Beneath the trapdoor danger lurks...

Wherever you go, you are bound to find spiders. They are an ancient class of predator and have learnt to use poisons, brute force and complex webs of silk to terrorise and instil fear into animals on every continent of the world except Antarctica. 

Typically, an easy way to tell the rough age of a species of spider is by looking at the complexity of the web it spins and the general rule is that the more elaborate the web, the younger the species of spider. This makes sense really as it would be expected for more complex structures, such as web scaffolding patterns, to take longer to evolve! Thus, the infamous tarantulas, which use silk only to line their burrows for warmth, are among of the oldest species of spider on the planet. 

Trapdoor spiders are another ancient lineage of arachnid, which is suggested by the simple manner in which they use silk. They use silk for the same purpose as many more ‘modern’ spiders since they rely on it to convey vibrations to them to show that prey is nearby, but do not spin it into complex webs. 

There are more than 500 different species of trapdoor spider that have been described so far, which can be found in tropical regions all across Earth. Despite being large and looking fairly intimidating, trapdoor spiders are rarely aggressive and are not dangerous to humans.

So instead of building silk nets like many newer species, trapdoor spiders dig a deep burrow in the soil (some species make a long tube of silk instead) and spin trip-lines that radiate out from the tunnel’s entrance. The spider then lurks near the mouth of its burrow, touching its trip-lines, and waits for an insect to knock one of the threads. When this happens, the spider feels the vibration and lunges out to grab, bite and poison its prey. 

Many species of trapdoor spider take this ambush tactic a step further and actually build a covering over the hole of their tunnel. This ‘trapdoor’ is what gives the family of spiders its name and is cleverly made from materials surrounding the burrow, such as soil, vegetation and silk, so it is camouflaged perfectly with the ground! 

Species that make a trapdoor always hinge their covering at one end with thick webbing and hold it down tightly using special claws on the ends of their feet. When its trip-lines are activated, the spider flips open its trapdoor, explodes out of its burrow and drags the hapless insect back inside for its dinner! And because trapdoors are typically very large spiders, almost all insects are on their menu – with meals commonly including cockroaches, crickets, grasshoppers, beetles, moths and other spiders. 

As would be expected, trapdoor spiders invest such a huge amount of time and energy in digging their burrows that they are a very shy and reclusive species. In fact, trapdoors rarely leave their burrows at all and female spiders typically spend their full 20 year lifespan in one burrow! It is usually only males that venture out from their burrows and even then, only once they have matured sexually and are seeking a mate. Like all spiders, male trapdoors mature near to the end of their lives (which are much shorter than those of females) so are inclined to take huge risks in finding a mate before they die. 

Once a male spider has mated with a viable female, the male dies (often to be eaten by the female) and the female remains in her burrow to feed her spiderlings when they hatch. Shortly after hatching, the spiderlings venture out of their mother’s burrow to dig their own home using their front legs and specialised barbs on their fangs called rastellum that help them to move soil.

Hangovers: what are they & can we avoid them?

With Christmas and New Years over, many of us will be looking back over the festive periods to remember the glittering decorations that adorned our homes, opening our presents, spending time with our loved ones and indulging in rich, expensive foods. And of course, no memories of the Christmas holidays are complete without those of the hangover and it's safe to say that many of us will have just as vivid memories of times spent inebriated and of those nursing the unpleasant headaches and tender stomachs that inevitably followed a night's heavy drinking. The hangover is unarguably the bane of many of our celebrations and often leads to promises of “never again”. 

Of course, there always is an again and we all know full well that we’re not fooling anyone when we make that particular promise. The call to drink when we're enjoying ourselves is just too strong! So, we will all drink again and will all suffer for it again. Yet despite knowing to expect a hangover the next morning, do we really know what one is? 

The British National Health Service (NHS) recommends that men should not regularly consume more than 3-4 units of alcohol per day and women should not regularly consume more than 2-3 units. By 'regularly', the NHS means drinking these amounts on most (more than four) days of the week.

The answer to this question is in the properties of ethanol, the alcohol present in drinks, itself. Basically, ethanol is a powerful diuretic drug (like those discussed in the earlier post: 'Coca Cola: Christmas in the toilet'), and dehydrates us by making our body absorb less water. As our body becomes dehydrated and less begin to lose water, the cells that form it shrink and contract – leading to severe problems for the brain! 

This is because the human brain is surrounded by three thin membranes that are collectively known as the meninges. Thus, as we become dehydrated and the cells in these membranes shrink, the meninges contracts and squeezes our brain. It is this squeezing effect that is responsible (predominantly) for the headache we suffer the next morning and, obviously, the more we drink, the more dehydrated we become so the brain is squeezed more and we have a worse headache for it! 

