DENNIS KUNKEL MICROSCOPY / SCIENCE PHOTO LIBRARY DENNIS KUNKEL MICROSCOPY / SCIENCE PHOTO LIBRARY
Brightfield light micrograph of Paramecium. First the micronuclei divide and redistribute throughout the cytoplasm and then the macronucleus forms two distinct halves. Paramecium are found mainly in stagnant ponds, feeding on bacteria and plant particles. They have a permanent mouth called an oral grove. Food taken in through the oral groove is digested within temporary digestive vacuoles in the cell cytoplasm. The two contractile vacuoles act as osmotic regulators, controlling the flow of water across the ciliate's membrane. The contractile vacuoles are surrounded by a halo of radiating channels. Excess water collects in the channels, drains into the vacuole and is then discharged through a pore at the surface. Magnification: x110 when shortest axis printed at 25 millimetres.
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