Soil mesofauna - scratching the surface | Biodiversity Projects

Soil mesofauna - scratching the surface

'Flying saucer' mite with smaller phoresic mite.  Photo C.Bell

Another weekend, another invertebrate training course! Last weekend I attended the four day Soil Mesofauna course, a Tom.bio-supported training course delivered by the country’s top experts in soil science, springtails and mites.

First question – what exactly is Soil Mesofauna? The quick answer is basically any invertebrate living in the soil which is visible to the naked eye – even if just as a speck - and about small enough to pass through a 2 mm mesh. So things like bacteria, most nematodes and most single-celled organisms are not ‘mesofauna’, but animals such as mites, springtails, smaller spiders, smaller beetles etc are.

The first day saw the group learning about soil – and what a fascinating subject it is! Dr Matthew Shepherd, Soil Scientist with Natural England, lead us through the incredible world of soil and blew our minds with various facts and figures. In no particular order, my top three soil facts are: 

  • In arable soil, there can be 5 tonnes of soil organisms per hectare. This equates to approximately 100 sheep! In grassland, this increases to 100 tonnes per hectare (or 2000 sheep!)
  • Soil is home to a quarter of the species on Earth. Most of these live in the top few cms.
  • Nematode worms are so numerous and abundant, that if you were to remove all other matter from the planet you would still see a ‘ghost’ Earth picked out in nematodes.

Truly incredible, and somewhat humbling!

Pete Shaw vacuum sampling.  Photo: C.BellWe also tested our various sampling techniques for soil mesofauna – including sieving and pooting, vacuum sampling (see photo left), and taking soil cores which were then placed in a DIY Tullgren Funnel (see photo below right) – a hot, bright light encourages the invertebrates to move down through the sample, eventually falling into the collecting pot beneath the funnel.

Homemade Tullgren funnels

Day 2 focused on springtails (Collembola), a fascinating group of creatures with some truly beautiful species, including the bright pink one recently found for the first time in the UK by Pete Boardman. With the help of both dissecting (low power) and compound (high power) microscopes, preserved specimens can usually be identified to species level. However, there are around 250 species in Britain, so care must be taken! We were taught how to look for and count features such as the number of segments on antennae, thorax and abdomen; the presence and number of ocelli (eyes) on the head; the presence, number and arrangement of anal spines on the body tip, and various other anatomical features. Guiding us through this was Dr Peter Shaw, the UK’s foremost springtail expert.

Four different types of mite found on thh course.  Photo: C.Bell

Day 3 was Mite Day – lead by mite expert Dr Felicity Crotty. Again, the numbers involved are mind blowing – over 50,000 mite species have been described worldwide.  And the taxonomy is, at first, baffling – and ever changing. After learning about mite morphology and anatomy, we concentrated on three different orders of mite – Mesostigmata, Prostigmata and Astigmata, and tried (sometimes even successfully!) to key them out to family level. What a fascinating class of animals – and, under the microscope, some of them are incredible beautiful.

On the final day, we attempted a soil ‘bioblitz’ – putting our new skills to the test in an attempt to identify every specimen from one of our soil cores. I’m not sure we managed the entire sample, as there were hundreds of invertebrates within it, but we certainly compiled a respectable species list.

I found the course a revelation. As ever when I use a microscope, I was struck by the whole new world which becomes apparent when you look down the eyepiece – amazing to think that a speck barely visible to the naked eye can, under 10x, 40x or 100x magnification, reveal features, colours, shapes, patterns, and a level of detail you could never imagine. During the presentations, it became apparent that, even on an intensive four day course, we were only barely scratching the surface (pardon the pun!) of Soil Mesofauna.

Springtail.  Photo: C.BellWhat also became apparently was just how much Soil Mesofauna contributes to the structure, composition and function of soil. Without them, soil fertility would plummet, crops would fail, and 'soil' as we know it would disappear. We owe so much to these tiny specks, yet know so little about them. And their sampling and identification, though not without its challenges, is incredible rewarding and fascinating.

 

 I hope that all course attendees, myself included, will continue to practice and hone their skills, and start recording some of the Soil Mesofauna near them. If you’re interested, then it’s likely that the course will also be run next year – keep an eye on our training page.

Compost (meadow arisings) - a favourite haunt of the mesofauna hunter
On the lookout for springtails on the surface film
A springtail's-eye view of mesofaunists
Demonstration of proper use of a pint glass (next to a pint of Shropshire Lass)
Hard at work in the classroom