28 March 2012

The world's smallest dog ever is born

About three weeks ago Beyonce, a Miniscule Dachshund cross, was born in the Grace Foundation Animal Shelter, California. Beyonce was so small when she was born that she fitted into a tablespoon and at just 10cm in length, she is smaller than a credit card or an iPhone! This makes Beyonce smaller than Boo Boo, a 10.16cm chihuahua, who currently holds the Guinness World Record for being the smallest dog ever and her application to Guinness has been submitted.

Beyonce was the last puppy to be born from a litter of five and was critically ill when she was born, which is not surprising really given her small size. Thankfully however, vets were able to help Beyonce using chest compressions and, amazingly, mouth-to-mouth resuscitation! As a result, Beyonce has cheated death 4 times and is doing fine at the animal shelter and will be available for adoption, along with her mother and siblings, within a couple of months.

Beyonce, the world's smallest dog ever!

Humans: the world's only super predator?

Everyone is familiar with how predators and prey interact with each other - predators try to eat prey species and prey species, which do not want to be eaten, fight back or run away. These interactions have led to an 'evolutionary arms race' between predators and prey: where predators evolve adaptations, such as weapons, to help them kill their prey; and their prey evolve defences to counteract these weapons.

A good example of this is the cheetah, which has evolved to be able to run extremely quickly in order to catch gazelle, their main source of prey. Gazelle have worked out that they cannot outrun cheetahs, which are the fastest land-animal, so instead have evolved to be able to abruptly change direction whilst running. This allows them to be able to twist and turn even when sprinting and helps to protect them from cheetahs, which can only run in near enough straight lines. Furthermore, cheetahs are under a great deal of strain whilst running and their core body temperature rises extremely quickly so they cannot run for long periods of time. Consequently, gazelle have also evolved to be good long-distance runners, with most of their muscles being made from fast oxidatve fibres, which allows them to run for much longer than cheetahs can. As the next step in the evolutionary arms race it may be predicted that cheetahs will evolve to be able to run for longer or develop greater manoeuvrability whilst running, allowing them to be able to hunt gazelle more efficiently.

A cheetah chasing a juvenile gazelle. The cat can reach speeds of up to 75mph during the chase and will try to knock the gazelle over, allowing it to grab the underside of the gazelle's throat and suffocate it.

Arms races such as this example are common and exist in some form or another for every species of predator and prey. This is expected by scientists and obviously, makes evolutionary sense. What does not make sense however is that although humans have been around for 2 million years, in which time we have hunted other animals extensively, we do not appear to be engaged in this arms race. We have evolved no specialised weaponry to hunt our prey and none of the species that we prey upon have evolved abilities to defend themselves against us.

Many scientists believe that this is due to the unique way in which we hunt our prey. As I'm sure you know, humans are extremely intelligent and we have always used this intelligence to help us hunt other animals. Our brains have allowed us to create a large variety of tools to overcome our lack of physical weaponry and to develop innovative tactics to overcome our prey's defences.

One such ability of ability of humans is that we are able to throw much more efficiently than any other living animals - both in terms of power and accuracy. Therefore once our ancestors had invented spears, the once cutting-edge technology, we were able to kill our prey from a distance by throwing it - the ability to kill from a distance is unique to us, no other animal is able to do this! Our ability to kill animals from a distance meant that we have had no need to develop weapons such as poisons, claws and large teeth and our prey has not had the opportunity to develop resistance to such a hunting method. This is partly because once an animal had realised that we could kill it, it is already dead and cannot pass its genes on, which is the mechanism by which evolution works. Our intelligence has also meant that we could fashion dull clothing and refine our tactics to sneak up on our prey, so that we have not needed to evolve camouflaged skin either. In fact, the main physical adaptations that throwing would have selected for is strong shoulder and leg muscles and good binocular vision (predators have eyes that are mounted on the front of their head, which gives more precise vision and better depth perception), both of which humans have.

Tribesmen throwing spears. Note how the men are standing sideways, holding the spear in their right arms. When they throw their spear they twist their body around. This greatly increase the force of the throw by using the torque generated in their hips and shoulders.

Human intelligence and the fact that we hunted in packs has also meant that we were able to overcome the  'ten times larger' rule, which is where large terrestrial herbivores that grow ten times heavier than their largest predator become safe from predation, since their predators are unable to develop jaws strong enough to kill them. This explains the large size of elephants for example, and why the adult individuals of such species have no natural predators other than man - simply put, they are just too large for predators for hunt and the risk of injury to the predator is too high! Our ability to hunt animals much larger than ourselves helped the rapid spread of humans across the globe and allowed us to live in areas that would have otherwise been uninhabitable, such as the cold tundra of Northern Europe and Siberia. Human colonisation of tundra climates was possible due to the presence of mammoths, a species of megafauna, for two main reasons. Firstly, mammoths had no natural predators until we arrived, so that we did not need to complete for them with other predators; and secondly, because of the enormous amount of resources than we could harvest from each individual. These resources included meat for food, fur for clothing and vitreous humour from their eyes to make glue. Unfortunately mammoths, like most species of megafauna, had evolved with immunity to their natural predators and consequently, had few defences other than their size. This meant that we were able to kill them very easily and sadly, we drove them to extinction. The extinction of megafauna is a characteristic of human colonisation in new areas and most giant species became extinct around 40 million years ago.

An artist's impression of a group of early humans hunting a mammoth.

Our ingenuity has also meant that humans have been able to overcome most of the poisons that many animals use as defence mechanisms. The most common ways that we do this is by cooking the animal before we eat it, which causes the poisons to break down; or we can remove the poisonous tissues, which is possible because defensive poisons are often concentrated into certain organs, such as the liver. Thus, humans can kill and eat many animals that are avoided by other predators.

Therefore humans are remarkable hunters, being the only animals that can kill others from a distance, kill species much bigger than ourselves and can remove poisonous toxins from our food, which greatly increases the scope of our diet. Thus, it may be fair to say that humans are not merely predators, but are in fact super predators and that we are the most effective and efficient killers that have ever lived.

