Two Photos (Long!)


Richard Carter
 

Charles,

Wow, a great response!  This is the sort of thing I had hoped for when the group was started.  Your points are very well taken, and very well stated.  I'll see if I can clarify what I meant to convey -- for further of my thoughts on this "species", you might check out

http://members.cox.net/rcarter26/A.%20curvatulus.html

if you haven't seen it already.

Diatomists have fretted over the distinction between Actinocyclus and Coscinodiscus for a long time.  Workers in the 19th century were already aware that there were "pairs" of species in the two genera, differing primarily in the presence/absence of the pseudonodulus.  A. curvatulus and C. curvatulus were one such pair.  (Another that comes to mind without going to the books is A. ingens and C. elegans.)  Several diatomists suggested collapsing such pairs into single species, in effect arguing that the pseudonodulus was a more trivial trait than some others. 

In 1975 Rainer Simonsen wrote a neat paper addressing the significance of the pseudonodulus:

Simonsen, Rainer, 1975, "On the pseudonodulus of the centric diatoms, or Hemidiscaceae reconsidered," Beihefte zur Nova Hedwigia, Issue 53, pp. 83-98.

I think most researchers came to the conclusion that the pseudonodulus was not too significant above the species level, and that Actinocyclus was best distinguished from Coscinodiscus by its possession of both a central annulus and fasciate striae.

The irregular form of the annulus in the two images I posted is best shown, I think, by comparing the two images with the size set to "original".  In the PC image, there appear to be five tiny hyaline spaces around the central clump of eight areolae.  Such spaces are produced by small voids around the edge of the annulus; there are always one or more such in this species.  In the COL image, we can see that there is a small "satellite" of the annulus, at the "northeast" edge, containing a single isolated areole.  These structures are also common in this species, but not always present.  This is what I meant by the annulus being "irregular", and I assume that's what other describers have meant, as well.  In this species, the annulus never looks exactly the same in any two specimens.

>>Are the process's at the ends pseudonodule's?<<  No, the pseudonodulus is always a solitary structure.  They are not all the same in ultrastructure, though, as Simonsen (inter alia) has shown.  They differ a great deal in size, also, to the point that the pseudonodulus can be too small to distinguish from an ordinary areole in the light microscope.  The PN is often located right on the bend between the valve face and mantle, too, which makes it even harder to see.  The processes at the end of the long rows at the fascicle edges are rimoportulae -- which also vary a lot in size and ultrastructure among different species.  I'm uploading another photo, this one of A. roperi (Brébisson) Grunow in Van Heurck, from a slide made by Leszek.  This species has megahumongous rimoportulae.

>>"Generally, subsequent workers, such as Hustedt (1930) have called forms possessing a pseudonodule A. curvatulus, and those without, C. curvatulus."<<  Until relatively recently, this was generally true.  And such resistance lasted even longer among paleontologists than among diatom taxonomists.  In 1986, George Andrews (my hero, don't get me wrong) bemoaned the fact that Coscinodiscus rothii could not be moved to Actinocyclus because there was no pseudonodulus.  And many of these species have still not been formally moved -- I suspect because a lot of taxonomists look down on publications that do nothing but formalize taxonomic changes.  (I've heard such papers called "resumé padding", for example.)

In the present instance, I think two quite different questions have become confused:

1.  Does C. curvatulus Grunow in Schmidt belong in the genus Actinocyclus?
2.  Are A. curvatulus Janisch in Schmidt and C. curvatulus Grunow in Schmidt the same taxon?

I answer these two questions "YES" and "NO", respectively.  I think there is a complex of species here.

What do you think?

Dick Carter



--- On Sun, 4/3/11, charles wrote:

From: charles
Subject: [diatom_forum] Re: Two Photos
To: diatom_forum@...
Date: Sunday, April 3, 2011, 1:17 AM

 

Hello Dick,
Interesting presentation and useful, personally I have a lot of difficulty with centric diatoms.

Going to Schmidt's Atlas Table 57, there is not a lot of difference between fig. 31 A. curvatulus and fig. 36. The biggest difference is size. Fig. 36 being C. curvatulus.

Your depiction, very clear in second image, of the annular ring is a little confusing to me.
From Hustedt we have ". . . Central area small, set with a very few scattered areolae, enclosed by an irregular circular ring."
I would have trouble calling your imaged ring in the second picture as irregular? Am I making to much of the dark circle?

From Hasle and Syvertsen we have their description of A. curvatulus as "Areola rows slightly curved. A process at the end of each side row of the fascicles. Central annulus irregular in shape. Areolae decreasing in size close to the margin. Small irregular pseudonodulus located close to valve mantle.

Again I see the word irregular.

