Observaciones de diatommy

Scale bar = 10µm

Valves are cylindrical and appear in mantle view. Striae curve to the right on most valves, but separation valves there will have striae which are straight and parallel to the pervalvar axis. Areolae are large, bold, and rectangular to wide elliptic in shape. Linking spines are short and triangular. One to two long separation spines occur on some valves, and are nearly as long as the mantle height. These valves also exhibit reciprocal separation spine grooves where striae is missing.

Scale bar = 10µm

Valves are circular and valve faces are flat. Fasicles are uniseriate at the valve center and become biseriate or triseriate towards the valve margin. A short marginal spine is present between each fasicle. At the valve center, areolae may become disorganized.

NOTE:

S. hantzschii fo. tenuis is an ecomorph of S. hantzschii and both forms are often cohabitant. To illustrate the differences between them, the two bottom right specimens in the image are included as examples of S. hantzschii fo. tenuis. Note the light silicification, less visible areolae, and more meandering fascicles. Note also that although the circle at the valve center is common of this form, it is not unique to it; the top rightmost specimen also exhibits this pattern.

Scale bar = 10µm

Valves are distinctly cruciform. Striae are slightly radiate, thick, and spaced out (5 per 10µm). Areolae are indistinct. Valve shape or striae pattern are sometimes irregular (see leftmost image).

Not pictured in these images, valves have short linking spines at the valve margin on the costae between each row of striae. Frustules form colonial chains.

Scale bar = 10µm

Valves are large (93-118 µm) and sigmoid with rounded ends. Central area is elliptical and connects parallel with raphe at each end. Striae run in a grid pattern along the apical and transapical axes, and are equally distinct in both directions. Striae are slightly radiate near the central area, and are otherwise strictly parallel and gridlike. Striae density is nearly identical in both axes (18-19 per 10µm longitudinally, 20 per 10µm transverse).

Scale bar = 10µm

In girdle view frustules are bent (image on right), so that in valve view one valve is concave and one is convex. On the convex valve, raphe extend to the valve center, and central area is small and oval to elliptic (not pictured). On concave valve, raphe are significantly shortened and end close to the apices; central area is absent (center image). Striae are 12-14 per 10µm. Internally, a pseudoseptum is present at both apices (image on left). Apical pore field is present at footpole, and cells grow on mucilage stalks.

Scale bar = 10µm

Valves are wide elliptic to sub-circular and display significant curvature along the apical axis (concave on raphe valve, convex on rapheless valve), making it difficult to view an entire valve face in focus at once. Frustules are monoraphid, with significant dimorphism between raphe and rapheless valves.

Raphe valve has straight raphe with enlarged and undeflected proximal ends. Small central area is circular to rhombic. Striae are fine but distinctly punctate and uniseriate. Striae are parallel at the central area and become radiate and strongly arched towards the valve margin. Rapheless valve has coarse, elongated, and irregular striae. Striae remain uniseriate.

Although size ranges and autecology overlap with C. placentula, the two species may be distinguished by the hyaline ring of C. placentula or by the wider, more warped valve face of C. pediculus.

Note: On the plate the two left-most images are of the same frustule, focused through to show both the raphe and rapheless valve.

Scale bar = 10µm.

Valves have highly variable morphology based on size. In larger specimens valves are elliptic with cuneately rounded apices, and the footpole has a noticeably more narrow point. In mid-size valves the outline becomes ovate. The smallest valves may become elleptic and nearly as wide as they are long. Under light microscope, the only way to distinguish between S. ovalis and S. brebissonii is to look at larger valves: S. ovalis has two cuneate apices, while S. brebissonii has a cuneate footpole and a broadly rounded headpole. Smaller valves are impossible to differentiate without SEM.

Striae are not resolvable under light microscopy, but costae at the sternum are 17-21 per 10µm, and marginal fibulae are 4-5 per 10µm.

In this population, small valves (>35µm) were very abundant but only one specimen was found to be large enough to positively identify as S. ovalis. It is assumed to be representative of the population. The population's constricted dimunitive size range may be indicative of recent failure to sexually reproduce.

