Sellaphora alastos | Species - Diatoms of North America

Category

Symmetric Biraphid
Length Range

41.0-82.0 µm
Width Range

11.0-17.0 µm
Striae in 10 µm

17-19 midway between valve center and apex

Contributor

Loren Bahls - Mar 2014
Reviewer

Sarah Spaulding - Mar 2014

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Identification

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Description

Valves are broadly linear, with parallel or weakly concave margins. Apices are obtusely rounded. The axial area is narrow and undulate, bordered on each side by a narrow conopeum. The conopea are continuous through the central area, where they expand laterally. Near the valve apex, the conopea are somewhat inflated before they terminate in a point. The central area is wide and transversely rectangular. The central nodule, defined by the inner margins of the conopea, is small, elliptic, and somewhat asymmetric. The raphe is filiform and follows the undulate margins of adjacent conopea. Proximal raphe ends are deflected slightly to one side and tipped with small pores. Distal raphe ends are comma-shaped. Striae surrounding the central area are parallel, straight, shorter, and more widely spaced than more distal striae, which are curved and radiate.

Autecology

Specimens of S. alastos pictured and described on this page were collected from five ponds and small lakes in the Rocky Mountains of Montana and Colorado and the North Cascade Mountains of Washington. pH ranged from 6.73 to 6.98 and specific conductance measured 22 to 71 µS/cm. Sellaphora alastos was described from a river in eastern Canada (Hohn and Hellerman 1963) and also reported from an oligo-dystrophic lake in Finland (Lange-Bertalot and Metzeltin 1996).

Size Range, µm3

1001-10000
Motility

Moderately motile
Attachment

Unattached
Habitat

Benthic
Colony

Solitary
Waterbody

Inland
Learn more about this

Credit: Ryan Davis, Adventurers and Scientists for Conservation

Lake Caroline, Chelan County, Washington: home of Sellaphora alastos.

Original Description

Basionym

Navicula americana var. alastos
Author

M.H.Hohn and Hellerman 1963
Length Range

56.7 µm
Width

12.5 µm
Striae in 10µm

12 at valve center, 16 near the apices

Original Images

Citations & Links

Citations

Cite This Page

Bahls, L. (2014). Sellaphora alastos. In Diatoms of North America. Retrieved December 16, 2024, from https://diatoms.org/species/49869/sellaphora_alastos

Responses

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