The central area in the first image I would probably accept as irregular in appearance. I am not disagreeing with you, I am only trying to apply printed definition to presented image. The fascicles, areolae, oriented radially, are clearly presented in the first image and the process at the end of each side row are visible in the first picture, I think. Are the process's at the ends pseudonodule's? From Wiki "Generally, subsequent workers, such as Hustedt (1930) have called forms possessing a pseudonodule A. curvatulus, and those without, C. curvatulus."

You see, I trouble me. So often I have fooled myself with an image, that is, I think I am imaging something important and it really was not. What makes a pleasing picture is not the same as what makes a scientifically accurate presentation. The question I am often asking myself is where to focus and what am I observing at this focus ?
Charles


Rob Kimmich <kimmich46@...>
 

This is a great discussion, leading us into the morass of diatom taxonomy. I really like the contrast Dick got of the two Actinocyclus, the one showing the sectors. I have one I labelled Coscinodiscus curvatulus using Cupp (1943) at http://micro.chemeketans.org/full_scale.asp?image_name=medium/2011_02_27_1099.JPG. Would A. curvatulus be more accurate? How dated (besides dated!) is Cupp?
 
Dick, can you take a moment apart from this discussion and describe the setup you used for these two photos? I'm also interested in your photo "work flow" including the technique you use for labelling, as you must have thousands of diatom images by now.
 
(I am using a stock, you could say, Labophot-2 with E-Plans, a 1.25 Abbe condenser, with an attached Canon digital SLR. I use the Canon software to catalog and enhance the photos. I am trying to keep the imaging side simple and have not invested in PhotoShop or the like.)
 
Rob K
 

----- Original Message -----
Sent: Sunday, April 03, 2011 9:46 AM
Subject: Re: [diatom_forum] Re: Two Photos (Long!)

 

Charles,

Wow, a great response!  This is the sort of thing I had hoped for when the group was started.  Your points are very well taken, and very well stated.  I'll see if I can clarify what I meant to convey -- for further of my thoughts on this "species", you might check out

http://members.cox.net/rcarter26/A.%20curvatulus.html

if you haven't seen it already.

Diatomists have fretted over the distinction between Actinocyclus and Coscinodiscus for a long time.  Workers in the 19th century were already aware that there were "pairs" of species in the two genera, differing primarily in the presence/absence of the pseudonodulus.  A. curvatulus and C. curvatulus were one such pair.  (Another that comes to mind without going to the books is A. ingens and C. elegans.)  Several diatomists suggested collapsing such pairs into single species, in effect arguing that the pseudonodulus was a more trivial trait than some others. 

In 1975 Rainer Simonsen wrote a neat paper addressing the significance of the pseudonodulus:

Simonsen, Rainer, 1975, "On the pseudonodulus of the centric diatoms, or Hemidiscaceae reconsidered," Beihefte zur Nova Hedwigia, Issue 53, pp. 83-98.

I think most researchers came to the conclusion that the pseudonodulus was not too significant above the species level, and that Actinocyclus was best distinguished from Coscinodiscus by its possession of both a central annulus and fasciate striae.

The irregular form of the annulus in the two images I posted is best shown, I think, by comparing the two images with the size set to "original".  In the PC image, there appear to be five tiny hyaline spaces around the central clump of eight areolae.  Such spaces are produced by small voids around the edge of the annulus; there are always one or more such in this species.  In the COL image, we can see that there is a small "satellite" of the annulus, at the "northeast" edge, containing a single isolated areole.  These structures are also common in this species, but not always present.  This is what I meant by the annulus being "irregular", and I assume that's what other describers have meant, as well.  In this species, the annulus never looks exactly the same in any two specimens.

>>Are the process's at the ends pseudonodule's?<<  No, the pseudonodulus is always a solitary structure.  They are not all the same in ultrastructure, though, as Simonsen (inter alia) has shown.  They differ a great deal in size, also, to the point that the pseudonodulus can be too small to distinguish from an ordinary areole in the light microscope.  The PN is often located right on the bend between the valve face and mantle, too, which makes it even harder to see.  The processes at the end of the long rows at the fascicle edges are rimoportulae -- which also vary a lot in size and ultrastructure among different species.  I'm uploading another photo, this one of A. roperi (Brébisson) Grunow in Van Heurck, from a slide made by Leszek.  This species has megahumongous rimoportulae.

>>"Generally, subsequent workers, such as Hustedt (1930) have called forms possessing a pseudonodule A. curvatulus, and those without, C. curvatulus."<<  Until relatively recently, this was generally true.  And such resistance lasted even longer among paleontologists than among diatom taxonomists.  In 1986, George Andrews (my hero, don't get me wrong) bemoaned the fact that Coscinodiscus rothii could not be moved to Actinocyclus because there was no pseudonodulus.  And many of these species have still not been formally moved -- I suspect because a lot of taxonomists look down on publications that do nothing but formalize taxonomic changes.  (I've heard such papers called "resumé padding", for example.)

