Ptychoidia

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The eight legs of the mite Arphthicarus heterotrichus can be completely drawn into the idiosoma . The prodorsum , which covers the head, serves as a closure flap and gives the mite a spherical or egg-shaped appearance in the defensive position.

Ptychoidie is the defense mechanism developed in some groups of horny mites , in which the legs and soft-skinned joints can be completely drawn into a recess in the body. The prodorsum serves as a closure cap and gives the mite a spherical appearance in the defensive position. This encapsulation serves to protect against eating.

Ptychoidia is a very complex morphological adaptation. It is made possible on the one hand by the division of the back armor ( dichoid ) and on the other hand by the interaction of a large number of muscle groups. The position of the muscles in relation to one another plays an important role in ensuring mechanical functionality. Since the ptychoidy arose several times in the evolution of the mites , there are also some differences in the mechanisms that occur in different groups of mites .

Are the functional morphology of the ptychoiden defenses elucidate various microscopic techniques such as scanning electron microscopy and synchrotron - X - microtomography (SRμCT) applied.

Exoskeletal and muscular adaptations for encapsulation have developed independently of one another at least three times in the horn mite. Two families from the group of the Enarthronotides , the Protoplophoridae and the Mesoplophoridae , developed the ptychoidy independently of each other. All other families with ptychoid defense reactions belong to the two superfamilies Phthiracaroidea and Euphthiracaroidea from the group of Ptyctima , which show a common development of the morphological structures for encapsulation.

Some species of mite from the Oribotritiidae family (superfamily Euphthiracaroidea) can evade an impending danger by jumping back suddenly. After jumping, they pull in their legs and land like a ball outside the danger zone.

Individual evidence

  1. ^ Sebastian Schmelzle, Lukas Helfen, Roy A. Norton, Michael Heethoff: The ptychoid defensive mechanism in Euphthiracaroidea (Acari: Oribatida): A comparison of exoskeletal elements. In: Soil Organisms. 80, 2008, pp. 233-247. ( PDF )
  2. ↑ Michael Heethoff: With X-rays in the microcosm. Synchrotron X-ray microtomography for non-invasive visualization of microscopic structures. In: Bioforum. 32, 5, 2009, pp. 14-16.
  3. ^ F. Grandjean: Considerations sur le classement des Oribates leur division en 6 groupes majeurs. In: Acarologia. 11, 1969, pp. 127-153.
  4. ^ RA Norton: Systematic relationships of Nothrolohmanniidae, and the evolutionary plasticity of body form in Enarthronota (Acari: Oribatida). In: RB Halliday, DE Walter, HC Proctor, RA Norton, MJ Colloff (eds.): Acarology: Proceedings of the 10th International Congress. CSIRO Publishing, Melbourne 2001, pp. 58-75.
  5. ↑ G. Wauthy, M. Leponce, N. Banaï, G. Sylin, J.-C. Lions: The backward jump of a box moss mite. In: Proceedings of the Royal Society. B, 265, 1998, pp. 2235-2242. PMC 1689509 (free full text).

literature

  • F. Grandjean: Considerations sur le classement des Oribates leur division en 6 groupes majeurs. 1. Les affinites de Collohmannia gigantea Selln., 1922.2. Suppression des Perlohmannoidea Grandj., 1958 Mixonomata nov. nom. 3. Articulation protero-hysterosomatique dichoidie et holoidie. 4. Ptychoidia. 5. Nouveau classement en 6 groupes majeurs. 6. Liens de parente entre groupes majeurs. In: Acarologia. 11, 1969, pp. 127-153.

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