• Category
  • Length Range
    28-51 µm
  • Width Range
    11-14 µm
  • Striae in 10 µm
  • Reported As
    Mastogloia smithii Morphotype II (Slate and Stevenson 2007)



Valves are elliptic-lanceolate with rostrate ends (small valves have subrostrate to round ends). Striae are punctate, gently radiate and become parallel at the apices. The striation pattern on the valve face continues unchanged onto the mantle. The central area is elliptic to polygonal, and is often asymmetric. Areolae are round to elliptic, 16 areolae per 10 µm, and some are reduced around the central area. The areolae are internally occluded by a cribrum. The raphe is straight with a median kink. The proximal raphe ends are expanded and pore-like and open into a spathulate groove. The distal raphe ends extend centrally over the mantle and hook to the same side. There is a small hyaline area where the curve of the distal raphe ends occurs.

Internally, the raphe is straight and encased in a thickened sternum. The internal proximal raphe ends are straight and the sternum fuses into the thickened central nodule. The internal distal raphe ends are occluded by pseudosepta. The partectal ring is closed, forming a complete band, and lacks a flange separating the ring from the valve margins. The partectal ring has a broad cleft at both apices. Pores are present between partecta near the advalvar edge of the partectal ring. Partecta are distributed along both sides of the partectal ring except near the apices. Partecta are clearly distinguishable and evenly sized, but are slightly larger closest to the apices, 6-8 partecta in 10 µm. The virgae and vimines are the same thickness throughout the valve interior. Cribral pores become irregular near the sternum and the central nodule.

Mastogloia pseudosmithii, M. calcarea, M. lacustris and M. albertii have all been misidentified as M. smithii, which has not yet been verified in North America. Mastogloia pseudosmithii and M. calcarea have not been verified outside of the Florida Everglades, the Caribbean and Mexico.


Comprises <1% of total diatom abundance in non-calcareous periphyton assemblages in waters of high conductivity, such as brackish areas near the coastal marshes of the Everglades, slightly acidic pH, and slightly higher periphyton total phosphorus. Weighted-averaging optima: water depth 41 cm, pH 6.7, conductivity 2500 µS/cm, and periphyton total phosphorus 480 μg/g.

Original Description

Mastogloia pseudosmithii sp. nov. Lee, Gaiser, Van de Vijver, Edlund & Spaulding (Figs 68–74; Table 7)

Description. Cells solitary. Valves elliptical-lanceolate with rostrate apices (small valves with subrostrate to rounded apices), 28–51μmlength, 11–14μmwidth, 16–17 striae in 10μm, 16 areolae in 10μm (Figs 68–71). Striae areolate, gently radiate, becoming parallel at the apices, stria arrangement on the valve face continues unchanged onto the mantle (Fig. 72). Central area elliptical to polygonal, commonly asymmetrical (Figs 68–72). Areolae rounded to elliptical, some reduced around the central area, internally occluded by a cribrum (Figs 72–74). Raphe straight with a median kink (Fig. 72). Proximal raphe ends expanded and pore-like, opening into a spathulate groove (Fig. 72). Distal raphe ends extending centrally over the mantle, hooked to the same side, with a small hyaline area where the curve occurs (Fig. 72). Internally, raphe straight, encased in a thickened sternum (Fig. 73). Internal proximal raphe ends straight, raphe sternum fusing into the thickened central nodule (Fig. 73). Internal distal raphe ends occluded by pseudosepta (Fig. 73). Partectal ring closed, without a flange separating the ring from the valve margins, with a broad cleft at both apices, with pores between partecta near the advalvar edge of the partectal ring sometimes arranged in a pattern (Figs 73–74). Partecta distributed along both sides of the partectal ring except near the apices, visibly distinguishable, evenly sized except slightly larger close to the apices (Fig. 74). Virgae and vimines (cross connections between virgae) of the same thickness present throughout the valve interior (Fig. 74). Cribral pores becoming irregular near the raphe sternum and central nodule (Figs 73–74).

Cite This Page

Lee, S. (2014). Mastogloia pseudosmithii. In Diatoms of North America. Retrieved April 21, 2024, from https://diatoms.org/species/mastogloia_pseudosmithii


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