In the present instance, I think two quite different questions have become confused:

1.  Does C. curvatulus Grunow in Schmidt belong in the genus Actinocyclus?
2.  Are A. curvatulus Janisch in Schmidt and C. curvatulus Grunow in Schmidt the same taxon?

I answer these two questions "YES" and "NO", respectively.  I think there is a complex of species here.

What do you think?

Dick Carter



--- On Sun, 4/3/11, charles wrote:

From: charles
Subject: [diatom_forum] Re: Two Photos
To: diatom_forum@...
Date: Sunday, April 3, 2011, 1:17 AM

 

Hello Dick,
Interesting presentation and useful, personally I have a lot of difficulty with centric diatoms.

Going to Schmidt's Atlas Table 57, there is not a lot of difference between fig. 31 A. curvatulus and fig. 36. The biggest difference is size. Fig. 36 being C. curvatulus.

Your depiction, very clear in second image, of the annular ring is a little confusing to me.
From Hustedt we have ". . . Central area small, set with a very few scattered areolae, enclosed by an irregular circular ring."
I would have trouble calling your imaged ring in the second picture as irregular? Am I making to much of the dark circle?

From Hasle and Syvertsen we have their description of A. curvatulus as "Areola rows slightly curved. A process at the end of each side row of the fascicles. Central annulus irregular in shape. Areolae decreasing in size close to the margin. Small irregular pseudonodulus located close to valve mantle.

Again I see the word irregular.

The central area in the first image I would probably accept as irregular in appearance. I am not disagreeing with you, I am only trying to apply printed definition to presented image. The fascicles, areolae, oriented radially, are clearly presented in the first image and the process at the end of each side row are visible in the first picture, I think. Are the process's at the ends pseudonodule's? From Wiki "Generally, subsequent workers, such as Hustedt (1930) have called forms possessing a pseudonodule A. curvatulus, and those without, C. curvatulus."

You see, I trouble me. So often I have fooled myself with an image, that is, I think I am imaging something important and it really was not. What makes a pleasing picture is not the same as what makes a scientifically accurate presentation. The question I am often asking myself is where to focus and what am I observing at this focus ?
Charles


Rob <kimmich46@...>
 

Dick,

I read your note about C. curvatulus belonging in Actinocyclus, so I will label mine Actinocyclus sp. for now...

Rob K

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

This is a great discussion, leading us into the morass of diatom taxonomy. I really like the contrast Dick got of the two Actinocyclus, the one showing the sectors. I have one I labelled Coscinodiscus curvatulus using Cupp (1943) at http://micro.chemeketans.org/full_scale.asp?image_name=medium/2011_02_27_1099.JPG. Would A. curvatulus be more accurate? How dated (besides dated!) is Cupp?

Dick, can you take a moment apart from this discussion and describe the setup you used for these two photos? I'm also interested in your photo "work flow" including the technique you use for labelling, as you must have thousands of diatom images by now.

(I am using a stock, you could say, Labophot-2 with E-Plans, a 1.25 Abbe condenser, with an attached Canon digital SLR. I use the Canon software to catalog and enhance the photos. I am trying to keep the imaging side simple and have not invested in PhotoShop or the like.)

Rob K

----- Original Message -----
From: Richard Carter
To: diatom_forum@...
Sent: Sunday, April 03, 2011 9:46 AM
Subject: Re: [diatom_forum] Re: Two Photos (Long!)



Charles,

Wow, a great response! This is the sort of thing I had hoped for when the group was started. Your points are very well taken, and very well stated. I'll see if I can clarify what I meant to convey -- for further of my thoughts on this "species", you might check out

http://members.cox.net/rcarter26/A.%20curvatulus.html

if you haven't seen it already.

Diatomists have fretted over the distinction between Actinocyclus and Coscinodiscus for a long time. Workers in the 19th century were already aware that there were "pairs" of species in the two genera, differing primarily in the presence/absence of the pseudonodulus. A. curvatulus and C. curvatulus were one such pair. (Another that comes to mind without going to the books is A. ingens and C. elegans.) Several diatomists suggested collapsing such pairs into single species, in effect arguing that the pseudonodulus was a more trivial trait than some others.

In 1975 Rainer Simonsen wrote a neat paper addressing the significance of the pseudonodulus:

Simonsen, Rainer, 1975, "On the pseudonodulus of the centric diatoms, or Hemidiscaceae reconsidered," Beihefte zur Nova Hedwigia, Issue 53, pp. 83-98.

I think most researchers came to the conclusion that the pseudonodulus was not too significant above the species level, and that Actinocyclus was best distinguished from Coscinodiscus by its possession of both a central annulus and fasciate striae.

