Protura is a group of tiny, primarily wingless hexapods (Hexapoda = Insecta + Protura + Diplura + Collembola) that live in soil. Proturans inhabit soils in all terrestrial regions of the earth (with the exception of the Arctic and Antarctic regions).They lack antennae and eyes, but hold their front legs forward and these apparently play an important role in sensing their environment.
Proturans were not described until 1907. Today, around 800 valid proturan species are recognized. Due to their small body size (body length between 0.5–2.5 mm) and soil-dwelling habit, our knowledge of the biology and ecology of proturans remains very limited. Diagnostic taxonomic characters are very inconspicuous and difficult to assess. Identification at the species level strongly depends on subtle chaetotaxic characters, such as the position and length ratio of certain bristles on the foretarsi. Resch et al. (2014) explored the usefulness of "DNA barcoding" for this group. In their study, clusters identified by COI mtDNA sequences and 28S rDNA were consistent with named species (and genera) identified by a proturan specialist using standard morphological characters.
Although the phylogenetic position of Protura is clearly basal to the the ectognaths (Ectognatha = jumping bistletails + silverfish and firebrats + winged insects), the relationship among Protura, Diplura, and Collembola remains unclear (Dell’Ampio et al. 2013).
Pass and Szucsich (2011) reviewed the history of research on Protura.
(Pass and Szucsich 2011 and references therein; Resch et al. 2014 and references therein)
- Dell’Ampio, E., K. Meusemann, N.U. Szucsich, et al. 2013. Decisive Data Sets in Phylogenomics: Lessons from Studies on the Phylogenetic Relationships of Primarily Wingless Insects. Molecular Biology and Evolution 31(1):239–249. doi:10.1093/molbev/mst196
- Dell’Ampio, E., N.U. Szucsich, and G. Pass. 2011. Protura and molecular phylogenetics: status quo of a young love.Soil Organisms 83(3): 347-358.
- Pass, G. and N.U. Szucsich. 2011. 100 years of research on the Protura: many secrets still retained. Soil Organisms 83(3): 309-334.
- Resch, M.C., J. Shrubovych, D. Bartel, et al. 2014. Where Taxonomy Based on Subtle Morphological Differences Is Perfectly Mirrored by Huge Genetic Distances: DNA Barcoding in Protura (Hexapoda). PLoS ONE 9(3): e90653. doi:10.1371/journal.pone.0090653
- Szeptycki, A. 2007. Catalogue of the World Protura. Acta Zool Cracov, B – Invertebrata 50: 1–210.
protos - first , oura- tail.
- antennae absent
- tentorium absent
- fore legs enlarged, with many sensilla; front legs serve role of antennae
- very small, less than 2 mm long
- abdomen with 12 segments as adult
- Mouth parts entognathous
- cerci absent
- legs 5-segmented
- anamorphic development (segments added at moults) vs. epimorphic in all other hexapods
The larva has nine abdominal segments, but the number increases through moulting until the full adult number of twelve is reached. Further moults may occur, but do not involve any additional body segments (Meyer 2005), and it is not known whether the adults continue to moult throughout their lives. Eggs have only been observed in a few species (Tipping 2004). Five developmental stages follow: the prelarva hatches from the egg and has only weakly developed mouthparts and nine abdominal segments; larva I follows and has fully developed mouthparts; larva II has ten abdominal segments; maturus junior has twelve abdominal segments and is followed by the adult (Tipping 2004). The family Acerentomidae differs in having an extra pre-imago stage, with partially developed genitalia, between the maturus junior and the adult (Tipping 2004).
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