient oceans would be like.

Voyage to the Silurian
‘A scuba diver transplanted to the Silurian would find the kinds of vertebrates swimming around in those ancient seas alien and unfamiliar,’ Matt Friedman of Oxford University’s Department of Earth Sciences, co-author of the Nature paper tells me. ‘At this time, jaw-bearing creatures with backbones (our closest relatives) were something of an oddity, with most vertebrate diversity tied up in various groups of bizarre armoured fishes without jaws.’

These jawless fishes were the ‘ostracoderms’ (‘bony skinned ones’), so called because they were covered in a protective armour made out of plates of bone. Typically between 15 and 60cm long, they had gills and balancing organs, and are thought to have sucked food into their mouths using a muscular pharynx.

They shared the balmy Silurian and Devonian seas with some familiar neighbours, such as sea lilies, snails, and corals, but also more bizarre animals; trilobites, giant predatory sea scorpions (at up to two metres across enough to give any time-travelling diver a fright) and the shelled relatives of squid and octopus - of which the chambered nautilus is the only surviving example.

Ostracoderms seem to have largely been slow-moving creatures that carved out a living at or near the sea floor. They were perhaps well placed to make the most of the vast, shallow oceans which washed over what are now continents due to higher sea levels in comparison to those of today.

‘I think by any reasonable measure you could argue that jawless fishes were pretty successful in the seas of the Silurian and Early Devonian,’ Matt comments. ‘There were many different kinds, and there were considerable anatomical and structural differences between those groups, suggesting a range of ecologies and habits.

‘These armoured ostracoderms seem to have been the dominant group of fish for the better part of 100 million years – by comparison mammals have only been the dominant group of land-living vertebrates for about 65 million years.’

The first jaws
Yet some members of this group began to change, evolving new kinds of mouthparts that would soon set them apart as ‘gnathostomes’ (‘jawed mouth ones’).

‘The closest extinct relatives of jawed fishes, and indeed the most primitive gnathostomes, all seem to have been bottom-feeding mud-grubbers,’ Matt explains. ‘Saying for certain why any new body-part evolves is always fraught with difficulty but perhaps the most straightforward explanation here is that jaws evolved as a means of helping regulate water flow through the mouth and throat.

‘It would have made good sense for them to develop a better way of controlling suction by elaborating the structures surrounding the mouth opening. These same components could then subsequently be modified - particularly after the origin of teeth - to take on a series of brand-new roles such as shell crushing, flesh biting, and more.’

These developments took place at a time of exceptional environmental change, with a major rise in oxygen levels in the atmosphere and then, towards the end of the Devonian, a series of extinction events which hit reefs first and later decimated vertebrate populations. Yet what exactly caused these extinctions, if it was one or a series of factors, is unclear.

Theories about the decline of jawless fishes have focused on either their response to these environmental changes or their being eaten or supplanted by their jawed cousins.

Decline and diversity
In Nature Matt and colleagues report how they put these theories to the test by analysing the functional diversity of early gnathostome jaws. They found that jawed vertebrates achieved high levels of functional - and probably ecological - diversity by the earliest Devonian, when they were still minor players compared to ostracoderms.

‘As it turns out, the range of jaw types in communities with many jawless fishes is indistinguishable from the diversity of mandibles in communities with few or no jawless fishes, and this diversity hardly changes during the Devonian. Collectively, these results cast serious doubt on the idea that the diversification of gnathostomes primarily reflected that group ‘taking over’ ecological roles previously held by ostracoderms,’ Matt tells me.

‘Jaws certainly opened up a series of new opportunities for gnathostomes, but that’s not all. In comparison to ostracoderms, which seem to have largely been slow-moving creatures living at or near the bottom, gnathostomes include many forms that were clearly powerful, active swimmers, suggesting that they were doing something totally different from their jawless predecessors.’

So perhaps it was this different lifestyle, rather than the superiority of jaws themselves, which enabled gnathostomes to weather the stormy waters of Devonian evolution.

Intriguingly, it may even be that it was events on land that would determine the fate of ancient fish: in particular the appearance of forests in the mid-Devonian.

‘In a roundabout way this probably did have a major influence on the future trajectory of jawed fish evolution. With the establishment of productive ecosystems on land, there was plenty of motivation for some fishes to start exploring the world at the water’s edge, and begin to make the transition to life on land,’ Matt comments.

