Ciliates again

[microplan]

Some ciliates again today.
Based on illustrations from the Internet, it's probably Euplotes, but I'm not sure.
There are plenty of these oranisms and matching them to the correct name is quite a feat.
Water collected from the pond in mid-February and kept in a jar at room temperature for several days.
Observation using 12.5x objectives; 25x and finally 40x.

Regards
Maciej

[DonSchaeffer]

They jump at things like they are grabbing prey but I don't see the prey they are grabbing. They don't see anything to grab at so what's going on here? Are they really grab-and-eat predators or is something else going on?

[Bruce Taylor]

They don't see anything to grab at so what's going on here? Are they really grab-and-eat predators or is something else going on?

There are two large ciliates here, both hypotrichs. The broad, darkly-coloured ones are Stylonychia. The slender ones are a species of Gonostomum, probably G. strenuum. Stylonychia is an omnivore with a rather big mouth, and it can consume bacteria, cyanobacteria, fungi, free-living flagellates, diatoms and other algae, small ciliates, organic detritus, and the eggs of small animals. These cells are capable of sensing and selecting appropriate prey, and will reject certain foodstuffs. While some ciliates--particularly those in the class Litostomatea--are genuine hunters, stalking and killing large prey, Stylonychia are more like wild pigs, rooting around in the underbrush gobbling small critters and deposits of tasty organic stuff. Gonostomum is mostly a bacterivore, scooting around in nutrient-rich muck, snuffling up bacteria.

[Free2Fish]

Thanks guys, nice video and great explanation. Getting those additional facts makes the video even more enjoyable. It’s going to be difficult getting that “wild pig” image out of my mind.
Harry