Apterygota
The Apterygota are a small subclass of primitive insects.
| Apterygota Temporal range: [1]
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| Petrobius maritimus (Archaeognatha: Machilidae) | |
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| Subclass: | Apterygota†
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They are insects which have never had wings at any time in their evolutionary history. Their first known occurrence in the fossil record is in the Rhynie chert of the Devonian period, ~400 million years ago. While some other insects, such as fleas, also lack wings, these are descended from winged insects, and have lost them during the course of evolution. By contrast, the apterygotes are a primitive group of insects that diverged from other orders before wings evolved.
They have some other primitive traits (features). The nymphs (younger stages) go through little or no metamorphosis, so they look like the adults. They continue to moult throughout life, with multiple instars (stages) after reaching sexual maturity. All other insects have only a single sexually mature adult stage. Their skin is thin, making them appear translucent.[2]
Currently, no species are listed as being at conservation risk.
History of the group
The classification of the Apterygota changed over time. By the mid 20th century, the subclass included four orders (Collembola, Protura, Diplura, and Thysanura). With the advent of a more rigorous cladistic methodology, the subclass turned out to be paraphyletic. The first three groups formed a monophyletic group, the Entognatha. The Thysanura is more closely related to winged insects.[3] thus rendering even the amyocerate apterygotes paraphyletic.
Some think the Collembola are no longer insects at all, but their position is not yet clear.[4][5][6][7][8]
Sources
- ↑ Hoell, H.V., Doyen, J.T. & Purcell, A.H. (1998). Introduction to Insect Biology and Diversity, 2nd ed. Oxford University Press. p. 320. ISBN 0-19-510033-6.
{{cite book}}: CS1 maint: multiple names: authors list (link) - ↑ Hoell, H.V., Doyen J.T. & Purcell A.H. (1998). Introduction to insect biology and diversity. 2nd ed, Oxford University Press. pp. 333–340. ISBN 0-19-510033-6.
{{cite book}}: CS1 maint: multiple names: authors list (link) - ↑ Orders – Thysanura & Archaeognatha
- ↑ Frédéric Delsuc, Matthew J. Phillips & David Penny (2003). "Comment on Hexapod origins: monophyletic or paraphyletic?" (PDF). Science. 301 (5639): 1482. doi:10.1126/science.1086558. PMID 12970547.
- ↑ Francesco Nardi, Giacomo Spinsanti, Jeffrey L. Boore, Antonio Calli, Romano Dallai & Francesco Frati (2003). "Hexapod origins: monophyletic or paraphyletic?". Science. 299 (5614): 1887–1889. doi:10.1126/science.1078607. PMID 12649480.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ↑ Francesco Nardi, Giacomo Spinsanti, Jeffrey L. Boore, Antonio Calli, Romano Dallai & Francesco Frati (2003). "Response to comment on Hexapod origins: monophyletic or paraphyletic?" (PDF). Science. 301 (5639): 1482. doi:10.1126/science.1087632.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ↑ Yan Gao, Yun Bu & Yun-Xia Luan (2008). "Phylogenetic relationships of basal hexapods reconstructed from nearly complete 18S and 28S rRNA gene sequences" (PDF). Zoological Science. 25 (11): 1139–1145. doi:10.2108/zsj.25.1139. PMID 19267625.
- ↑ 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" (PDF). Molecular Phylogenetics and Evolution. 38 (1): 100–116. doi:10.1016/j.ympev.2005.09.012. PMID 16290034.
- Firefly Encyclopedia of Insects and Spiders, edited by Christopher O'Toole, ISBN 1-55297-612-2, 2002
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