Coleps: The Piraña of the ciliates

One of the most deadly ciliates that can even take on larger predatory ciliates like Didinium is Coleps. These are barrel-shaped ciliates with characteristic plate-like structures. They often hunt in packs and clean up dead ciliates or weakened ones. I have been inadvertently growing Coleps, while studying interactions between Didinium (the T-Rex of the ciliate world), and its prey Paramecium. To my disappointment, whenever I would set up predator-prey assays, the Didiniums would all but disappear– no cysts either. I often wondered what the issue was until now. Here is a somewhat bizarre incident. A Didinium is caught swallowing another of its kind (my first observation of a cannibalistic interaction), and while this was happening it was attacked by a school of Coleps. You will agree that it resembles a Piraña attack. It actually raises some interesting questions and a hypothesis which are listed after the movie.

Note that the video was accelerated at various points. The whole process took about 3-5 min.
  1. Clearly, some aspect of the inner cytoplasm attracts Coleps. While the Didinium was swallowing another, the Coleps congregated around the kill. I have seen on numerous occasions that whenever Didinium attacks a Paramecium (will upload soon), it attracts a large number of Coleps to it. What might this principle be? Could it just be a salt such as Calcium or perhaps released intracellular organelles such as alveolar sacs?
  2. If you put Didinium and Paramecium together, the former completely obliterates the latter, which is itself a bizzare Predator-Prey dynamic. Beyond this, cannibalizing its own kind is even more bizzare. It is like an eating machine that almost eats itself. What is the evolutionary advantage of this hedonism in Didinium?

6 Comments Add yours

  1. Manu Prakash says:

    Dear Laks,

    You know I love many of your posts. But this might be my all time favouirate – so far.

    I need to urgently send you the tracking microscope with real time statistics (similar instrument we built for the Lacry study). This way, we can get real statistics on the events and put some numbers (and a game theory) argument to this bizarre behavior. Can you send me your latest address?

    Now, on to the hypothesis of attraction. 1) Could it be that the process of generating “large” engulfment (a massive vacuole of a kind), some amount of cytoplasm is released – which acts as an attcator.
    2) secondly, we have been looking at maximum stretch ciliates can handle – and my hunch is “micro-cracks” might begin to appear on organisms that are eating a very large prey. The cell is still intact – and it can repair this slowly – but transiently, we would see a leakage leading to cracks and fractures (imagine a dry out skin). I have a setup I made for stretching ciliates where we can test this out.

    Can you send me some didinuims and coleps; and I will setup a parallel experiment. It would give me a sense of what real time identification algorithms we need to build – since these long term movies will be massive in size! Let’s really try to map the phase space of this interaction.

    Absolutely amazing data sets.. time to make this quantitative and test some hypothesis.


  2. laksiyer says:

    Dear Manu:

    I completely agree, there is some fantastic science waiting to be uncovered. I also feel that these communicate with each other and each time there is contact, there is likely to be some kind of signal of interaction (ca+2 spike??) that determines their future response. I shall send you my home address on your phone. I shall send you the cultures.

  3. Mitali says:

    I could watch that all day!

    1. laksiyer says:

      Mitali. Looking forward to your explorations during your holidays 🙂

  4. Manu Prakash says:

    @laks: shipping new instrument on Thursday/friday next week. Will ping when shipment has tracking number.


    1. laksiyer says:

      Excited to read this. Am scaling up the cultures and hopefully will send it through Max

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