• Category
  • Length Range
    46-78 µm
  • Width Range
    17.8-22.5 µm
  • Striae in 10 µm
    7-8 in the center valve, up to 12 at the ends



Valves are strongly dorsiventral, with broad rounded apices. The dorsal margin is strongly arched, whereas the ventral margin is slightly concave, usually with slightly tumid central portion. The central area is circular and about one third of the valve width in diameter, but somewhat smaller in shorter valves. Three to four stigmata are arranged in a line in the ventral part of the central area. The axial area is narrow, almost central. The raphe is lateral near the middle of the valve, becoming filiform near the distal and proximal ends. The outer and inner raphe slits usually do not appear to cross, but sometimes the proximal and distal raphe ends can be seen as very slightly reverse-lateral. The proximal raphe ends have bulbous central pores that curve to the ventral margin. Apical pore fields are present at both apices. Striae are radiate. Areolae number 14-16 in 10 µm.


Cymbella proxima f. gravida has been so far known only from the type locality, Lake Maxinkuckee, Indiana.

Original Description

Differs principally in shape from the nominate variety. Valves reniform, tapering but slightly from valve center to extremities. Other features as in var. proxima. Striae, 8-9 in 10µ, becoming ca. 11 in 10µ near the extremities. Puncta, ca. 14-15 in 10 µ. Length, 45-60µ. Breadth, 20-24µ.

  • Author
    Reimer in R.M.Patrick and Reimer 1975
  • Length Range
    45-60 µm
  • Width
    20-24 µm
  • Striae in 10µm
    8-9 in the center valve, 11 at the ends

Original Images

Cymbella Grav  Or Ill001
Cymbella proxima f. gravida orig descr

Cite This Page

Potapova, M. (2012). Cymbella proxima f. gravida. In Diatoms of North America. Retrieved July 13, 2024, from https://diatoms.org/species/cymbella_proxima_f._gravida


The 15 response plots show an environmental variable (x axis) against the relative abundance (y axis) of Cymbella proxima f. gravida 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.