The irregular form of the annulus in the two images I posted is best shown, I think, by comparing the two images with the size set to "original". In the PC image, there appear to be five tiny hyaline spaces around the central clump of eight areolae. Such spaces are produced by small voids around the edge of the annulus; there are always one or more such in this species. In the COL image, we can see that there is a small "satellite" of the annulus, at the "northeast" edge, containing a single isolated areole. These structures are also common in this species, but not always present. This is what I meant by the annulus being "irregular", and I assume that's what other describers have meant, as well. In this species, the annulus never looks exactly the same in any two specimens.

>>Are the process's at the ends pseudonodule's?<< No, the pseudonodulus is always a solitary structure. They are not all the same in ultrastructure, though, as Simonsen (inter alia) has shown. They differ a great deal in size, also, to the point that the pseudonodulus can be too small to distinguish from an ordinary areole in the light microscope. The PN is often located right on the bend between the valve face and mantle, too, which makes it even harder to see. The processes at the end of the long rows at the fascicle edges are rimoportulae -- which also vary a lot in size and ultrastructure among different species. I'm uploading another photo, this one of A. roperi (Br�bisson) Grunow in Van Heurck, from a slide made by Leszek. This species has megahumongous rimoportulae.

>>"Generally, subsequent workers, such as Hustedt (1930) have called forms possessing a pseudonodule A. curvatulus, and those without, C. curvatulus."<< Until relatively recently, this was generally true. And such resistance lasted even longer among paleontologists than among diatom taxonomists. In 1986, George Andrews (my hero, don't get me wrong) bemoaned the fact that Coscinodiscus rothii could not be moved to Actinocyclus because there was no pseudonodulus. And many of these species have still not been formally moved -- I suspect because a lot of taxonomists look down on publications that do nothing but formalize taxonomic changes. (I've heard such papers called "resum� padding", for example.)

In the present instance, I think two quite different questions have become confused:

1. Does C. curvatulus Grunow in Schmidt belong in the genus Actinocyclus?
2. Are A. curvatulus Janisch in Schmidt and C. curvatulus Grunow in Schmidt the same taxon?

I answer these two questions "YES" and "NO", respectively. I think there is a complex of species here.

What do you think?

Dick Carter




--- On Sun, 4/3/11, charles <suslavage@...> wrote:


From: charles <suslavage@...>
Subject: [diatom_forum] Re: Two Photos
To: diatom_forum@...
Date: Sunday, April 3, 2011, 1:17 AM



Hello Dick,
Interesting presentation and useful, personally I have a lot of difficulty with centric diatoms.

Going to Schmidt's Atlas Table 57, there is not a lot of difference between fig. 31 A. curvatulus and fig. 36. The biggest difference is size. Fig. 36 being C. curvatulus.

Your depiction, very clear in second image, of the annular ring is a little confusing to me.
From Hustedt we have ". . . Central area small, set with a very few scattered areolae, enclosed by an irregular circular ring."
I would have trouble calling your imaged ring in the second picture as irregular? Am I making to much of the dark circle?

From Hasle and Syvertsen we have their description of A. curvatulus as "Areola rows slightly curved. A process at the end of each side row of the fascicles. Central annulus irregular in shape. Areolae decreasing in size close to the margin. Small irregular pseudonodulus located close to valve mantle.

Again I see the word irregular.

The central area in the first image I would probably accept as irregular in appearance. I am not disagreeing with you, I am only trying to apply printed definition to presented image. The fascicles, areolae, oriented radially, are clearly presented in the first image and the process at the end of each side row are visible in the first picture, I think. Are the process's at the ends pseudonodule's? From Wiki "Generally, subsequent workers, such as Hustedt (1930) have called forms possessing a pseudonodule A. curvatulus, and those without, C. curvatulus."

You see, I trouble me. So often I have fooled myself with an image, that is, I think I am imaging something important and it really was not. What makes a pleasing picture is not the same as what makes a scientifically accurate presentation. The question I am often asking myself is where to focus and what am I observing at this focus ?
Charles


Charles Suslavage
 

Hello Dick,

Oooops! Viewing the images at their orginal size is a lot better. I had to poke around a bit but I did find the option. Full size the hyaline spaces are very clear and I think I am observing the annulus itself, a thickened silica ring from which the silica ribs radiate. The eight areolae are distinctly separate from the overall structure of the valve face and these eight make up the annulus or are within the annulus. The ring from which the silica ribs radiate is a bit difficult to apply other then the radiating pattern begins at the annulus.

The pseudonodule on the diatom from Royal Sound, Kerquelen Island looks perhaps like a blemish. If I was not directed to it I might not have noticed it at all. On a large diatom we often view imperfections. With the LM a blemish might be mistaken as a pseudonodule and vise versa.

