Springtail (Dicyrtomina minuta) Photo by By AJC1 – https://www.flickr.com/photos/47353092@N00/45793739845/, CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=82910512
Dear Readers, if you have ever turned over some leaf litter in the garden and noticed some tiny creatures pinging away in all directions, you might have encountered some springtails. Once upon a time, they were regarded as primitive insects, but these days they are considered to be such an ancient lineage that they’re described as ‘non-insect hexapods (hexapod meaning ‘six-legged’). The scientific name for springtails is ‘Collembola’, which means ‘glue-peg’ – this relates to a strange organ called the collophore, which, as we shall see, is a vital part of the way the springtail gets around.
The springtail Deutonura monticola (Photo by By Philippe Garcelon – Deutonura monticola, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=93328444)
Because they are so small, springtails go largely unnoticed, which is surprising as there may be 30 to 40 species per square metre in deciduous woodland, and up to 100 species in the same area in the tropics. Some estimates suggest that a square metre of soil can contain up to 100,000 individual springtails. Although we will notice them most when digging in the garden, they can be found right up into the forest canopy, and hopping about on the snow in North America – this particular species is known as a snow flea (Hypogastrura nivicola) and it contains a protein which enables it to be active when most other small invertebrates are torpid.
Snow Flea (Photo by By Daniel Tompkins, en:User:Plantman2 – en:Image:Snow Flea close up.JPG, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=3380961)
So, what are springtails doing in the soil, in such numbers? Some are detritivores, breaking down organic material and releasing its nutrients into the soil. Some are predatory, and eat a wide variety of other invertebrates and even microbes. They are clearly important in maintaining soil health, and yet we know so little about them. One thing that is clear is that they are very prone to desiccation, and that they emit a pheromone that attracts them to one another – this helps them to find a safe, damp space where they can live together and share the same safe environment. While some species are very adaptable, others are not, and changes to land practices can cause the total elimination of some of the slower-moving, more specialised species. One species has been used as a model to test soil toxicity, herbicides and pesticides.
Folsomia candida – a model species used in laboratories to test everything from pesticide resistance to circadian rhythms (Photo By Andy Murray – Folsomia candida, CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=44266481)
Springtails are also food for a wide variety of other organisms, including mites, spiders and harvestmen. And so, they have developed a very particular way of escaping when threatened. Springtails have an organ called a furca, which extends like a stick at the end of the body, and is used as a kind of lever to flick the animal into the air.
Springtail Isotoma habitus – you can see the furca protruding at the end of the body (Photo by By U. Burkhardt – Taken and uploaded on de:WP the 01/06/2006 by de:Benutzer:Onychiurus, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=793827)
And what a flick! Scientists Adrian Smith and Jacob Harrison filmed some springtails after they’d given them a prod with a paintbrush, and discovered that they can leap up to 80 body lengths away from where they started in a single jump, rotating 368 times per second as they did so.
There seemed to be two types of landing – Smith described one as an ‘uncontrolled bounce and tumble’, and the other as an ‘anchored stop’ – the latter involved that organ for which this group is named, the collophore, which is a sticky tube (you can see it in the middle of the body of the springtail in the photo above). The tube is normally used for things like controlling fluid balance in the springtail’s body, but can also be used to anchor the body of the springtail after a jump.
You can watch the springtails ‘doing their stuff’ on the New Scientist Youtube page here. Highly recommended!
Composite photo of a springtail jumping (Photo by Adrian Smith, from https://www.newscientist.com/article/2445665-backflipping-springtails-are-the-fastest-spinners-known-in-nature/)
I’ll leave the last word to Adrian Smith:
“People might think that everything in nature is described and known, says Smith, but this isn’t so. “There’s so many things that are right there in and amongst us that are incredible.”
The New Scientist article is here.
The research paper is here.