‘These early explorers are, of course, the precursors of terrestrial vertebrates, including humans. This is a huge part of the evolutionary success of jawed fishes, because, in essence, half of jawed fishes alive today have arms and legs and live on dry land!’   

A set of glasses packed with technology normally seen in smartphones and games consoles is the main draw at one of the featured stands at this year’s Royal Society Summer Science Exhibition.

But the exhibit isn’t about the latest gadget must-have, it’s all about aiding those with poor vision and giving them greater independence.

‘We want to be able to enhance vision in those who’ve lost it or who have little left or almost none,’ explains Dr Stephen Hicks of the Department of Clinical Neurology at Oxford University. ‘The glasses should allow people to be more independent – finding their own directions and signposts, and spotting warning signals,’ he says.

Technology developed for mobile phones and computer gaming – such as video cameras, position detectors, face recognition and tracking software, and depth sensors – is now readily and cheaply available. So Oxford researchers have been looking at ways that this technology can be combined into a normal-looking pair of glasses to help those who might have just a small area of vision left, have cloudy or blurry vision, or can’t process detailed images.

The glasses should be appropriate for common types of visual impairment such as age-related macular degeneration and diabetic retinopathy. NHS Choices estimates around 30% of people who are over 75 have early signs of age-related macular degeneration, and about 7% have more advanced forms.

‘The types of poor vision we are talking about are where you might be able to see your own hand moving in front of you, but you can’t define the fingers,’ explains Stephen.

The glasses have video cameras mounted at the corners to capture what the wearer is looking at, while a display of tiny lights embedded in the see-through lenses of the glasses feed back extra information about objects, people or obstacles in view.

In between, a smartphone-type computer running in your pocket recognises objects in the video image or tracks where a person is, driving the lights in the display in real time.

The extra information the glasses display about their surroundings should allow people to navigate round a room, pick out the most relevant things and locate objects placed nearby.

‘The glasses must look discrete, allow eye contact between people and present a simplified image to people with poor vision, to help them maintain independence in life,’ says Stephen. These guiding principles are important for coming up with an aid that is acceptable for people to wear in public, with eye contact being so important in social relationships, he explains.

The see-through display means other people can see you, while different light colours might allow different types of information to be fed back to the wearer, Stephen says. You could have different colours for people, or important objects, and brightness could tell you how near things were.

Stephen even suggests it may be possible for the technology to read back newspaper headlines. He says something called optical character recognition is coming on, so it possible to foresee a computer distinguishing headlines from a video image then have these read back to the wearer through earphones coming with the glasses. A whole stream of such ideas and uses are possible, he suggests. There are barcode readers in some mobile phones that download the prices of products; such barcode and price tag readers could also be useful additions to the glasses.

Stephen believes these hi-tech glasses can be realised for similar costs as smartphones – around £500. For comparison, a guide dog costs around £25-30,000 to train, he estimates.

He adds that people will have to get used to the extra information relayed on the glasses’ display, but that it might be similar to physiotherapy – the glasses will need to be tailored for individuals, their vision and their needs, and it will take a bit of time and practise to start seeing the benefits.

The exhibit at the Royal Society will take visitors through how the technology will work. ‘The primary aim is to simulate the experience of a visual prosthetic to give people an idea of what can be seen and how it might look,’ Stephen says.

A giant screen with video images of the exhibition floor itself will show people-tracking and depth perception at work. Another screen will invite visitors to see how good they are at navigating with this information. A small display added to the lenses of ski goggles should give people sufficient information to find their way round a set of tasks. An early prototype of a transparent LED array for the eventual glasses will also be on display.

All of this is very much at an early stage. The group is still assembling prototypes of their glasses. But as well as being one of the featured stands at the Royal Society’s exhibition, they have funding from the National Institute of Health Research to do a year-long feasibility study and plan to try out early systems with a few people in their own homes later this year.

The Royal Society’s Summer Science Exhibition begins today and runs all week until Sunday 10 July. It includes 20 exhibits showing some of the latest UK science that is changing our world and gives the chance to talk to and question the researchers involved.

Half the elephants from West and Central African savannahs have vanished in the past 40 years, scientists report in PLoS One.

A team, including Iain Douglas-Hamilton of Oxford University’s Department of Zoology, estimate that around 7,750 elephants remain in the Sudano-Sahelian zone, which covers 20% of the continent, a 50% decline in four decades.