Valve outline is ovate to narrow ovate, with rounded footpole. Apical porefield is visible on footpole. Proximal raphe slightly deflect unilaterally. Striae are arched and radiate near the central area, becoming slightly radiate at the footpole and nearly parallel at the headpole. Areolae are difficult to resolve, except for a distinct enlarged centermost areolae on the large striae closest to the central area. Unlike the four central stigma on Gomphonema olivaceoides var. densestriata, these distinct areolae do not appear separate from the striae.

Scale bar = 10µm

Gomphonema intractum var. vibrio is a species with a complex of morphotypes: three main morphotypes are described, and additional rare morphotypes are noted (Tobias and Gaiser 2006) . On the plate presented here, specimens 1 and 3 (from the left) align most closely with morph. 1, and specimens 2 and 4 align most closely with morph. 2.

Valves are narrow lanceolate with acutely rounded apices. Headpole tapers linearly, while footpole tapers more quickly. Raphe is lateral and slightly undulate. Slight asymmetry across the apical axis is present in most frustules, where one margin is more dorsally arched and the other gibbous; this asymmetry is more distinct in morph. 2. Striae are distinctly punctate and uniseriate. Striae are slightly radiate to nearly parallel. Striae are 10-12 per 10µm near the center and 13-16 at the poles; there does not seem to be a difference in striae density between the headpole and footpole. A single punctate stigmata is located at one side of the central area, and is associated with a single shortened striae on the opposite side in some specimens.

Note that the description of populations from the Everglades (Tobias and Gaiser 2006) notes some morphological differences from the population originally described by Husted (1985), but cites the highly variable morphology of frustules as substantial reason for remaining in the species.

Scale bar = 10µm

Valves narrow elliptic with subrostrate to rostrate apices. Raphe are slightly undulate. Striae are coarsely punctate. Striae are nearly parallel at the central area, become radiate towards the apices, and then become parallel again right at the apices. Areolae are 18-20 per 10µm. Central area is small.

Internally, partecta are 5-6 per 10µm.

Plate is arranged to display layers of valve and partecta through optical dissection: individual specimens are aligned in columns, with comparisons to other individuals along rows. Center-right specimen is in girdle view.

Scale bar = 10µm

Asymmetry is subtle. Valves are elliptic with subcapitate to capitate apices. Central area is absent. Proximal raphe arch slightly in the same direction. Striae are parallel near the center and becomes slightly radiate near the apicies.

NOTE:
Length range for E. subminuta on DONA is significantly narrower (10-15µm) than recorded in Krammer's original description (10-25µm) and in the Florida Coastal Everglades Diatom Database (10-25µm, with note that some specimens exceed this range). These specimens, collected from the Everglades, meet these latter criteria (19.2-20.0µm).

Scale bar = 10µm

Species is formerly known as Cymatopleura solea.

Valve outline is panduriform with bluntly pointed apices. Marginal fibulae line the valve (7-8 per 10µm). Large undulations across the valve face (see rightmost image) make striae counts very difficult under the light microscope. Striae are very fine and indistinct.

Scale bar = 10µm

Valve face is flat or transversely undulate. Central area is blank, but may have very faint radiate patterns. Central area contains 1-4 distinct fultoportulae. Costae around the valve margin are 7-8 per 10 µm. Small marginal spines may be present (see girdle view image on right of plate).

C. meneghiniana is commonly planktonic in waters across the US.

Scale bar = 10µm

Valve face is flat. Striae are fine and uniseriate, ending irregularly 1/3 to 2/3 of the way into the valve. The central area has 2-6 larger dots in a concentric pattern, known as orbiculi depressii and papillae.

Note: largest specimen is of a degraded valve with a worn-down striae area. Specimen is included to display variability of striae area width even in larger valves.

G. truncatum has a strongly undulate valve margin and a large, broadly rounded headpole. There is another widening at the valve center, and the footpole is thin and also rounded at its apex.

Raphe are also distinctly undulate. Striae are uniseriate with visible areolae. Striae are parallel from the headpole to the center, radiate at the center, and then radiate in undulating degrees along the footpole. The central area is small and sometimes interrupted by a striae in its middle.

A single stigma is present on one side of the central area.

