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 http://www.marinespecies.org/aphia.php?p=taxdetails&id=142191