The pseudonodule is definitely a problem for amateurs like myself who only have standard biologic light microscopes. It seems to this amateur that I would join the camp that regards the pseudonodule as a less import feature. This in turn implies that I would combine C. curvatulus and A. curvatulus into a common species within a single genus. So to the question "Does C. curvatulus Grunow in Schmidt belong in the genus Actinocyclus?" I would agree with YES as an answere.

The second question "Are A. curvatulus Janisch in Schmidt and C. curvatulus Grunow in Schmidt the same taxon?" and your answer No is difficult to understand. What would be required at this point, I think, is examples of much higher quality then what is presented in the copy of Schmidt at my disposal. At the beginning of this discussion I thought that the only significant difference as presented in Schmidt's Atlas was size so if there is a complex of species more details need to be brought forward.

The image of A. roperi is very good. Now, if you identified this from Van Heurch's Synopsis Des Diatomees De Belgique I am indeed impressed, very impressed. I do not think I would have made the connection. The magahumongous rimoportulae are very conspicuous. Magahumongous, always something new.

Charles

--- In diatom_forum@..., Richard Carter <rcarter68502@...> wrote:

Charles,

Wow, a great response!  This is the sort of thing I had hoped for when
the group was started.  Your points are very well taken, and very well stated.  I'll see if I can clarify what I meant to convey -- for further of my thoughts on this "species", you might check out

http://members.cox.net/rcarter26/A.%20curvatulus.html

if you haven't seen it already.

Diatomists have fretted over the
distinction between Actinocyclus and Coscinodiscus for a long time.  Workers in the 19th century were already aware that there were "pairs" of species in the two genera, differing primarily in the presence/absence of the pseudonodulus.  A.
curvatulus and C. curvatulus were one such pair.  (Another that comes to mind without going to the books is A. ingens and C. elegans.)  Several diatomists suggested collapsing such pairs into single species, in effect arguing that the pseudonodulus was a more trivial trait than some others. 

In 1975 Rainer Simonsen wrote a neat paper addressing the significance of the pseudonodulus:

Simonsen, Rainer, 1975, "On the pseudonodulus of the centric diatoms, or Hemidiscaceae reconsidered," Beihefte zur Nova Hedwigia, Issue 53, pp. 83-98.

I think most researchers came to the conclusion that the pseudonodulus was not too significant above the species level, and that Actinocyclus was best distinguished from Coscinodiscus by its possession of both a central annulus and fasciate striae.

The irregular form of the annulus in the two images I posted is best shown, I think, by comparing the two images with the size set to "original".  In the PC image, there appear to be five tiny hyaline spaces around the central clump of eight areolae.  Such spaces are produced by small voids around the edge of the annulus; there are always one or more such in this species.  In the COL image, we can see that there is a small "satellite" of the annulus, at the "northeast" edge, containing a single isolated areole.  These structures are also common in this species, but not always present.  This is what I meant by the annulus being "irregular", and I assume that's what other describers have meant, as well.  In this species, the annulus never looks exactly the same in any two specimens.

Are the process's at the ends pseudonodule's?<<  No, the pseudonodulus is always a
solitary
structure.  They are not all the same in ultrastructure, though, as Simonsen (inter alia) has shown.  They differ a great deal in size, also, to the point that the pseudonodulus can be too small to distinguish from an ordinary areole in the light microscope.  The PN is often located right on the bend between the valve face and mantle, too, which makes it even harder to see.  The processes at the end of the long rows at the fascicle edges are rimoportulae -- which also vary a lot in size and ultrastructure among different species.  I'm uploading another photo, this one of A. roperi (Brébisson) Grunow in Van Heurck, from a slide made by Leszek.  This species has megahumongous rimoportulae.

"Generally, subsequent workers, such as Hustedt (1930) have called forms
possessing a pseudonodule A. curvatulus, and those without, C.
curvatulus."<<  Until relatively recently, this was generally true.  And such resistance lasted even longer among paleontologists than among diatom taxonomists.  In 1986, George Andrews (my hero, don't get me wrong) bemoaned the fact that Coscinodiscus rothii could not be moved to Actinocyclus because there was no pseudonodulus.  And many of these species have still not been formally moved -- I suspect because a lot of taxonomists look down on publications that do nothing but formalize taxonomic changes.  (I've heard such papers called "resumé padding", for example.)

In the present instance, I think two quite different questions have become confused:

1.  Does C. curvatulus Grunow in Schmidt belong in the genus Actinocyclus?
2.  Are A. curvatulus Janisch in Schmidt and C. curvatulus Grunow in Schmidt the same taxon?

I answer these two questions "YES" and "NO", respectively.  I think there is a complex of species here.

What do you think?