25 March 2012

The Alpine ibex - a lesson in outbreeding depression

The Alpine ibex, Capra ibex, is a species of wild goat that lives in the European Alps. Historically the goat ranged throughout the whole mountain range, but the heavy hunting beginning in the 1500s caused dramatic declines in its populations. As a result of this overexploitation, the goat became extinct in France, Switzerland and Germany by the 18th Century and in Austria and north-east Italy by the 19th. Fortunately, the Italian Gran Paradiso National Park was established in 1922 in order to protect the ibex and its population was used to help recolonise other areas of its historical range.

The anti-poaching enforcement efforts in Gran Paradiso were successful and, as a result, the population of the ibex began to rise. Once the population had grown large enough the next stage of the conservation plan was implemented and the ibex were used in the recolonisation efforts of the species in the Tatra Mountains in Czechoslovakia, one of the areas that it was now extinct. However, this was where a massive and unpredicted problem began. Capra ibex ibex from the park was not the only subspecies of the mountain goat used the scheme, since conservationists believed that their population would grow faster and the scheme would be more successful if they used as many goats as possible to recolonise the mountain range. Thus, the subspecies Capra ibex nubiana from Sinai and Capra aegagrus from Turkey were also used in the scheme and bred with Capra ibex ibex. The problem with is was that these additional subspecies of goat were from much warmer drier climates; climates to which they had become locally adapted to.

The Alpine ibex, Capra ibex ibex.

Consequently, when the additional ibex subspecies' mated with Capra ibex ibex, the hybrid offspring had genes that had been selected for by the environmental conditions of the hotter climates. As a result, the hybrids rutted in autumn instead of winter and the resulting kids (baby goats) were born in February, the coldest month of the year and the whole population rapidly became extinct. Thus, the scheme failed because conservationists had failed to predict the effects of mixing different sub-populations, with slightly different adaptations, together.

This problem is known as outbreeding depression, which occurs because populations in different geographical areas do not breed with each other and are under selection pressures from their environment. Over time, these selection pressures cause different alleles to be most favourably expressed in the different populations and if they breed, the young will likely have reduced fitness (survival and reproductive ability). This problem of local adaptation is an issue for all conservation schemes that move species from one habitat to another; so, before such a scheme's implementation, conservationists must first research whether or not outbreeding depression will be an issue. If it is, the scheme will likely fail at great monetary expense and expense to the endangered species itself, which will already have a small population. Unfortunately, extensive research isn't always possible because of the rapid rate at which species are disappearing and often, management decisions have to made very quickly, without complete genetic knowledge.

However, even though this particular reintroduction scheme failed, the population of the Alpine ibex is now well over 20, 000 and the species is listed under 'Least Concern' by the IUCN

22 March 2012

The bite of a killer is unpleasant indeed

Komodo dragons, sometimes called Komodo monitors, are the largest living species of lizard and can grow to lengths of 3 metres, weighing up to 70kg. Their large size means that they dominate the island ecosystems of Indonesia where there are no other carnivorous animals for them to compete with and they prey upon invertebrates, birds and mammals alike. Komodo dragons are highly intelligent have frequently been seen hunting in packs - the only species of lizard known to do this!

The large size of the lizards is unusual and is believed to be due a phenomenon called island gigantism, which is where species that are isolated on islands can grow to much larger sizes than those on mainlands due to the lack of competition for resources and the absence of predators. Island gigantism explains the Komodo dragons huge size in part, but the species also belongs to the ancient Asian Varanus genus that contained many species of large lizard, so it likely that the dragons' should be big anyway. The genus was isolated in Australia 40 million years ago and many larger cousins of the Komodo dragon once stalked its lands. However these larger cousins, which were species of megafauna, became extinct with the arrival of humans in Australia and the changes that we caused to their environment. Thus only their smaller cousins, which are believed to have evolved in Queensland and spread into Indonesia during a period of glaciation when sea levels were lower, survive today.

The Komodo dragon, Varanus komodoensis. Like all reptiles, the lizards 'smell' by tasting the air with their forked tongues and rubbing the odorants that they pick up onto the roof of their mouth. These odorants are then detected by a specially modified organ called the vomeronasal organ.

The one the most well known facts about Komodo dragons is that they have saliva that contains an extremely high number of bacterial species, which frequently causes fatal infections in animals that they bite. However, this is a misconception and although Komodo dragons do have a large range of bacterial species in their saliva, which can be as high as 57 different species, it is not unusually high for a predator. In fact, human saliva contains many more species of bacteria than a Komodo dragon and we have one of the most infectious bites of any organism in the world! However, although Komodo saliva contains no more types of bacteria than other predators, it is still highly unusual. This is because when Komodos bite their prey, they tear off its flesh by pulling their head back in a circular motion, which works in the same way as a can opener. This twisting motion is very damaging to their teeth and as a result, their gums are prone to bleeding. Thus, their saliva often has a high blood content, which enables bacterial colonies to grow to extremely large sizes so that when they bite their prey, they overload its blood with bacteria - giving the wound a greater chance of becoming infected!

Komodo dragons have very viscous saliva that often remains hanging from their mouths for long periods of time. This allows bacteria to build up in it, since the Indonesian climate is perfect for bacterial growth; meaning that the environment is very infectious.

In addition to having incredibly infectious saliva, Komodo dragons are also poisonous. This was only recently discovered and makes Komodo dragons one of only three known poisonous species of lizard. (The other two are the American Gila monster and the Mexican beaded lizard). Its venom, secreted into its saliva from two large glands beneath its tongue, is highly toxic and works like an anti-coagulant to stop blood from clotting. Clotting is the body's normal response to a cut and basically, once the body realises it's been cut it activates certain proteins in plasma, the fluid that erythrocytes (red blood cells) are suspended in. The activated proteins, called platelets, change shape and form a 'net' that traps erythrocytes at the site of the wound, forming a scab. As I'm sure you know, scabs prevent blood loss, so anti-coagulant poisons stop this from happening. As a result of this, an animal bitten by a Komodo dragon will eventually bleed to death, whilst becoming weaker and weaker as they lose more blood. Komodos take advantage of this by biting their prey a few times and then backing off, which reduces their risk of injury from their prey. They then follow the wounded animal at a safe distance until it dies, or becomes too weak to struggle.

