Finally back to some science after an exciting few weeks in which I secured my next job…more about that later 😉
We often hear about biodiversity and the need to protect whole ecosystems and not just the large and beautiful animals that live on our planet. We also sometimes hear about the need to protect plants, as they may harbour chemicals that could be the basis of new drugs, as well as providing a habitat for many other things to live in. We’ve also been reminded recently about the great importance of bees but how often do we stop to consider the amazing variety of invertebrates on our planet.
I’m not even going to hazard a guess as to when and how creepy crawlies became established in our minds as something a bit yuck but they certainly don’t have a great reception from most people. It can’t be simply because some of them are poisonous and others like to drink our blood because lets face it that beautiful fluffy tiger everyone wants to see could kill you in just a few seconds! It can’t just be because they’re not beautiful because no one dislikes Rhino’s and they aren’t exactly pretty. Many of the invertebrates which are too small to see with the naked eye, or are so small they are just dots to us, are more ignored than disliked, except of course flees and mites, and that I can understand. Unless we have a particular reason to most of us don’t spend much time thinking about the things we can’t see.
So the invertebrate I want to introduce you to today is actually quite cute, well OK, some of the species are cute!
It’s a tardigrada, it’s name is made up of tardus, which means slow, and gradu which means step and their common name is water bear. Unlike the huge mammalian bears they are very tiny, ranging from just 0.05mm to 1.2mm, so you can see the largest ones with the naked eye but not well enough to see in detail what they look like.
930 species have been described to date and as their name suggests they mostly live in water, some in fresh water, some in sea water and some miraculously live in the thin film of water often found on vegetation, particularly algae and moss. This is why I think they’re incredible. The can live for up to 60 years (Possibly longer, you have to be very patient to do that kind of study!) because if the water evaporates around them they also loose their body water as it evaporates through their permeable cuticle and they shrivel up in to barrel shaped dried out forms called tuns. In this state their oxygen consumption is reduced to 1/600th of normal and they can suvive temperatures as low as -272°C (Colder than liquid nitrogen!) and up to 150°C. They can also do a neat party trick called encystment when they detach themselves from the cuticle which is their outer skin, pull in their legs and curl up in a ball inside the cuticle for protection.
Like many other invertebrates they are suctorial feeders meaning they apply their mouth to the food, a pair of stylets then pierce the food and they suck out the contents. They don’t bite people though, some are vegetarian and others are carnivorous feeding on other equally small creatures and sometimes other tardigrades.