Dick Carter





--- On Sun, 4/3/11, charles <suslavage@...> wrote:

From: charles <suslavage@...>
Subject: [diatom_forum] Re: Two Photos
To: diatom_forum@...
Date: Sunday, April 3, 2011, 1:17 AM







 









Hello Dick,

Interesting presentation and useful, personally I have a lot of difficulty with centric diatoms.



Going to Schmidt's Atlas Table 57, there is not a lot of difference between fig. 31 A. curvatulus and fig. 36. The biggest difference is size. Fig. 36 being C. curvatulus.



Your depiction, very clear in second image, of the annular ring is a little confusing to me.

From Hustedt we have ". . . Central area small, set with a very few scattered areolae, enclosed by an irregular circular ring."

I would have trouble calling your imaged ring in the second picture as irregular? Am I making to much of the dark circle?



From Hasle and Syvertsen we have their description of A. curvatulus as "Areola rows slightly curved. A process at the end of each side row of the fascicles. Central annulus irregular in shape. Areolae decreasing in size close to the margin. Small irregular pseudonodulus located close to valve mantle.



Again I see the word irregular.



The central area in the first image I would probably accept as irregular in appearance. I am not disagreeing with you, I am only trying to apply printed definition to presented image. The fascicles, areolae, oriented radially, are clearly presented in the first image and the process at the end of each side row are visible in the first picture, I think. Are the process's at the ends pseudonodule's? From Wiki "Generally, subsequent workers, such as Hustedt (1930) have called forms possessing a pseudonodule A. curvatulus, and those without, C. curvatulus."



You see, I trouble me. So often I have fooled myself with an image, that is, I think I am imaging something important and it really was not. What makes a pleasing picture is not the same as what makes a scientifically accurate presentation. The question I am often asking myself is where to focus and what am I observing at this focus ?

Charles


Richard Carter
 

Rob,

With regard to your linked image: this does not look like the eccentric "curvatulus-type" fasciation to me, in fact it doesn't seem to have any form of fasciation.  There are clearly local areas on the valve surface in which the striae show some degree of organization, but it's pretty confused.  The arcs of areolae all around the margins are often seen with lineatus-type organization, though.  I do not recognize this diatom at all -- which doesn't mean much, since I can currently recognize only 3/4, at best, of the discoids on my slides.  If this were indeed a lineatus-type structure, then it looks most like Thalassiosira eccentrica -- but not enough that I would label it as such.  The area along the left edge in your image, just below center, shows rows of areoles that look to be perfectly parallel, and that's lineatus.  Elsewhere, there are clearly rows that are radiate and converging, typical radiatus-structure.  Confusing, at least to me.  Perhaps this is one of the Coscinodiscus species that show a mixture of structural types?  I don't think there are any that are very common, though.

The Cupp paper was excellent for its time, and still extremely useful -- I refer to it often.  The taxonomy was correct as of its time, but a lot of names have changed in the interim as our understanding of diatom structure and phylogeny has improved. 

As for the photos: I use a pretty routine setup, a trinocular head with a 5 Mp Tucsen camera permanently mounted.  Software for the camera and some image storage is managed by a dedicated laptop computer.  (The Tucsen software was not compatible with 64-bit operating systems when I bought it, so the laptop runs under Vista.)  I post-process rather heavily, lots of cropping, adjustments in brightness and contrast, a little bit of unsharp masking often brings out details, etc.  (Most people think my photos are still much too dark!)  I do this on my desktop, where I have a big HD monitor, and use Paintshop Pro, the poor man's photoshop.  It has all of the bells and whistles I'd ever use...............  Labelling is done with this program, also.  I detest scalebars, preferring to put accurate measurements right on the photo, when necessary.  The Tucsen software is very easy to use in making measurements.  For diatoms that have a lot of depth, I often do an image stack with CombineZP.  The two curvatulus images didn't need it, of course.  The whole system is quite cheap -- bottom of the line equipment, entirely.  I envy most of the people here, with the great optics they are using!

Dick


--- On Sun, 4/3/11, Rob Kimmich wrote:

From: Rob Kimmich
Subject: Re: [diatom_forum] Re: Two Photos (Long!)
To: diatom_forum@...
Date: Sunday, April 3, 2011, 1:11 PM

 

This is a great discussion, leading us into the morass of diatom taxonomy. I really like the contrast Dick got of the two Actinocyclus, the one showing the sectors. I have one I labelled Coscinodiscus curvatulus using Cupp (1943) at http://micro.chemeketans.org/full_scale.asp?image_name=medium/2011_02_27_1099.JPG. Would A. curvatulus be more accurate? How dated (besides dated!) is Cupp?
 
Dick, can you take a moment apart from this discussion and describe the setup you used for these two photos? I'm also interested in your photo "work flow" including the technique you use for labelling, as you must have thousands of diatom images by now.
 
