Credit: Photo by: Katherine M. Johnson
Pleurosigma inflatum (left) and P. diversestriatum (right) in dark field.
Pleurosigma inflatum
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Category
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Length Range65-75 µm
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Width Range16-19 µm
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Striae in 10 µm28-32
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ContributorKatie Johnson - Jun 2016
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ReviewerSarah Spaulding - Jul 2016
Identification
Description
Valves are broadly lanceolate to slightly rhombic, and moderately sigmoid. The valve face is broadly arched. Apices are acutely rounded. The raphe is sigmoid and eccentric near the apices. The distal raphe ends are bilaterally deflected. Proximal raphe ends are variable, and may extend into the central area. The axial area is narrow and opens to a distinct, circular central area. Striae are decussate. At the apices, striae are more numerous and curve slightly as they continue from the valve face to the valve mantle. The valve length to width ratio is 3.8-4.9.
Species in the genus Pleurosigma may be distinguished by measurement of the angle of divergence of the oblique striae from the raphe, termed "raphe angle" (Sterrenburg 2002). Sterrenburg (2001) reported +8° to +13° raphe angles for P. inflatum, compared to +17° to +21° for P. diversestriatum. The specimens imaged here show large variability in raphe angle within the population. Raphe angle measurements in this observed population (Edisto Marina, South Carolina) range from 10-17°.
Autecology
Pleurosigma inflatum is a marine taxon found in warm and tropical waters. However, it has also been observed in the North Sea and Normandy (Peragallo 1889), and the Newfoundland Banks (Lohman 1942). The specimens posted on this page are from estuarine waters of the Edisto Marina, near the coast of South Carolina.
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Size Range, µm3
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Motility
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Attachment
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Habitat
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Colony
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Waterbody
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Original Description
The genus Pleurosigma has no less than five species, two being quite new, and both having the markings arranged diagonally, that is, with (what the Rev. W. Smith considers) cells placed alternately in contiguous rows. The outline of the largest (fig. 8) is very clumsy and the ends obtuse, and the median line but slightly flexed—this I call validum; the other, P.inflatum, on the contrary, is of a graceful outline, the apices acute, the flexure of the median line considerable, and is broad in proportion to its length (fig. 9).
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AuthorShadbolt 1853
Original Images
Citations & Links
Citations
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Publication Link: 10.1635/0097-3157(2001)151[0121:SOTGPA]2.0.CO;2
Links
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Index Nominum Algarum
Cite This Page
Johnson, K. (2016). Pleurosigma inflatum. In Diatoms of North America. Retrieved December 16, 2024, from https://diatoms.org/species/51568/pleurosigma_inflatum
Responses
The 15 response plots show an environmental variable (x axis) against the relative abundance (y axis) of Pleurosigma inflatum 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.
Pleurosigma inflatum
- Valves sigmoid, broadly lanceolate to slightly rhombic
- Valves face convex or arched
- Apices accutely rounded
- Raphe sigmoid and eccentric
- Central area circular
The valve face is arched, so that only a portion of the valve face will be in focus. Apices are acutely rounded. The raphe is sigmoid and eccentric. The central area is circular.