Williams 1985 Category: Araphid
BASIONYM: Meridion lineare Williams 1985
REPORTED AS: Diatoma hiemale (Grimes and Rushforth 1982)
Contributor: Loren Bahls - April 2012
Length Range: 11-31 µm
Width Range: 4.8-8.0 µm
Striae in 10 µm: 11-19, mostly 16-18
Valves are isopolar, but irregular in valve outline. Larger specimens are linear-lanceolate, while specimens at the lower end of the size range are nearly oval. Apicies are broadly rounded. The central sternum is faint. Transapical costae are prominent, mostly horizontal, and number 4-6 in 10 µm. Transapical striae are irregularly spaced and distinct in LM. Internal valves are present in many specimens. The internal valves possess striae, but lack costae, and may be common in populations. Frustules typically attach to one another by the valve face and form long, ribbon-like colonies. Linking spines are present at the valve/mantle junction and are evident in girdle view.
The name Meridion lineare is considered to be invalid by the California Academy of Sciences names catalogue. The original description lacks a Latin component, or reference to one.
Basionym: Meridion lineare
Author: Williams 1985
Length Range: 20-65 µm
Width Range: 5-6 µm
Striae in 10 µm: "irregular"
Valves bilateral, isopolar with strongly rounded poles, mantle tapers from the centre of the valve down towards the poles. This shape is constant in the populations studied. Apical axis 20-65 µm, transapical axis 5-6 µm. The transapical ribs are very prominent, mainly primary and secondary ribs, irregularly placed, measuring 4 in 10 µm. Striae, virgae distinct, irregular, fairly wide relative to the vimines. Sternum, faint but distinct as a centrally dividing line. A single labiate process is present infrequently, appearing in approximately 10 valves per 50 counted. It has not been established from cleaned colonies whether the labiate process has any fixed functional position within the living colony.
Kociolek, J.P. and Lowe, R.L. (1993). Taxonomy and ultrastructure of Meridion lineare D.M. Williams (Bacillariophyceae) from North America. Nova Hedwigia 57: 381-391.
Williams, D.M. (1985). Morphology, taxonomy and inter-relationships of the ribbed araphid diatoms from the genera Diatoma and Meridion (Diatomaceae: Bacillariophyta). Bibliotheca Diatomologica 8: 1-228.
Meridion lineare has been collected from the benthos of several ponds and small lakes in the northern Rocky Mountains. Here pH ranges from 7.34 to 7.57 and specific conductance ranges from 16 to 55 µS/cm. This uncommon species appears to be restricted to standing water habitats in the middle latitudes of North America.
Belly River Beaver Pond, Glacier National Park, Montana: home of Meridion lineare.
Credit/Source: E. William Schweiger, National Park Service