(I am using a stock, you could say, Labophot-2 with E-Plans, a 1.25 Abbe condenser, with an attached Canon digital SLR. I use the Canon software to catalog and enhance the photos. I am trying to keep the imaging side simple and have not invested in PhotoShop or the like.)
 
Rob K
 
----- Original Message -----
Sent: Sunday, April 03, 2011 9:46 AM
Subject: Re: [diatom_forum] Re: Two Photos (Long!)

 

Charles,

Wow, a great response!  This is the sort of thing I had hoped for when the group was started.  Your points are very well taken, and very well stated.  I'll see if I can clarify what I meant to convey -- for further of my thoughts on this "species", you might check out

http://members.cox.net/rcarter26/A.%20curvatulus.html

if you haven't seen it already.

Diatomists have fretted over the distinction between Actinocyclus and Coscinodiscus for a long time.  Workers in the 19th century were already aware that there were "pairs" of species in the two genera, differing primarily in the presence/absence of the pseudonodulus.  A. curvatulus and C. curvatulus were one such pair.  (Another that comes to mind without going to the books is A. ingens and C. elegans.)  Several diatomists suggested collapsing such pairs into single species, in effect arguing that the pseudonodulus was a more trivial trait than some others. 

In 1975 Rainer Simonsen wrote a neat paper addressing the significance of the pseudonodulus:

Simonsen, Rainer, 1975, "On the pseudonodulus of the centric diatoms, or Hemidiscaceae reconsidered," Beihefte zur Nova Hedwigia, Issue 53, pp. 83-98.

I think most researchers came to the conclusion that the pseudonodulus was not too significant above the species level, and that Actinocyclus was best distinguished from Coscinodiscus by its possession of both a central annulus and fasciate striae.

The irregular form of the annulus in the two images I posted is best shown, I think, by comparing the two images with the size set to "original".  In the PC image, there appear to be five tiny hyaline spaces around the central clump of eight areolae.  Such spaces are produced by small voids around the edge of the annulus; there are always one or more such in this species.  In the COL image, we can see that there is a small "satellite" of the annulus, at the "northeast" edge, containing a single isolated areole.  These structures are also common in this species, but not always present.  This is what I meant by the annulus being "irregular", and I assume that's what other describers have meant, as well.  In this species, the annulus never looks exactly the same in any two specimens.

>>Are the process's at the ends pseudonodule's?<<  No, the pseudonodulus is always a solitary structure.  They are not all the same in ultrastructure, though, as Simonsen (inter alia) has shown.  They differ a great deal in size, also, to the point that the pseudonodulus can be too small to distinguish from an ordinary areole in the light microscope.  The PN is often located right on the bend between the valve face and mantle, too, which makes it even harder to see.  The processes at the end of the long rows at the fascicle edges are rimoportulae -- which also vary a lot in size and ultrastructure among different species.  I'm uploading another photo, this one of A. roperi (Brébisson) Grunow in Van Heurck, from a slide made by Leszek.  This species has megahumongous rimoportulae.

>>"Generally, subsequent workers, such as Hustedt (1930) have called forms possessing a pseudonodule A. curvatulus, and those without, C. curvatulus."<<  Until relatively recently, this was generally true.  And such resistance lasted even longer among paleontologists than among diatom taxonomists.  In 1986, George Andrews (my hero, don't get me wrong) bemoaned the fact that Coscinodiscus rothii could not be moved to Actinocyclus because there was no pseudonodulus.  And many of these species have still not been formally moved -- I suspect because a lot of taxonomists look down on publications that do nothing but formalize taxonomic changes.  (I've heard such papers called "resumé padding", for example.)

In the present instance, I think two quite different questions have become confused:

1.  Does C. curvatulus Grunow in Schmidt belong in the genus Actinocyclus?
2.  Are A. curvatulus Janisch in Schmidt and C. curvatulus Grunow in Schmidt the same taxon?

I answer these two questions "YES" and "NO", respectively.  I think there is a complex of species here.

What do you think?

Dick Carter



--- On Sun, 4/3/11, charles <suslavage@...> wrote:

From: charles
Subject: [diatom_forum] Re: Two Photos
To: diatom_forum@...
Date: Sunday, April 3, 2011, 1:17 AM

 

Hello Dick,
Interesting presentation and useful, personally I have a lot of difficulty with centric diatoms.

Going to Schmidt's Atlas Table 57, there is not a lot of difference between fig. 31 A. curvatulus and fig. 36. The biggest difference is size. Fig. 36 being C. curvatulus.

Your depiction, very clear in second image, of the annular ring is a little confusing to me.
From Hustedt we have ". . . Central area small, set with a very few scattered areolae, enclosed by an irregular circular ring."
I would have trouble calling your imaged ring in the second picture as irregular? Am I making to much of the dark circle?

