Maxilliped

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The maxillipedes , sometimes also called jaw feet, are extremities that are attached to the anterior segments of the trunk section or thorax of the arthropods (Phylum Arthropoda) and are functionally in the service of eating. The maxillipedas thus complement the extremities attached to the head section, the mouthparts . Anatomically, they belong to the trunk extremities or thoracopods.

Maxillipedas occur in the crustaceans (sub-strain Crustacea) and in the millipedes (sub-strain Myriapoda) of the arthropods. There are no maxillipedas in the two other sub-tribes, the hexipedes or Hexapoda and the jaw-claw carriers or Chelicerata.

Crustacean maxillipedas

In most crustaceans, the first thoracopods, i.e. the extremities of the first trunk segment, are transformed into maxillipedes. The remaining thoracopods are often used for walking and are designed as striding legs or peraeopods , while the maxillipedes are no longer used for locomotion. In some groups of crustaceans even more extremities have become maxillipedas, they have two or three pairs of them; the decapods or decapods , for example, have three pairs of maxillipedas. The maxillipedas (or if there are several pairs of them: their rearmost pair) often close the vestibule like a lid or trough towards the rear. They are then often connected to one another by bristles, and in some groups (e.g. the amphipods ) their base links are even fused together. Mostly they are also involved in holding, transporting and sorting the food particles.

It is believed that the maxillipedas in different classes of crustaceans are not homologous to one another , but that they evolved several times independently from unspecialized limbs. Nor do they occur in all crustaceans. The primeval Remipedia have a pair of maxillipedas, but they are missing from the gill- pods, for example . In development, the formation of maxillipedes is controlled by the so-called Hox genes , especially the Ubx and Scr genes, with their specific concentration lying between that typical for oral limbs and that for typical striding legs, thus simulating the intermediate morphology. In the case of experimental interventions or mutations, for example, instead of the second maxilla , maxillipedas can also be formed on the head, i.e. in the wrong place (ectopic).

Centipede maxillipedes

In the case of the centipedes (Chilopoda), the first trunk segment is functionally included in the head section, its extremities are used to procure food. The base limbs, the coxae or hips of these maxillipedas are fused together to form a uniform plate, the coxosternite, which closes the back of the mouth, from which the scientific name Chilopoda (= lip-footer) goes back. The maxillipedas, also called forcipula here, are otherwise transformed into powerful poisonous claws with which the prey is seized and killed by the poisonous bite. The structure of the maxillipedas is similar to that of the other trunk bones, only the trochanter and prefemur are fused into one limb. The tarsus and pretarsus are also fused and together form the claw link with the mouth of the poison glands.

Literature and Sources

  • Hans-Eckhard Gruner: Class Crustacea. in: HE Gruner (Ed.): Arthropoda (without Insecta). Textbook of special zoology. Volume 1, part 4. Gustav Fischer, Stuttgart / Jena 1993, ISBN 3-334-60404-7 . Page 468–470.
  • Les Watling: Feeding an digestive system. Chapter 8 in Les Watling & Martin Thiel (editors): The Natural History of the Crustacea. Volume 1 Functional Morphology and Diversity. Oxford University Press, 2013. ISBN 978 0 19 539803 8
  • Michalis Vverof, Anastasios Pavlopoulos, Zacharias Kontarakis (2010): Evolution of new appendage types by gradual changes in Hox gene expression - the case of crustacean maxillipeds. Palaeodiversity 3, Supplement: 141-146.
  • Jörg Rosenberg: The centipedes. Neue-Brehm-Bücherei Volume 285.Westarp Sciences, Hohenwarsleben, 2009. ISBN 978 3 89432 712 5
  • Lucio Bonato, Gregory D. Edgecombe, John GE Lewis, Alessandro Minelli, Luis A. Pereira, Rowland M. Shelley, Marzio Zapparoli (2010): A common terminology for the external anatomy of centipedes (Chilopoda). ZooKeys 69: 17-51. doi: 10.3897 / zookeys.69.737