Friday, 28 February 2014

Kings of the New World (3): The Black Caiman

by Rob Cooper

Picture a set of black jaws emerging from the water as you stoop to drink; the consummate ease with which they move through the air belaying the sluggish appearance of the creature it belongs to as they close around your throat. Unfortunately this is far from the killing blow. The teeth of crocodilians are designed to grab and hold not to pierce or crush despite there being enough force to shatter bone. You are dragged into the waters of the amazon desperately flailing, held captive by a creature both far more at home and more powerful than you. Your dreaded captor then allows itself to sink dragging you along for the ride. The truth will soon emerge that crocodilians rarely actually kill their prey they simply immerse them in the lethal waterways they call home. The final of the great Amazonian predators is itself a living fossil. The black caiman is one of largest extant reptiles and is the largest predator in the amazon Basin. Akin to all modern crocodiles the black caiman shows little deviance from the genesis of the crocodilians over 200 million years ago. This giant reptile can. In some areas, routinely reach lengths of 4-5 metres and can reportedly reach 6 metres long and weigh over a tonne. 

In an earlier article I highlighted how the Jaguar often preys on the various caiman species in its environments. The black caiman however is the one exceptions. Whilst juvenile caiman are eaten by all manner of predators including snakes, storks and other caimans the adults have no natural enemies other than man and can be up to ten times the size of the Jaguar, putting them firmly off the menu.

As the caiman grow their diet shifts quiet remarkably. Young caimans eat crustaceans and insects than graduate to eating fish such as piranha and catfish and the adults often hunt large mammals that come to drink at the water’s edge such as Tapir, capybara, deer and jaguar. This is an example of different aged animals occupying different niches in order to reduce intraspecific competition (between members of the same species). The advantage of having less competition is that there is more food available to each individual because fewer organisms are taking a share so genes and behaviour promoting this system is perpetuated by natural selection.

Caiman also show a great deal of motherly attention. Mother caiman are well documented to help the hatchlings out of their eggs upon hearing their characteristic squeaking sound from within the egg. The young caiman upon hatching from the nest form a pod that is protected from predators by the presence of a large female. Pods can also contain individuals from other nests who became separated from their siblings. This behaviour has led to a great deal of speculation about the parental habits of dinosaurs as the brains of crocodilians share many features with that of therapod dinosaurs such as Allosaurus and Tyrannosaurus; many more similarities than when compared to birds, the other close relative of dinosaurs.

Unfortunately the black caiman recently nearly went the same way as the dinosaurs. Between 1950 and 1970 (when the species was classified as endangered) hunting decimated the populations in South America in order to collect its commercially valuable hide. Fortunately since then the black caiman populations have been increasing although conservation efforts face a problem when the creature in question is large and dangerous and according to the locals can regularly predate upon humans of all ages as well as dogs and livestock of any size. Normally people tend to be removed from the habitats of the black caiman but some groups such as the Rupununi River people live on the river itself in one of the last strongholds of the black caiman and live their lives fearing attacks from the deep and mourning loved ones lost to the primeval reptiles. Clearly such a struggle between man and beast is not easy to resolve.

The ancient giant Purussaurus
But what makes the black caiman stand out from contemporary crocodiles such as the American alligator or the Nile crocodile? Apart from being the largest member of the alligator family the black caiman in particular has a spectacularly large head even amongst crocodilians. A 3.9 metre long black caiman has a significantly longer skull than a 4.8 metre Nile crocodile. This adaption is thought to be geared towards the taking of larger prey items but there are few statistical studies due to low level of information regarding the black caiman. In addition most caiman species are characterised by large skull sizes without specifically taking large prey items, although other species could be limited by body size. The giant extinct caiman Purussaurus, which died out merely 8 million years ago, took this adaption to its zenith with a titanic 1.4 metre long skull on its 11-12 metre body. The black caiman is the closest organism we have today to such giants.

