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The Planktonic Rotifers. 
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Rotifers: Home Bdelloid Loricate Planktonic Sessile

  Planktonic Rotifers.

These are rotifers which swim freely in the open, usually surface, waters of the pond or stream. They are strong swimmers, and some of the larger ones are predaceous; most often preying on smaller rotifers.

Asplanchna Asplanchna can be thought of as the killer whale of the rotifer world. It grows to around a millimetre in length, is a powerful swimmer, and feeds upon smaller rotifers by projecting its jaws forward, seizing the prey, and hauling it inside its highly transparent body in one rapid action.
The young develop to maturity within the parent's body, and are born live. Two mature daughters, ready for birth, can be seen (one clearly) in the lower body area of this specimen.
Darkfield, 100X.
Filinia Filinia is another common planktonic rotifer, smaller than Asplanchna, with two long lateral bristles which it uses to jump rapidly backwards when threatened. This female specimen has a single egg attatched to the rear of its abdomen.
Darkfield, 300X.
Synchaeta Synchaeta is a fast-swimming planktonic rotifer characterised by an extremely thin transparent cuticle and, in addition to the corona, two "ears" or auricles bearing groups of cirri which further aid swimming. There are usually also four sensory bristles projecting forwards. This female specimen (no males have been observed) has a developing egg in its lower body.
Darkfield, 300X.
Testudinella Testudinella is a fairly sensitive creature, and can spend a good deal of its time contracted inside its very flattened tortoise-like lorica. Like most rotifers, they feed and swim by means of their corona, and are not predaceous. This one has two red eyes.
Darkfield, 300X.

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