Nassula (200µ) (A healthy Nassula 400X

Nassula (200µ)Nassula with raging suctorian infestation

As the Nassula in my petri dishes used up their Oscillatoria food supply all turned an opaque white color and shortly thereafter encysted. However, in one Nassula culture the stereo microscope showed that the organisms were not encysting, and, although they continued to swim about, their shapes had become irregular, like jellybeans that had been stepped on.

Microscopic examination showed small suctorians clinging to the outside, and inside some cells were found large yellowish bodies, some still bearing tentacles. Interestingly the "infection" apparently prevented the host cells from forming cysts, an advantage to a parasite that is able to enjoy a longer period of growth at its hostOs expense.

Suctorian on Nassula’s outer surface

Suctorian reproductive bodies

Most suctorians are predators that nab smaller organisms that come into range of their tentacles. Their hollow tentacles are then used to suck out their prey's cytoplasm. The suctorians that attacked Nassula appear to be making a transition from predator to parasite.

I have allowed the culture to dry out (a normal event in habitats where Nassula is found) and will watch with interest when water is again added to the chips of the dried material.