• Category
  • Length Range
    9-15 µm
  • Width Range
    4.5-5.0 µm
  • Striae in 10 µm
    48-48

Identification

Description

Valves are broadly elliptical-lanceolate with apiculate apices, 9 – 15 μm long, 4.5 – 5.0 μm wide. Frustules are heterovalvar; one valve has a raphe and the other lacks a raphe. The rapheless valve has one to four elongated slits in the distal part of the axial area that appear to be vestiges of raphe slits. Striae are slightly radiate to parallel on the raphe valve, more radiate on the rapheless valve, 48 to 58 in 10 μm. The axial area of the raphe valve is linear to lanceolate and expands into a one-sided central area that is rectangular to slightly wedge shaped. The axial area of the rapheless valve is narrow near the apices, but lanceolate in the middle part of the valve. The central area is broad, one-sided and wedge shaped. The central area on the rapheless valve is typically twice as wide as the central area on the raphe valve. The raphe is linear, straight and has distal raphe fissures that deflect in the same direction, extending onto the mantle. The proximal raphe endings are straight and end as small tear-drop shaped pores. Internally, the distal raphe ends terminate in small helictoglossae. The proximal raphe ends are straight. Externally, the areolae are transapically elliptical to rectangular, and covered with hymenes. Internally, the areolae are smaller in diameter than their external expression, and circular to elliptical in shape. The mantle has a single row of elongated areolae that encircles the apices. A siliceous ridge is present along the valve margin, often more pronounced on the rapheless valve.

Autecology

Original Description

Valves are broadly elliptical-lanceolate with apiculate apices and range in size from 9 to 15 x 4.5–5.0 μm (Figs 1A–M and 2A–F). Valves of a frustule are heteromorphic with respect to raphe development and the nature of the central and axial areas. One valve possesses a fully formed raphe (Figs 1A,C–E,H,K and 2A–C) and the other lacks a raphe (Figs 1B,F,G,I,K–M and 2D–F), but has one to four elongated slits positioned in the distal part of the axial area (Fig. 3E–H). Striae are slightly radiate to parallel on the raphebearing valve, more radiate on the opposite valve and range from 48 to 58 in 10 mm. On the raphe-bearing valve, the axial area is linear to lanceolate and expands into a one-sided fascia that is rectangular to slightly bow-tie shaped (Figs 2A–C and 3A,B). On the valve bearing the raphe-like slits, the axial area is narrow near the apices, but expands into a broadly lanceolate central area with an equally broad one-sided bow-tie shaped fascia (Figs 2E,F and 3C). The fascia on this same valve is typically twice as wide as the one on the raphe-bearing valve. The raphe is linear, straight and has distal raphe fissures that deflect in the same direction down onto the mantle (Fig. 2B). The proximal raphe fissures are straight and end as small tear-drop shaped pores (Fig. 3A). Internally, the distal raphe ends terminate as small helictoglossa and the proximal raphe ends are straight and do not deflect in any direction (Fig. 2A). The valve opposite to the raphe-bearing one has one to four elongated slits aligned in a row within the distal end of the apical area (Fig. 3E–H). Externally, the areolae are elliptical to rectangular, aligned with the transapical valve axis, and covered with a hymen (Fig. 2D). Internally, the areolae are smaller in diameter, circular to elliptical and lack coverings. As a result of the different size openings, the sides of the areolae more or less taper from the wider external opening to the smaller internal openings situated in the bottom of the structure. The mantle consists of a single row of elongated areolae that also encircles the apices (Fig. 3E–H). A siliceous ridge is present along the valve margin that is often more pronounced on the rapheless valve (Fig. 2D). It should be noted that the slits on N. scissura specimens can be difficult to observe at low magnification on the external surface of valves with intact hymen coverings (e.g. Fig. 2D).

  • Author
    Siver, Hamilton and E.Morales 2007
  • Length Range
    9-15 µm
  • Width
    4.5-5.0 µm
  • Striae in 10µm
    48-58

Original Images

N Scissura Orig
Nusciss  Orig Descr

Cite This Page

Hamilton, P, and Potapova, M. (2011). Nupela scissura. In Diatoms of North America. Retrieved July 20, 2018, from https://diatoms.org/species/nupela_scissura

Responses

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