The Stentor.

 

These two photographs show Stentor, a common spirotrich ciliate which can be found in great quantities in fresh water habitats feeding on algae, bacteria and other protozoa. The species shown is probably Stentor polymorphus. Stentor will attach its self to the substrate and commence feeding by using its cilia to create a vortex, which sucks plant, and animals in towards its adoral zone membrane, which encircles the peristome. The process of feeding and forming food vacuoles is easily observed through the microscope. When a food vacuole is full it pinches off and then starts to move around the cell body while the process of digestion takes place. Many cilia surround the whole body of Stentor and can best be viewed with phase contrast. Stentor can be found, attached to detritus or algal filaments and even to the microscope glass slide. The length of Stentor can vary but can be up to a few millimetres in length when fully stretched out. The colour of Stentor can also vary depending on what it has been feeding on; many also have their own pigmentation. When disturbed it contracts down to a ball shape but will quickly return to feeding once the disturbance as passed. It is a voracious feeder and when observed for any length of time many food vacuoles can be seen forming and then drifting around the inside of the body. The black and white photograph was taken with a Leitz X25 water immersion objective. Film used T-max 100.

 

   

These two photographs show the holdfast of the Stentor that I photographed with phase contrast. The spreading out of the base of the organism to create many fine cilia like projections must glue the organism very well to the substrate and therefore enabling it to create currents that draw any prey towards its feeding end with great ease and speed. I have never succeeded in making the observation of the protozoan actually forming this structure so I am unsure how fast this occurs. It is incredible to watch this ciliate dance around the pivotal point while it goes about its business of catching its food. X25, X40 Phase

 
  Fig 3 This photograph is of the ciliate stentor with the single celled alga called chlorella that lives within the body of Stentor in a symbiotic relationship. Not all Chlorella choose to live this way most are free living and can be found in great numbers in water and damp soil. Chlorella was used extensively for research in the past. The photograph was taken with a X16 brightfield objective but with a dark field condenser in place.

Introduction to photomicrography.