As I alluded to in the first paragraph the killing strategy of these caiman is something very reminiscent of a horror movie. The kill is not quick or clean; but it is very efficient. The teeth of all crocodilians, the caiman included are conical and sharp but not serrated. These teeth can trap small slippery prey such as fish to be swallowed hole and firmly keep hold of larger prey such as a tapir in order to drag it under water where the prey can be safely drowned without the predator having to grapple too closely with the prey species or evolve ways of killing them. All the caiman needs is its impressive skull and 1900 newton bite force to finish of almost any prey item equipping them to tackle all prey items in their environment including other caimans. 

What can we learn from the black caiman then? Firstly I think it is both thrilling and terrifying to consider the great rainforests of the world still harbour such impressive wildlife. Secondly that conservation isn’t always the simplest matter in the world. It would be lovely if we could protect all wildlife still remaining but the harrowing stories of natives eaten by black caiman remind us of a past time when man really was at the mercy of the bigger, more powerful animals around him. Finally the most positive message is that we can save animal species. One simple change in the law to prevent hunting of black caiman has saved the species from an untimely demise and that is a promising message for the future. For all his capacity to do wrong man also has the capacity to do good. 

Monday, 24 February 2014

Liquid crystals: revolutionary science

by Toby Benham

Once a scientific curiosity on the fringes of scientific research, the liquid crystal industry is now estimated to be worth around £56 billion. They are essential to everyday items such as mobile phones, laptops and televisions in creating liquid crystal displays (LCD). Although the UK doesn't profit largely from the industry, all these technologies can be accredited to the breakthrough made by the late British Professor George Gray of Hull University and the research his team conducted in the 1970s.

Originally shunned financial support for his research, it was the minister for technology, John Stonehouse, who initiated the advance in the field. He wanted a technology to replace the expensive cathode ray tubes causing a hole in the Ministry of Defence's budget in producing flat screen colour displays. Liquid crystals were known but little appreciated. They can be described as anisotropic molecules with long range orientational order and some degree of liquid like order. In other words they possess crystalline structure while still maintaining the ability to flow like a fluid in certain directions. This means that they interact with light differently in different directions due to differences in polarisability. The main reason that they are so useful is because applying an electric field can lead to a switch in alignment of the crystal. This feature can be exploited to display different colours when different voltages are applied.

By 1973, Gray and his team had been  able to exploit this, having synthesised a new class of liquid crystals called cyanobiphenyls which were stable, yet still “flippable”. The first liquid crystal devices appeared the following year and Gray became a Professor of Organic Chemistry. Described as a brilliant teacher, most of his students went on to leading positions in industry and academe.

He was appointed CBE in 1991, but his favourite prize was reportedly having a train named in his honour. Gray never won the Nobel Prize and is little known but should be remembered as a British great who contributed much not only to his field of science but to modern day life. Liquid crystals are of great use with so many applications and the field is in constant development of what Gray started. 

Wednesday, 19 February 2014

Whale spotting from space

How many whales exist in our oceans? Land based methods of counting whales can require trained researchers spending hours of their time recording numbers and this can be costly and inefficient. Now high resolution satellite imagery has been used in an attempt to count whale numbers from space.  Peter Fretwell and colleagues counted Southern right whales in part of the Golfo Nuevo in Argentina. It appears certain species of whale may be easy to locate from space making this a perfect technique.  This will help us gain important information about prey populations and their marine ecosystem. Hopefully this new technique can now be used for various whale species to give an accurate prediction of numbers.

More information

Saturday, 15 February 2014

Kings of the New World (2): The Green Anaconda

by Rob Cooper

In the modern world snakes are often associated with malice and deception relating back to figures such as the snake from the Garden of Eden and the Medusa slain by Perseus in Greek mythology. But is this reputation deserved? After all, in many lesser exposed cultures, such as those of ancient Egyptians, snakes are esteemed symbols of nature, power and worship and many modern cultures still worship snakes to this day. Perhaps the most infamous of all snakes is the Green Anaconda for its enormous size and power. In this article I will analyse if its malign reputation is well deserved.

