This particle – an aggregate of sand, organic debris and microorganisms – is probably a rich food source, so three different kinds of ciliates busily go in and out of the particle. They do not not collide or interfere with each other, as they seem to be completely absorbed in looking for food.
Commentary by Prof. Yuji Tsukii, Hosei University We can see three kinds of ciliates in this video. The one that is present from the beginning to the end may be identified as Holosticha polystylata from its reddish body with well-developed cirri.
Identification of the other two ciliates is more difficult because they appear for only a brief moment.
The ciliate that appears first may belong to class Spirotrichea,
but the last ciliate may be something else because it has a different type of cytoplasm. Although its cytoplasm is similar to that of Frontonia, Loxocephalus and Dexiotrica, we cannot say to which group the latter ciliate belongs without checking the shape and position of the cytostome (mouth).
Flagellates and ciliates gathering around a food source
Various sizes of flagellates and ciliates are swimming around, and they sometimes enter aggregates containing a variety of foods. One of the large ciliates is 400 microns in diameter, dark brown and oval shaped. The side-view of the organism shows it is slender, slightly narrow at both ends, and entirely covered with short cilia. Its motion has become slow because it is bloated with food from successful foraging.
Commentary by Prof. Yuji Tsukii, Hosei University The leading character in this video is Frontonia acuminata. In contrast with other ciliates in the Frontonia group whose cytostome is located in the center of the “abdomen”, the cytostome of Frontonia acuminate is slightly shifted from the actual center. In this way the organism resembles Disematostoma, but from other criteria, it can be identified as Frontonia. For example, the top of Disematostoma is slightly pointed, but the top of this organism is round like others in the Frontonia group.
Being sandwiched between a long algae and a particle, this Pleuronema ciliate cannot move freely. Only a transparent membranous structure on one side of the body is quivering. A few long cilia at its rear end are not moving. Ciliates of various sizes are swimming nearby, and sometimes bump into the Pleuronema.
Commentary by Prof. Yuji Tsukii, Hosei University The velum - lined cilia arranged like curtain – indicates that the organism is probably Pleuronema. If so, it may be Pleuronema marinum with a large body size.
Histobalantium natans has a similar body size and also has a velum. However, the velum of Histobalantium natans features cilia of variety lengths, whereas the cilia of Pleuronema marinum are all the same length.