P. gastrum has a wide elliptic valve, with broad rounded to slightly rostrate apices which set it apart from other members of its genus. Raphe are straight throughout the valve length, and curved in the same direction at the distal ends. Striae are radiate and widely spaced apart. The central area is small and indistinct.

Frustules are clavate in valve view, and are wedge shaped in girdle view (right-most specimen on plate). Headpoles can have rostrate to capitate ends (this is what distinguishes this variety), and footpoles can be rounded to capitate. Headpoles often have an expanded "shoulder" just below them. Frustules grow in fan-shaped colonies.

Striae are grouped into bundles between thick transapical costae which are irregularly placed along the valve. A thin sternum is present along the apical axis, although it may be offset from the valve center.

Meridion tends to grow in cold, clean waters like springs and streams. These specimens were collected from a vernal pond in a protected prairie.

U. ulna var. subaequalis is a very long (272-280 µm) linear diatom with rounded ends. Valve ends show slight pinching just before the tip. Valve margins are parallel, and striae are parallel, and the final 3-4 striae at the apicies become strongly radiate. The central area is usually absent, and is small when present (see top specimen). There is a rimoportula present at each valve tip.

U. ulna var. subaequalis varies from U. ulna var. danica by its wider and rounder apicies, its often-missing central area, and its linear valve shape rather than linear-lanceolate.

S. niagarae is a large centric diatom with large marginal spines. Its valve face is dramatically concentrically undulate, to the point where it is often impossible to focus on both the valve center and margin at the same time.

At the valve center, areolae may be concentrically arranged or random. Fascicles are made of single rows of areolae near the valve center, and typically move to two rows of staggered areolae towards the valve margin. Marginal spines are spaced every 2-3 fascicles.

S. niagarae may be distinguished from S. reimeri most easily bu the density of its areolae: S. niagarae has areolae which are more spread out and circular, while S. reimeri has crowded areolae that butt up against each other and make the areolae more square or hexagonal to fit.

S. niagarae is a common planktonic species in WI lakes.

N. reinhardtii is an easily distinguishable species within Navicula, set aspart by its thick curved striae which have distinct lineolate areolae. Striae are strongly radiate at the center and become slightly radiate at the apicies. The valve outline is elliptical, with wide rounded ends.

Valves are elliptical, sometimes becoming almost circular in smaller specimens. Striae are strongly radiate, with distinct spaced out areolae that are punctate to slightly linear. Some striae near the central area do not reach the valve center.

Dorsal and ventral margins are both arched; dorsal to a greater degree. Ends are rounded or rostrate. Distal raphe ends do not reach the valve margin, and striae extend all the way around these ends.
Striae are radiate near the valve center and become convergent towards the apicies. Proximal raphe ends deflect to dorsal margin. Areolae are pronounced and lineolate.

Encyonaema do not have apical pore fields, but rather create mucilage tube colonies.

C. placentula is a small epiphytic diatom which often grows on strands of Cladophora. Its raphe and rapheless valves both have small radiate striae, but the areolae on the rapheless valve tend to be coarser and more lineolate.

P. placentula can sometimes be confused with P. pediculus. P. placentula valves tend to be more elongated and flatter, while P. pediculus sends to be fatter and more concave/convex across the apical axis.

In plate, the left and center specimens are of the raphe valve; the specimen on the right is a rapheless valve.

N. dubium is somewhat unique among the Neidium species because its proximal raphe ends do not deflect toward either valve margin. N. dubium also displays valve ends that are more pig snout-shaped, with broader "shoulders" than other Neidium species.

Scale bar = 10µm

F. capucina has a filiform valve and an outline that subtly narrows linearly towards the apicies. Striae are parallel, and faint or appearing absent in the central area.

F. capucina may be differentiated from F. mesolepta by its lack of a pinched central area and rounded apices.

Scale bar = 10µm

Fragilaria mesolepta is set apart from other species in its genus by its unique silhouette: a thin valve with rostrate ends and a pinched central area with ghost or absent striae. Striae on the rest of the valve are parallel, gradually shifting to slightly radiant at the apices, and faint.

F. mesolepta may be distinguished from F. capucina by its pinched central area and more noticeably rostrate ends.