25 December 2012

Christmas message

Hi all!

2012 has been a remarkable year for me and I must admit, I'm fairly sad to see it pass. It has seen me graduate with honours from the University of Manchester, pass through two jobs, begin writing my first novel and, probably of most interest to you, has seen the creation of this blog; watching as it evolved from the humble dave's science blog (as seen in the URL), which I developed out of necessity for my final year project, to this world we live in - a blog of 63 posts and one of my favourite hobbies!

I hope that you have all found 2012 as prolific as I have and, if not, then remember that 2013 is a new year year and promises a fresh start! I also hope that you have enjoyed reading the posts on this blog as much as I have have in writing them and take the time to check out my Christmas Special post, which talks about the myriad of amazing techniques animals employ to survive the harsh inclement of winter.

I sincerely wish you all a Merry Christmas and a Happy New Year! And hope that you continue to read my blog in the future!

David Taylor

Surviving the cold

If you think that we have it tough in the winter and have an excuse to moan about the cold while we pass from one heated building to the next, bundled tightly in warm clothes and thick coats, then image how hard wild animals find it. There are no insects or berries for them to eat so food is scarce; there is little canopy cover in trees to hide from predators and keep the wind, rain and snow off them; and, to top it all off, they should be eating copious amounts of food just to keep warm!

Due to these rather brutal living conditions, animals have had to be clever in order to survive. Consequently,  they have had to perfect the use a range of physical and/or behavioural adaptations to give them the edge they need to keep one step ahead of the cold.

The most obvious of these adaptations are those that involve specialised behaviours, which typically involve migrating to warmer continents or hibernating through the inclement of winter until spring arrives, bringing  more hospitable weather with it and a much needed abundance of food!

Hibernation then, is essentially just a state of extremely deep sleep that aims to allow an animal to preserve as much energy as possible. In order to do this, a hibernating animal's brain activity drops to a very low level of activity (which is unusual for sleep) and their metabolism virtually stops - allowing them to save enough energy to survive until spring. The process is surprisingly efficient and, as such, scientists have recorded many species of animals that hibernate, although it is most commonly seen in mammals, such bears, bats and hedgehogs, and in certain species of insects, such as bumblebees.

Contrary to popular belief, most animals that hibernate do not sleep continuously and wake sporadically throughout their hibernation in order to defecate and (occasionally) to eat from their food reserves.  This photograph provides a good example of this, showing a doormouse hibernating with emergency hazelnuts close to hand.

For many animals however, hibernation isn't an option since it leaves such individuals very vulnerable to active predators and human disturbances, but they still lack the specialised physical adaptations (like thick coats) that are needed to keep them warm. These animals then, have chosen to simply 'opt out' of the cold winter months and migrate for thousands of miles each year until they reach warmer climates where food is still plentiful. Migration is particularly common in birds, such as house martins, swallows and swifts, and in many species of whale, such as humpback whales that can travel over 25, 000 kilometres a year!

Although many animals survive well using hibernation and migration, they are both extremely risky methods of enduring/avoiding the cold that are fraught with their own disadvantages, such as falling prey to storms while migrating over oceans and not being able to build up enough fat reserves in the spring to sleep through winter! Due to this, many animals not only opt to remain in cold areas, but chose to stay active and alert over the coldest months.

This has meant that many animals, especially species that live in the cold all year round, have evolved a wide range of physical adaptations that help to keep them warm. The most common of these, which has been mentioned above, is to posses a thick coat of fur (just look at the coats of wolves and reindeer), which acts as an excellent insulator against the cold by trapping layer of air above the skin. This layer of air gets warmed by the animal's own body heat and effectively acts as an electric blanket because it can't escape!

In addition to having a thick pelt that covers them, many animals that live in the cold have a thick layer of fat beneath their skin called blubber, which insulates heat and effectively acts as a 'blanket' that traps warmth inside their body. These layers can be extremely thick, with the 4 inch layer found in polar bears being a good example.

Many animals also possess other physical adaptations that are much less obvious since they involve internal changes rather than outside defences. A good example of this can be found in many species of fish that live in the Antarctic, which produce a natural 'antifreeze' in their blood that alters the way water molecules move in a manner that stops them from freezing. The antifreeze is made from glycoproteins, a very common class of biological 'building blocks' and is rather imaginatively called Antifreeze glycoprotein (AFGP), allowing fish to survive in extremely cold waters with a temperature far below 0C.

The wood frog, Rana Sylvatica, has a remarkable survival strategy to survive the winter and actually allows itself to freeze completely solid. As it freezes, the frog packs its cells with glucose and urea (found in urine), which helps to stop their cells from shrinking and splitting as they freeze. As much as 65% of their total body mass can freeze over winter; thawing out in the spring as if nothing has happened!

Many animals that live in algid climates also employ the use of specialised forms of mitochondria and enzymes, called isozymes or allozymes (depending on whether or not its gene is coded on the same chromosome as the original), which work much better at low temperatures than normal forms of enzymes do. Thus, the animal's body simply becomes better at functioning in the cold than it otherwise would have - providing them with a huge survival advantage.

In fact all animals, including humans, have many different isozymes and allozymes in their body that replace normal enzymes after spending a few weeks in a new climate. This is why we appear to 'get used to the temperature' when we move between seasons or go on holiday - unbelievably, we actually are getting used to it!

So there you have it - a few examples of the remarkable methods that animals have developed so they can  survive in (or avoid) the brutal conditions and biting cold of winter! I sincerely hope that you have enjoyed reading this post, along with all the rest in this blog, and hope that you continue to visit my site in the coming year! I already have a whole bunch of (hopefully) interesting ideas for articles and creature features planned for you!

Have a very Merry Christmas!

16 December 2012

The icefish: life without respiratory pigments

Wherever you look for life on Earth, you find it. From free-floating bacteria in the upper atmosphere to tiny organisms that make their home deep within the solid crust of its surface. Animals have been found thriving in deserts hot enough to cook them alive and, similarly, have been recorded living abundantly in environments that are cold enough to freeze their bodies solid!

Living in such hostile conditions places huge strains on the organisms that live there, which, as a necessity, have had to evolve specialised physiological adaptations if they are to survive for long enough to reproduce and pass on their genes. There are many examples of extreme and unique adaptations for this purpose, with those of the Antarctic icefish being among the most bizarre.

Icefish are found throughout the cold waters that surround Antarctica and South America, belonging to the Channichthyidae family - a small group of fish that have no respiratory pigments in their blood. 

Rather uniquely among species of animals, Antarctic icefish do not rely on respiratory pigments to carry oxygen in their blood and lack them altogether! Such respiratory pigments were once believed to be essential for multicellular life to exist since they chaperone oxygen so that it can be removed from the air and absorbed by the blood, where it is at a much higher concentration than in the surrounding atmosphere. This is an important 'law' that life must overcome if it is to grow bigger than a single-celled organism because molecules naturally diffuse from an area of high concentration to one of a low concentration and not the other way around! So, simply put, without respiratory pigments the oxygen content of blood would be too low to fuel life as we know it!

