Recently about two weeks ago in class, we were given the opportunity to study zooplankton and phytoplankton under a compound microscope. During which, I discovered what I found out to be a Vorticella. For the remainder of the class period, I watched the Vorticella, waiting for it to spring forward and coil back, as it engulfed a piece of nutrients in the water surrounding it. I was so fascinated by the Vorticella that I began some research into it, and thus, this blog post, as I am sure others from my class were also curious about this Vorticella.
What is the Vorticella?
A Vorticella is an aquatic, strictly fresh-water protozoan that is a microscopic, unicellular eukaryotic animal. Being apart of the ciliates genus with 100 different species, it is one of the fastest cellular machines to generate cellular and molecular movement. Newly budded and formed Vorticella are free swimming, while older and more mature Vorticella are actually attached to some sort of substrate. The Vorticella is famous for it’s fast contractile movement, it’s almost too quick to see with the naked eye! Their contractile movement can allow for feeding, as well as responding to any environmental disturbances. In addition to their amazing contractile motion, they also have the ability to reproduce asexually and sexually, and may be found in large groups, or even individually. Vorticella typically eat bacteria
The Vorticella is comprised of a long stalk, which is approximately 100-500 µm in length, 2-3 µm in diameter, typically embedded and attached to a substrate such as a plant, rocks, or even other animals such as crustaceans. Attached to this long stalk at the top is a bell-shaped zooid, 30-60 µm in diameter.
The stalk of the Vorticella itself is made up of several layers, of those layers, one of them includes the structure that contracts, called myoneme, also known as a spasmoneme. As pictured above, it is a thin, helical structure that allows it to contract and produce a coiling pattern. The myoneme can spontaneously contract within milliseconds, and re-extend itself within 2-9 seconds.The myoneme, approximately 1-2µm in diameter contains filaments that shrink longitudinally. In the presence of Ca2+, it induces the contraction of the myoneme, thus concluding that ATP hydrolysis is not responsible for the contractile movement, but Ca2+ induces the motion, and only re-extends when Ca2+ is absent.
The cilia are located along the outer rim of the mouth, pictured above, can actually sweep bacteria into the peristome. The current produced by the Vorticella ultimately sweeps the bacteria into the zooid, where the zooid contracts, and the bacteria are then digested through phagocytosis.
Vorticella’s Contractile Movement
The contractile movement of the Vorticella’s zooid has been described a similar to a damped harmonic oscillator due to the Hooke’s Law of spring force. The force is applied to the stalk of the zooid, the zooid is actually also subjected to a frictional force. The contraction begins in the zooid (the cell body) and spreads down the myoneme. This can also affect the speed in which the Vorticella contracts.
The speed of the Vorticella’s movement can be summed up into an equation:
Where Vmax is the maximum speed of the Vorticella in the aqueous media, τs is the characteristic time of the contraction, and β is an index value that ranges between 1 and 2, and is dependent upon the viscosity of the media surrounding the Vorticella. Thus, the contractile speed ultimately depends on the environment and viscosity of the environment surrounding it.
After watching the Vorticella’s contractile movements for over an hour in class, and on top of all of this additional research I performed, I have learned so much already, and I can not wait to continue to learn in and outside the classroom, not just in regards to these organisms, but the billions of other organisms out there. It is absolutely amazing how something so microscopic and simple can perform such complex motions and tasks.