This allows them to bring down animals much larger than themselves and sadly, the lizards have been known to kill humans. However, despite being fearsome predators with deadly saliva and the intelligence and brute force needed for ambushes, Komodo dragons are predominately scavengers that feed off carrion, eating anything that they come across.

Unfortunately, the loss of Komodo dragons habitat due to human activity, illegal poaching and the effects of improperly managed tourism means that there are now less than 5, 000 individuals living in the wild and it is believed that there may be as few as 350 breeding females left. Consequently, the species is classified as 'vulnerable' by the IUCN and may soon disappear, being on the agency's Red List.

19 March 2012

Please help me out

Hi all!

The blog post beneath this, entitled 'Fungi: rotting civilisation from its very foundations', was written as part of my final year project for my university course. As part of this assignment, I have to assess the post's effectiveness in communicating the science of its topics to you and I would be very grateful if after reading it, you could spend 2 - 3 minutes of your time to answer 10 multiple-choice questions by clicking here. All responses are anonymous.

Thanks for your help!


The questionnaire is now closed and I would like to send a big thank you to everyone who filled in the questionnaire and so, helped out with my project! Your help was greatly appreciated and has enabled me to analyse the effectiveness of the post quantitatively.

Fungi: rotting civilisation from its very foundations

Wood is one of the most useful natural resources to man due to its unique and remarkable mechanical properties and consequently, has been heavily used by humans throughout our history. In particular, wood has been heavily exploited for its use in building and furniture construction, mainly since it is readily available and is able to bear heavy loads at a relatively small diameter. Wood is also extremely important as the basis of paper, an industry that produces over 300 million metric tons of paper-based products every year.

The main reason that wood has such remarkable and desirable properties is due to the fact that each individual wood cell is very strong, with thick cell walls made from the dense wood matrix. This matrix is a complex mixture of polysaccharides (cellulose and hemicelluloses), lignin, starch, pectin and various other proteins; and although the relative quantities of lignin and hemicelluloses differ between hardwoods and softwoods, wood remains highly resilient to degradation and very few organisms are able to break it down.

The most abundant and arguably, most important, organisms that are able to break down wood are wood decaying fungi, which include white-rot, brown-rot and soft-rot species; and wood decolourising fungi, such as moulds and blue stain fungi. Such organisms are extremely common and break down enormous quantities of wood each year, having important roles in ecological nutrient recycling systems, such as the Carbon and Nitrogen Cycles, where they release the nutrients that are 'locked away' in dead biological material back into the environment.

Although wood decolourising fungi are not technically true wood decaying fungi because they mainly deteriorate the aesthetic properties of wood and do not weaken its strength, they are still highly destructive. This is mainly because they increase the permeability of wood cells by riddling them with holes, which makes them more vulnerable to colonisation by true wood-rotting fungi, discussed below, that actively degrade the wood. The main issue then, that humans have with wood decolourising fungi is that it can severely damage and even completely ruin pieces of artwork. This is mainly because such species of fungi are highly resilient and are able to digest both the paint dyes themselves and the canvas or paper that the artwork was created on. Thus, wood decolourising fungi are a nightmare for art galleries and museums, being extremely difficult to remove without further damaging the art. A further problem that wood decolourising fungi can cause is that many species produce volatile chemicals and mycotoxins that can cause allergic reactions in some people, or release spores that can cause respiratory diseases. A common example of this is Aspergillosis, caused by Aspergillus moulds.

This photograph shows a painting (left) that had been invaded by wood decolourising fungi and (right) the same painting after it had been treated for the fungi using a plant oil conservation technique. Note however, that although much of the painting has been restored, it is still irreversible damaged.

Although losing pieces of art to wood decolourising fungi is annoying and sometimes even heartbreaking, it is nothing compared to the damage that can be caused by true wood-rotting fungi. True wood decaying fungi degrade all of the different polymers in wood, which causes significant and irreversible structural damage that greatly reduces its overall strength - effects that are incredibly detrimental to wood used in the construction of buildings, ships and furniture! There are three main types of true wood decaying fungi: white-rot fungi, brown-rot fungi and soft-rot fungi, which each affect hardwoods and softwoods differently and have varying prominence among different climates.

Brown-rot fungi predominantly attack wood by degrading its constituent polysaccharides and cause little, if any, damage to lignin. Brown-rot decay mainly effects softwoods and is characterised by a rapid depolymerisation of cellulose that causes a reduction in the mechanical properties of wood. The breakdown of cellulose is believed to be accomplished via an oxidative process, which involves the production of a highly reactive compound called hydrogen peroxide when the fungi breaks down hemicelluloses. It is thought that these molecules of hydrogen peroxide then diffuse into the middle, or S2 layer, of wood cell walls and cause the general decay of cellulose; although scientists don't know for sure... However, whatever the mechanism by which brown-rot fungi works, it gives the wood a brown colouration (hence the rots name) and the wood usually displays a brick-like pattern of cracks and splits, which results from an uneven pattern of decay. Brown-rot is most commonly seen in buildings and species such as Antrodia and Gloeophyllum are frequently seen on furniture, the main products made using softwood.

The brown-rot Serpula lacrymans, commonly known as dry rot, attacking an abandoned house in the USA.