The Green Anaconda is generally considered to be the heaviest snake in the world. Whilst the reticulated python can reach 7.5 meters in length a 5 meter anaconda would still outweigh the python.  Anacondas show a large degree of difference in size between the sexes (sexual dimorphism) and the largest individual ever officially measured was a female 521cm long and 97.5kg in weight. It has been estimated that female anacondas have a maximum length of 6.7 meters before they can no longer reproduce. However there are numerous tales of titanic snakes stretching to lengths of 12 meters have been described by travellers. Although it is telling that a $50,000 dollar prize for a snake over 9.1 meters in length is as of yet unclaimed. 

Female anaconda alongside male, showing sexual-dimorphism
Anacondas show remarkable growth over their thirty year life spans and the average adult is 500 times larger than it was as a hatchling. To put that into context the average human new born is 3.4kg making the average adult 1.7 tonnes… If we followed the growth pattern of anacondas, which we fortunately do not. Anaconda mating also brings us to a rather sinister tendency of females to cannibalise males. Even more harrowing (for a male anaconda) is that most cases have shown that the female had recently finished breeding leading to an unsettling hypothesis that opportunistic females cannibalise their mate in order to supply nutrients for the development of the embryo. 

Much like the Jaguar, the anaconda is very at home in water and has both its eyes and nostrils situated on the top of its head allowing it to breathe and see its prey whilst remaining underwater. Belaying their sluggish nature on land anacondas are very strong swimmers although they are often known to drift down faster flowing rivers and swim to the side once they have found a favourable locations. The anaconda eats any species that it can restrain and commonly predates on smaller caiman species, deer, capybara, dogs, sheep, tapir and even Jaguar and humans on occasion, although attacks on humans are very rare. Like all snakes their metabolism is remarkably slow and they can often go one or two months between meals. The record is held by a captive anaconda that didn't eat for an entire two years. 

A member of the boa family (and often known as ‘the water boa’) the anaconda shares a typical attack style with the other members of the family. Firstly the snake latches its jaw onto the prey item in order to pin it between over 100 razor sharp recurved teeth which point back into the snake’s throat keenly preventing the animal from escaping. The snake then wraps first one, then two coils around the prey item. In a nightmarish turn, every time the prey item breathes out the coils tighten making it harder and harder to breathe. An adult anaconda is capable of squeezing with around 65,000 Pascal’s of pressure which is roughly equivalent to having a single decker bus being supported by the human chest (if we assume humans as the prey item in question). This, it hardly needs saying, is rather impressive for any animal, let alone one that is relatively small. The force that the enormous titanaboa (extinct snake, estimated at over a tonne in weight) could have exerted hardly bears thinking about. 

Documented attacks of anaconda on humans are rather rare which is perhaps due to low population density in areas were anacondas are common and their habit of hunting nocturnally in the water which limits the human contact they receive. However there are several recorded attacks on field researchers. These attacks also seem to be predatory as the snakes are not disturbed prior to the attacks and were known to follow the target for several meters still submerged and so able to make a safe escape. It is also often the case that large disturbed snakes are often docile and rarely try to bite even when handled, although they will resist when being restrained and moved. The snakes also seem picky with targets, so far the only recorded attacks have been on smaller individuals who fall inside the weight range of anaconda prey and larger individuals have been ignored possibly due to being too large for the anaconda to swallow. All documented attacks have also occurred in areas that are seldom travelled by people. 

This suggests that the anaconda seems to have no fear of predating on people, which a trait uncommon to most mammalian predators yet strangely manifested in some reptilian predators such as crocodilians. Does this suggest that the anaconda is the monster that it is made out to be by the numerous horror films snakes feature in? I would maintain not. The anaconda is simply a generalist and humans, which it encounters rarely, which happen to fall within its prey size range are simply a good way of recovering the energy deficit inflicted by giving birth or from long periods of starvation. 

