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Cymbella

Cymbella is a biraphid genus that is asymmetrical over the apical (lengthwise) axis.  Often, its cells look like cymbals, which is likely how it got its name.  Its raphe deflect to the dorsal side at both tips, and its striae are uniseriate.  It is a large genus with substantial variety, but most of its species live in the bottoms of lakes and rivers and may attach to surfaces with a mucus they secrete from their tips. 

Dorsal side

Ventral side

C. hantzschia

  • Cells are 26-47 µm in length, 7.6-11.2 µm in width.

  • Rows of striae per 10 µm are 9-12 near the center, and up to 14 near the tips.

  • Ventral margin is arched slightly in the same direction as the dorsal margin, with a slight bulge near the center.

  • Raphe are "squiggly," closer to the ventral side near the center and tips but closer to the dorsal side otherwise.

  • Striae are radiate, and more so near the tips.

  • The best way to differentiate between C. hantzschia and C. proxima is by their raphe, striae density, and size.  C. hantzschia has wavy raphe, more widely spaced striae, and is smaller; C. proxima has straight raphe, closer striae rows, and is larger.

For more information, visit diatoms.org here.

C. proxima

  • Cells are 51-104 µm in length, 8-17 µm in width.

  • Rows of striae are 10-12 per 10 µm.

  • Ventral margin is arched slightly in the same direction as the dorsal margin, with a slight bulge near the center.

  • Raphe are straight.

  • Striae are radiate, and more so near the tips.

  • Ventral side of the center area may have 2-5 separated areolae.

  • The best way to differentiate between C. hantzschia and C. proxima is by their raphe, striae density, and size.  C. hantzschia has wavy raphe, more widely spaced striae, and is smaller; C. proxima has straight raphe, closer striae rows, and is larger.

For more information, visit diatoms.org here.

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