Hydroskeleton
The hydrostatic skeleton is the phylogenetically oldest form of muscular skeletal system's . A part of the musculature works against a non-compressible liquid cushion, but this must be present as a plump filling in order to be able to transmit mechanical forces effectively. The functionality is comparable to a technical hydraulic system . Hydrostatic muscles , on the other hand, work without a fluid-filled bladder.
Hydroskeletons are found, for example, in nematodes in the form of a uniform fluid space, as well as in annelids , in which the fluid spaces are divided into the individual body segments and have a longitudinal division as well as a transverse subdivision (reduction phenomena due to the dissolution of the separating tissue walls are very common). These fluid-filled cavities are voluminous and therefore easily recognizable: in the nematodes as a so-called pseudocoel , in the annelids as a coelom . The coelom spaces in particular are a common feature of many animal forms. However, there is disagreement about their homologation with regard to many groups: They could have a common origin, but they could also have arisen several times independently.
In many arthropods, the flexors of the leg joints work against an internal fluid filling, which results in effective (energy-saving) running movements, or even wide jumps (often due to sudden increases in pressure). The fluid stretches the leg while the flexor muscle pushes it out of the leg and into the body, causing the joint to flex. In the case of the arthropods, despite a clearly developed exoskeleton, the hydroskeleton, which was previously developed in phylogeny, is still used. These hydraulic mechanisms are particularly vital during the moulting process in order to pull the body with all its attachments out of the old exoskeleton covering.
The gastric space or the gastrovascular system of the cnidarians can also be viewed as a voluminous hydroskeleton . In flatworms, on the other hand, it is formed by fluid-filled crevices in the parenchyma , and the parenchymal cells themselves also represent small hydraulic units.
The firmness of herbaceous, non-woody plants is also based on a hydroskeleton. This is based on the turgor , the osmotic pressure of water-filled vacuoles , which fill up to 95% of the cell volume and press against the robust cell wall made of cellulose .
Due to the widespread use in the animal kingdom, attempts have been made to gradually understand the evolution of the various animal construction plans based on the characteristics of the hydro-skeleton. The idea is that the various fluid cushions in animals are always related in a certain way to the musculoskeletal system , especially the muscles, but also to various connective tissue structures that can be associated with the muscles, for example. Since the musculoskeletal system cannot be rebuilt suddenly and in any way in evolution, hydroskeleton systems offer the possibility of gradually realizing functional rebuilds even in those groups in which one has little hope of extensive rows of fossils due to the purely soft-bodied construction. This applies to the majority of animal phyla, namely to most invertebrates.
See also
Individual evidence
- ↑ Hydroskeleton . In: Herder-Lexikon Biologie . tape 4 . Spectrum Academic Publishing House, Heidelberg Berlin Oxford 1994, p. 312 .
- ↑ Support structures and plants. In: Handout support structures ( Memento of the original from January 19, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. of the canton school Kreuzlingen (Thurgau)
- ↑ WF Gutmann: The hydroskeleton theory . In: Essays and speeches by the Senckenberg Natural Research Society . tape 21 , 1972, p. 1-91 .