The anaconda is a remarkable and terrifying creature but should it not be the goal of man to be able to look past simple emotional reactions and remember that, whilst intimidating, the anaconda has a majesty all of its own and is an animal just like any other and if any form of right to life exists the anaconda is just as deserving as we are.

Thursday, 13 February 2014

Dementia: is a cure around the corner?

by Jonathan Smith

Amidst regular breaking news stories of promising developments in the fight against dementia, we’re still no closer to being able to stop its progression. The company that finds a cure for dementia would not only start a revolution in treatments, but also make huge profits doing so. If this is the case, then why are we still waiting for effective treatments after decades of research into this oppressive disease? 

Prevalence and treatments for dementia

It’s no secret that dementia is a widespread condition. According to the Alzheimer’s Society, the established prevalence of dementia for 70-79 years is 1 in 25. For those over 80, the rate soars to 1 in 6. Considering the colossal cost to healthcare systems worldwide, the potential benefits of finding an effective treatment far outweigh the cost of making it. However, the current treatments available for dementia are minimal. Drugs such as Donepezil, Galantamine and Memantine serve to temporarily reduce the cognitive impairment caused by Alzheimer’s Disease, but do not target the pathology directly. This means that the more advanced cases eventually cease responding to treatment altogether. The brain tissue is just too damaged to salvage by then. What is desperately needed is a treatment that can actually alter the disease itself, resulting in a slower or even halted progression.

It’s not as if pharmaceutical companies haven’t been trying to find disease-modifying treatments of course. Last year the drug Semagecestat failed a massive clinical trial in Alzheimer’s Disease patients. It turned out that patients actually got worse with the drug! In the same year, the catchily-named drug LY2886721 was withdrawn from development due to abnormal liver tests in some trial patients. And failures are costly in the pharmaceutical business. Getting a drug to market can cost millions of pounds and can take over a decade for a company. Thus in the UK at least, industrial research into dementia treatments is getting less funding than ever. This still leaves the question: Why have the drugs failed to work? 

Understanding the neuropathology in dementia

The only simple answer so far is that, being a neurological disease, dementia is an extremely complex puzzle to unravel. Take Alzheimer’s Disease for example. A popular hypothesis of its origin is called the Amyloid Cascade Hypothesis. This suggests that the protein Amyloid-beta starts to get produced abnormally in the brain and clumps together outside cells, gradually causing neurons to malfunction and degenerate, resulting in the symptoms we see in Alzheimer’s Disease. One key piece of evidence for this is that a small proportion of patients get early-onset Alzheimer’s Disease and they all have hereditary mutations causing huge amounts of amyloid-beta production. Not only that, but Down’s Syndrome is also associated with amyloid-beta and guess what? Down’s Syndrome sufferers have a high risk of developing Alzheimer’s Disease. From this evidence, it appeared that a good way to slow Alzheimer’s Disease is by reducing the amyloid-beta production in the brain. As shown by Semagecestat and other failed amyloid-beta-modifying compounds, it turned out to be not that simple.

For one thing, Amyloid-beta is not the only factor to consider in Alzheimer’s Disease. There are many other hypotheses regarding other proteins and cellular systems involved in the symptoms of Alzheimer’s Disease. The result is a rather confusing jumble of different pathologies that neatly overlap with many other types of dementia, such as Vascular Dementia. Additionally, the stage of dementia is a massive factor. Current treatments stop working because there is so much damage to our brain tissue. Perhaps this is also the case with disease-modifying treatments? What if the only way to slow dementia is to tackle it before it causes extensive damage? To investigate this possibility, companies such as Merck are trialling previously failed drugs in patients with early-stage dementia. 

