• Category
  • Length Range
    57-74 µm
  • Width Range
    8.8-10.2 µm
  • Striae in 10 µm
    9-10

Identification

Description

Valves are linear-lanceolate, with rostrate apices. The axial area is broad and rhombic, which gradually widens to the central area. A narrow transverse fascia is present and may, in some specimens, contains a few short striae. The fascia may be absent in smaller specimens. The raphe is lateral, with question mark-shaped terminal fissures. Striae are radiate in the center, becoming convergent toward the apices.

Autecology

This taxon was described during the course of a survey of Carolina bays (Gaiser and Johansen 2000). They report that this taxon was found 13 Carolina bays. It reached its greatest abundance growing in sites with leaf litter, floating algal mats, and Lemna spp. at an optimum pH of 5.2 and water depth of 11 cm.

Original Description

Pinnularia subgibba var. lanceolata Gaiser & Johansen var. nov. (Figs 90, 91)

Valva linearilanceolata ad extrema rostrata decrescens, ratione longitudinis latitudine variabili, centro extremo 2-3plo latiore, 9-12 µm lata, 60-85 µm longa. Area axialis lata, circa 1/3 lata quam valva, ad extrema decrescens. Area centralis fascia transersa formans, interdum a striis paucis obliterata. Raphe filiformis fissuris terminalibus unciformibus. Striae ad centrum breves radiatae, ad extrema longae convergentes, 8-11 in 10 µm.

Valve linear-lanceolate, tapering to rostrate apices with variable length-to-breadth ratio, center of valve 2-3 times broader than the ends, 9-12 µm wide (mean = 10.8 µm), 60-85 µm long (mean = 74.7 µm). Axial area broad, about 1/3 breadth of valve, tapering at valve ends. Central area a transverse fascia, sometimes containing a few short striae. Raphe filamentous with rounded question-mark shaped terminal fissures. Striae short and radiate at valve center, longer and convergent towards valve ends, 8-11 in 10 µm.

Holotype: Dry Bay (Bay 31), 2-7-94, Epiphytic on Panicum stems (Gaiser Coll. No. EG940205, ANSP A-GC 57547a).

Isotype: Dry Bay (Bay 31), 2-7-94, Epiphytic on Panicum stems (Gaiser Coll. No. EG940205, ANSP A-GC 57547b).

Paratype: Dry Bay (Bay 31), 2-7-94, Epiphytic on Nuphar (Gaiser Coll. No. EG940209, CAS 219089).

Type locality: Epiphytic on stems of Panicum hemitomon in Dry Bay (Bay 31), a shallow Carolina bay on the Savannah River Site in Aiken County, South Carolina, U.S.A., 33°15' 0.36" N, 81°44' 46.1" W.

This taxon is related to the P. gibba Ehrenberg, P. subgibba and P. gibbiformis species complexes (including P. abaujensis). It conforms to any of these taxa with respect to valve length and breadth and density and character of the striae. However, the consistently rostrate ends set it apart from P. gibba, which has protracted, nearly capitate apices. It has a lower length to breadth ratio (approximately 6:1) than P. gibbiformis (10-12:1) and has a wider central area (6-8 µm) that usually contains a central fascia. We designate a new variety in the P. subgibba complex based on these characters.

Population characteristics: Taxon exhibits substantial variation in width of axial and central area. It often co-occurs with P. gibbiformis and P. subgibba var. gracilis.

Autecology and distribution: This taxon was found infrequently in 13 bays. It was uncommon to rare in Nelumbo lutea, Nuphar luteum, Panicum spp., Utricularia spp., leaf litter, sediment, woody debris, tree root, and phytoplankton samples. It was common in 3 bays in leaf litter, floating algal mat and Lemna spp. samples. Optimum pH (awm) = 5.2; water depth (awm) = 11 cm.

  • Author
    Gaiser and Johansen 2000
  • Length Range
    60-85 µm
  • Width
    9-12 µm
  • Striae in 10µm
    8-11

Original Images

Pinn subgibba var lannceolata org img
Pinn subgibba var lannceolata org descrp

Cite This Page

Aycock, L. (2022). Pinnularia subgibba var. lanceolata. In Diatoms of North America. Retrieved May 30, 2024, from https://diatoms.org/species/pinnularia-subgibba-var-lanceolata

Responses

The 15 response plots show an environmental variable (x axis) against the relative abundance (y axis) of Pinnularia subgibba var. lanceolata 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.