It’s nice to find out that – old and jaded as I am – biology can still delight me.

Earlier this week, I covered a first-year practical teaching microscopy skills to first-years, through the medium of pond water. As well as the usual desmids, rotifers, Daphnia and nematodes, one lucky student found a little clump of Vorticella (or some near relative, I’m not a protistologist!)

Their German name Glockentierchen (“little bell creatures”) delights me almost as much as they do:

Vorticella micrograph [CC-BY-SA-3.0 Steve Cook]

Vorticella clump: sorry about the rather poor quality of the image: the trinocular microscope was broken, so this was taken with an iPhone pointed down the eyepiece. Miracle it worked at all!

They’re actually quite common in freshwater, but this is the first time I’ve seen them in our pond samples. Each one is a single cell, attached to the substrate by a thin stalk, which can contract like a spring. Despite their cute bounciness, they’re voracious predators: the ‘head’ end has a cell-sized mouth (cytostome) surrounded by tiny beating hairs (cilia) which help funnel prey into the cell to be digested. The diagram below is of Stentor rather than  Vorticella, but gives you the rough idea:

Stentor diagram [CC-BY-SA-3.0 Steve Cook]

Stentor is another predatory ciliate with a similar form to Vorticella: the main difference being that the ‘stalk’ in Stentor is much fatter, whereas that of Vorticella is thin and contractile.

Vorticella is one example of a very large group of single-celled organisms called ciliates, which include the slightly more well known Paramecium. Their cells are amazingly intricate, and have sub-cellular compartments (organelles) playing similar roles to those that multicellular organisms have entire organs for. That such complexity can exist in a drop of pond-water smaller than your fingernail is one of the things that makes biology truly awesome.

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