Thus, the vast majority of multi-celled organisms have blood that is packed with respiratory pigments. These pigments are usually constructed from 1 of 2 key metals, with which one being used depending on an organism's evolutionary history and can be used to synthesise a number of different pigments:

  • Iron, which is the most common basis of respiratory pigments, can be used to produce:
    • Haemoglobin, which is found in humans and turns red when oxgenated.
    • Hemethryins, which are found in terrestrial worms and brachiopods, and turn violet when oxygenated.
    • Chlorocruorin, which is found in aquatic worms and turns green when oxygenated.
  • Copper, which is used to make hemocyanins. Hemocyanins are blue when oxygenated and are usually found in families of molluscs and arthropods.

The fact that icefish lack such respiratory pigments is puzzling at first glance, but actually makes sense when it is considered carefully since it provides the fish with a huge advantage in their ability to survive in the harsh cold of Antarctica. Basically this advantage stems from the fact that the colder water is, the more oxygen can dissolve in it. Thus, the frigid Antarctic waters carry much more oxygen than warmer waters do so icefish breathe in more oxygen with each 'breath'. This, coupled with the fact that they have twice as much blood fluid in their body than another species of fish their size, means that they can still provide their muscles with enough oxygen to work effectively.

But why is this advantageous to their survival? Well, the fact that icefish can supply enough oxygen to their muscles in order to survive without respiratory pigments means that they do not have to make any; saving them huge amounts of energy each year that can be used for more useful tasks instead, such as feeding, reproducing and evading predators!

Furthermore having no respiratory pigments in their blood decreases its overall viscosity by about 25%, which means that their heart has to work far less hard to pump blood around their body than it otherwise would have. In addition to placing less strain on the organ so they can live for much longer before it gives out, having thinner blood also reduces their energy expenditure and allows them to move 4 times more blood which each beat than a typical fish their size - saving even more energy!

Thus, the icefish has evolved to possess one of nature's most bizarre and unprecedented adaptations that allows it to thrive in one of the most extreme environments on Earth! Without this adaptation, or another that gave it a similar advantage, the strange fish would have undoubtedly died out long ago, being unable to to survive and reproduce in the freezing waters of the Antarctic...

1 December 2012

Coca Cola: Christmas in the toilet!

Christmas is fast approaching and, as it gets nearer, we all make more and more excuses to indulge in fatty foods and sweet drinks that we know can be very bad for our health! Chief candidates among these luxury foods and beverages are the family of carbonated drinks, such as Coca Cola and Pepsi, which are often drunk in much greater quantities than normal throughout the festive season.

Coca Cola and Pepsi are both examples of carbonated drinks, which essentially means that they have had carbon dioxide gas dissolved in them under high pressure to improve their taste, texture and to give them their fizzy characteristics.

Most of us understand that such carbonated drinks can be damaging to our health if we drink them excessively, over long periods of time, and know that they are associated with a range of clinical problems that include obesitytooth decay and diabetes, which are all related to their high sugar content.

What many of us don't know however, is that drinking large quantities of drinks like Coca Cola and Pepsi in one sitting also has side-effects; mainly, in making us need the toilet more often! Although this isn't quite as serious as, say, becoming diabetic, having to regularly queue for the toilet during Christmas festivities can be highly irritating to say the least!

Basically Coca Cola and Pepsi (along with tea - another popular drink here in the UK), contain chemicals in them that belong to a family of compounds called diuretics, which essentially alter the body so that it absorbs less water; meaning that its bladder fills up faster and we have to urinate more regularly. The diuretics found in these drinks are not particularly strong however and are not associated with any negative side-effects like any of artificial powerful diuretic drugs you may know, so don't worry - they carry no cause for concern!

Although the diuretics found in Coca Cola and Pepsi are weaker than medicinal drugs, they do however, work in the same manner and assert their effects by modulating the synthesis of antidiuretic hormone* (ADH), which controls how much water is absorbed and secreted from the body.

As you may have guessed by its name, ADH stimulates the body so that it retains water in its kidneys - making us urinate less often. ADH does this by activating normally dormant protein carriers called aquaporins, causing them to bind to the walls of the Distal Convoluted Tubule (DCT) in the kidney and to those of the collecting duct that the DCT opens into. Once present in the walls of these vessels, the tiny aquaporins actively collect molecules of water and transport them back into the bloodstream via the vasa recta.

Diuretic compounds then, interfere with the expression of ADH and cause less to be secreted by the brain's posterior pituitary gland. Thus, less water is reabsorbed back into the bloodstream and our bladders fill up faster - meaning that if we drink glasses and glasses of Coca Cola or Pepsi, the only place for the liquid to go is out!

* commonly called vasopressin

20 November 2012

Do we really eat spiders in our sleep?

Urban mythology claims that each year, a certain number of spiders crawl into out mouths while we are asleep and are consequently eaten. While the exact number of spiders that we are supposed to eat varies widely, the common theme remains the same and the stories usually suggest that there is nothing we can do to prevent this from happening.

Spider silk is one of most amazing chemicals in nature, being both incredibly light and having a tensile strength that is far greater than steel. In fact, the silk of the golden orb weaver (not shown above) is 6 times stronger than steel and is 10 times more efficient at absorbing energy than military-grade kevlar, being tough enough to capture bats and small birds!

Whereas it is doubtful that we could stop spiders from crawling or lowering themselves into our mouths if they wanted to (we are asleep afterall), there is actually no need as a spider would not be interested in creeping down our throats, so that in fact, we have nothing to worry about whatsoever!

This is mainly due to the content of our breath, which is warm, humid and has a much higher carbon dioxide to oxygen ratio than 'normal' air does. If a spider was crawling towards our mouth, it would sense such conditions when we breathed over it and would actively avoid them since they signal that the conditions within are mouth are harsher than those outside. Imagine, for example, smelling smoke coming from your living room - even if you couldn't see or feel the flames, you would know that something was wrong and that there may be a danger in the room. Thus, you would most likely avoid going in!

For similar reasons it is unlikely that a spider would want to enter your mouth and, if one was on your face, would probably turn tail and run once it came close enough to feel your breath!

17 November 2012

Better red than dead

Many people consider autumn to be the most beautiful season of the year, where the normally green leaves of trees take on striking hues of red and yellow and swathes of gossamer glitter in the morning dew. It is a season where both plants and animals brace themselves for the oncoming inclement of winter, and, as this post is written, is gripping the United Kingdom in full force.

