• Category
  • Length Range
    26-42 µm
  • Width Range
    8.5-12 µm
  • Striae in 10 µm
    9-10 in center valve, 13-14 at apices



Valves are moderately dorsi-ventral, with slightly protracted apices. The dorsal margin is strongly arched, whereas the ventral margin is slightly convex. The central area is small, elliptical. A single elongated stigma is present at the end of the middle striae. Rarely in larger valves there may be two stigmata. The proximal raphe ends have central pores that curve to the ventral margin. The raphe is lateral, becoming filiform near the distal end. Striae are radiate. The areolae are apically elongated, they number 22-25 in 10 μm.


Original Description

Cymbella tropica nov. spec. [Figs 44: 1-10]

Cymbella turgidula sensu Metzeltin & Lange-Bertalot 1998, figs 133: 14-16

Type locality: Venezuela, Rio Manizanes, leg. Rumrich 4.4.90. slide 1015D IOK.

Valves slightly dorsiventral, broadly-lanceolate, dorsal margin strongly arched, ventral margin moderately convex. Ends not protracted or slightly subrostrate and bluntly rounded. Length 35-44 μm, breadth 10-12 μm, maximal length/breadth ratio 4. Axial area narrow, linear, broadening slightly into a very small rounded or indistinct central area. Raphe not ventrally displaced, distinctly lateral, becoming filiform near the distal ends and slightly reverse-lateral just at the proximal ends. Proximal raphe ends slightly rounded; terminal fissures indistinct but, when noted, dorsally deflected. Striae slightly radiate from the middle to the ends, punctate. One large isolated stigma just at the end of the middle stria on the ventral side, in larger specimens sometimes two. Striae in the middle portion 9-11/10 μm (dorsal and ventral), becoming 12/10 μm towards the ends, puncta 21-24/10 μm (var. 25- 28/10 μm).

  • Author
    Krammer 2002

Original Images

Cymbella tropica orig illus
Cymbella Tropica  Descr

Citations & Links

Cite This Page

Potapova, M. (2011). Cymbella tropica. In Diatoms of North America. Retrieved June 23, 2018, from https://diatoms.org/species/cymbella_tropica


The 15 response plots show an environmental variable (x axis) against the relative abundance (y axis) of Cymbella tropica from all the stream reaches where it was present. Note that the relative abundance scale is the same on each plot. Explanation of each environmental variable and units are as follows:

ELEVATION = stream reach elevation (meters)
STRAHLER = distribution plot of the Strahler Stream Order
SLOPE = stream reach gradient (degrees)
W1_HALL = an index that is a measure of streamside (riparian) human activity that ranges from 0 - 10, with a value of 0 indicating of minimal disturbance to a value of 10 indicating severe disturbance.
PHSTVL = pH measured in a sealed syringe sample (pH units)
log_COND = log concentration of specific conductivity (µS/cm)
log_PTL = log concentration of total phosphorus (µg/L)
log_NO3 = log concentration of nitrate (µeq/L)
log_DOC = log concentration of dissolved organic carbon (mg/L)
log_SIO2 = log concentration of silicon (mg/L)
log_NA = log concentration of sodium (µeq/L)
log_HCO3 = log concentration of the bicarbonate ion (µeq/L)
EMBED = percent of the stream substrate that is embedded by sand and fine sediment
log_TURBIDITY = log of turbidity, a measure of cloudiness of water, in nephelometric turbidity units (NTU).
DISTOT = an index of total human disturbance in the watershed that ranges from 1 - 100, with a value of 0 indicating of minimal disturbance to a value of 100 indicating severe disturbance.