Of the 23 elephant populations studied half are now thought to number fewer than 200 animals and so are unlikely to survive. The survey covered protected areas so populations in unprotected regions are likely to have fared even worse.

A reduction in rainfall and increasing competition with humans for land and water resources used for livestock and agriculture are, the researchers believe, the main factors behind the decline. Warfare and the illegal trade in ivory have also helped to drive some elephant populations to the brink of extinction.

The loss of these elephant populations would affect many other species which rely on the habitat created by these giant herbivores as they browse, clear the brush and disperse seeds.

To protect the remaining animals the researchers propose that eight new protective corridors be established as soon as possible to connect the main elephant populations.

They also recommend working with private sector wildlife initiatives and channelling more wildlife revenues to local communities as a way of securing the future for elephants on Africa’s northern savannahs.

The mechanisms used by the brain to distinguish contrasting sounds may be similar to those used to visually pick out a face in the crowd.

Scientists at Oxford University’s Department of Physiology, Anatomy and Genetics are studying the ways in which sound is represented in the brain and their latest research, published in the journal Neuron, looks at how the brain’s nerve cells respond to sounds heard under different conditions.

The study, carried out by Neil Rabinowitz, Ben Willmore, Jan Schnupp and Andrew King, shows that neurons in the auditory cortex of the ferret's brain adjust their activity to compensate for the contrast between a sound and its background. Examples in human terms could be situations where the underlying environment is silent or very quiet - such as the countryside at night - or very loud, as in a busy pub or high street.

This is known as contrast gain control, a mechanism that our visual systems are thought to use to help focus attention on a particular object. Professor King says: ‘There could be a similar mechanism in the auditory system for picking out sounds of interest against a background of other sounds of different frequencies.’

The research is contributing to the efforts of Professor King’s group to unravel the way the brain processes sound. ‘Auditory scenes around us are changing all the time. We are interested in how our experience of this influences the way information is processed in the brain, and whether that helps to maintain a reliable perception of where and what a sound is under different listening conditions.’

These findings could have significance for our understanding of how the brain compensates for partial loss of hearing and, in time, have implications for the development of cochlear implants and hearing aids.

‘For cochlear implants and hearing aids to work the brain must be able to re-learn how to interpret sounds that have been restored,’ Professor King explains.

Professor King and his team have already shown that the brain can compensate for partial hearing loss. In research published last year, human subjects wore an earplug in one ear and were asked to identify which of several speakers was producing a sound.

‘Our ability to place sound relies on the comparison of signals between our two ears and when tested, when the earplug was first worn, subjects were very poor at locating the sound. But with practice several times a day for a week they re-learnt how to localise the sounds and once again became very accurate. In other words although the inputs received by the brain had changed, by practising the task, the study showed that we can recover from partial hearing loss.’

Professor King and colleagues are working closely with clinicians and with the hearing charities Deafness Research UK and Action on Hearing Loss (RNID), which aim to help those suffering hearing loss.

‘We hope our work will lead to improvements in the design of devices aimed at restoring hearing. Being aware of the plasticity or adaptability of the brain is important in understanding our ability to respond to hearing loss.’

Back in World War II there was a clever idea to use icebergs as floating aircraft carriers, but now we know birds of prey got there first.

A recent study that tracked the seasonal movements of 48 gyrfalcons with radio transmitters showed that some birds spent most of the winter over the ocean, probably using sea ice and icebergs as floating bases to hunt from.

A report of the research is published in the journal Ibis.

Kurt Burnham, who led the research whilst at Oxford University’s Edward Grey Institute and now runs the High Arctic Institute, told Matt Walker at BBC Nature:
‘I was very surprised by this finding… These birds are not moving between land masses, but actually using the ice floes or pack ice as winter habitat for extended periods of time.'

It’s almost unheard of for a land-based predatory bird to behave in this way, the only other example is the Snowy Owl, which is known to spend up to three months living on sea ice. An abundance of prey such as gulls, black guillemots, and sea ducks are believed to tempt the gyrfalcons into adopting this unusual lifestyle.

‘In the big picture this shows how adaptable and mobile gyrfalcons have to be in order to survive and reproduce in the harsh arctic environment they live in,’ Kurt comments.

The Edward Grey Institute is part of Oxford University's Department of Zoology.