White-rot fungi differ from brown-rot species because they degrade both lignin (they are the only known organisms are are able to digest it completely) and polysaccharides. White-rot is more common in hardwoods, where they digest lignin by secreting non-specific lignin mineralising enzymes (LMEs) into the surrounding wood. The most important LME is laccase, which breaks lignin down into carbon dioxide. Lignin is a brown pigment and is responsible for giving wood its dark colouration. Thus, white-rot fungi 'bleaches' the wood that it has invaded and turns it paler over time, as it digests more and more  lignin for food - giving the rot its name.

Fomitopsis pinicola, a species of white-rot fungi that has invaded a broken tree trunk and  is completely stripping it of lignin. The digested wood is white and very brittle.

Soft-rot decay is characteristic of wood in wet or damp conditions, such as the wood in ships, fence posts and windowsills in buildings (if they condense frequently). Such decay mainly involves the degradation of polysaccharides and only very rarely the breakdown of lignin. Soft-rots attack hardwoods and softwoods non-preferentially, which they accomplish by extending long tube-like growths called hyphae, into individual wood cells. Their hyphae usually enter cells through pits on the cell's surface and once inside, they split into fine-penetration branches that grow through the inner layer of the wall and into the cellulose-rich S2 layer. Thus, they are able to digest the polysaccharides in the wood and cause havoc for humans because they can degrade wood incredibly quickly.

As mentioned before, wood decaying fungi are extremely important in nature and are essential organisms in food chains. The natural breakdown of wood and dead biological material is even useful to humans, particularly for farmers, as it helps to maintain the fertility of soils so that their crops grow better. The main problem of decaying fungi however, occurs when they invade wood that has an anthropogenic use because they are extremely destructive. This destruction has many impacts for humans as decaying fungi can undermine the structural stability of buildings so that they become unsafe and eventually, collapse; rot away any clothing that uses natural, cellulose-based fibres, such as cotton; and destroy books and paper-based products, which was a much bigger issue in the past since books were the primary way of recording information and knowledge.

Mould that has invaded a room and is degrading the walls from their base. Eventually, the wood will become too weak and degraded to hold the weight that it is supporting and the wall will collapse.

Fortunately, methods have been devised to control wood decaying fungi, although it is impossible to prevent their invasion forever. The most common way of protecting wood from rotting fungi is adding an anti-fungal preservative to it either during its production or onto the finished product, usually as an ingredient of a paint or varnish. Common preservatives include copper azole and chromated copper arsenate.

Thus, despite the high efficiency of wood decaying fungi and wood decolourising fungi in invading and degrading wood, the damage that they cause can be prevented with regular cleaning and by using appropriate anti-fungal chemicals. Therefore wood, one of the most important natural resources to man, can be effectively protected and as a result, the wood treatment industry is a huge and incredibly profitable business that is critical to the stability of our civilisation.

17 March 2012

Think Thumbelina, but as a monkey...

Pygmy marmosets are the smallest true monkey in the world, standing at just 5 inches tall (not including the length of their tail) and weighing 4.5 ounces. They inhabit the Amazon Rainforest in South America, climbing to the tops of the trees, as their small size allows them to cling to branches that are too thin to hold the weight most animals. Despite the name however, the monkeys are not true marmosets and its genus, Cebuella, is unique; true marmosets belong to the genera Callithrix or Mico.

The tiny pygmy marmoset monkey, Cebuella pygmaea.

The marmosets prefer to inhabit trees on the banks of rivers, where the upper foliage is usually more easily assessable and the open view makes it easier to spot birds of prey, one of their main predators. The monkeys occupy a similar niche to squirrels in Europe, although their diet predominantly consists of tree gums and saps and is occasionally complimented with insects. The monkeys are highly mobile, being able to jump distances of up to 5 metres at a time! This is possible due to their small size, as they exert much more force in their muscles compared to the size of their body than larger animals, like humans, do - the same reason that ants can carry objects much bigger than themselves. This amazing jumping ability allows them to easily traverse great distances, well for them at least, in search of food and is a fantastic defence against predators.

Although pygmy marmosets aren't particularly intelligent for a primate and have an unusually underdeveloped brain, they have a surprisingly developed communication system. Their 'language' consists of clicks and squeaks, many of which are too high pitched for humans to hear and scientists have identified certain calls that have specific meanings, such as that a predator is in the vicinity.

The monkeys are also highly territorial, with males competing with each other to be the dominant, breeding male. Rather than fighting with each other, which many animals do at great physical cost, the monkeys flatten the fur on their head and pull faces at each other, whilst simultaneously grabbing and displaying their genitals. Whereas this may look hilarious to us, for the competing males it is an epic duel and signifies their place in the group's social hierarchy, including whether or not they are allowed to mate.

Fortunately, the monkeys haven't been too badly effected by the mass deforestation of their habitats as of yet; maybe because their small size means that they don't need much space to survive in. Although, this could change very soon - species have a habit of appearing to fine for an extended period of time and then, suddenly plummet in number to become an endangered species in a matter of years. Hopefully though, this will never happen and the comical primate will survive for generations to come.

Notice the pygmy marmosets hands that have claws instead of nails and, since they are New World monkeys, do not have opposable thumbs.

14 March 2012

Mystery of the horned humans

During the 1800s a number of human skeletons were uncovered in a burial mound in Sayre, Pennsylvania by a reputable group of antiquarians. Although finding human remains is fairly common, these skeletons were very odd. Firstly, each of the skeletons was extremely tall and the individuals of all those found would have stood at heights well over 7 foot. However, although this is extremely unusual by itself, it wasn't the strangest thing about them - each of the skulls had two horns that extended upwards from their eyebrows! The skeletons were immediately sent to the American Investigating Museum in Philadelphia (a museum that oddly, has no other reference on the Internet except linked with this story), where they vanished and have never been seen again.

A photograph of one of the horned human skulls found in Sayre that was taken before the skeletons abruptly vanished, never to be seen or heard from again. The skeletons were believed to have been buried in 1200 AD.

This has led to many conspiracy theories and much speculation about whether the skeletons found in Sayre were those of aliens and that they were seized by the US government. However, whilst this is difficult to speculate on, humans having horns is biologically possible and there have been other, better documented cases of such phenomena.