From Hasle and Syvertsen we have their description of A. curvatulus as "Areola rows slightly curved. A process at the end of each side row of the fascicles. Central annulus irregular in shape. Areolae decreasing in size close to the margin. Small irregular pseudonodulus located close to valve mantle.

Again I see the word irregular.

The central area in the first image I would probably accept as irregular in appearance. I am not disagreeing with you, I am only trying to apply printed definition to presented image. The fascicles, areolae, oriented radially, are clearly presented in the first image and the process at the end of each side row are visible in the first picture, I think. Are the process's at the ends pseudonodule's? From Wiki "Generally, subsequent workers, such as Hustedt (1930) have called forms possessing a pseudonodule A. curvatulus, and those without, C. curvatulus."

You see, I trouble me. So often I have fooled myself with an image, that is, I think I am imaging something important and it really was not. What makes a pleasing picture is not the same as what makes a scientifically accurate presentation. The question I am often asking myself is where to focus and what am I observing at this focus ?
Charles


Richard Carter
 

Charles,

I agree with you when you say that a pseudonodulus can look like a blemish.  Usually, one can see the difference, but I have certainly misled myself on several occasions.  Ideally, one has several specimens of a taxon to compare.  This is the case with the Kerguelen population: my slide has several, quite perfect specimens of this taxon, and all possess the pseudonodulus in exactly the same place.  This is also true of my sample from Herendeen Bay.  And there are literally thousands of specimens of the Miocene taxon on my many slides, from both California and Maryland, and I have never detected a pseudonodulus on any of them.  Plenty of blemishes, but of different shapes, sizes, and locations.  Consistency is the key.

And this is my reason for claiming that the modern populations I've illustrated, from Kerguelen, Herendeen Bay, and the Kerimba Islands, constitute one taxon, while those from the Miocene constitute a different taxon.  In each taxon, the different populations show consistent similarities, while between the two taxa there are consistent differences.  I think both taxa belong in Actinocyclus because they share certain defining traits: fasciate striae, a central annulus, and no central rimoportula.  (The latter trait helps distinguish these taxa from Azpeitia, which has both an annulus and a central rimoportula on the annulus margin.)  I think the two taxa are indeed two, because there are consistent differences: the modern populations have an easily visible pseudonodulus (significant at the species level?), and the Miocene ones don't.  The modern populations average larger in size, and the areolae are consistently finer and closer-set.  The resulting gestalts, at least to me, are fairly distinct.  And several taxonomists have suggested that there are other modern populations that are consistently distinct from the ones that I've illustrated, arguing that there is probably more than one species at present.  I have not seen specimens from those populations, and so cannot comment further.

As for megahumongous: my friends are always disgusted by my ridiculous penchant for noxious neologisms..............

Regards,

Dick


--- On Sun, 4/3/11, charles wrote:

From: charles
Subject: [diatom_forum] Re: Two Photos (Long!)
To: diatom_forum@...
Date: Sunday, April 3, 2011, 11:25 PM

 

Hello Dick,

Oooops! Viewing the images at their orginal size is a lot better. I had to poke around a bit but I did find the option. Full size the hyaline spaces are very clear and I think I am observing the annulus itself, a thickened silica ring from which the silica ribs radiate. The eight areolae are distinctly separate from the overall structure of the valve face and these eight make up the annulus or are within the annulus. The ring from which the silica ribs radiate is a bit difficult to apply other then the radiating pattern begins at the annulus.

The pseudonodule on the diatom from Royal Sound, Kerquelen Island looks perhaps like a blemish. If I was not directed to it I might not have noticed it at all. On a large diatom we often view imperfections. With the LM a blemish might be mistaken as a pseudonodule and vise versa.

The pseudonodule is definitely a problem for amateurs like myself who only have standard biologic light microscopes. It seems to this amateur that I would join the camp that regards the pseudonodule as a less import feature. This in turn implies that I would combine C. curvatulus and A. curvatulus into a common species within a single genus. So to the question "Does C. curvatulus Grunow in Schmidt belong in the genus Actinocyclus?" I would agree with YES as an answere.

The second question "Are A. curvatulus Janisch in Schmidt and C. curvatulus Grunow in Schmidt the same taxon?" and your answer No is difficult to understand. What would be required at this point, I think, is examples of much higher quality then what is presented in the copy of Schmidt at my disposal. At the beginning of this discussion I thought that the only significant difference as presented in Schmidt's Atlas was size so if there is a complex of species more details need to be brought forward.

The image of A. roperi is very good. Now, if you identified this from Van Heurch's Synopsis Des Diatomees De Belgique I am indeed impressed, very impressed. I do not think I would have made the connection. The magahumongous rimoportulae are very conspicuous. Magahumongous, always something new.

Charles