Steeling food?

Collotheca ambigua is a rotifer species in the family Collothecidae. The scientific name of this species is first validly published in 1883 by Hudson. Rotifers are extremely common and can be found in many freshwater environments and in moist soil, where they inhabit the thin films of water surrounding soil particles. Their habitats may include still water environments, such as lake bottoms, as well as
rivers or streams. They are also commonly found in many other moist environments.

This video was recorded with a Motic AE31 Elite Inverted Microscope with LWD objectives in brightfield and in phase contrast. It seems that a ciliate (Lepocinclis sp.) takes on food from the inside of the rotifer, instead of being eaten itself. By using an inverted microscope - as opposed to an upright microscope - life in water samples can be examined very user-friendly, because:

• Relatively large amounts of sample can be examined at one time by using Petri dishes of various sizes in combination with LWD objectives. 

• By using a 35 mm imaging dish, with a standard glass bottom of 170 micron thickness, the sample can even be studied with standard objectives which have a smaller working distance but a higher numerical aperture, resulting in a higher resolution.

• The dish containing a few milliliters of sample, makes it possible that water life can be observed for an extended period of time ‘in 3D’, as the organisms are not squeezed to flat by a coverslip.