As mentioned above, one of the of the most notable aspects of autumn is the colour change in deciduous leaves before they fall (via senescence). Whereas senescence may seem to be a waste of resources for a tree, as they will have to regrow their leaves in the following spring, it is actually a necessary stage in a clever life cycle that allows them to maximise their photosynthetic output during the summer. Simply put, their large, broad leaves are big enough to contain huge quantities of a pigment called chlorophyll, which captures the energy in sunlight and uses it to produce sugars and proteins (via photosynthesis). Thus, the leaves of deciduous trees can produce much more energy during the summer than the narrower, needle-like leaves of evergreen trees. Obviously, this is a huge advantage to a tree and will make them much more likely to survive during the spring and summer. However, to use an apt quotation from George R. R. Martin's A Song of Ice and Fire: "winter is coming", and this is where deciduous leaves hit their main problem - they are too big to defend against the cold. So, rather than allow their leaves to die and greatly increase their risk of infection, deciduous trees shed their leaves before they can be damaged by frosts; opting instead to regrow them next spring.

Autumn landscapes can be stunning, with leaves taking on a wide range of beautiful red and yellow hues.

The main problem that this tactic for survival has, is in the huge waste of the resources that a tree has invested in growing its leaves in the first place. For example, imagine how much protein and bone would be wasted if you shed your arm every year only to regrow it at a later date! Fortunately, it seems that deciduous trees became wise to this fact a very long time ago and, before they shed their leaves, they reabsorb much of the chlorophyll and useful proteins, which are then used to produce new leaves the following spring. In fact, it is this 'recycling' of chemicals and removal of leaf colouring pigments that produce the yellow colour of autumn leaves, which becomes more intense as more chemicals are stripped from its cells.

This is a very simple biological idea and has been accepted within the scientific community for decades. But, there is one aspect of senescence that is still widely disputed among plant physiologists and biologists alike - the reason behind the red colour of senescing leaves, which is produced by a class of pigment chemicals called anthocyanins. To briefly summarise the strife, many scientists are adamant that anthocyanins serve no function in senescence and believe that they are merely a waste product of reabsorbance; resulting from a complicated carbohydrate overflow process. Other scientists however, believe that is is not the case as anthocyanins are actually manufactured by trees via a very energetically expensive process; thus, arguing that they must serve a specific function or they wouldn't be produced.

This idea is supported by recent research, which indicates that anthocyanins may be crucial for the survival of a deciduous tree. Within this research, there are 2 major theories that offer explanations for the presence of anthocyanins:

  • The first, purposed by Taylor S. Feild, suggests that anthocyanins act as optical screening pigments to protect chloroplasts from being damaged by destructive ultraviolet (UV) radiation, which effectively counters the reabsorbance of normal screening pigments and allows leaves to photosynthesise for longer.
  • The second, developed by the famous geneticist William D. Hamilton, is called the 'coevolution theory' and argues that the bright red displays are produced by deciduous trees as a warning to deter destructive aphids that colonise them throughout autumn.

The first theory works using the knowledge that UV radiation is just as dangerous to trees as it is to human skin and, in accordance with this, plant physiologists discovered long ago that trees produce screening pigments in their leaves that act in the same way as sun cream. When trees begin to reabsorb these screening pigments before shedding their leaves, they expose their chloroplasts to much greater levels of UV radiation. These levels are easily high enough to destroy chlorophyll pigments and thus, stops a tree from being able to photosynthesise efficiently.

In his research, Feild found that senescing leaves produced more anthocyanins as the intensity of the UV radiation they were exposed to increased, supporting his idea that they are produced as protective screening pigments.

Feild argues that a deciduous tree counters this by investing in the production of anthocyanins, which serve as 'replacements' for the screening pigments that are reabsorbed. Thus, the presence of the red pigments allows a tree to photosynthesise for much longer than it could have ordinarily, making it much more likely to survive the winter. Furthermore, due to the relative toxicity of anthocyanins, a tree would have little incentive to reabsorb them and would have no qualms in losing the pigments when their leaves fall.

Hamilton's coevolution theory differs from Feild's hypothesis in that it considers the effects that the red colouration of foliage has, assuming that it is an honest signal to pests about a tree's defensive investment. As said above, anthocyanins are relatively toxic and are harmful to herbivorous aphids that are known to colonise trees throughout autumn. Thus, by producing more anthocyanins, which in turn makes leaves redder, a tree invests in defences that will help it to survive the winter; i.e. the more anthocyanins it produces, the less likely it is that pests can survive by living on it.

Hamilton argues that aphids have learnt to avoid trees with the brightest red foliage as they know that these will be the most difficult trees to survive on, instead colonising trees with a lower defensive commitment. Due to this active selection by aphids and other pests, producing a bright red foliage would be under a strong evolutionary pressure since such trees will be healthier in the spring and thus, will be more likely to reproduce and pass on their genes so that overtime, leaves produce more and more anthocyanins.

Hamilton noticed that the amount of anthocyanins synthesised by trees varied, evidenced by the variety of red hues that are displayed between individual trees. If the pigments were produced solely to protect against UV light, it would be expected for all of the members of a species to show the same levels of anthocyanins in their leaves, which is not the case. Furthermore, Hamilton found that the trees displaying the reddest foliage showed the lowest concentrations of aphid pests.

Both of the theories discussed above are very controversial within the scientific community at the moment and are not widely accepted. Despite this, there are many botanists and biologists that believe at least one of them to be correct, as they are unable to accept that such energetically expensive pigments as anthocyanins would be produced without a good purpose - this is not how nature works and proteins are only produced if they are needed or the resources are used to produce something else. For example, human muscle mass begins to deteriorate after about 2 weeks of inactivity as their body determines that it is not being used anymore and stops expending resources and energy to maintain it. 

Many biologists however, myself included, go even further than just believing one of these theories to be true and have noted that neither of these theories appear to contradict each other. In fact, they do not and are not mutually exclusive. Thus, it may well be that anthocyanins have a dual purpose and were originally produced by trees to extend the length of time that they could photosynthesise for and, due to their bright colour, soon developed a secondary role in deterring aphid invasion!

7 November 2012

World's most poisonous animals

The world is a cruel and unforgiving place; particularly for wild animals who spend their lives roaming the Great Outdoors. Only the best and fittest individuals are able to survive in it, which largely involves evading capture or the hunting and killing of smaller and weaker animals. Simply put, an animal must either kill or be killed if it is to carry on living. As melodramatic as this sounds, it's one of the most fundamental rules of Nature.

Due to this, animals have come up with a whole range of ingenious weapons to fight with and defences that guard against their demise. From horns to armour plating, animal evolution has been driven the effectiveness of their arsenals and no weapons are more deadly and feared that poisons - toxic chemicals that are injected via bites, stings or touch to incapacitate or kill both predators and prey alike.

Although there are thousands of different poisonous animals, there is a huge range in their toxicity and the damage that they can cause, meaning that not all poisonous animals are deadly. However, there are many that are incredibly dangerous and this post provides a comprehensive list of the most poisonous animals in the world.

10: Pufferfish

Pufferfish mainly use their poison in self defence. When they are threatened by a predator, pufferfish swallow large quantities of water and inflate their body so that their toxic spines stand on end.

Pufferfish poison produces a rapid and violent death within 24 hours of being stung, where an individual experiences heart palpitations, difficulty in breathing, muscle spasms/paralysis and vomiting. There is no known cure to their poison and victims eventually find themselves unable to breath, and die.

