While in Bayer et al., 1983 double disks are sclerites characteristic of several genus, capstans are one of the characteristic sclerites of Swiftia species. Is there any Swiftia where this kind of sclerites are present?
Hi Iris,
We have some versions of Swifia in southern Australia. They look like the real thing, but such a distribution makes me a bit suspicious.
They do have capstans-like sclerites, but they are quite irregular and do not have such a broad waist as in the in sclerite you have illustrated. I have attached an image to give you some idea. Sclerite A is one example of the capstans present. However, when you flip them over many have one or more tubercles with longitudinal ridges as arrowed in pink in part B. These are small forms of the disks as arrowed in blue.
Cheers,
Phil.
Dear Dr. Phil,
Thanks a lot for your help. I never realized they had disks.
Would you call the first sclerite I uploaded double sphere or capstan?
The sclerite I upload now I would name as capstan 8-radiate and is also present. However, the one with the broad waist is more common and I can not find in any description of Swiftia species of the Atlantic. What do you think? Is there any possibility of this one be a small form of the one I call double sphere?
Kind regards,
Íris
Hi Iris,
Swiftia certainly has sclerites with disk-like processes. In my experience they are generally not well-formed like images 152-154 in Bayer et al. 1983. They are more commonly like those labelled as "b" in Carpine and Grasshoff' 1975 plate 34.
The terminology for sclerite shapes is not clear-cut. It will always remain quite subjective because there are so many variations on the nominal shapes as defined in Bayer et al 1983, with which I don't always agree. The sclerite you first uploaded has well defined neck region and therefore falls partway between images 159 and 160, double head.
The second sclerite you uploaded has one end that is obviously larger then the other and so it is a club - quite like image 163 from Junceella. If both ends were the same as the largest end then I would probably call it a double head. But sclerites like this one and the first one you uploaded have also been referred to as capstans. The reason is obvious if you check the image I have attached an image of one form of a modern nautical capstan, which would be motor driven.
Currently, sclerites like images 147 - 151 are referred to as "capstans", and it is usual to put the number of radii before the word "capstan" - eg. 7-radiate capstan fig 147. I think it can safely be assumed that the name derives from the old style capstans that were turned by manpower alone (see the attached figure).
To refer to a capstan as and 8-radiate, the 8 "radii" or warts should be reasonable well defined as they are in images 148-149. I have drawn on your image to show how someone could define the warts. As you can see, only the small end probably has 4 warts.
I hope this helps,
Cheers,
Phil.
Dear Dr. Phil,
It is a great explanation about sclerite forms that is so hard to get nowadays. Thank you very much for your clear and complete description.
As Bayer et al., 1983 as a starting point to classify the sclerites, I understand it is not complete or straight forward. But sclerite terminology is, in my opinion, essential to clarify if a special kind of sclerite is typical of a species or widespread through genus, families, etc. It would be amazing to link all the known types of sclerites with all the species where they occur.
Despite the name of the sclerites I uploaded before, I realize they are different from the ones described for Swiftia occuring in the NE Atlantic.
I really appreciate your help.
Kind regards,
Íris
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