For example, the naturalist Caspari Bartholini mentioned a man with a 12 inch horn growing out of his forehead in his book 'Anatomicae Institutiones Corporis Humani' and there is a well known case of an old women in France presenting her amputated horn to King Louis XIV in 1696. Interestingly, many of the accounts reporting the removal of human horns go onto say that they often grew back. This suggests that they are a genetically controlled tissue that are encoded for by the individuals DNA, possibly due to a gene linked to hair and nail tissues, which obviously, grow continuously. This notion is further supported by a case where a father and son, supposedly, both had horns.

Wang, the 'Human Unicorn' from the 1930s. Note however, that although this is supposed to be genuine case, Wang vanished and did not appear in the media again despite the extensive efforts to find him. There are two possible explanations for this: the photo was a fake or that Wang didn't want to be in the midst of a media storm...

The leading legitimate theory regarding human horns (this blog ignores the popular speculations that they stem from alien DNA), is that they are made from keratin (the protein that forms hair and nails), just like the horns of other mammals. It is believed that the horns are a 'genetic throwback', which are well documented and scientifically supported phenomena, from a time in human evolution before our ancestors had diverged away from those animals that went on to develop horns. The theory assumes that many, if not all, humans carry the genes necessary to produce horns, but in most of us they are inactive and are not used. Our DNA is full of useless and unused genes such as this, called introns, which are essentially just junk DNA. This is why scientists are frequently heard to say that humans share 96% of our DNA with a fruit fly - we do, except that we mostly use completely different genes, which is fairly obvious really...

A baby born with a tail. This is another example of a genetic throwback and is more common then you might think. The tail is normally removed at birth, or when the individual is still relatively young and unlike human horns, do not grow back.

Although the documented cases of horned humans are rare, the mythology and legends of many cultures are full of stories that feature humans with horns. Examples include Satan, who is believed to have horns and cloven hooves; the Minotaur from Greek mythology, which was said to have been a man with the head of a bull; and the Celtic god, Cernunnos. Thus, horned humans may have been appearing throughout human history, have a plausible and legitimate scientific explanation and may have had a deep cultural significance.

A coin featuring Alexander the Great, who is depicted with horns. Historically, horns were believed to signify great wisdom and strength and thus, often represented kingship.

13 March 2012

Red meat can kill us? I'm sceptical...

It is in the news today  that regularly eating red meat a few times a week greatly increases your chance of dying from various health issues, such as heart disease and cancer. Furthermore, news stories are claiming that for every additional day each week that you eat red meat, you increase your chance of dying by a fifth. Whereas I don't disagree that eating too much red meat is harmful to your health - too much of any type of food isn't healthy - I do criticise these speculations.

Cuts of red meat can supposedly harm your health, increasing your risk of dying early.

Many people forget and overlook the fact that humans, simply put, are just animals. Despite all we've built and accomplished at global levels, we still evolved from single-celled organisms like every other form of life on the planet. As such, we have evolved to eat meat - humans are omnivores, which are essentially species of herbivores whose ancestors began to eat meat and are still in the evolutionary transitional phase before evolving into carnivores, hence eat both plants and meat. Thus red meat, which is highly nutritious, is part of our diet and we have evolved in order to be able to eat it.

The Telegraph: "Red meat is blamed for 1 in 10 early deaths"

Therefore, I think that these speculations, quite frankly, are absurd. The study that these findings are based on was an observational study over 20 years  in the USA, which found a positive correlation between eating red meat and dying early, suggesting that the factors are linked. However, the study did not take into account other factors, such as what else they ate and their overall health. Many people in Northern America are severely overweight and the USA has the highest levels of clinical obesity in the world. Thus, many of the participants in the study may have been overweight and could have died from such issues anyway. The main problem of the study is that it is purely observational and does not control for such factors, like a lab-based study would. A lab study, for example, may have only used healthy participants of average weight, so its findings would be much more applicable to the general population.

Although eating excessive quantities of red meat a week could be unhealthy, I think that by itself, eating too much red meat is very unlikely to cause any significant harm to our health. The study did not control for other health factors and until a better, more convincing experiment comes to light telling me otherwise, I will continue to eat red meat and suggest that you don't worry and do the same.

12 March 2012

Spit: the smell of survival

The Australian outback can reach blistering temperatures as high as 50 degrees Celsius during the day and its landscape often lacks trees, making it is hard to find shade. This makes it extremely difficult for animals to survive in, mainly due to the dangers of dehydration and overheating. Overheating damages enzymes, which are important for digestion and many key biological processes, causing them to denature (lose their specific structure) and become non-functional; meaning that the animal may die.

In order to survive in such hostile conditions, the species that live in the outback have evolved many physiological and behavioural adaptations that allow them to cope with high temperatures and often, limited access to water. The most obvious behavioural adaptations are restricting activity to the night (nocturnal) or to the twilight (crepuscular) hours, when the temperature is much cooler. Most physiological adaptations are designed to increase the amount of heat energy lost by an organism and a striking example of this is having extremely large ears. Although this may look comical to us, it is actually a very clever way of cooling down since large ears have a very high surface area, from which the body's excess heat energy can be lost and are very thin. This high surface area to volume ratio makes them perfect for losing heat energy and they contain many blood vessels, which continuously carry the hot blood from the animals core to their ears. Thus, losing heat energy via the ears is extremely efficient and makes it possible for them to remain cool enough to survive. In addition, it also improves their hearing as large ears can 'collect' more sound waves than smaller ones, helping them stay alert for the sounds of predators or prey, respectively.

A bilby in Australia. Its large ears lose a lot of heat energy, helping it to survive in the extremely hot conditions of the Australian outback.

