A. Schmidt 1877 Category: Surirelloid
BASIONYM: Surirella cruciata A. Schmidt 1877
Contributor: Jana Veselá - November 2012
Length Range: 48-160 µm
Width Range: 24–61 µm
Striae in 10 µm: 19–29 in the center valve, 22–30 at the ends
Valves are obovoid with cuneate footpoles and broadly rounded headpoles. Valves are distinctly heteropolar in larger specimens, becoming less heteropolar in smaller specimens, with the valve length to width ratio ranging from 1.6 to 3.2. The valve face is distinctly and abruptly raised in the central third of the valve, depressed and shallowly concave in the apical thirds of the valve. The wings are well developed and raised prominently from the valve face. Raphe is situated in a raised raphe canal. The alar canals are narrower than the fenestrae, usually even in density throughout, but becoming occasionally variable in density in a single valve, 11–26 in 100 μm. The fenestrae are greater in hight than width in the central part of the wing, having 5–9 fenestral bars (8-9 in the middle part, 5 near apices), occluded or partially open between bars. The axial area is narrow, elevated in a shallow keel that is raised above the level of the porcae, without ornamentation or pores. The porcae are pronounced in the central part of valve, shallow and shortened in the outer thirds of the valve. The arrangement of porcae is opposite to alternate in the same valve. The porcae are unornamented, with a depression between porcae bearing minute granules, which are more or less visible in LM. The striae are bi- to triseriate, often becoming uniseriate towards the axial area and radiate at the apices. The areolae, 53–64 in 10 μm, are occluded externally, circular and opened with a small rim internally. Numerous silica plaques are present on the valve mantle near the edge with the valvocopula. The girdle bands are unornamented, thin and open. Chloroplasts were not observed.
Basionym: Surirella cruciata
Author: A. Schmidt 1877
Length Range: (Measured by us from the original drawings): 75.5-80.3 µm
Width Range: (Measured by us from the original drawings): 38.3-39.8 µm
Striae in 10 µm:
No written description is given in the publication.
Boyer, C.S. (1895). Diatomaceous deposit from an artesian well at Wildwood, N. J. Bulletin of the Torrey Botanical Club 22: 260–266.
Boyer, C.S. (1916). The Diatomaceae of Philadelphia and vicinity. Reprinted 1973 by Henry Tripp, Inc., Lafargeville, New York. 143 pp, 40 pl.
Boyer, C.S. (1927). Synopsis of North American Diatomaceae, Part II. – Naviculatae, Surirellatae. Proceedings of The Academy of Natural Sciences of Philadelphia 79: 229– 583.
Schmidt, A. (-). (1874-1959). Atlas der Diatomaceen-Kunde, von Adolf Schmidt, continued by Martin Schmidt, Friedrich Fricke, Heinrich Heiden, Otto Muller, Friedrich Hustedt. Reprint 1984, Koeltz Scientific Books, Konigstein, 480 plates.
Veselá, J., Johansen, J.R. and Potapova, M. (2013). Surirella terryi and S. cruciata: two rare diatoms in North America. Diatom Research . 10.1080/0269249X.2013.853697
Wolle, F. (1890). Diatomaceae of North America. The Commenius Press, Bethlehem, Pennsylvania. 47 pp., 112 pl.
S. cruciata was observed in 11 freshwater localities in northeastern North America (including 6 sites in Maine; Sycamore Lake, NJ; Hamlin’s Pond, CT; Grays Ferry, PA; Little Simon Pond, NY; and a pond in Nova Scotia, Canada), and in Lake Ozette in Washington State on the west coast of the USA. In addition to the clearly freshwater habitats, S. cruciata was also found in 3 freshwater habitats with clear marine intrusions, as evidenced by the presence of both strictly freshwater and strictly marine taxa. These sites of unclear or variable salinity included Pensacola in Florida, Delaware River in New Jersey and Nanticoke River in Delaware. The specimens from the localities with marine–brackish influence tended to be smaller [48–82(92) μm long, 24–42 μm wide] and had slightly finer striation (26–29 in 10 μm) compared with the populations from strictly freshwater habitats (62–160 μm long, 27–61 μm wide, 19–29 striae in 10 μm). The populations from Nova Scotia, Canada, and New York State, USA, also appeared distinctive, having a larger length to breadth ratio than the other freshwater populations. The New York populations were also evidently more granular on their valve surfaces.