9: Golden dart frog

The venom of the golden dart (or poison) frog, Phyllobates terribilis, was once rubbed onto darts and arrowheads by hunters in South America to make their weapons even more deadly.

The golden dart frog is the most poisonous amphibian on Earth and excretes its toxins directly onto its skin. Due to this, it is extremely dangerous to pick up one of the frogs, and there is enough venom spread over the surface of its body to kill 20, 000 mice or 10 adult humans.

8: King cobra

The snake-eating king cobra, Ophiophagus hannah, is the world's longest venomous snake and can grow to lengths of 5.6 metres (18.5 feet).

As well as possessing a very potent poison that can kill in itself, the king cobra is the master of 'overkill' and injects huge quantities of venom with each bite. For example, it injects 5 times more poison into its victims than does the infamously violent black mamba. In fact the king cobra injects enough venom to kill an elephant within 3 hours, if it bites them in a vulnerable area such as on their trunk.

7: Brazilian wandering spider

The Brazilian wandering spider, Phoneutria nigriventer, is also called the armed spider and is extremely aggressive, living in banana plantations throughout Brazil.

The Brazilian wandering spider is the most deadly arachnid in the world and is named due its tendency to wander into peoples homes and clothing, where they hide during the day. Their bite is not only deadly and extremely painful, but can also lead to sustained and highly uncomfortable erections in men (priapisms) that often leads to long-term impotence.

6: Stonefish

Stonefish are found in the shallow waters of Eastern Australia and actually use their poison for self defence, raising their spines only when threatened rather than to hunt their prey of shrimps and small fish.

The toxins that the stonefish inject through their spines are said to be so painful that many who have been stung have said that they would rather have had their limb amputated than have endured the pain. In fact, the pain that they cause is believed to be on the threshold of human sensation, being described by many female victims as being infinitely worse than childbirth. Once stung, an adult will normally die within two hours if they do not seek immediate medical help.

5: Deathstalker scorpion

The Deathstalker scorpion, Leiurus quinquestriatus, probably has one of the most unpleasant poisons on this list. After being stung, a person will suffer from unbearable pain before falling into a deep coma. While in this coma, the scorpion's toxins destroy the person's nervous system, leading to irreversible paralysis and eventually, death.

Despite having one of the most potent venoms in nature, the Deathstalker scorpion will probably save more lives in the future than it ends. Their poison contains a unique clorotoxin that can be modified by scientists so that it attaches only to cancerous cells in the human brain, leaving healthy cells alone. Chemotherapeutic drugs can be attached the chlorotoxin before it is injected, effectively forming a 'magic bullet' drug that hunts down and destroys the cells in brain tumours.

4: Blue-ringed octopus

The blue-ringed octopus, Hapalochlaena lunulata, is tiny, being scarcely larger than a  golf ball and typically feeds off small crabs and shrimps.

Like all species of octopus, the blue-ringed octopus possess specialised skin cells that allow them to change colour depending on their mood. Oddly, their lethal and incurable bite is painless and usually contains enough venom to kill 26 adult humans.

3: Marbled cone snail

The marbled cone snail, Conus marmoreus, is a predatory snail that lives in the Indo-Pacific Ocean. Relative to its size, the snail is the most poisonous animal on the planet.

Due to the slow and cumbersome nature of snails, some of you no doubt find the whole idea of a predatory snail as being unlikely. It would seem that you are not alone in this and the snails appear to have noticed their limitations in speed and manoeuvrability as well, actually hunting via a poisonous 'harpoon' that they launch at fish that get too close. This harpoon is absolutely lethal, being loaded with enough poison to kill 20 adult humans.

2: Inland taipan

Also called the small-scaled snake and the fierce snake, the inland taipan, Oxyuranus microlepidotus, is native to Australia and is the most venomous snake in the world; with its poison being able to kill an adult human within 45 minutes after being bitten.

An adult inland taipan is thought to have enough venom in its body at any one time to kill 250, 000 mice or 100 humans! Unbelievably, its nervous system attacking venom has been calculated to be 50 times more deadly than the common cobra and 10 times as toxic as the Mojave rattlesnake.

Fortunately for us, the inland taipan is an exceedingly shy snake that rarely bites unless it has been provoked;  and even then, bites are rare. Due to this docile nature, no human deaths* have ever been recorded.

1: Box jellyfish

There are several different species of box jellyfish spread throughout many tropical and subtropical oceans, which all contain extremely damaging toxins, and can be easily distinguished by their cube-shaped 'heads'.

Sadly, box jellyfish have been responsible for more than 5, 500 recorded deaths since 1954*. Their poison is highly potent and attacks their victim's heart, skin and nervous tissue. If stung by a box jellyfish, a person has little chance of survival unless they receive medical help almost immediately. Fortunately, the acetic acid found in vinegar can counteract some of the effects of the poison and stop any undischarged nematocysts from injecting more venom into the wound caused by their tentacles.

Despite its incredibly potent venom and the vast number of deaths box jellyfish have caused, it is worth noting that some scientists argue that they not actually the most poisonous animal in the world and that the highly esteemed honour should be awarded to its closely related cousin, the tiny Irukandji jellyfish.

* to the best of my knowledge, the figure was correct at the time this article was published.

4 November 2012

Lyes of attraction

Except for the occasional white lie here and there, most of us try to avoid deceiving our families and friends and dislike being lied to by others. Lying is not considered a positive trait and people who tell fibs too often are mistrusted and usually find that they have fewer friends than they thought they did.

As you undoubtedly know, lying is a particularly huge issue in relationships and has probably broken up more couples over human history than we can record. This comes as no surprise and dumped liars rarely receive sympathy as we all know that it's their own fault. What is odd though, is that not all animals share our views on lying and for one species in particular, the Australian lyrebird, the better an individual can lie the more popular they are!

Lyrebirds are among the most esteemed of Australia's native animals and are famous for their impressive prowess of 'lying'.  There are just 2 species of lyrebird: the superb lyrebird (Menura novaehollandiae) that is pictured above and Albert's lyrebird (Menura alberti), which belong to their own unique genus.

In fact, being able to lie well is much more important than simply for making an individual popular - it is an essential skill that a male bird must master if he wants to attract a mate! Lyrebirds, you see, have one of the most sophisticated courtship rituals in nature, which involves splaying their luxurious tail feathers (in much the same way as a peacock), and mimicking as many noises as they possibly can. These sounds, which can be imitations of anything, such as other bird calls, car alarms and even chainsaws felling trees, are then incorporated into an elaborate song that the male may sing for up to 4 hours a day during breeding season (June to August)!

It appears that the more complex the courtship song, the more successful the male bird is in attracting a mate. Once a male lyrebird has successfully mated with a female bird, she lays a single egg in a nest that she's made on the ground, and incubates it as the sole parent for nearly 2 months.

