• Category
  • Length Range
    5.6-9.8 µm
  • Width Range
    3.1-3.8 µm
  • Striae in 10 µm



Valves are elliptic to narrowly elliptic, with broadly rounded apices. The raphe is composed of two short branches. Internal proximal raphe ends are simple, while external proximal raphe ends are slightly expanded. The external apical raphe ends are slightly expanded and terminate prior to the apices. Internal apical raphe ends terminate in small, indistinct helictoglossae. The raphe sternum is slightly elevated internally. Transapical striae are arranged as a peripheral ring of single areolae along the valve margin. Externally, the areolae are occluded by vermiculate cribra. Internally, the areolae appear to have hymenate occlusions, numbering 28-32 in 10 μm. Live cells exhibit two girdle-appressed plate-like plastids.

Amicula vermiculata differs from the other two Amicula species by having vermiculate external cribra covering the areolae. Amicula vermiculata differs from A. micronesica also in having a coarser stria density.


This taxon is newly described and has yet to be found outside of its type locality. It was described from carbonate marine sediments from 20 meters water depth near the Marquesas Keys, Florida between Key West and the Dry Tortugas. It was observed in a rich and diverse benthic diatom community consisting of many undescribed Diploneis spp.

Amicula vermiculata live
Credit: Andrzej Witkowski
Live cell from culture, two girdle-appressed plate-like plastids

Original Description

Valves elliptical to narrowly elliptical with broadly rounded apices, 5.6-9.8 μm long, 3.1-3.8 μm wide. Raphe composed of two short branches. Internal central raphe ends simple, external central raphe ends slightly expanded. External apical raphe ends slightly expanded, terminating prior to apices. Internal apical raphe ends in small, indistinct helictoglossae at apices. Raphe sternum slightly elevated internally. Transapical striae arranged as a peripheral ring of single areolae along the valve margin, occluded externally by vermiculate cribra and apparently hymenate occlusions internally, 28-32 in 10 μm.

  • Author
    C.Li, Wachnicka, Frankovich and A.Witkowski 2022
  • Length Range
    5.6-9.8 µm
  • Width
    3.1-3.8 µm
  • Striae in 10µm

Original Images

Amicula vermiculata orig illus
Amicula vermiculata orig desc

Cite This Page

Frankovich, T. (2023). Amicula vermiculata. In Diatoms of North America. Retrieved October 03, 2023, from https://diatoms.org/species/amicula-vermiculata


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