Betty Sasser

Professor: Dr. Clarck

Laboratory Science

25 June 2001

 

ROTIFERS

 

 

Rotifers are multicellular animals, many of them have a length of 0.04 to 2.5mm. They are called "wheel animalcules" too. Rotifers are founded in every lake and stream, ponds, in moist, forest, in the tropics and even in the artic.

Rotifers come in different sizes, shapes, and types. They are so small, and not many people know about their existence. They have a crown of cilia that it look like a tiny wheels, and they use this for locomotion, this id use to wave food in their mouth too. Rotifers got the mastax where the food passed after being in the mouth, that is like a set of jaws made from hardened proteins, then the food is processed in the trophy and sent it direct towards the gut.

The rotifers are organisms very transparent, is that you can see all their organs all way through. They have red eye spots (2) and this are very sensitive to the light. The rotifers foot can excrete a sticky substance for attachment to a surface. They do their locomotion by walking with head and foot or they use the crown of cilia to propel themselves.

There is a lot of variety of body shapes in rotifers, for example the crown of cilia rotifers use for feeding and locomotion vary a lot in design. Example of rotifers: the Lecane, Asplanchnopus, and Collotheca.

Their continually moving cilia produce circular currents in the water and those currents move the food supply in reach of the mouth. Between the mouth and the stomach is the mastax containing hard pointed jaws to chop the food. Most rotifers are females, the males are few and not able to feed, so they donít live more than a few days.

World wide there are around 2,000 species with a great variety of body forms. They are found every where is a little water, like most water living microorganism, they can survive during hot summers. After death the bodies cloud over.

There is a kind of rotifers called Conochillus Unicornis, that is very interesting to me. Is a colony of rotifers, larger species and has a hundred individuals that form this colony easily visible. The colonies are very fragile , so it is impossible to find out the number of individuals per colony. The picture of the colony looks like a big flower in the water.

When you observe the colony en the microscope, the central area is a gelatinous sphere and each rotifer has a single spike arising from the corona. Sometimes when they are collected or transferred from a sample to a watch glass or slide, they can get damage.

The name of this organism, unicornis, derives from the fact that each rotifer has a single spike arising from the corona.

Rotifers are called weird microorganisms and one of the reasons is because they posses the mastax which is unique in the animal kingdom. Another weird thing is that most of them are females. In the bdelloids, reproduction is parthenogenetic so is no fertilization, all offspring are females.

Another thing will be very interesting to me is to observe a rotifer birth in the microscope, watch the egg open up, I wonder how long will take, and how it will look like. Some reports I read about a rotifer birth said the egg opened up, and a thing pushed its way out. This was observed in the microscope.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

References

Howey. Richard L. (1999). Welcome to the Wonderfully Weird World of Rotifers. [on line]. Available: http://www.microscopy-uk.org.uk/mag/artnov99/rotih.html.

Egmond Van Wim. Rotifers [on line]. Available. http://www.microscopy-uk/wismall/rotidr.html.

Dingley. Mike. Observing a Rotifer Birth. [on line]. Available.http://www.microscopy-uk/mag/art97b/dingrot/html.