 Amyloid-beta protein
Another consideration is that the best way to trial a treatment early on is to test it in animals like mice and rats. In order to show its effects, we clearly need to give the animal dementia first. To give mice dementia, we first have to insert the mutated genes involved in amyloid-beta production into mice, straight from early-onset patients. As it turns out, it’s really difficult to make mice with Alzheimer’s Disease using genes selected from these patients. Firstly, the vast majority of Alzheimer’s sufferers have no such mutation and secondly, most mouse models of Alzheimer’s Disease show only bits of the condition. Some are cognitively impaired in some tests, others show amyloid-beta clumps, however, none show Alzheimer’s Disease in its entirety. It’s for this reason that many sensational headline cures for dementia found in rodents remain in rodents. It’s just not possible to perfectly translate a complex condition like dementia between rodents and humans. At least, not at the moment.

A cure is around a corner

Despite the recent setbacks in clinical trials, researchers are increasing our knowledge about developing treatments for dementia. Not only that, but steps are being made in improving the diagnosis of Alzheimer’s Disease early on, perhaps at a stage when a difference can be made to the outcome. As animal models of dementia are improved, we can begin to make better translation between animals and human patients. Furthermore, if as much funding for dementia is poured into these efforts as there is for cancer studies, we can increase the speed at which really effective treatments become available. For now, though, the best ways to reduce the risk of dementia are through a balanced diet, regular exercise and regular glasses of red wine!

Monday, 10 February 2014

Is it safe to reuse plastic bottles?

by Rachel Argo

Typically, I will buy a bottle of water and re-use it until I loose it. We all know that re-using a plastic bottle is good for both the environment and our pockets, but by doing this are we increasing our risk of exposure to ‘dangerous’ chemicals in the plastics? Recently bottles have been designed and marketed as being ‘BPA free’. But what is BPA and why have we never heard of it before?

Maybe you have seen strange shaped bottles with coloured filters appearing in people’s handbags, at the gym or on the high street? ‘Bobble’ bottles are an example of these BPA free plastic products. They are made from recycled materials, are recyclable and contain replaceable filters that claim to remove impurities in the water and improve the taste. Bisphenol A (BPA) is a synthetic organic molecule that is used to make certain plastics such as ‘polycarbonate’. Polycarbonate is commonly used to make household items like drinks bottles and tupperware. BPA is also found in epoxy resins that are used to line drinks cans and tins. We come into contact with plastic all the time and admittedly it would be very difficult to exclude from our day-to-day lives. Until recently no one questioned the effect of this plastic heavy lifestyle on our health, so should we stop re-using that water bottle and buy a BPA free one?

Studies have suggested that BPA possesses the ability to pass from the containers to the food or beverages inside. The concern around this possible seeping stems from the chemical’s ability to act as a mimic of the hormone oestradiol and therefore have potential to interrupt hormone patterns and signaling pathways. Animal studies in rats and mice have linked BPA exposure to a range of health problems such as obesity, fertility impairment, respiratory disorders and inflammation, however there is little or no research into the effects on humans and no single study that conclusively proves that BPA is the cause of these diseases. 

A review in 2006 by the European Food Safety Authority (EFSA), concluded that the Tolerable Daily Intake (TDI) of BPA was 0.05 mg/kg body weight/day. This value is an estimation of the amount of BPA that can be ingested per day per kg of body weight daily, over a lifetime without significant risk to health. BPA is licensed by the EU for use in food contact materials, however a directive in January 2011 prevented the use of BPA containing plastics in the manufacture of baby bottles. The most recent review of the molecule’s safety (July 2013) provisionally suggests that diet is the main source of exposure, that the estimation of this exposure is much lower than EFSAs previous estimations and well below the suggested TDIs. 

Due to the lack of conclusive evidence of BPA safety in humans and changing opinion on TDI values, it is hard to decide if it is worth investing in a BPA free bottle. I initially thought that this was a trendy case of false science, but on closer inspection it seems there may be some truth in their safety claims even if we have not established the extent of it.