Six-footed
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Honey bee ( apis ) |
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| Hexapoda | ||||||||||
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The hexapods (Greek: Hexapoda) or Hexapods belong to the trunk of the arthropods (Arthropoda), they form a sub- trunk of these. The Hexapoda are the insects (Insecta), double tails (Diplura), leg tracers (Protura) and springtails (Collembola).
The taxon six-footed, which was first presented in this compilation in 1987 by J. Kukalová-Peck, corresponds to the classic summary of insects ( Hennig 1953) and was previously regarded as a synonym for this group of animals. The insects according to the new definition, on the other hand, correspond to the group of animals formerly known as Freikiefler (Ectognatha), so the double-tails, leg-teasers and springtails are no longer counted among the insects.
Characteristics of the six-footed
The hexipedes have a few characteristics that make them a natural group:
Above all, this includes the body that has a fixed number of segments . The head probably consists of six fused segments, which can be recognized by the head limbs and especially the nerve nodes ( ganglia ) in the head area. The head carries a pair of antennae and three pairs of mouthparts known as the mandibles , maxillae, and labium . The labium corresponds to the 2nd maxillae of crustaceans and millipedes; it is most likely a result of a fusion of the paired 3rd mouth extremities.
The chest area ( thorax ) always consists of three segments, each of which carries a pair of legs (makes three pairs of legs and six legs) and thus gave this group its name. With the flying insects (Pterygota) the last two breast segments carry the wings .
The basic pattern of the abdomen consists of 11 segments plus a so-called telson . These segments can be partially fused in the different groups within the hexipedes.
Further characteristics of the hexipedes: tail appendages , consisting of (two cerci and one terminal filum ); the so-called styli, residual structures of the former two-branch extremities. In addition, the six-footed animals in the basic plan have compound eyes and pinpoint eyes as well as a well-developed tracheal system .
System of the six-footed
The systematics of the six-footed is not yet definitively established. In the classic variant, the insects are compared to the remaining groups, which are collectively referred to as Sackkiefler (Entognatha) because of their mouth pocket (Hypothesis 1; Hennig 1953, 1969 (mod.)). Another hypothesis only summarizes the springtails and pegs as a taxon called Ellipura and then assigns the double-tails as the first branch to the insects (Hypothesis 2; Kukalova-Peck 1987, 1991; Koch 1997; Kraus 1997; Beutel & Gorb 2006).
Hypothesis 1 : The leg tracers, double tails and springtails form the sister group of insects:
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Hypothesis 2 : The leg tractors and springtails form the sister group of insects and double tails:
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literature
- DT Anderson: Invertebrate Zoology. 2nd Edition. Oxford Univ. Press, 2001, ISBN 0-19-551368-1 , p. 232, chap. 11.
- RSK Barnes, P. Calow, PJW Olive, DW Golding, JI Spicer: The invertebrates - a synthesis. 3. Edition. Blackwell, 2001, ISBN 0-632-04761-5 , p. 183, chap. 8.5.3b.
- RC Brusca, GJ Brusca: Invertebrates. 2nd Edition. Sinauer Associates, 2003, ISBN 0-87893-097-3 , p. 589, chap. 17th
- J. Moore: An Introduction to the Invertebrates. Cambridge Univ. Press, 2001, ISBN 0-521-77914-6 , p. 223, chap. 15th
- EE Ruppert, RS Fox, RP Barnes: Invertebrate Zoology - A functional evolutionary approach. Brooks / Cole, 2004, ISBN 0-03-025982-7 , p. 723, chap. 21st
Scientific literature
- RG Beutel, SN Gorb: Ultrastructure of attachment specializations of hexapods, (Arthropoda): evolutionary patterns inferred from a revised ordinal phylogeny. In: Journal of Zoological Systematics and Evolutionary Research. 39, 2001, p. 177.
- F. Nardi, G. Spinsanti, JL Boore, A. Carapelli, R. Dallai, F. Frati: Hexapod origins: monophyletic or paraphyletic? In: Science. 299 (5614), 2003, p. 1887.
- WC Wheeler, M. Whiting, QD Wheeler, JM Carpenter: The phylogeny of the extant hexapod orders. In: Cladistics. 17, 2001, p. 113.
