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Ciliates

Stentor

Stentor (trumpet ciliates)

A trumpet-shaped giant among ciliates. Some species are visible to the naked eye as blue-green or brownish specks.

What to look for

Trumpet or horn shape when attached; a wide ring of membranelles around the top sweeps food in.
Usually anchored by the narrow end, but can let go and swim, becoming pear-shaped.
Contracts into a ball when disturbed and slowly stretches out again.
Stentor coeruleus is blue-green from a pigment; S. polymorphus is green from algae living inside it.

Size in the field

Stretched out, a big Stentor can fill most of the field at 100×.

Where to find it

Among water plants and on submerged leaves in clean, still water.

Group: Ciliates
Moves by: Attached, contracts
Colour: Blue-green
Size: roughly 200 µm to 2 mm

Often confused with

Bell animalcules: Vorticella is a small bell on a thin stalk that coils like a spring; Stentor has no stalk.
Rotifers: Rotifers have a jaw that pumps inside and a forked foot; Stentor is a single cell with no internal organs.

Way through the key

How does it move? It is fixed to something by a stalk, a foot or a base, and contracts when disturbed
What is attached? A large trumpet with a ring of cilia around the wide end; may let go and swim

How does it move? It swims or glides, and you can see a fringe of fine hairs or whirling crowns
One cell, or an animal with a jaw? A single cell: no jaw, no gut, cilia over the surface or in rows
What shape and colour is the ciliate? A large trumpet, often blue-green

Clips 0

No clip of this group is on the site yet. The description above is enough to check your own observation.