Thigmokinesis

∞ generated and posted on 2016.12.21 ∞

Randomly oriented movement that varies in terms of an organism's speed of movement as a function of contact with materials, particular other than dissolved substances.

Thigmokinesis is seen particularly among woodlice which tend to slow down their movement when more of their body is in contact with a solid substrate. The result is that these animals tend to congregate within cracks and crevices as well as aggregate against each other.

See similarly orthokinesis or, generally, kinesis. See, by contrast, klinokinesis, taxis, chemotaxis, and phototaxis. Note that one can also distinguish between a positive and negative thigmokinesis meaning, respectively, slowing movement given contact with a surface so as to maintain favorable circumstances versus increasing the speed of movement given contact so a to reduce unfavorable circumstances. The former can be viewed as finding a good place to stay, given contact, versus running away or otherwise responding through movement given contact. Unfortunately, however, negative thigmokinesis does not seem to be used in a consistent manner so please take my discussion of it along with the following figure with a "grain of salt".

Figure legend: Randomly oriented movement that is modified in terms of speed in response to contact with a surface, that is, thigmokinesis, can be differentiated into positive and negative forms. In positive thigmokinesis, an organism slows its movement in response to contact with a surface. In negative thigmonkinesis, at least as defined here, an organism instead speeds up its movement given contact with a surface. These qualifications of thigmokinesis, again as employed here, can be viewed as equivalent to positive and negative taxis, i.e., moving towards something versus moving away from something.

I have proposed that the association of otherwise planktonic bacteria with surfaces, as towards biofilm formation, can be viewed as a form of thigmokinesis. Here the contact is made with an abiotic surface or, alternatively, with other microorganisms (or organisms) to which bacteria can specifically adhere, resulting in a slowing of their movement. More formal adherence involving especially production of extracellular polymeric substance then ensues.

To the extent that specific interactions are not possible, then simply reduced shear forces nearer to surfaces could result intrinsically in a slowing of cell movement that in turn could give rise to more actively bacteria-mediated adherence. The latter, however, too may be viewed as a form of thigmokinesis and indeed could be more consistent with the standard concept of thigmokinesis versus contact with substrate that is sensed through cell binding to specific surface-associated molecules.


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