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Bacillariophyta: Diatoms

Bacillariophyta: Diatoms. Diatom morphology. More diatom morphology . Centrales: centric diatoms. Radial symmetry Striae composed of linear punctae May be single-celled like Cyclotella (above )or colonial: in filaments or like Tabellaria (above). Pennales: pennate diatoms. Pennales.

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Bacillariophyta: Diatoms

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  1. Bacillariophyta: Diatoms

  2. Diatom morphology

  3. More diatom morphology

  4. Centrales: centric diatoms • Radial symmetry • Striae composed of linear punctae • May be single-celled like Cyclotella (above )or colonial: in filaments or like Tabellaria (above)

  5. Pennales: pennate diatoms

  6. Pennales • Bilateral symmetry • Many groups possess a raphe-these are motile; some have a pseudoraphe • Many are epilithic, benthic, etc. (provides substrate for gliding • Generalization: pennate diatoms are more common in eutrophic waters, centrics in oligotrophic waters; • hence, A/C (araphidinieae : centric) index is one indicator of water quality (in lakes of low alkalinity)

  7. Preparation of diatoms for microscopic observation

  8. Characteristics • Frustules made of silica (often a limiting nutrient) • Unicellular or colonial • Form diatomaceous earth • Opal is the mineralized form of sedimented diatoms • Reproduction: produces auxospores

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