|The first brittle star, captured in a plastic cup. Missing half an arm.|
Brittle stars are not starfish, but are related to them. They do not use suction cups on tube feet to move, but rather wave the arms about wildly to swim, in a haphazard fashion, going where the current takes them.
The arms break off easily, leaving a hungry predator with a mouth full of spines and no meat. The star grows the arm, or arms (up to 4) back. The detached arms themselves don't regenerate a new brittle star, though. (As some starfish do.)
|A second brittle star, in the aquarium. Parts of two arms missing. The star-shaped opening at the centre is the mouth.|
These are possibly the dwarf brittle star, Amphipholis squamata, aka the holdfast brittle star, aka the small serpent star (for the movement of the long arms). The ones we found a few years ago in Campbell River had much longer arms, and were probably the long-armed brittle star, Amphiodia occidentalis.
|Much bigger, much more wriggly. More here and here.|
Within a few minutes of being placed in the tank, all three had disappeared. I've been looking for them since Brat intervals, with a lens and flashlight, but have seen no sign of them. They seem to prosper in other aquaria, so they may show up again, with all their arms intact.
I've been watching that bigger starfish; the more I look, the more interesting it gets. I just took another batch of photos, to process tomorrow, I hope.