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Pennate diatoms. The cells are enclosed in siliceous valves. There are typically two valves - a top one and a lower one, and they are joined together with fine bands or girdle strips. With plastids containing chlorophylls a and c (they are stramenopiles after all). Genera and species distinguished largely by the shape of the organism and the pattern of pores and sculptings of the siliceous shell or frustule. This pennate diatom is seen in valve view, there is an H shaped zone without sculptings in the frustule. Large plastids. The raphe is the two-part line running axially along the centre of the valve. Differential interference contrast.
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Centre of valve showing the inner termini of the raphe structure, phase contrast micrograph of empty frustule.
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Pennate diatom, valve view of an empty frustule (shell). Phase contrast optics.
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The larger more boat-like frustules are of Anomoeoneis, the squarer ones are probably Surirella. Phase contast optics.
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Frustules.Some kind of differential interference contrast optics.
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Cymbella (sim-bell-a) a pennate diatom with a slightly asymmetric body form, one face convex, other face flat. Frustule only. Differential interference contrast.
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Cymbella (sim-bell-a) a pennate diatom with a slightly asymmetric body form, one face convex, other face flat. Differential interference contrast. This one stuck on the toe of a chironomid larva. Phase contrast.
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This pennate diatom usually occurs in the benthos as epilithic on stones of Lake Kinneret, infrequently it is found in the plankton.
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Achnanthes sp. (Bacillarophyta, Pennales) is a small (length ca. 10 um) unicellular diatom occurring in the Kinneret littoral zone in the benthos, but also in the plankton and as epiphytes. At least 3 species of Achnanthes occur in the lake. Achnanthes usually grows on agar when we try to isolate other species from the lake plankton. This picture of Achnanthes grown in culture shows the cells from both top view (elongated oval shape) and valve view (rectangular shape).
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Cocconeis (cock-owe-neigh-us) one isolated valve seen from valve view, the perforations in this siliceous shell allow the cells which normally live within to exchange nutrients etc. with the outside world. Phase contrast micrograph.
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Pinnularia (pin-you-lair-ee-a). a pennate diatom, found either individually or in clusters as here. As with other diatoms with a siliceous cell wall. Nucleus central. Phase contrast.
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Pinnularia (pin-you-lair-ee-a). a pennate diatom, found either individually or in clusters as here. As with other diatoms with a siliceous cell wall. Nucleus central. Differential interference contrast.
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Pinnularia (pin-you-lair-ee-a) a pennate diatom, the upper cell is the empty siliceous wall or frustule, the lower cell is a living cell with brown-ish chloroplast and central nucleus. Diatoms are mostly identified and classified using the markings on the surface of the frustule. The central line is the raphe, and is associated with the gliding movements of the cell. Differential interference contrast. Material from Nymph Lake, thermal sites within Yellowstone National Park, photograph by Kathy Sheehan and David Patterson.
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Pinnularia (pin-you-lair-ee-a), large pennate diatom. Margins reveal strengthening struts. The plastid has a browny-green colour. Phase contrast.
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The intricate frustule of the diatom Pinnularia. Frustules have ridges, grooves, and pores that are useful for identification of different diatoms. The two grooves in the center of the cell form the raphe and the raphe is used for propelling the diatom.
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Diatom frustules are brittle and delicate. This Pinnularia frustule was broken when it was flattened between the microscope slide and the coverslip.
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Collected from Le Barron white cedar swamp on July 1, 2004.
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Originally referred to by Haeckel as Navicula lyra.
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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.