Analysis of the songs made by courting lyrebirds has found that they are usually split into 7 clearly distinct sections, where about 80% of the entire song is made from mimicry. Male and female lyrebirds both become sexually mature before they are 10 years old, although it should be noted that females mature a few years earlier than males do. Due to this, male birds don't actually start singing properly until they are almost a decade old. Before then, males are believed to practise 'lying' where they learn to modulate their highly developed voice box so that it can mimic almost any sound they hear.

Thus, the ability to lie and produce a whole host of sounds that are not normally made by lyrebirds is a huge part of their culture and has made the passerine (song) birds one of the most noted birds in Australia, and maybe even in the world.

19 October 2012

Age of first sexual encounter may effect relationship happiness and success in later life

It is widely accepted that modern society runs at a faster pace than it used to, with children and teenagers experiencing many life events at much younger ages than did their parents and grandparents. This 'growing up fast' way-of-life is of great concern to many parents, especially when their children's ventures into sexual relationships are concerned, who are worried that their children are not ready such encounters. Is there really a cause for concern, however, or are parents just fussing and worrying for nothing?

Humans are a very social species and, in resource-abundant environments, usually favour a mating pattern called monogamy, where one person has just one sexual partner for a long period of time. Such relationships are rewarding and healthy when they work, creating stable conditions in which to raise a family.

Recent research from the University of Texas has suggested that, unfortunately, there is. The study, which was carried out by psychologist Paige Harden, has tried to determine whether the timing of an individual's first sexual encounter affects their romantic relationships later in life and whether it can predict factors like relationship satisfaction, the likelihood to marry and the number of sexual partners.

Dr. Harden conducted this research via a meta-analysis, using data from the [US] National Longitudinal Study on Adolescent Health and followed 1659 people from their early teens to young adulthood (<29 years old). As part of this research, Harden classified each participant in one of three categories in regard to their age at their first experience of having sexual intercourse: Early (<15), On-time (15-19) or Late (>19), before comparing the qualities of their romantic relationships/encounters.

As she predicted, the most highly educated participants from greater income families were older at the time of their first experience of sexual intercourse. The study appears to show that first experiencing sex at a later age is beneficial to an individual, as those in the study showed greater levels of marriage (or living with their partner), were less likely to be dissatisfied with their partner, were less likely to persist in an abusive relationship and typically had less sexual partners over the course of their life.

In contrast, those who were younger at their first encounter tended to have many more sexual partners and typically showed a greater level of romantic dissatisfaction. This data also fit with a clear pattern: those in the 'Early' group showed much more exaggerated trends than those in the 'On-Time' category.

Dr. Harden explains these results by suggesting that waiting until later to first have sexual intercourse may be beneficial to an individual as it allows their cognitive and mental development to have finished first. As well as having obvious benefits such as greater confidence, which makes an individual more likely to walk away from abuse and inappropriate pressure, being fully developed [mentally] also appears to enable an individual to learn more 'healthy' relationship skills. Harden suggests that it is these skills in particular that allow an individual to form healthier and happier relationships, which are more likely to endure for longer periods of time.

Although these findings are worrying, and seem to show that being young when having sexual intercourse for the first time can have series and long-term negative side-effects,  more research needs to be carried out into these ideas before any significant statement can be made. Dr. Harden has acknowledged this, saying that "we are just beginning to understand how adolescents' sexual experiences influence their future developments and relationships". For the time being, however, it looks like parents are right after all, and children may indeed, be 'growing up too fast'.

14 October 2012

Black mamba venom may be a super painkiller!

French scientists have recently identified that the toxic venom of the black mamba, one of Africa's most dangerous and feared snakes, has a huge potential for its use in medicine. The research, carried out by Dr. Eric Lingueglia from the Institute of Molecular and Cellular Pharmacology near Nice, has identified that the snake's poison contains a unique class of chemicals called mambalgins, which act as painkillers in mice that are as strong as morphine but have none of its associated side effects.

The black mamba, Dendroaspis polylepis, is named after the dark skin inside its mouth rather than after the colour of its scales. As well as being among the most poisonous snakes in the world, the 3 metre long mamba is also the fastest and can even outrun humans. These attributes, along with its highly aggressive nature, have made the snake highly feared among all the African peoples that live alongside it.

These properties of black mamba venom are of huge interest to the healthcare sector because, despite its heavy use, morphine is highly addictive and has many severe side effects for those taking the drug, which include headaches, a reduction in their thinking capacity, nausea and muscle spasms. A new painkiller then, which is effective enough to remove the same agonising pains as morphine but with none of its side effects would be like a 'magic bullet' in pharmacology, being hugely popular among both doctors and their patients.

Research has identified that these useful mambalgins may work in such a beneficial way because they operate via a previously unseen neural pathway that is not targeted by any other studied venom or by the palliative drugs currently in production. Dr. Nicholas Casewell, a world-leading expert in snake venom from the Liverpool School of Tropical Medicine, is avid over the potential implications of black mamba toxins to medicine and has said that mambalgins are "a really great example of drugs from venom, we're talking about an entirely new class of analgesics".

Dr. Lingueglia believes that this rather surprising property of black mamba venom may be as an intentional effect of the poison, which helps to incapacitate the snake's prey so that it is less likely to escape; or may be due to a chance, but useful, fluke in mice, resulting from the differences in brain chemistry between the rodents and the snake's usual prey.

Whatever the reason for the venom's remarkable analgesic properties in mice however, scientists are excited about the discovery and are hopeful that the toxins will have the same effects in humans as our brain chemistry is very similar to that of the rodents (which is why mice are often used in scientific studies). It is likely that there will be extensive research into mambalgins in the near future, which will hopefully lead to a new drug that acts as a safer alternative to morphine.

10 October 2012

From black to white: is calcium really that important?

The majority of us are at ease with Darwin's concept of evolution and understand how the 'survival of the fittest' has led to the vast abundance of life on Earth. Obviously, humans are no exception to this rule and evolution has moulded us into what we are today. Evolution, for example, selected for the first of us who began to move on two legs as this freed up our hands for better tool use; and selected for those who chose to live in social groups, which provided much more protection and help than did living alone. Without evolution it is doubtful that any life would exist on Earth at all, especially not in the form of hugely sophisticated organisms like humans.

Life on Earth began sometime around 4 billion years ago. It is believed that single-celled organisms first evolved on the shores of primordial oceans, which were abundant in the resources needed for life. Over time, these cells eventually evolved into the countless forms of life that we see on Earth today.

Most of you won't be surprised by any of this; it makes sense, after all. Something you might find surprising however, is why scientists believe that the early humans settling Europe evolved from being black to white. Obviously the sun's rays are less intense in Europe than they are in Africa, meaning that European settlers wouldn't have needed to produce as much of the pigment melanin in their skin, which absorbs ultraviolet (UV) radiation. Producing less melanin then would have provided such individuals with an advantage as they wouldn't have been wasting energy producing proteins their body didn't really need. This saved energy could then have been dedicated to more important processes (like keeping warm in the colder climate, for one thing).

