• Category
  • Length Range
    38-98 µm
  • Width Range
    11-16 µm
  • Striae in 10 µm



Valves are lanceolate and dorsiventral with narrowly rounded apices. The dorsal margin is moderately arched. The ventral margin is nearly flat, to weakly convex, and in some specimens, with a gibbous middle. The axial area is narrow and slightly displaced toward the ventral side of the valve. The small central area is elliptic. The raphe is lateral, becoming reverse lateral near the proximal ends. Proximal raphe ends are deflected ventrally and terminate in small round central pores. Distal raphe ends are filiform and deflected dorsally at about 45 degrees. Striae are radiate throughout, becoming more strongly radiate near the apices. Areolae are distinct in LM and number 18-28 in 10 µm. Isolated stigmata number 2-7 at some distance from the proximal ends of the median ventral striae.


Cymbella fontinalis has been collected from 17 locations in the Rocky Mountains of western Montana, mostly springs, spring seeps and spring creeks, where it was often found living among macrophytes, bryophytes and other cryptogams. Living cells were observed to be unattached and weakly motile in an apex-first direction. Mucilage stalks were not observed. Weighted averages of selected chemical and physical variables measured at collection sites indicate that C. fontinalis is found in cool alkaline waters with moderate conductivity. The type locality, Giant Springs (photo below), had a pH of 7.50 and a specific conductance of 590 µS/cm (Bahls 2018).

Other diatom species found with Cymbella fontinalis at the type locality include Ellebeckia arenaria (Moore ex Ralfs), Melosira undulata (Ehrenb.) Cleve and Cymbella mexicana (Ehrenb.) Cleve.

A larger undescribed morphotype, similar to this taxon has been collected from Ney Springs in Siskiyou County, northern California (Bahls 2018). Ney Springs has a pH of 8.02 and a specific conductance of 136 µS/cm.

Giant Springs  Mdfwp
Credit: Montana Department of Fish, Wildlife & Parks
Giant Springs near Great Falls in Cascade County, Montana: Type locality of Cymbella fontinalis
Cymbella Fontinalis Live Cell 3
Credit: Loren Bahls
Live cell showing H-shaped plastid and dorsal chloroplast fold

Original Description

Holotype: slide no. 50-21, University of Montana Herbarum (MONTU), Missoula. Fig. 33 is an image of the holotype specimen; sample no. 492301, Montana Diatom Collection, Helena (collected by L. Bahls on 24 October 2017).

Isotype: slide no. 136-87, Montana Diatom Collection, Helena.

Type locality: USA, Montana, Cascade County, Giant Springs near Great Falls.

Etymology: The attributive adjective fontinalis means "of or from the fountain" and refers to the seeps, springs and spring creeks where this taxon is most often found.

Description: Plastids are H-shaped with a central saddle-shaped pyrenoid lying on the dorsal side of the girdle (Figs 11-14). Vavles are dorsiventral with actutely rounded apices. Dorsal margin is moderately arched; ventral margin is slightly convex to nearly flat. Valve length = 38-98 µm; valve width = 11-16 µm. Axial area is very narrow, barely wider than the raphe. Central area is elliptic and small to moderately large. Raphe is distinctly lateral, becoming reverse-lateral at the proximal ends. Proximal raphe ends are deflected dorsally at a 45°angle. Dorsal striae are radiate throughout; ventral striae are parallel in the valve center and radiate towards the apices. Striae are uniseriate and number 8-10 in 10 µm in the valve center, 11-13 in 10 µm near the apices. Stigmata number 2-7 and are somewhat separated from the ends of the median ventral striae. Areolae number 18-28 in 10 µm.

SEM: External foramina of the areolae are slightly curved, apically elongate slits (Figs 42-44). Striae continue uninterrupted onto the valve mantle (Fig. 44). Proximal raphe ends are strongly looped towards the ventral margin (Fig. 43). Striae terminate at the distal raphe ends on the dorsal side of the valve; on the ventral side they transition to a well-developed apical pore field (Fig.42). Valve cingula are without ornamentation (Fig. 42). Internally, the intermssio (the gap between the proximal raphe ends) is obscured by a flap of silica, the edgy of which gives the appearance of a continuous raphe fissure across the central nodule (Figs 45-47). Internal areola openings are ellipsoid and separated by wide vimines (Figs 46,47). No hymenes or cribra were observed. The margins of the stigmata are lined with tooth-like projections (Fig. 46). The terminal raphe fissure bisects a lobed helictoglossa that is inclined dorsally at some distance from the valve apex (Fig. 47). Internally, each column of poroids in the apical pore field is partially covered by a knobby jointed ridge of silica (Fig. 48).

  • Author
    Bahls 2018
  • Length Range
    38-98 µm
  • Width
    11-16 µm
  • Striae in 10µm
    8-10 in valve center, 11-13 near apices

Original Images

Cymbella Fontinalis Lm Type

Cite This Page

Bahls, L. (2018). Cymbella fontinalis. In Diatoms of North America. Retrieved June 23, 2024, from https://diatoms.org/species/cymbella_fontinalis


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