A metachronal rhythm or metachronal wave refers to wavy movements produced by the sequential action (as opposed to synchronized) of structures such as
cilia
The cilium, plural cilia (), is a membrane-bound organelle found on most types of eukaryotic cell, and certain microorganisms known as ciliates. Cilia are absent in bacteria and archaea. The cilium has the shape of a slender threadlike proje ...
, segments of worms, or legs. These movements produce the appearance of a travelling wave.
A
Mexican wave is a large scale example of a metachronal wave. This pattern is found widely in nature such as on the cilia of many aquatic organisms such as
ctenophore
Ctenophora (; ctenophore ; ) comprise a phylum of marine invertebrates, commonly known as comb jellies, that inhabit sea waters worldwide. They are notable for the groups of cilia they use for swimming (commonly referred to as "combs"), an ...
s,
mollusc
Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is est ...
s,
ciliate
The ciliates are a group of alveolates characterized by the presence of hair-like organelles called cilia, which are identical in structure to eukaryotic flagella, but are in general shorter and present in much larger numbers, with a differen ...
s as well as on the
epithelial surfaces of many body organs. Individual cilia, when part of a metachronal wave being used for
protist
A protist () is any eukaryotic organism (that is, an organism whose cells contain a cell nucleus) that is not an animal, plant, or fungus. While it is likely that protists share a common ancestor (the last eukaryotic common ancestor), the e ...
locomotion, individually beat in a pattern similar to the planar stroke of a
flagellum
A flagellum (; ) is a hairlike appendage that protrudes from certain plant and animal sperm cells, and from a wide range of microorganisms to provide motility. Many protists with flagella are termed as flagellates.
A microorganism may have f ...
. The difference is that the recovery stroke is at 90 degrees to the
power stroke, so that the cilia avoid hitting each other.
Metachronal rhythms may be seen in the coordinated movements of the legs of
millipede
Millipedes are a group of arthropods that are characterised by having two pairs of jointed legs on most body segments; they are known scientifically as the class Diplopoda, the name derived from this feature. Each double-legged segment is a resu ...
s and other multi-legged land invertebrates, as well as in the coordinated movements of social insects.
Such metachronal motion has been shown to enhance fluid transport properties in natural cilia. Metachronal motion has also been replicated in synthetic microfluidic systems using magnetic filaments.
[Hanasoge et al., Metachronal motion of artificial magnetic cilia, Soft Matter, 2018,14, 3689-3693, DOI: 10.1039/C8SM00549D]
See also
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Beta movement
The term Beta movement is used for the optical illusion of apparent motion in which the very short projection of one figure and a subsequent very short projection of a more or less similar figure in a different location are experienced as one fi ...
*
Phi phenomenon
The term phi phenomenon is used in a narrow sense for an apparent motion that is observed if two nearby optical stimuli are presented in alternation with a relatively high frequency. In contrast to beta movement, seen at lower frequencies, the s ...
References
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External links
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Metachronal swimmingCiliaMathematical model of millipede gaits
Animal locomotion
Waves
Articles containing video clips