Springtails (Collembola)


Kingdom: Animalia

Phylum: Arthropoda

Subphylum: Hexapoda

Class: Entognatha

Subclass: Collembola

Springtails (Collembola) form the largest group of hexapods. Similar to Protura and Diplura they are not considered insects.

Springtails are cryptozoa frequently found in leaf litter and other decaying material,  where they are primarily detritivores and microbivores, and one of the main biological agents responsible for the control and the dissemination of soil microorganisms.

They are reputed to be one of the most abundant of all macroscopic animals, with estimates of 100,000 individuals per cubic meter of topsoil, essentially everywhere on Earth where soil and related habitats (moss cushions, fallen wood, grass tufts, ant and termite nests) occur.

As a group, springtails are highly sensitive to desiccation, because of their tegumentary respiration. The gregarious behaviour of Collembola, mostly driven by the attractive power of pheromones excreted by adults,   gives more chance to every juvenile or adult individual to find suitable, better protected places, where desiccation could be avoided and reproduction rate could be kept at an optimum. Sensitivity to drought varies from species to species and increases during ecdysis. Given that springtails are moulting repeatedly during their entire life (an ancestral character in Hexapoda) they spend much time in concealed micro-sites where they can find protection against desiccation and predation. The high humidity environment of many caves also favours springtails and there are numerous cave adapted species.

Springtails are currently used in laboratory tests for the early detection of soil pollution. Acute and chronic toxicity tests have been performed by researchers, mostly using the parthenogenetic isotomid Folsomia candida. These tests have been standardized. More recently, avoidance tests have been also performed. They are in way to be standardized, too. Avoidance tests are complementary to toxicity tests, but they also offer several advantages: they are more rapid (thus cheaper), more sensitive and they are environmentally more reliable, because in the real world Collembola may move far from pollution sources. It may be hypothesized that the soil could become locally depauperated in animals (and thus improper to normal use) while below thresholds of toxicity. Contrary to earthworms, and like many insects and molluscs, Collembola are very sensitive to herbicides and thus are threatened in no-tillage agriculture, which makes a more intense use of herbicides than conventional agriculture.



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