(Cleve) Atazadeh and Edlund in Atazadeh et al. 2014 Category: Symmetrical biraphid
BASIONYM: Stauroneis pachycephala P.T. Cleve 1881
SYNONYM(S): Schizonema pachycephalum (Cleve) Kuntze 1898
Valves are lanceolate to sub-lanceolate. The apices are capitate and broadly rounded. The central area is a distinct fascia that widens slightly near the valve margins. The axial area is distinctly thickened and narrows toward the apices. The raphe is straight. Proximal raphe ends are slightly expanded. Terminal raphe fissures are sigmoid; they are hooked to opposite sides and widen at the ends. The striae are radiate in the center of the valve and become convergent near the apices.
Striae are difficult to resolve with light microscopy because the areolae are entirely covered by external hymenes.
This taxon is unusual within the genus Envekadea for the presence of a fascia and fine striae. It is also unusual for its broad environmental tolerance (see AUTECOLOGY section).
Basionym: Stauroneis pachycephala
Author: P.T. Cleve 1881
Length Range: 45-60 µm
Width Range: 8-10 µm
Striae in 10 µm: 24.5-29.5
Linear, gibbous in the middle and at the ends, which are broadly rounded and capitate. Striae oblique, very fine, about 29 in 0,01 mm., reaching the median line. Stauros reaching the margin. Median line straight. Terminal nodules turned in opposite direction.
Length 0,055 mm. Breadth 0,009 mm. PI. Ill, fig. 43, 100%.
Fresh or slightly brackish water, Baakens River, Port Elizabeth, South Africa in sample sent by Mr. Joshua (Cl. et Moll. N:o 197). This species comes nearest to St. desiderata Cl. (in Cl. et Grun. Arctische Diat. PI. Ill, fig. 58), which also has the terminal nodules turned in opposite direction, but the outline of this species is different and its striae are almost parallel and much coarser. Both belong to section parallel with Grunows section Pseudopleurosigma of Navicula.
Cite This Page:
Lee, S., and Atazadeh, E. (2015). Envekadea pachycephala. In Diatoms of the United States. Retrieved March 25, 2017, from http://westerndiatoms.colorado.edu/taxa/species/envekadea_pachycephala
Species: Envekadea pachycephala
Reviewer: Sarah Spaulding
Atazadeh, I., Edlund, M.B., van de Vijver, B. Mills, K. Spaulding, S.A., Gell, P.A., Crawford, S., Barton, A.F., Lee, S.S., Smith, K.E.L., Newall, P. and Potapova, M. (2014). Morphology, ecology and biogeography of Stauroneis pachycephala P.T. Cleve (Bacillariophyta) and its transfer to the genus Envekadea. Diatom Research 29: 455-464. 10.1080/0269249X.2014.927006
Cleve, P.T. (1881). On some new and little known diatoms. Kongliga Svenska-Vetenskaps Akademiens Handlingar 18(5):1-28.
Gligorga, M., Kralj, K., Plenkovic-Moraj, A., Hinz, F., Acs, E., Grigorszky, I., Cocquyt, C. and Van de Vijver, B. (2009). Observations on the diatom Navicula hedinii Hustedt (Bacillariophyceae) and its transfer to a new genus Envekadea Van de Vijver et al. gen. nov. European Journal of Phycology 44(1): 123-138. 10.1080/09670260802389783
Smith, K.E.L. (2012). Paleoecological study of coastal marsh in the Chenier Plain, Louisiana: Investigating the diatom composition of hurricane-deposited sediments and a diatom-based quantitative reconstruction of sea-level characteristics. Ph.D. Dissertation, University of Florida, Gainesville, 203 pp.
Envekadea pachycephala was collected in Everglades National Park, Florida and the Arthur R. Marshall Loxahatchee National Wildlife Refuge (LNWR). It was found within benthic flocculent detritus, Utricularia purpurea (bladderwort), and recently burned Cladium jamaicense (sawgrass). The taxon is very rare in Florida (< 6% relative abundance), with the greatest abundances found in LNWR, a distinctive, soft-water environment of the Everglades. The waters of LNWR are low in conductivity (97-263 μS/cm), pH (5.2-7.6) and total phosphorus (405-595 μg/g dry weight) of periphyton (E. Gaiser, unpublished data). The lower conductivity in the LNWR results from a deep peat layer that impedes direct biogeochemical interactions between the limestone bedrock, groundwater, surface water, and biota.
In North America, E. pachycephala has been documented in coastal marshes of Louisiana (Smith 2012).
Envekadea pachycephala has also been found around the world in an unusual combination of locations: South Africa, Sweden, Sri Lanka, Australia, New Zealand, Cuba, and Papua New Guinea. In these sites, this taxon occurs across broad salinity and nutrient conditions. Additional work on the ecophysiology of this taxon is warranted to define its salinity and nutrient tolerances (Atazadeh et al. 2014).