• Category
  • Length Range
    28-47 µm
  • Width Range
    8.9-9.8 µm
  • Striae in 10 µm
    20-23
  • Reported As
    Navicula cristula (Hohn 1961, p. 162, pl. 2, fig. 6)

Identification

Description

Valves are elliptic to linear-elliptic with subrostrate apices. The raphe branches have a groove on each side. The grooves are approximately 1 µm wide and covered externally by non-porous conopea. Both grooves and conopea are interrupted by a transversely rectangular or bow-tie-shaped central area bordered by irregularly, shortened striae. The raphe is straight with expanded external central raphe ends and terminal fissures deflected toward the secondary side. The striae are radiate, becoming convergent near apices.

Autecology

Sellaphora hohnii has only been reported, so far, from Silver Springs, Florida. The waters are circumneutral (pH 7.1-7.2), of average mineral content (conductivity 430-460 S/cm), low phosphorus concentrations (dissolved orthophosphate below detection limit) and moderate concentration of nitrogen.

Original Description

Sellaphora hohnii Potapova & Ponader, sp. nov. TYPE: USA. Florida: Silver Springs, 20 September 1955, J.L. Yount. (Holotype: ANSP GC 44484). Fig. 3A. Synonym: Navicula cristula Hohn excl. Typus, Trans. Am. Micr. Soc. 53(2): Fig. 2/6, 1961. Valvae ellipticae, apicibus subrostratis, 28--47 µm longae, 8.9--9.8 µm latae. Area axialis recta. Sulci utroque fissurae raphis latere, ca. 1 µm lati, conopeis non porosis. Sulci et conopea area centralis interruptis. Area centralis transverse rectangulata, versus marginem dilatata. Striae uniseriatae, radiatae, ad apices parallelae vel convergentes, 20-23 in 10 µm. Areolae parvae circulares, 53-55 in 10 µm. Raphe recta, extremis centralis dilatatis, fissurae terminales deflectis ad latus secundarium valvae. Valves are elliptical, with subrostrate apices, 28-47 µm long, 8.9-9.8 µm wide (Fig. 3). The axial area is straight, formed by grooves, one at each side of the raphe. Grooves are approximately 1 µm wide and are covered externally by non-porous conopeum (Fig. 3E, F, H). Grooves and conopea are interrupted by the central area, which is transversely rectangular or bow-tie-shaped, and bordered by striae of an irregular length. The striae are uniseriate, radiate throughout most of the valve, but parallel or convergent near the apices, 20-23 in 10 µm near the valve ends, the striae are interrupted and internally form "polar bars" (Fig. 3G), which are also visible on LM photographs (Figs 3A-D). The areolae are small, rounded, approximately 53-55 in 10 µm. As in other species of Sellaphora they are occluded internally by hymens (Fig. 3G). The raphe is straight, with expanded central endings, and terminal fissures curved to the secondary side of the valve (Fig. 3F). This species closely resembles S. californica Potapova (Potapova and Charles, 2004), but differs from it by having wider and less drawn-out apices. In quantitative terms, this shape difference is partly described by the ratio of the pole width to maximum valve width, which is ca. 1: 1.8 in S. hohnii, and ca. 1: 2.5 in S. californica. S. hohnii is also similar to S. tibia Antoniades & Hamilton (Antoniades et al., 2008) which has the same conopeum and raphe structure, but S. tibia has a more linear valve form and lower areolae density. Etymology: Hohn (1961) found this species in Silver Springs, Florida and identified it as Navicula geitleri Guermeur & Manguin. The name “N. geitleri Guermeur & Manguin” was, however, illegitimate because of the earlier N. geitleri Hustedt. Hohn, therefore, established N. cristula as a replacement name for N. geitleri Guermeur & Manguin. Examination of the drawing of “N. geitleri” in Guermeur and Mangiun (1953) shows that this diatom, described from Europe, is different morphologically from the Sellaphora found in Silver Springs. Since the type of N. cristula is a diatom described by Guermeur & Manguin, and this species is different from the Sellaphora from Silver Springs, we describe the latter as a new species and name it in honor of Dr. Matthew H. Hohn.

  • Author
    Potapova and Ponader 2008
  • Length Range
    28-47 µm
  • Width
    8.9-9.8 µm
  • Striae in 10µm
    20-23

Original Images

Orig Ill 1

Cite This Page

Potapova, M. (2013). Sellaphora hohnii. In Diatoms of North America. Retrieved August 18, 2018, from https://diatoms.org/species/sellaphora_hohnii

Responses

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