How fast does an Amoeba travel?
contributions from Bill Amos (US) and Ron Neumeyer (Canada)
The Microscopy UK / Micscape group regularly receive emails from around the world from youngsters, hobbyists, students, teachers and others asking the group's advice on a wide range of issues.
The loose knit Microscopy UK group i.e. those who contribute material to the site, or who either sponsor or support us in other ways, come from a wide variety of backgrounds with both amateur and professional interests in microscopy, teaching, nature and the sciences. There is usually someone in the group who can help out or suggest resources to the enquirer. The group are pleased to devote time and effort to help on a one to one basis, as this is one of the aims of the site i.e. to provide a forum for people to help each other and share ideas. The Site Editors thank the group for helping in this way.
Many of the ensuing discussions arising from these enquiries are potentially of a wider interest, so we will be publishing a selection on an occasional basis in Micscape. One of the queries we received this month was 'how fast does an amoeba travel'.
Kevin Justice (US) asked us:
'Would you happen to know the
velocity at which an amoeba travels? I am doing a short
assignment which requires this piece of information, any ideas?
Thanks in advance, Kevin Justice.'
Dave Walker (UK) commented while seeking the group's help:
'Thanks for your interesting
query. I've copied this query to a few of my colleagues who may
have some thoughts or suggest references.
It would be an interesting experiment to measure their velocity if you have access to a microscope, an amoeba culture, stop watch and calibrated eyepiece (or put 1mm square graph paper under the slide) . It could be dependent on parameters like temp., directional light sources and substrate the amoeba is on.
I've often wondered myself how fast a protozoa moves relative to its size compared with the fastest human athlete, cheetah etc. Some of the free-swimming species move very rapidly across the field of view of my wide field 10x stereo eyepiece, so relative to their size they probably have quite a turn of speed.'
Image right shows amoeba (Subphylum Sarcodina) feeding on bacteria (the tiny rod-like forms). Image taken using phase contrast illumination. © Ron Neumeyer.
Ron Neumeyer (Canada) commented:
'According to Pennak's, "Freshwater Invertebrates of the United States", 1989, amoeba (Sarcodina) with finger-like pseudopodia blast along at between 0.5 and 3.0 microns per second (a micron is 1/1000th of a millimetre). Which, if my maths is correct, the fastest time for the "one millimeter dash" would be around 5 minutes.'
Bill Amos (US) added to
As Ron noted, Bob Pennak's figures are only for those amoebas with lobopodia. There are three other major types of pseudopodia, all with different rates of activity. Pennak's top speed is relatively slow. Some bacteria move up to 11 microns per second, and can be beaten by a fast-moving amoeba.
Bill Amos (US) replied to the original question by Kevin Justice:
'I hope the following comments
may be helpful rather than disappointing.
There are a great many species of amoeboid protozoans, only some of which are placed in the genus Amoeba. Even there, however, there is great disparity between species. My remarks pertain to ALL (unarmored) rhizopods ("amoebas") in the Phylum (formerly Class) Sarcodina.
First, there is an enormous range in size of "amoeba" species. A giant such as Chaos carolinense would be several thousand times the size of many very small species. Obviously a large one is going to cover more ground in a given amount of time than a small one.
Second, there are several major basic morphological kinds of unarmored amoeba, i.e., (a) those with many pseudopods, into any one of which the animal may flow, and (b) those with essentially only one pseudopod (the limax, or slug type). Those with many pseudopods often change direction as conditions vary slowing and hesitating as they do so, whereas those with a single pseudopod flow along more or less steadily in one direction that can be altered somewhat.
Third, temperature is a critical environmental factor that clearly affects metabolism, therefore degree of activity and therefore velocity.
Fourth, the precise means of an amoeba's creeping over a surface differs according to the general type of amoeba. More than one mechanism is at work. Speed over a flat surface differs from speed in confined three-dimensional spaces.
Fifth, an amoeba enters "resting" stages (I'm not referring to cysts) under certain conditions, and at other times hurries along in pursuit of food it may detect by sensory chemical means. Presence or absence of a chemical stimulus may affect an amoeba's direction and velocity.
I'm sorry to say there is no
easy answer to your question. I've watched thousands of amoebas
under a microscope over many years and don't have the faintest
idea how to answer your question, unless you do the following:
If you select a single species, such as Amoeba proteus, make sure it is fully grown (i.e. has not recently undergone fission), place it in a favorable environment at a favorable temperature (i.e. ambient temperature of a summer pond), then go ahead and measure its rate of progression with a stage or ocular micrometer, or a home-made device as Dave suggests --- then, and only then will you have a reliable figure to go by. It must be able to be replicated at any time by any other person, as long as they know the species and the exact conditions of your experiment.
Apart from the specifics of your question, movement by microscopic organisms in water is a very different affair from anything you and I experience in water. I urge you to read up on viscosity in fluids, especially water, and how it affects moving objects. If you wish, I could provide more information on this, but simply put, if a person's swimming pool had the viscosity experienced by an amoeba in its micro-world, then you would find yourself swimming at least in gelatin, more likely in molasses or some other thick syrup.
Check your university library for papers and books by David B. Dusenbery (Georgia Tech). He is a biophysicist who discusses amoeboid movement on pp. 40-42 in his book, 'Life At A Small Scale'.'
Comments to the author sent via our contacts page quoting page url plus : ('rneumeyer','')">Ron
Neumeyer and Comments to the author sent via our contacts page quoting page url plus : ('wamos','')">Bill
Amos would be pleased
to receive comments on this interesting topic.
We hope this query and comments
are of interest, and we hope to publish more email discussions
arising from readers queries in future Micscape issues. If
you have some thoughts on this topic, or perhaps carried out
research on protozoan velocities which you would like to share,
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