Bory de Saint-Vincent 1824 Category: Araphid
TYPE SPECIES: Diatoma vulgaris Bory de Saint-Vincent
Smallest to largest - 5 taxa sorted by maximum length
The genus Diatoma possesses characteristic thickened transverse costae, septae are absent. Each valve has a single rimoportula, positioned near a valve terminus and oriented transapically. Furthermore, a raised central sternum is present. Under SEM, Diatoma has a ligula on the second girdle band that attaches to the polar position of the valve, adjacent to the interlocking valvocopula. The phylogenetic relationships within the genus have been investigated (Williams 1985) and two subgenera are currently recognized.
Subgenus Diatoma: The striae of the subgenus are comprised of uniseriate rows. Internal transapical ribs are prominent, raised, and extend from the sternum to both mantles. The tip of the valve mantle is connected by an overlapping internal rim. Spines are scattered near the polar pore fields, but are absent elsewhere. Living cells contain numerous discoid or platelike plastids. Examples of species within the subgenus include, Diatoma vulgare Bory and Diatoma tenue Ag.
Subgenus Odontidium: The sternum of the subgenus is wide and diffuse. Spines are present, but are considered non-functional. The cingulum, or girdle bands, are differentiated into three components. The copulae possess porose ligulae. Living cells contain multiple elliptical lobed plastids. Examples: Diatoma mesodon (Ehrenb.) Kütz. and Diatoma hiemale (Roth) Heib.
Cite This Page:
Spaulding, S., and Edlund, M. (2008). Diatoma. In Diatoms of the United States. Retrieved August 24, 2016, from http://westerndiatoms.colorado.edu/taxa/genus/Diatoma