Comparison: Twocups or Rocket-ship Sipho?
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by
yshish
moderator, translator
There have been some questions about distinguishing between the #Twocups Siphos and the #Rocket-ship Siphos, so I decided to make a little comparison using image examples from the data set. I'm not entirely sure about correctness of my description, so better wait for a confirmation by a scientist. It's just how I understand to the differences based on my experience from the classification and articles and videos about Siphonophores I saw.
Twocups Siphos
As the nickname implies, their 'body' (which actually isn't a real body since all Siphonophores are a colony of many individuals living together as a single animal) consists of two muscular swimming bells (called Nectosome) and a hollow stem consisting of many repeated units (Siphosome). Each of them has components of different functions as well as branching tentacles. The biggest ones (gelatinous Bracts) provide defence, tentacles come from Gastrozooids which have digestive function, Gonozooids have reproductive function.
Often, you can see them in a larval stage (planula) in the form of a swimming bell which may have Gastrozooid and branching tentacle. The larval form looks very similar to Rocket-ship ones and can be easily confused. If you look very carefully at both images and compare the larvae of both categories, you may notice the difference: Twocups larvae have 'double' swimming bell. While the doubleness is not as distinct as in adults, it is already emerging/developing.Click here for the FULL resolution!!
Rocket-ship Siphos
There are two main types of Rocket-ships, both having a single swimming bell. The first type has got round top of the swimming bell and reminds of a helmet or a thimble (We used to call them R-S Thimble in the previous version). The second type is pointy and reminds of a real rocket-ship or a triangle (We nicknamed them R-S Triangle).
While the Triangles are easily recognizable, the Thimble ones may be easily confused with Twocups, especially in the larval stage. That's why I focus on the Thimbles only in my comparison.
You won't see the big thick gelatinous Bracts of Siphosome as you can see in Twocups. The stem is short and hidden by the swimming bell. They have just a single branching tentacle which also may be very short or missing in the larval stage. As they grow up they start budding on the tentacle - then you'll see less or more new swimming bells like individuals attached to the stem. After a while, they separate from the colony and swim freely in the ocean. R-Ss tent to keep small colonies.Click here for the FULL resolution!!
Hope it isn't misleading and will help you to tell these two categories apart.
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kirstenr
Thank you for all your effort, yshish, in putting these together. The montages are such amazing work! Unfortunately for me, this still doesn't clear up my confusion, because there is not enough detail about the one feature I am stuck on. I don't really see the difference between the double swimming bell of the two cups in the planula phase and the single swimming bell of the R-S sipho. What features am I looking at?
In some of the two cups images, I can see what I would call a "cleft" in the swimming bell (oriented vertically at the top of the bell). Is that what I am looking for? But in some of the images, it is missing. In both the two cups and the R-S siphos, I see an oval opening within the bell that reminds me of a doorway or the entrance to a tunnel. Is there something distinct about this feature I can focus on? It seems to be shaped a little more like a rounded triangular opening in the two cups and like more of an arch in the R-S siphos; but again, not always. To be honest, some of these two cup siphos still look like they have a single bell to me; so I'm not seeing the defining feature. Despite the language difference between us, you are doing a great job of teaching, so don't give up on your student! 😃 I really appreciate your efforts, and they help bring the whole cadre of classifiers along, not just one or two, and raise our work to a higher level.
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yshish
moderator, translator
Well, not sure how to explain it in words, so I tried to draw it here, into the same Twocups montage. Look at the red marks (sorry they aren't nicely drawn, using just a track point). I added the marks only to the most unclear bells, not to the obvious ones. (Can't you see two two swimming bells developing there?)
So if unsure, just focus on the bottom part of the swimming bell, around the tunnel-like structure. When it is 'doubled' (w-shaped), mark it is the Twocups one.
Click HERE for the full resolution.
Hope it helps!
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kirstenr
That helps a lot, yshish! I believe that will improve my accuracy in 90% of the cases. I just sent you an email with some images from the rocket ship sipho montage that I'm still confused about. Thanks for creating such useful tools to have a discussion around!
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