27 January 2013

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.

3 January 2013

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.