Although this theory makes sense logically and saving energy by producing less melanin could quite plausibly have been the difference between life and death in the harsh European winters, is it really enough to have driven the evolution of one of our most noticeable racial polymorphisms?

Many scientists believe not, at least not by itself anyway, and research into this question has provided a rather odd alternative. Simply put, many scientists now believe that Europeans evolved from having black skin to white skin due to calcium!

Calcium is an fundamental resource for our bodies, with its ions having essential roles in muscle contraction; in propagating nerve impulses; and, arguably most importantly, in forming our skeletons (via binding with phosphorous to form a very stable salt called calcium phosphate). Despite its importance, calcium is rare in nature and is extremely difficult to acquire naturally as part of our diets. As always however, Nature provided early man with an ingenious way around this and all humans are able to make vitamin D in their skin when it is exposed to sunlight (in much the same way as plants photosynthesise sugars from sunlight to use as energy). Vitamin D greatly increases the affinity of calcium absorption in the gut, allowing the body to absorb much more of any calcium that it consumed than it would otherwise be able to.

Due to this ability, most people are able to acquire enough calcium (especially during the summer) to lead normal and healthy lives, and indeed, our African ancestors would have had strong bones and efficient muscles. The problems arose however, when early explorers entered Europe where the sun's rays are much less intense. This meant that the melanin pigments in their black skin were able to absorb much more sunlight than they could while in Africa and, as a result, vitamin D could no longer be produced.

Fossil evidence suggests that it was not long before the health of these explorers deteriorated, and many adult skeletons from the period show symptoms of osteomalacia (a disease where bones soften due to lack of calcium and deform under the weight of walking), and many may have suffered from a range of muscle weakness and epileptic disorders as their reserves of calcium were depleted and less and less could be replaced from bone stripping. Obviously such ill effects greatly reduced an individual's chances of survival and those with slightly lighter skin would have been more likely to live longer. Being healthier and living longer meant that they would have been more likely to survive to reproduce and slowly, the 'lighter' genes (which produced less melanin), would have spread through the population. In each generation the palest individuals would have been most successful at surviving and breeding so, over time, European humans would have got paler and paler until their skin was as white as it is in their descendants now.

As if this selection pressure wasn't enough to drive for whiter skin, having low levels of calcium and brittle bones had another major problem for women in particular - it hindered childbirth. Many women had such brittle pelvises that they broke under the strain of labour, virtually guaranteeing that both the infant and the mother would die. Furthermore, many children suffered from severe rickets due to a lack of calcium during childhood and puberty. This meant that such individuals were physically smaller than they should have been and many women suffered from underdeveloped hips that were too narrow for a baby to pass through. As a result, such a mother and her baby would have died during labour. Thus, many of the darker individuals would have been unable to give birth so that the darker genes disappeared from the European populations very quickly - being strongly selected against by Nature!

The degree of deformity that rickets can lead to can be very extreme, almost completely debilitating a child suffering with the condition throughout their entire life.

Scientists also believe that this explains why the vast majority of Europeans (and those in their descendent colonies such as Australia and the USA) can eat dairy as a stable component of their diet. This is actually quite abnormal, both in the animal kingdom and among other ethnicities of humans, as rennin (the enzyme required to digest milk) usually stops being produced by the body in infancy after the individual has been fully weaned. Thus, most humans are lactose intolerant and experience unpleasant symptoms if they drink milk or eat too much dairy-based produce. Humans evolving in Europe however, needed as much calcium as possible and would have been under strong selection pressure to continue producing rennin throughout their lives as milk is an unrivalled source of calcium.

Thus, the importance of calcium to the human body has made it an invaluable component that we need to survive. Too little calcium leads to severe health conditions that are so extreme that they can even drive evolution into turning black humans, who have very active melanocytes (melanin-producing skin cells), into white humans who have very little sun-protective pigments in their skin (allowing them to produce more vitamin D).

26 September 2012

Mountain gorillas seen disarming poachers traps!

Everyday, animal trackers set out from the Karisoke Research Center into an isolated area of Rwandan rainforest aiming to find and disarm as many of the dangerous and illegal traps set by poachers as they can find. The trackers efforts are crucial in helping to protect the extremely rare mountain gorillas (Gorilla beringei beringei) that inhabit the region, which are classified as being 'Critically Endangered' by the IUCN and are predicted to become extinct within 10 years if we fail to conserve them.

When tracker John Ndayambaje set out one morning he was fully expecting to see poachers traps. Sure enough, he located a clan of gorillas and spotted a snare trap nearby. Although many poachers don't set snare traps to catch gorillas, as adults of the species are easily strong enough to break free, they are capable of killing juveniles so he knew that he must disarm it.

When John moved to approach the trap however, a silverback called Vubu grunted at him, presumably warning him to stay away. As John watched, two younger gorillas named Rwema and Dukore made their way over to it and carefully broke it, working confidently and quickly, which suggests that they've had extensive experience with the traps in the past. Rwema and Dukore then searched the surrounding foliage, joined by a third member of the Kuryama Clan called Tetero, and disarmed several more traps that John hadn't yet seen.

Rwema and Dukore work together to disarm a snare trap set by poachers.

This remarkable ingenuity has undoubtedly arisen in response to the very real dangers that the traps pose and is a superb example of mountain gorilla intelligence and their ability to learn. Researchers at the Karisoke Research Center believe that the gorillas watched human trackers tackling the traps and copied how they disarmed them. Although fascinating to watch, Veronica Vecellio (the Centre's gorilla program coordinator) was not surprised by the events and said that she is "always amazed and very proud when we [the Centre's researchers] can confirm that they are smart".

18 September 2012

Mirrors can cure phantom pains? Who knew...

Many people who have lost limbs in accidents, to amputation and even those born without correctly formed limbs, experience strange sensations in the absent limb or appendage. These feelings are known as phantom sensations and are very common, with around 70% of amputees experiencing phantom limbs.

Although scientists do not know what causes phantom limbs definitively, the common consensus is that the sensations are formed by the reorganisation of somatosensory cortex in the brain. It is believed that once the nerves for the missing limb stop receiving stimuli, they are removed by the brain to give more room to functional neurones. This also explains why a person's hearing gets better if they lose their sight - by replacing the now redundant 'eye processing' neurones with those that deal with hearing, the brain can analyse sounds more efficiently. Phantom limbs are thought to occur when this reorganisation is maladaptive, or is not fully completed, so that the brain still receives phantom signals from neurones for limbs that are no longer present.

The symptoms of phantom limbs offer some support for this theory since the sensations that patients experience are often similar. Usually, patients describe the phantom limb as being shorter than the original was. The difference in size can be very pronounced, being as much as 6 inches shorter in some cases! Many patients also describe feeling itches and tingling sensations in their phantom limb, which are symptoms that can all be explained by the reduction in processing capacity for the limb in the brain.

