This taxon is a member of the Cocconeis placentula species complex (also termed sensu lato). Note that for practical purposes, presents several varieties and species within the species complex. We recommend such treatment for assessment programs.

For those who wish to distinguish species in the strict sense (termed sensu stricto), the details are here.

The rapheless valves of C. placentula and C. placentula var. euglypta have a maximum of six longitudinal lines per hemivalve.

The valves of Cocconeis lineata and C. coreana are more elongate, elliptic, proportionally longer, and have more rounded apices.

The largest valves of C. czarneckii have a similar pattern in areolae to C. klamathensis and C. grovei. Cocconeis klamathensis, however, has large, strongly arched valves and C. grovei has larger valves, with lower stria density.

LM scalebar = 10 µm
Cocconeis czarneckii LM4 Cocconeis czarneckii LM1 Cocconeis czarneckii LM5 Cocconeis czarneckii LM6 Cocconeis czarneckii LM2 Cocconeis czarneckii LM3
Length Range
17.7-51 µm
Width Range
11.3-37.9 µm
Striae in 10 µm
Raphe valve 18-30, rapheless valve 20-26

Cocconeis placentula sensu lato

Ehrenb. 1838

Cocconeis placentula LM1 Gc109658  Mo000285  Ccplac2 Ed Gc109658  Mo000285  Ccplac3 Ed Gc100282  Gs016353  Cclplac1 Ed Gc109658  Mo000285  Ccplac1 Ed Gc108381  Nx000030  Ccpseudol1 Ed Gc100282  Gs016353  Cclplac2 Ed
Length Range
9-68 µm
Width Range
7-32 µm
Striae in 10 µm
20-24 on raphe valve, 15-25 on rapheless valve

Cocconeis klamathensis

Sovereign 1958

Cocconeis klamathensis LM3 Cocconeis klamathensis LM4 Cocconeis klamathensis LM5 Cocconeis klamathensis LM2 Cocconeis klamathensis LM6 Cocconeis klamathensis LM7 Cocconeis klamathensis LM1
Length Range
15-44 µm
Width Range
12-28 µm
Striae in 10 µm

Cocconeis grovei

A. Schmidt 1894

Cocconeis grovei LM4 Cocconeis grovei LM1 Cocconeis grovei LM5 Cocconeis grovei LM3 Cocconeis grovei LM2
Length Range
45-78 µm
Width Range
30-56 µm
Striae in 10 µm
14-17 raphe valves, 14-22 rapheless valves

Cocconeis coreana

R. Jahn and B.M. Suh 2020

Cocconeis coreana auxospore Cocconeis coreana LM3 Cocconeis coreana LM6 Cocconeis coreana LM2 Cocconeis coreana LM16 Cocconeis coreana LM15 Cocconeis coreana LM1
Length Range
21-58 µm
Width Range
11.5-36.6 µm
Striae in 10 µm
18-24 raphe valve, 18-24 rapheless valve

Cocconeis cascadensis

Stancheva 2018

Cocconeis Cascadensis Lm08 Cocconeis Cascadensis Lm04 Cocconeis Cascadensis Lm02 Cocconeis Cascadensis Lm07 Cocconeis Cascadensis Lm03 Cocconeis Cascadensis Lm06 Cocconeis Cascadensis Lm05
Length Range
15.7-40 µm
Width Range
8.7-22 µm
Striae in 10 µm
Raphe valve 15-18.5, rapheless valve 7–12

Also compare to

Cocconeis placentula var. euglypta

BioData Reference
Krammer and Lange-Bertalot 2/4 Pl 53 Fig 1-19