Day 17: A Worm meets an explosive end.

The pond water has reached a stable state with several animals below the duckweed top layer. Animals like rotifers and Daphnia are a healthy sign that the water is not depleted of oxygen. A small moving object caught my attention, and I put it on the slide along with some duckweed. It was a quick moving worm. At first we thought it was a flatworm, then based on its tail, we thought it was a nematode which is how I originally wrote it. Manu (see comments), then pointed to the fact that it looked like a Gnathostomuliid, but after more searching and prodding, the Catenulid worm Stenostomum seems a better fit.


I followed it around to see if I could image its locomotion and eating style, when suddenly, it split into two …


and disintegrated like dust. I don’t know what made it split and even after splitting it twitched a bit and spewed out its cells. Fascinating!! Is this a suicidal behavior, or a case of crushed-by-coverslip?  I wonder if like in the spider, the  worm disintegrated due to loss of hydrostatic pressure.


Stenostoma are basal flatworms. For more details see

5 Comments Add yours

  1. Manu Prakash says:

    @laks: incredible worm.. It’s a mystery to me. One thing I noticed which might help; is that the surface of the worm is ciliated. I saw when it was spewing it’s own cells; Sind if them were getting caught in the flow caused by the cilia.

    The disintegration looks active again – so now you are becoming a master of disintegration 🙂

    Also; I just noticed a new phylogenetic tree for flatworms was just published in elife – see here:

    And here:


  2. Manu Prakash says:

    @Laks: I had written a comment but it just disappeared. I will wrote it again.

    1) I could see some evidence of cilia on the surface; because of a vortex in which its own cells are caught. So I tgought – it’s ciliates – at least around the head.

    2) I found a series of flatworms that also have a sharp thin tail. I jut saw an elife paper with the new family tree of flatworm; look at the second image in the tree. See figure 6 of this paper.

    It looks like
    Gnathostomula peregrina


    Ps: finally – while reading about flatworms; I ended up at this paper that characterized sperm geometries – very neat..

  3. laksiyer says:

    Thanks @Manu. You have hit the nail as always and Aravind confirms. He tells me that these are mainly marine, so it might be a first (or unprecedented) for a freshwater version (Will check the literature). Gnathostomuliids were iniitally classified as flatfworms, but now they have been found closer to rotifers and acanthocephalans. In the tree of fig. 6 the platyhelminth group are the flatworms and these are shown outside of that group. Now I have to start looking for it again to see if I can image this more carefully for this might be a record useful for those who study them! Everyday I hit this bottle of pond water, something new crops up. I could spend the rest of winter with this 🙂

  4. Manu says:

    @Laks: Yes, I am so excited about the “pond in a bottle” experiment. Please image it nicely; since as you said – this might be the first record of finding them in fresh water.

    Also; could you make a post documenting how you made your “pond in a bottle” with a picture of the same as well. I think many people would find that very useful. If you have some way to asses the health of the “pond” and also what volume you choose (I can imagine too small a volume would not be good; and finally influence of direct sunlight, heat and evaporation.


    1. laksiyer says:

      Hi @Manu. I surely will put up a post. We now have seen two of these and are leaning towards Stenostomum, a flatworm. It seems to show a dimorphism.Ref1 Ref2
      This is the third time I am changing my mind, which means I need to study the flatworm anatomies a bit more carefully, but this is what I like about the process.

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