Apterygota

Apterygota

Apterygota
Temporal range: Devonian–Recent [1]
Petrobius maritimus
(Archaeognatha: Machilidae)
Scientific classification
Kingdom:
Animalia
Phylum:
Arthropoda
Class:
Insecta
Subclass:
Apterygota†
Orders

The Apterygota are a small subclass of primitive insects.

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. Males deposit sperm packages rather than fertilising the female internally.[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

  1. ↑ 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)
  2. ↑ 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)
  3. ↑ Orders – Thysanura & Archaeognatha
  4. ↑ 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. S2CID 43942720.
  5. ↑ Francesco Nardi, Giacomo Spinsanti, Jeffrey L. Boore, Antonio Carapelli, Romano Dallai & Francesco Frati (2003). "Hexapod origins: monophyletic or paraphyletic?". Science. 299 (5614): 1887–1889. Bibcode:2003Sci...299.1887N. doi:10.1126/science.1078607. PMID 12649480. S2CID 38792657.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  6. ↑ Francesco Nardi, Giacomo Spinsanti, Jeffrey L. Boore, Antonio Carapelli, Romano Dallai & Francesco Frati (2003). "Response to comment on Hexapod origins: monophyletic or paraphyletic?" (PDF). Science. 301 (5639): 1482. doi:10.1126/science.1087632. S2CID 82407120.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  7. ↑ 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. S2CID 10783597.
  8. ↑ 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. Bibcode:2006MolPE..38..100H. doi:10.1016/j.ympev.2005.09.012. PMID 16290034. Archived from the original (PDF) on 2012-10-09. Retrieved 2012-11-28.
  • Firefly Encyclopedia of Insects and Spiders, edited by Christopher O'Toole, ISBN 1-55297-612-2, 2002

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