Navicula

Navicula is a large genus, containing over 260 known species. Many of these species are very similar looking and can be difficult to accurately identify; however, they all function and look in a similar manner. Navicula tend to be shaped like diamonds, elongated ovals, or wine bottle necks. Their areolae, when visible, are dash-like, not rounded. They tend to live in the sediments at the bottoms of lakes and rivers.

N. caroliniae

Cells are 23-41 µm in length, 8-10 µm in width.
Rows of striae are 11-14 per 10 µm.
Ends are shaped like wine bottle heads.
Striae are evenly spaced and radiate at the center, becoming parallel to convergent at the ends.
Central area is large, round, and asymmetrically larger on the side that the raphe central ends point toward.

For more information, visit diatoms.org here.

The "dashed" linear areolae seen here are characteristic of Navicula species.

A3m1 Navicula caroliniae_edited

N. reinhartii

Cells are 34-48 µm in length, 14.5-17 µm in width.
Rows of striae are 8-9 per 10 µm.
Valves are distinctly oval shaped, with wide rounded ends.
Striae are very broad. They begin very radiate and become almost parallel by the ends.

For more information, visit diatoms.org here.

A8m1 Navicula reinhardtii_edited

N. tripunctata

Cells are 32-60 µm in length, 14.5-17 µm in width.
Rows of striae are 9-12 per 10 µm.
Valves are thin and elongated.
Striae are close to parallel throughout the valve. They are weakly radiate near the center and weakly convergent near the ends.

For more information, visit diatoms.org here.

A5m1 Navicula tripunctata2_edited

A3m3 Navicula tripunctata_edited

A8m1 Navicula tripunctata sp1_edited

A5m1 Navicula tripunctata_edited

Unidentified Navicula species present in Lake Mendota

There are a number of Navicula in Lake Mendota which are difficult to define as a specific species, either because of photo resolution, valve damage, or too many close potential species. However, some of these do seem to fall into certain groups of size and shape and so should be noted here.
The pictures below have been organized by size and grouped by similar shape when possible.