Bear hunting

Magnified tardigrade (from http://www.sciencephoto.com/media/481794/view)

Today I did something I've been meaning to do for years - hunt for tardigrades in the garden!
Tardigrades are arthropods of the class Tardigrada, they are often called 'water bears' or 'mosspigs', which is where the name of my blog comes from. They are usually 0.1 - 0.5 mm long and can be found living in the damp moss or lichen that grows on trees and walls.

Since Unky Steve was kind enough to bestow me with a classic binocular microscope recently, so I thought there was nothing better to take it for a test run on than a tardigrade hunt!

In the garden i took a couple of pinches of moss from the garden wall, the bottom of a tree, and a pinch of green lichen from the same tree, putting them into separate small plastic bags to be examined later. I transferred the samples to three petri dishes and filled them with water to submerge the moss.

Samples L - R: Lichen, Tree Moss, Wall Moss

After leaving them to soak for a bit I started my search in the lichen but unfortunately the was nothing much to be found. In the tree moss sample I found myself in bear country, with my first ever tardigrade waving at me after only a few seconds of searching :)

The little white thing with stumps in the centre of the photo is a tardigrade, I promise!

Here's a video of the little guy, probably best to make it full screen :)

Tardigrade next to the tip of a mounted needle

Moss pigs are extremely hardy creatures, you might have heard that some have been sent into space and have survived being outside in the radiation and vacuum of outer space. They can also withstand temperatures from just above absolute zero (-272.8) to above 100 degrees Celsius, and are able to survive extreme drying out, or dessication, by going into a period of suspended animation called cryptobiosis from which they can be reanimated just by adding water! It is thought that they evolved these amazing adaptations in the move from the oceans, where they originally evolved, onto land. It might be difficult to visualise just how tiny these guys are, so see below for a comparison with a mounted needle.

Mounted needle with my forefinger for scale.

The tiny jungle of moss also harbors many other organisms, including countless nematode worms, mites and rotifers. Rotifers are also called 'wheel animals', as they have a structure on their head called a corona, which has loads of tiny hairs (cilia) used to sweep food into the mouth. Certain species (out of over 2000) of these guys called Bdeloid rotifers can survive long periods of dessication similar to the tardigrades. They also have strange sex lives and are able to reproduce without males (parthogenesis) which enables them to survive less favourable environmental conditions.

A rotifer.

The view down my microscope: Nematode bottom left, rotifer top centre.

You can read all about the remarkable moss pig in greater detail at this BBC article, and delve into the weird world of rotifers here!