Controlling the times of activity and possessing adaptations like large ears are fine for smaller animals, such as biblies, but kangaroos are large and very active. A particular problem they have is that hopping, their main method of locomotion, is very energy expensive and produces lots of waste heat energy. Thus, these common methods of controlling body temperature would be inadequate to allow kangaroos to survive in such extreme conditions by themselves. So, to increase the amount of heat energy they lose, kangaroos use a novel behavioural trait - they lick the insides of their forearms. Although this may seem strange, it is highly efficient at losing heat energy and works by the same principles as sweating, which makes sense since kangaroos, like many mammals, are unable to sweat and rely on panting as a method of water loss instead. The process loses heat because the water on the skin absorbs heat energy, which it uses to evaporate. As the water leaves the skin, it carries the energy it has absorbed with it, cooling the skin down. Therefore, kangaroos can lose an enormous amount of heat energy via 'spit bathing' as it is called, helping them to stay cool

The importance that spit bathing plays for the survival of kangaroos is indicated by the highly developed salivary glands in their mouth. Of particular importance is the the parotid salivary glands, which are very large and are twice as heavy in relation to a kangaroo's body size than in other ruminants, such as sheep. They also have an extremely large number of serous-type secretary cells that constantly produce saliva, which is unusual because in most animals they are mainly active when food is actually being eaten. Thus, kangaroos can constantly produce large quantities of saliva.

A red kangaroo lounging in a hole that it has dug in the shade beneath a tree. Note its large ears and long thin forearms, perfect for losing heat energy.

However, there is a major problem with using saliva to cool themselves down - it wastes valuable water in an environment where it is already scarce. How then do kangaroos manage to keep enough water to maintain their blood pressure, whilst using enough to cool down? Firstly, kangaroos are able to concentrate their urine by absorbing much more water back from the filtrate in their kidneys than humans are able to do, which reduces the volume of urine that they produce and thereby, limits water loss. Secondly, they slow down their metabolism during the hottest parts of the day so that their body uses up less water in respiration.

Thus, kangaroos are able to survive in the hot, arid conditions of the Australian outback, despite their large size and active lifestyle.

10 March 2012

Hunting in the depths

The sperm whale, Physeter macrocephalus (previously Physeter catodon), is a fearsome hunter and frequently dives to depths as deep as 3km in search of its main source of food - giant squid. Even though 3km doesn't sound like much, it is so deep that we struggle to build submarines that can withstand the extreme pressures even now; making the whales an amazing feat of evolutionary engineering, being one of the few animals that can survive the radical pressure change between the oceans' surface and its depths. Sperms whales can live for more than 70 years and males, which are more than 40% more massive than females, can grow to over 20 metres in length, weighing up to 57, 000kg. They have the largest brain of any animal and are also the largest living toothed species, although only males actually possess teeth, which can weigh up to a kilogram each.

A male sperm whale breaking up out of the ocean. Note its slender lower jaw, which increases the pressure of its bite (making it more powerful) and the thin, conical teeth that fit into alcoves in the whale's upper jaw - helping to trap anything that it bites in its mouth.

Sperm whales are named due to the large and well developed spermaceti organ that forms most of their head, which at times, can make up a third of an individual's total body length. This gives the whales a distinct body shape, making it difficult to confuse them with another species. Unfortunately, this made them easy targets for whalers in the Industrial Revolution, where they were killed for the whale oil that was harvested from the organ itself and from their blubber. Sadly, their population fell dramatically and, as a result, sperm whales are now protected and the species is classified as 'vulnerable' by the ICUN. Even though the organ has largely brought about the downfall the species, it is critical for their survival. This is fairly obvious really, when you think about the organ's large size compared to the whale's body and the energy that it must take in order to produce and maintain it.

A sperm whale, with its box-like spermaceti organ clearly visible. The whale also has a very powerful, muscular body and thick, triangular flukes that allows it to dive to such extreme depths.

The oldest known function of the spermaceti organ is as a buoyancy aid. At the surface, whales reduce the blood flow to the organ by contracting the diameter all of the blood vessels it contains, in a process known as vasoconstriction. This causes the temperature of the organ to fall and the spermaceti wax solidifies, increasing in density. As the organ is in the whales head, it sinks and pulls the whale downwards head-first; thereby, helping it dive and stay submerged. When the whale wants to rise to the surface, usually to breathe (sperm whales can stay submerged for about 90 minutes at a time), the converse it true and the blood vessels dilate (expand), causing the wax to melt and decrease in density. Thus, the whale is pulled upwards head-first, which allows it to ascend more quickly. This could be potentially life-saving for a whale - imagine running out of breath 3km underwater...

Sperm whales live in small social groups, rather unimaginatively called units, which consist of multiple related females, one unrelated male and calves (both male and female - males leave the group once they sexually mature). In this photo, the unit is sleeping, which is identifiable since the whales always sleep in this vertical position; kept afloat by their spermaceti organs.

However, buoyancy aid is only a secondary function of the spermaceti organ, with it being primarily involved in echolocation. Water is an excellent absorber of light, so that 3km down it is completely dark - no sunlight penetrates to such depths. Interestingly, even if light did reach such depths, sperm whales would be unable to see as they shut their eyes very tightly to protect them against the pressure and cannot open them. Therefore sperm whales are completely blind at these depths, which isn't ideal for a predator. Echolocation, also seen in bats, is an ingenuous adaptation that allows the whales to form an image of their surroundings by generating a series of clicks using the phonic lips at the front of their nose. These clicks then pass into Junk Bodies in the spermaceti organ and are forced out into the water through the Junk's lens-like structure. The whales can then process these clicks as they are reflected back, bouncing off the objects in the water. This allows them to form a 'mental image' of their surroundings, which may be part of the reason why they have such large brains - forming the images requires a large amount of neural processing.

