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Diatoms are algae which live in little glass boxes or frustules - rather like little petri dishes. Pennate diatoms are motile, and rely on, we believe, the excretion of mucus through a slit in the wall - the slit is the raphe and runs down the flat faces of the petri dishes (frustules in diatom terminology). The frustule is perforated with tiny holes to allow the diatom to excrete waste products, and pick up nutrients, dissolved gases etc. from the surrounding water. This image shows the raphe and the pattern of sculpting in the frustule. Phase contrast.
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Navicula (na-vick-you-la), small to medium pennate diatom, common in sediments. With browny coloured plastid contracted to the centre of the cell. Refractile globules are lipid inclusions. The cell is located within a shell (frustule) made of silica (glass) and the patterns of pores and strengthening elements is used to distinguish different taxa. Differential interference contrast.
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Navicula (na-vick-you-la), small to medium pennate diatom, common in sediments. With browny coloured plastid located around the edges of the cell. Refractile globules are lipid inclusions. The cell is located within a shell (frustule) made of silica (glass) and the patterns of pores and strengthening elements is used to distinguish different taxa. Differential interference contrast.
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Two kinds of specialized membrane-bound organelles, the brown chloroplast and the stringy-looking mitochondria, are clearly visible inside this Navicula.
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Collected from Cumloden Swamp on April 18, 2004.
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A common planktonic pennate diatom.
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Material from the Netherlands.