Furthermore, this squeezing effect is also slightly responsible for any memories we may have lost, working in conjunction with the disruptive effects that ethanol has on the normal activities of the brain’s neurotransmitters (which leads to the associated behavioural changes and loss of coordination and response speed that are also experienced when drinking alcohol). And, as the brain is squeezed, it compresses the areas of our brain that deal with the formation and storage of memory - impairing its blood flow. This means that these areas work less much efficiently than they do normally and we end up with ‘holes’ in the night’s events when we look back on it. 

Whereas dehydration is responsible for our headaches, it is not the cause of the feeling of nausea that is also associated with hangovers. This feeling is due to another of ethanol’s particular properties, in that it is one of the few chemicals to be absorbed straight into our bodies through our stomach lining (paracetamol is another, which is why the drug alleviates pain so quickly). As well as meaning that alcohol affects us very quickly, particularly on an empty stomach, large amounts of ethanol passing through the stomach lining can leave it feeling sore and inflamed – which is also what causes the stomach ulcers that are a common symptom of long-term alcohol abuse! 

Fairly obviously then, if our stomachs are sore then they are not going to be very welcoming of food – particularly those that are heard to digest. Furthermore, vomiting the night before (which is actually beneficial for the body as it’s a protect reflex it uses to expel ethanol once it knows that much more is being absorbed than can be broken down safely), would make the feeling worse as it could itself damage the stomach lining and leave the stomach muscles strained and fatigued. 

As well as due to ethanol, the feeling of illness and lethargy experienced in hangovers are also caused by impurities in the drinks themselves, which are a result from the brewing or fermenting process. These impurities affect the body in many different ways and often require investments of large amounts of energy to break them down (which is why you should avoid mixing drinks). Due to the nature by which these impurities are created, different drinks contain different culprit chemicals. So your body might be coping, say, with those present in your red wine, but when you switch to whiskey later, it will have to start synthesising different enzymes to break the new chemicals in the whiskey down. As there are only so many enzymes that can be made at any one time (and a finite allocation of resources to use), the body ends up not producing enough enzymes to cope with either of the chemicals – meaning of course, that your hangover will be much worse! 

And so, now that you have a fair understanding of what hangovers are you might want to know whether or not they're possible to avoid. Sadly, they're not – not unless you cease drinking anyway, which let’s face it, isn't going to happen and seems a little excessive... But hangovers are possible to minimise, with surprisingly little effort. 

1. Don’t drink on an empty stomach. Eating a large meal of foods that are high in carbohydrates, such as pasta- or rice-based dishes, before you begin drinking will absorb some of the alcohol and so slow the rate it passes into your bloodstream. Likewise, drinking full-cream milk or eating high fat foods beforehand are beneficial since fat actually inhibits alcohol absorption, so less will be absorbed into your system. 
2. Avoid ‘dark’ drinks. As a general rule, darker beverages such as red wine, brandy and whiskey, contain more of the contaminants discussed above so will harder for your body to process. Instead, try drinking clear drinks like white wine, vodka and gin. 
3. If you're out and about, avoid buying ‘rounds’. Everyone drinks at different rates and have their own limits and so, by drinking rounds, you are having to match your own consumption to those around you (and let’s face it, the quickest drinkers always pressurise others to hurry up so “we can get the next round in”), which may be more than you can handle or want to drink that night. 
4. Stop drinking early. Usually, we drink to get drunk. So when we are finally drunk, we've normally got a lot of surplus alcohol in our stomachs’ that has yet to be absorbed. If you take this into consideration and stop drinking once you've reached your limit (or at least slow down), your body will have longer before the morning to have cleared the alcohol from your system and your hangover will be less severe as the result. 
5. Drink as much water as you can before bed and take a bottle of water with you. This way, you’re drinking water that will not only dilute the alcohol left in your stomach and system, but will rehydrate some of the water that you've lost over the course of the night - alleviating the crushing pressure on your brain. 
6. Try and force a ‘full-English breakfast’ down in the morning, or something similar (like McDonald's). As discussed earlier, fatty foods inhibit alcohol absorption so by eating foods such as sausage, bacon and eggs, you can stop the last ‘dregs’ of alcohol in your digestive tract from being absorbed. 
7. Avoid drinking caffeine. Caffeine is another diuretic, so although they may make you feel better in the short term, drinks like tea and coffee will only make you more dehydrated. This will not only make your headache worse, but will prolong it as well. Instead, drink fruit juices (not from concentrates if possible), as the sugars and vitamins they contain will ‘refresh’ your body and help to restore its vitality.

If you're concerned about the effects and dangers of alcohol or want more information, click here to be taken to the NHS' alcohol help and guidance pages.

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!

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...