Life on Discs – Episode 2

Bdelloid (dell-oy-d) rotifers are microscopic free-swimming organisms found in freshwater environments, although a couple of species have been found in saltwater too.

 

These tiny creatures are characterised by the corona on their head. In more primitive species, this forms a simple ring of cilia around the mouth from which an additional band of cilia stretches over the back of the head. However, in the great majority of rotifers this evolved into a more complex structure.

In Bdelloids, the band splits into 2 rotating wheels raised up on a pedestal projecting from the upper surface of the head. 

 

The feeding behaviour of Bdelloids is varied, but most use the rings of cilia to create currents of water that blow food through the mouth into the mastax organ which has been adapted for grinding food. 

Food includes suspended bacteria, algae, detritus and other organic matter. 

 

There appear to be 3 main methods of movement;

 

– Free-swimming 

– Inch-worming along a substrate (this involves taking alternate steps with the head and tail, like a leech)

– Seccility (remaining immobile)

 

Rotifers are an important part of the freshwater zooplankton, being a major food source and contributing to the decomposition of soil organic matter. 

 

The presence of rotifers indicates that the biological waste treatment process is working efficiently.

 

Rotifers = A happy treatment plant!