Navicula and Nitzschia questions... another reference #glossary


urginia
 

hi Rob,

i have just discovered another reference with a formal definition of a Voigt fault:

"An amended terminology for the siliceous component of the diatom cell" 1979

http://rbg-web2.rbge.org.uk/algae/publications/Ross_etal_1979_minimal.pdf

this may also be of interest to those interested in a glossary for diatom bits and pieces,

tchau
Brian

--- In diatom_forum@..., "Rob Kimmich" <kimmich46@...> wrote:

Dick,

Here's another try, all in oil, as it were, with the 100x objective. In Rob K Questions I have Navicula sp1 (2 images; interesting notches at each end), Nitzschia sp1 (three depths), and Nitzschia sp2. I will certainly understand if it's not possible to name them based on these images.

Also, what's the Voight discordance in Navicula? Spaulding and CAS don't cover it in their glossaries.

Thanks,
Rob


------------------------------------------------------------------------------
From: Richard Carter <rcarter68502@...>
To: "diatom_forum@..." <diatom_forum@...>
Sent: Saturday, May 21, 2011 7:44 AM
Subject: Re: [diatom_forum] Pinnularia Questions



Rob,


The photos are excellent, and I'm sure that all but the Navicula could be identified. The Navicula image is too small and not well enough resolved; any chance you could use an immersion lens on it? In particular, we would need to see the central nodule: are the central raphe ends straight or deflected, and if the latter, are they deflected toward the primary side or the secondary side? (The secondary side has the Voight discordances.) This is the main character for distinguishing between the two great sections of Navicula species.



I will probably not be able to help you with the Encyonema specimen, as I have no access to Krammer's revisionary works on this group of cymbelloids. It is a very speciose group! Perhaps someone else has access? If not, I may try interlibrary loan; I have a lot of unidentified members of this genus in my own collection. A small number are easily identified due to a unique gestalt, but most (including yours) are not.


I'll work on the Pinnularia later today.



The larger Nitzschia specimen is Nitzschia linearis (Agardh) W. Smith, a cosmopolitan freshwater diatom with very broad ecological tolerances. It is abundant all over North America. It is fairly easy to recognize: straight, with scalpelliform ends, and an obvious break in the raphe canal at the center. It can be confused with N. sigmoidea, but that species is typically much larger, and the raphe canal a bit removed from the margin. And sigmoid, of course -- but often very weakly so in valve view. N. linearis can be tricky in some ways, though, particularly in the apparent form of the valve ends. The appearance varies a great deal depending on very small differences in valve orientation. The scalpelliform shape seems to disappear if the valve is even slightly tipped, when it will often seem to be pointed. And there are closely similar species with a continuous raphe canal, too. That trait is pretty obvious in these species, though, and usually causes no problem.


Hope these remarks are useful,


Dick



------------------------------------------------------------------------------
From: Rob Kimmich <kimmich46@...>
To: diatom_forum@...
Sent: Friday, May 20, 2011 10:00 PM
Subject: Re: [diatom_forum] Pinnularia Questions




Dick,

A big thanks for this wealth of info. I've started looking at the U of O catalog. The U is an hour from here but with digital photos as you say it might be worth some day trips. I might try camping with friends in San Francisco and going to the CAS library, too.

Two resources with photos I've had recommended from the Deep Sea Drilling papers for Cenozoics are Vol 18, Chapt 17 and Vol 24, Chapt 22. They are each over 10 MB so I thought I should not upload them.

I see now that my innocent Pinnularia request opened a world all its own. I might have guessed. After recovering from feeling overwhelmed and humbled by diatoms yet again, I've included a more modest set of five photos with measurements (in RobK Questions), if you would like to try names for them -- I think I have an Encyonema, a Navicula, a Nitzschia, and only one form of Pinnularia! These come from a neighbor's "water feature" of slabs of faux stone that grow Oscillatoria quite nicely, providing safe harbor for a lot of diatoms and other creatures.

As part of my confused wanderings over the last few days, I ran into two interesting papers by Kociolek about polymorphism and about the state of diatom science. I put these in the folder, Quandries, along with some downloaded text on diatom speciation from the Botanic Garden in Edinburgh. From this last, I see where Leszek may have gotten his figure of only 10% of species known!

I'm a couple of years behind you on the senility curve but with diatoms to distract me maybe I won't notice when it arrives.

Rob


scitech200
 

.../Ross_etal_1979_minimal.pdf
Great find!
Thanks very much Brian.

-Keith


"urginia" wrote:
hi Rob,
i have just discovered another reference with a formal definition of a Voigt fault:

"An amended terminology for the siliceous component of the diatom cell" 1979

http://rbg-web2.rbge.org.uk/algae/publications/Ross_etal_1979_minimal.pdf

this may also be of interest to those interested in a glossary for diatom bits and pieces,

tchau
Brian