The spermaceti organ also has a third and much more sinister function. The broad-beam clicks that it uses to generate an image of its surroundings can be focused into a much narrower, more intense beam. This beam is used for hunting and is 'fired' at potential prey targets once they have been located. It is so intense that it stuns and completely disorientates its prey, allowing the whale to get close enough to bite it, which normally means game over for the unlucky animal. Further to this, the depths of the ocean are filled with bioluminescent phytoplankton and cyanobacteria, which light up when stressed. Thus, when they are hit by the narrow beam they light up and the sudden surge of flashing light can disorientate the giant squid, which can see at such depths, even more.

A photograph taken by a deep-water submersible that shows a male sperm whale attacking its prey, a giant squid. Giant squid are a formidable killer in their own right, possessing thousands of suckers that each contain razor sharp chitin rings and a great quantity of scars can be seen on the whale, as a result from past encounters.

As said previously, one of the most amazing abilities of sperm whales is their ability to dive down from the relatively low pressure of the surface, to the abyssal depths that are under enormous pressure. So, as you would expect, they have many physiological adaptations that allow them to do this. The main ones are that their entire body, including all of their viscera (internal organs) are designed to be crushed, yet continue to function. Their rib cage is highly flexible and can fold almost flat; their lungs secrete a unique pulmonary surfactant that contains detergents to stop their delicate alveoli sticking together; and their heart virtually stops beating during the dive, which is accomplished by a massive drop in their metabolism. The fact that their metabolism and heart rate slows down so dramatically allows them to hold their breath for much longer than they could have otherwise. However, this still wouldn't allow them to hold their breath for a dive of 90 minutes so, to increase this time, they have an enormous quantity of blood, which therefore, can hold an enormous quantity of oxygen. Sperm whales also have extensive reserves of a pigment in their muscles called myoglobin, which acts as an emergency store of oxygen. Thus, sperm whales are able to dive at great depths for an extended period of time.

Despite still being rare, the population of sperm whales is beginning to rise and it is faring much better than other endangered species of whale. Mainly because its hunting is now banned in almost every country, meaning that commercial whaling of sperm whales has ceased, it has no natural predators and giant squid are not fished by humans, so its food source is not declining. Therefore, it is likely that this truly amazing animal has survived industrial whaling and will grace our oceans for many years to come.

9 March 2012

Cancerous coke & perilous pepsi?

Recently, Californian legislation has changed to classify 4-methylimidazole (4-MEI), a colouring ingredient in Coca-Cola and Pepsi, as a possible carcinogen to humans. This change will require the companies to display a 'cancer warning' on the packaging of their products. However, instead of doing this both companies have opted to alter the recipes of their drinks in the USA by replacing 4-MEI with another caramel-based colouring agent, thereby circumnavigating the new law.

Both of the popular drinks are already being sold with the new recipe in California.

Despite this new legislation, a statement from Coca-Cola has said that "not one single regulatory agency around the world considers the exposure of the public to 4-MEI as present in caramels as an issue" and consequently, the recipes of the drinks sold throughout Europe will not change. Experts say that there is no risk from the chemical, which is also present in many roasted foods, dyes and agricultural chemicals, claiming that an individual would have to drink over 1, 000 cans of either of the drinks a day in order to be risk.

However, the chemical does correlate with an increased incidence of tumour development in lab mice, so is it really safe for humans to consume? The answer, simply put, is difficult to conclude. Mice do have a different physiology to us and obviously, are much smaller. Thus, the chemical could quite plausibly pose no risk to us. On the other hand however, it may and officials in California obviously have cause for concern...

8 March 2012

Species conservation: simple right?

You may think that conserving a particular species is easy, assuming that all you have to do is stick a few individuals into a zoo, breed them and then release their babies back into the wild. However, you'd be wrong and it is actually much more complex than this, with lots of unpredictable factors that only become apparent once a conservation scheme has been launched. The conservation of the black-footed ferret, Mustela nigripes, in the USA helps to highlight just this.

The black-footed ferret is a small mustelid, from the same family as European and Siberian polecats, such as weasels that were historically found across most prairie grasslands in the USA. However during the mid 20th century, the population of the ferrets began to decline and by the 1960s they were considered rare. In response to this, they were listed as endangered under the Endangered Species Act of 1973 and a conservation scheme was developed in order to help save the species. However, this took far too long and by the time conservationists were ready to implement the plan, the ferret had disappeared, seemingly becoming extinct. By chance, the species was rediscovered in Wyoming in 1985 and conservationists leapt into action to remove 6 ferrets from the wild, placing them into a captive breeding program. 

The black-footed ferret, Mustela nigripes

However, the initial excitement of capturing the ferrets soon turned into despair. Two of the captured ferrets carried canine distemper, a disease to which the ferret is unusually susceptible to and, as a result, all of the ferrets died. This meant that 6 new ferrets had to be removed from the wild for breeding, further reducing an already small population. Very small populations of a species are a major issue for conservation because the population soon becomes inbred, meaning that deleterious alleles of genes begin to build up and they lose genetic diversity. This problem, which is known as inbreeding depression, means that the species suffers from greatly reduced fitness and is less able to cope with environmental changes; thus, becoming much more likely to fall extinct.

Therefore, removing 6 additional ferrets from the population was of great concern to conservationists, especially because the wild population continued to decline. Around this time, it was discovered that the population of black-tailed, Gunnison's and white-tailed prairie dogs, the main diet of black-footed ferrets, was also decreasing due to the Sylvatic plague. With horror, conservationists realised that the main reason black-footed ferrets were going extinct was because its main source of food was declining - they should have been trying conserve the prairie dogs all of this time, rather than the ferret itself. However, by now the distribution of prairie dogs had fallen to only 2% of its historical geographical range, due to both the plague and the actions of farmers, who wrongly believed them to be pests. To make matters worse, conservationists couldn't merely focus on saving the prairie dogs because only 4 black-footed ferrets now remained in the wild!

The now endangered Gunnison's prairie dog, Cynomys gunnisoni.

