Springtail
From Wikipedia, the free encyclopedia
| Springtails Fossil range: Devonian - Recent |
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 Isotoma sp.
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Suborder Arthropleona
Suborder Symphypleona
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Springtails (Order Collembola) form the largest of the three orders of modern hexapods (along with the Protura and Diplura) that are no longer considered insects. The three orders are sometimes grouped together in a class called Entognatha because they have internal mouthparts, but they do not appear to be more closely related to one another than to insects, which have external mouthparts. Recent genetic studies suggest that Collembola are a separate evolutionary line from the other Hexapoda [2][3][4].
Members of Collembola are normally less than 6 mm long, have six or fewer abdominal segments and possess an eversible tubular appendage (the collophore or ventral tube) projecting ventrally from the first abdominal segment. Most species have an abdominal, tail-like appendage, the furcula, that is folded beneath the body to be used for jumping when the animal is threatened. It is held under tension by a small structure called the retinaculum and when released, snaps against the substrate, flinging the springtail into the air.
Suborder Arthropleona has an elongated body, while Symphypleona (without sensory fields on the body) and Neelipleona (with sensory fields) have a globular body.
Springtails are cryptozoa frequently found in leaf litter and other decaying material [5], where they are primarily detritivores and microbivores, and one of the main biological agents responsible for the control and the dissemination of microorganisms[6]. In sheer numbers, 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 nests) occur; only nematodes, crustaceans, and mites are likely to have global populations of similar magnitude, and each of those groups is of a higher taxonomic rank (nematodes are a phylum, crustaceans a subphylum, and mites are a subclass). Most springtails are small and difficult to see by casual observation, but one species, Hypogastrura nivicola (the so-called snow flea), is readily observed on warm winter days when it is active and its dark color contrasts sharply with a background of snow.
In addition, a few species routinely climb trees and form a dominant component of canopy faunas, where they may be collected by beating or insecticide fogging. These tend to be the larger (>2mm) species, mainly in the genera Entomobrya, Orchesella and Lepidocyrtus, though the densities on a per square metre basis are typically 1-2 orders of magnitude lower than soil populations of the same species. A very few species (e.g. Anurophorus spp., Entomobrya albocincta) are almost exclusively arboreal.
Various sources and publications have suggested that some springtails may parasitize humans, but this is entirely inconsistent with their biology, and no such phenomenon has ever been scientifically confirmed, though it has been documented that the scales or hairs from collembolans can cause irritation when rubbed into the flesh [7]. They can sometimes be abundant indoors in damp places such as bathrooms and basements[2], and under such circumstances may be found on one's person, but this is only accidental. Claims of persistent human skin infection by springtails indicate delusory parasitosis, a psychological not entomological problem. However Hopkin[8] reports one instance of an entomologist aspirating an Isotoma species and accidentally inhaling some of their eggs, which hatched in his nasal cavity and made him quite ill until they were flushed out.
The main ecological factor driving locally the distribution of species is the vertical stratification of the environment: a continuous change in species assemblages can be observed from tree canopies to ground vegetation then to plant litter down to deeper soil horizons[9].
[edit] References
- ^ Frans Janssens (2006-08-26). Checklist of the Collembola.
- ^ Alexandre Hassanin (2006). Phylogeny of Arthropoda inferred from mitochondrial sequences: Strategies for limiting the misleading effects of multiple changes in pattern and rates of substitution. Molecular Phylogenetic and Evolution 38: 100–116. doi:.
- ^ David Whitehouse. "Evolution's new line", BBC News, 2003-04-08.
- ^ Bob Beale. "Insects result of convergent evolution", ABC Online, 2003-03-24.
- ^ Hopkin, Steve. The Biology of the Collembola. Natural History Museum.
- ^ Ponge, J.F., 1991. Food resources and diets of soil animals in a small area of Scots pine litter. Geoderma 49:33–62.[1]
- ^ Frans Janssens & Kenneth A. Christiansen (2007-05-08). Synanthropic Collembola, Springtails in Association with Man. Checklist of the Collembola.
- ^ Hopkin, Steve. The Biology of the Collembola. Natural History Museum.
- ^ Ponge, J.F., 1993. Biocenoses of Collembola in atlantic temperate grass-woodland ecosystems. Pedobiologia 37:223-244.
[edit] External links
- Collembola (TSN 99237). Integrated Taxonomic Information System.
- Maps of Collembola (Britain and Ireland) also Photolibrary
- General information on Collembola]
- Site by Frans Janssens, information on biology and evolution, an image gallery, a glossary of terms, and a checklist of world species
- The Biology of the Collembola
- Tree of Life
- The Springtails (Collembola) of South Africa
- North American Collembola