Whereas this is all very interesting, the phantom sensations don't stop here for many patients and the majority of individuals who experience this phenomenon suffer from varying degrees of discomfort and pain. Phantom Limb Pain (PLP) is very common and, as with phantom limb syndrome, doctors don't really know why it occurs. There are 3 leading theories however, which all have strong support within the medical and scientific communities:

  • The first is called maladaptive plasticity and is the same as the theory discussed above, suggesting that PLP is the result of maladaptive changes in the neuronal distribution of the somatosensory cortex following amputation.
  • The second suggests that PLP is a result of the conflict between the signals from the missing limb's old neurones, which are telling the brain that the limb is there, with the information from the patient's eyes, which is telling them that the limb is not there. It is believed that the conflict between this information confuses the brain, leading to intense pain in the phantom limb.
  • The last generally accepted explanation suggests that vivid memories of limb positions kick in after it has been amputated, and that these memories hold the limb in a certain position that the patient is unable to alter.

Without further understanding of the causes of PLP however, it is unlikely that scientists can develop a 'fix all' cure for patients due to the complexity of the condition. This is a real problem for many patients of PLP since the condition is most likely neurological, meaning that pain killers have no effect as a palliative and attempts to use drugs have repeatedly failed in the past.

A promising treatment for PLP does exist however, which has been successful in many cases. The treatment was developed by Vilayanur S. Ramachandran and his colleagues in the 1990's and involves the use of mirrors to trick a patient's senses into thinking that they are moving their phantom limb. 

This trickery is accomplished using a mirror box, in which the patient places their healthy limb in one hole and their stump in the neighbouring one. The top of the box is covered over their amputated limb, which the patient then appears to see as being whole again by watching the reflection of their healthy limb. When ready, the patient is asked to perform  'mirror symmetric' movements in both limbs simultaneously. Their brain then interprets moving their phantom limb and appears to 'see' it moving so any conflicting signals disappear, allowing the limp to shift from uncomfortable, painful positions.

Ramachandran's mirror box. Patients suffering from PLP put their healthy and phantom limbs into the box and, due to  the reflection of the mirror, appear to have two healthy limbs again.

A good example for mirror box therapy (based on an actual case), would be to imagine that one of your hands has been amputated. Following the operation you experience the sensation that your missing hand is constantly clenched, with the feeling being so strong that you are continuously in pain. In the therapy you are asked to clench and unclench both of your hands at the same time. By appearing to see your phantom hand move, your brain interprets that it is now unclenched and the pain disappears. 

Regular sessions of mirror box treatment have been able to alleviate PLP in many patients until it eventually disappears by itself, which occurs in most cases given enough time. As with the causes of phantom limbs and its associated pain, scientists can only offer theories to how mirror therapy works and it is possible that we may never know definitively due to the complexity of the human brain. Developing our understanding of mirror therapy may help to resolve an exceedingly curious phenomenon that has long baffled scientists and medics alike.

13 September 2012

First new monkey discovered in 28 years!

Recently, a team of scientists have been cataloguing the animals present in the Tshuapa-Lomami-Lualaba region in the Democratic Republic of Congo. The area consists of around 6, 500 square miles of undisturbed forest and is one of the few unexplored areas left in Africa. Very early on, their efforts found the region to have an abundance of primate life, being home to bonobos and at least 10 other primate species, making it an important link in understanding the evolution of primate diversity.

Scientists have named the newly discovered Lesula monkey after the nearby Lomami River, calling it Cercopithecus lomamiensis.

What is even more remarkable than this significance, is what the researchers found in Opala, one of the towns that they were using as a base for their research. In a visit to a local primary school, the team was shown a young female monkey that was being kept as a pet by one of the directors. What is truly remarkable, is that this monkey was a member of a new species that had never before been seen by scientists. Known as a  lesula by the locals, the species belongs to the family of African guenons - a group which scientists previously believed that they knew very well! It appears that the two nearest rivers, the Congo and the Lomami, have isolated the species from its cousins so that the lesula evolved fairly independently via a process known as allopatric speciation.

Extensive investigation has revealed many more individuals of lesula kept in captivity in the surrounding area and individuals have been found living freely in the forest. It is hoped that the uniqueness of the species, along with the fact that many more undiscovered animals could be waiting in the forest, will be enough to legally protect the diversity of the area. Plans are already in motion to officially declare this protection, turning the Congo Basin into the Lomami National Park.

4 September 2012

Masters of subjugation

Slavery is unarguably a terrible thing that has sadly ruined the lives of countless human beings throughout our violent history. Slaves were used to build the Egyptian pyramids, constructed the Mayan temples and were even used as a source of profit for many European empires during their colonial histories. Fortunately however, slavery is now illegal and has been banned for centuries in many countries. Great Britain for example, passed the Slavery Abolition Act in 1833 that banned slaves being possessed or sold anywhere within the British Empire and its dependencies. Due to its negativity and historical importance, the concept of slavery isn't new to anyone. What may surprise you however, is that humans are not the only animals to have enslaved others and certain species of ants run their entire colonies using only conquered workers!

Rather unimaginatively, such species have been termed 'slavemaker ants' and can be found across the Americas, Europe and some parts of Asia. Slavemaker ants are usually rare, but highly successful species and colonies of around 3, 000 of the ants can have as many as 60, 000 slaves working for them that cater for their every need! In fact, the genealogy of slavemaker species shows just how successful they are as most species are completely unrelated to each other. This fact suggests that their behaviour has evolved independently on several different occasions, so enslaving others must be a beneficial and rewarding way for ants to live. 

Formica sanguinea is a species of slavermaker ant that is native to the British Isles, being found most commonly in the Scottish Highlands and in the south-east of England. The species is unusually large, growing to over a centimetre long, and organises itself into multiple 'platoons' of about 100 workers before an assault. Eggs and workers from the attacked nest are carried back to their 'mother nest' to be enslaved with pheromones secreted by the slavemaker queen.

Although subjugating behaviour is clearly advantageous for slavemaker ants now, why it evolved in the first place is confusing. This is because colonies of slavermaker ants are typically very small and prefer to attack only the biggest and most strongly guarded colonies of other species. As well as carrying high risk for the attacking ants, which may be wiped out in the attack (thus ending the colony as all of its members are required for each assault), the urge to enslave has come at a price and slavemaker ants are incapable of running a colony by themselves. In fact, slavemaker workers seem to have completely forgotten the basic foraging, building and nursing behaviours seen in all other species of ant and only their queen seems to be able to function normally (who lays new eggs of slavemakers).

The loss of these normal behaviours have come at the gain of new ones however, and slavemakers have many different tactics for invading nests. Their tactics are usually used to reach one of two different goals: some species invade an existing nest and take up residence there, while others destroy a nest and carry their unborn young/survivors back to their own queen.

Slavemaker invasion of existing nests is usually carried out using 'distraction' techniques. In such assaults, the majority of slavemaker workers attack the nest to provide a diversion for the colony and draw their soldier class into focusing on them. The pre-mated slavemaker queen then uses the ensuing medley to sneak into their nest with a small raiding party and kills their actual queen, whom she then mimics. This is accomplished by rolling in her pheromones (the chemicals that ants use to identify those of their own colony from hostile invaders) and thus, when the assault is over, the workers of the nest are none the wiser to the exchange and care for the slavemaker queen as their own while she produces more slavemaker ants.