To try and preserve both species, the decision was made to pull the remaining black-footed ferrets from the wild and add them to the breeding program, whilst applying the burrows of prairie dogs with a poison that would kill fleas, the vectors (carriers) of the Sylvatic plague. It was hoped that this would be sufficient to help their populations to recover. At the same time, just to be sure, they launched an education campaign in order to change the long-held beliefs of farmers that the prairie dogs were pests and that they had to be preserved, or else they could become extinct.

Fortunately, the populations of both species are now beginning to recover, even though they are both still rare. The black-footed ferret has been a particular success, with kit (baby ferrets) reintroduction schemes running since 1991. However, the species may not have been so fortunate and the case study highlights the importance of identifying why species are declining in the first place. Ironically, by trying to save the black-footed ferret, we could have easily driven it to extinction as we did not fully consider the complicating factors of the ecosystem and the full impact of humans on the ferret. This is a lesson that needs to be learnt for new species conservation schemes, elsewise they could fail, at great expense to conservation funds.

7 March 2012

Poisonous spiders in the UK? That's got to be false!

Everyone knows that the only dangerous poisonous animal on the British Isles is the common adder, Vipera berus, right? Wrong. For over a century now, a relative of the infamous black widow spider known as the false widow, has been an unwelcome guest on our shores. Up until now however, it has been restricted to the south of Britain where it is warm enough for the spider to survive through the winter, but increasingly mild winters have allowed it to advance further northwards and it has recently been spotted in Bristol, Berkshire and Norfolk.

The spider belongs to the genus Steatoda and is relatively small, being no bigger than a 5p piece. False widows get their name because they look very similar to black widows, mainly due to the shape of their body. However, they are no where near as poisonous and deaths resulting from their bite are rare, usually only because the individual goes into anaphylactic shock like with bee stings. Although this doesn't mean that its bite is harmless, as it injects enough venom in every bite to cause severe pain and inflammation. The pain is intense enough for doctors to have given its own unique name: steatodism.

The small false widow spider on the top of a man's hand. Notice the white ring around the edge of its abdomen, which can be used to identify the spider.

Fortunately bites from false widows are rare, meaning that until recently, their presence in the UK has been unknown by most of the population. However, this is beginning to change after a man collapsed in a toy store after being bitten ten times on the neck by the spider, which is believed to have dropped into his hood. He collapsed within moments, feeling light headed, hot and began to gag. An ambulance was called and the man was rushed to Southampton General Hospital, where he was treated and kept in overnight. Luckily, long term damage from false widow bites is uncommon and he has made a full recovery, simply saying that he was "just thankful that it never jumped out and got onto my [the man's] daughter".

Our milder winters mean that the false widow is likely to spread through more of the UK, meaning that many more of us are likely to come into contact with it. Despite this, there is no cause for concern since bites from the spider are rare. Only a handful have ever been reported in the UK and none have ever resulted in a death. Like most wild animals, the spider will only bite a human in self-defence if it feels threatened; so, as long it is left alone, there's no cause for concern.

6 March 2012

Irradiated parasites? Good for your health?

Malaria is one of the biggest killers of man, with 300 - 500 million cases of the disease each year, causing 2 - 3 million deaths worldwide. Sadly, the majority of these deaths are children younger than 5 in sub-Saharan Africa. The disease is caused by small, protozoan parasites from the Plasmodium family, which predominately live in their host's erythrocytes (red blood cells) as merozoites, where they replicate by dividing over and over again. Eventually, an erythrocyte becomes so full of parasites that it ruptures and they burst out into the bloodstream and invade the surrounding red blood cells. And, once inside, they begin to divide all over again. It is this bursting of red blood cells that causes the symptoms of malaria, which include fever, headaches, sweating, coughing and muscle pains.

Red blood cells that have been infected with malaria and have ruptured. Small merozoites can be seen in the surrounding plasma that will enter and infect the nearby red blood cells.

Despite scientists having a good understanding of the complex life cycle of malaria and knowing that it is spread by female Anopheles mosquitoes (male mosquitoes drink plant fluids and not blood, so cannot spread the disease), no effective vaccine has yet been developed - the best we have at the moment is drugs that can prevent malarial infection in the short term by regularly taking a drug. Chloroquine is probably the most well known example of an anti-malaria drug. However, whereas this method of prevention is useful to those living in rich, developed countries as they can afford to buy the often expensive drugs, it is not much use in the poorer countries where malaria is actually endemic. This is mainly because the people there can't afford the drugs in the first place and there is often no way of getting drugs to people in isolated villages, as many of the countries lack a proper road network. This however, may be about to change.

New research by Sanaria, supported by the Bill & Melinda Gates Foundation, has identified a possible and highly promising vaccine for malaria called PfSPZ that protected 6 out of 7 participants in a clinical trial, providing them with lasting protection for about two months. The vaccine is made by irradiating mosquitoes that have been infected with malaria and then by harvesting sporozoites (the infectious form of its life cycle) from their salivary glands. These weakened, or attenuated, parasites are then used as the basis of the vaccine. When a weakened parasite such as this, is injected into an individual it is unable to make them as sick as it could have normally, meaning that the individual's body 'learns' how to kill malaria without the usual dangers from the disease. Once their body has 'learnt' how to kill malaria parasites, it remembers for a long period of time. This means that if the vaccinated person is bitten by an infected mosquito, their body will be able to mount a much more effective immune response in a shorter period of time and they will not become as ill as they otherwise would have, meaning that they are much more likely to survive the disease.

A researcher harvesting sporozoites from an irradiated mosquito's salivary glands.

Despite showing great promise at clinical trials, this vaccine has one major and unfortunate limitation. Sporozoites are tiny and an infected mosquito usually only carries around 1, 000 of them. Therefore, unless a more efficient method of producing irradiated sporozoites is developed, it is unlikely that the drug will ever become commercially viable as a vaccine for malaria, simply due to the sheer number of mosquitoes that would need to be harvested and the amount of time and effort that this would take. So, despite its potential, PfSPZ may never make it into mass production. Still, the vaccine holds great promise and in a number of years, it may potentially save millions of lives every year.