Slavemaker species that seek to completely destroy a nest often have clever biological tricks up their sleeves as their numbers are normally too few to win in an all-out assault. Saying this, it should be noted that some species of slavemaker ant like F. sanguinea have grown to be very large and thus, do rely merely on brute force. Most species don't however, and perhaps the most interesting method used is seen in some South American species, which secrete a chemical that causes ants to abandon their nest. Once empty, the slavemaker workers simply enter it and take the unhatched pupae, carrying them back to their own 'mother nest'. Once these ants hatch, they accept the slavemaker queen's pheromones as their own and spend their lives serving her and her nest.

So there you have it! Ants that conquer the nests of other species and enslave their workers for their own colony's survival! Unlike human slavery however, this is unlikely to stop and ants will likely continue to master the art of subjugation for years to come...

20 August 2012

Ocean Giants

Throughout its history Earth has been home to animals of epic proportions. These monsters have included dragonflies the size of small planes, dinosaurs that were so big that the very ground trembled when they walked and huge land mammals such as the woolly mammoth, which were actually seen by early man! Most of these colossal animals are now extinct however, with only the occasional over-sized fossil being found as the the only indication that they ever even existed. Despite the loss of these species, Earth is still filled with giants and none are bigger and heavier than the whales. 

10: Gray whale - 45 feet/40 tonnes

The gray whale, Eschrichtius robustus, is the only surviving member of its family,  Eschrichtiidae, which first appeared  over 30 million years ago. Gray whales were nicknamed devil fish during the whaling era because of their violent behaviour when hunted.

Gray whales are famous for their 14, 000 mile (22, 000 kilometre) migration route that takes them from the Bering and Chukchi Seas in the summer to Mexico over the winter. This route was once believed to have been the longest migratory journey undertaken by any animal, but recent evidence now suggests that some humpback whales can travel even further!

9: Sei whale - 48 feet/45 tonnes

The sei whale, Balaenoptera borealis, is one of the fastest species of cetaceans (the family of whales, dolphins and porpoises) and has been recorded swimming at speeds of 30 mph (50 kph).

Sei whales need to consume nearly 1, 000 kilograms of copepods (small crustaceans), krill and zooplankton every day in order to meet their energy requirements. Sei whales are a type of baleen whale, which means that they eat by filtering the organisms out of the water as they swim. Sei whales can be found in most of the world's oceans, although they are not found in polar waters.

8: Humpback whale - 45 feet/48 tonnes

The humpback whale, Megaptera novaeangliae, is easily identifiable by its  knobbly head and unusually long pectoral fins. Male humpbacks produce one of the most complex songs out of any whale species, which can last for as long as 20 minutes and are often repeated for hours at a time. Although the function of their songs is not conclusively known, it is believed that they have a role in attracting a mate.

Humpback whales are one of the most wide-spread species of whale and can be found throughout the world's oceans. They have an intensive migration route and travel over 16, 000 miles (25, 000 kilometres) a year from the cold polar waters where they spend their summer to the tropical or subtropical waters where they breed and give birth in the winter.

7: Sperm whale - 50 feet/60 tonnes

The sperm whale, Physeter macrocephalus, is the largest living species of toothed animal and has the  largest brain of any animal in the world.

Sperm whales feed predominantly on giant squid, which they dive for to depths of up to 3 kilometres. This feat makes them the deepest diving animal and they navigate in the complete darkness using echolocation. The clicks that they produce  for their echolocation have a range of 60 kilometres and are the loudest sound produced by any animal.

6: Bowhead whale - 55 feet/75 tonnes

The bowhead whale, Balaena mysticetus, lives in the frigid waters within the Arctic Circle. In order to keep warm here the whale has a huge layer of blubber that accounts for up to 50% of its total body mass.

Bowhead whales are unique among mammals because their bones never fuse. This means that they keep growing throughout their entire lives and individuals as long as 70 feet have been found (although this post uses the average length of each species, else it would be higher up the list). Remarkably bowhead whales are believed to live for over 200 years due to their low body temperature and females have been found over the age of 100 that are still fertile!

5: North Atlantic right whale - 52 feet/100 tonnes

With only 400 individuals of the species left in existence, the North Atlantic right whale (Eubalaena glacialis) is one of the most endangered whales in the world. This is despite its protection under the Marine Mammal Protection Act of 1972 and the U.S. Endangered Species Act of 1973.

Like all right whales, North Atlantic right whales can be distinguished by their broad back that lacks a dorsal fin and the callosities (thickened skin) above its eyes.  They continuously feed on copepods and other small invertebrates such as krill, pteropods and larval barnacles by skimming them out of the water and migrate from the Gulf of Maine to their calving areas off Georgia and Florida in the winter.

4: Finback whale - 90 feet/74 tonnes

The finback whale, Balaenoptera physalus, is also called the fin whale, razorback whale or  the common rorqual.  It is  the second longest animal in the world, but its thin body means it is lighter than some species of much shorter whale.

Finback whales feed off schooling fish, squid, crustaceans and krill and are unbelievably fast. So fast in fact, that they are faster than the quickest ocean steamship! This attribute has earned them the esteemed title of being the 'greyhounds of the sea'.

3: Southern right whale - 58 feet/110 tonnes

The Southern right whale, Eubalaenna australis, is recovering well since it became protected in 1937 and is now classified as being of 'Least Concern' by the IUCN, with its population growing by an estimated 7% each year.

Southern right whales spend much the summer close to Antarctica where their calves are safer from being predated by killer whales and great white sharks. During the winter, when the conditions of Antarctica become too harsh for them to remain there, they migrate north to the warmer waters of Argentina and seem to spend many hours in a unique behaviour called 'sailing'. This behaviour is believed to be recreational and consists of the whales catching the wind in their flukes and letting it propel them through the water like  boats!

2: North Pacific right whale - 60 feet/120 tonnes 

The North pacific right whale, Eubalaena japonica, feeds mainly on copepods that it constantly filters out of the water while swimming. Its prey is so small that it needs to consume millions of them each day in order to provide the energy that it needs to survive.

Unlike many other species of whale, the North Pacific right whale does not seem to have a clear migratory pattern and the only notable annual difference in their distribution is when they are breeding, where they tend to move closer inland.

1: Blue whale - 100 feet/190 tonnes

The blue whale, Balaenoptera musculus, is a peaceful whale that eats krill - one of the smallest organisms on the planet. Although there were once believed to have been 200, 000 blue whales in the oceans, it is estimated that there are now only 10, 000 left due to their historical over hunting. Sadly, and despite now being protected, their numbers are not expected to recover due to their slow life cycles.

As far as we know the blue whale is the largest animal that has ever lived on this planet and is twice the weight of the biggest known dinosaur. In fact, blue whales are so big that their tongues alone can weigh as much as an elephant and their hearts as much as a small car!