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siphonophores

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siphonophores

Postby Waylah » Mon Sep 02, 2013 8:23 am

Hi everyone, I'm Julia, a physicist/biochemist. I love all science!

So bluebottles, or Portuguese men o' war, are not jellyfish but are colonies of zooids: polyps and medusae,
So, this is really weird and awesome (like lots of biology!).
I have some questions:

1. There are four different types of zooid in a bluebottle. In a single bluebottle, do the four types of zooid all come from the one original cell? It's hard finding straight answers. It seems maybe they do all come from one fertilised egg, but maybe that's just every zooid WITHIN a given group of zooids, like the digestion ones for example. Though from reading, by now I'm pretty sure the whole entire thing comes from one egg. (if so, then how the four specialised colonies go about speciallising would be pretty interesting!)

2. Is a zooid multicellular? If so, how big are they?

3. how long would a zooid live if it was picked off the colony? I hear there are some siphonophores that can shed a few medusae that can live on their own, but this is the exception, not the rule.

4. how many zooids (roughly!) would there be in a single bluebottle?

5. any guesses on the evolution of these things?

Thanks guys!
Waylah
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Re: siphonophores

Postby fumpledrumpskin » Sun Sep 15, 2013 3:08 pm

Hi Julia!
You're right biology is awesome!

There are roughly 200 spp of Siphonophore the species you mention is Physalia physalis which is the only species that floats, the vast majority swim underwater.

1) The initial zooid arises from a fertilised egg, the rest of the colony is formed by budding which is a type of asexual reproduction. I have no idea the mechanisms behind HOW the zooids become specialised but I do know that zooids that are used for propulsion for example do not feed and vice versa so it would seem that there is a basic plan of each zooid which is modified to it's job.... if that makes sense.

2) I believe the zooids are multicellular but sizes will vary between species but for sake of argument, probably very small!

3)Because most are specialised for a particular job, chances are not very long, if it had no food supply it would die quite quickly!

4)They are colonies as you mention so the size would be based on food availability. (some have been found 30-40m long!)

5) The evolution question is interesting, they are technically a group of single organisms but behave as an individual much like our cells making up us. For the most part the colony lives and dies as one so any selection pressures on the organism today would be pressures at the whole colony level, this would suggest the whole colony is one individual but that can be argued. It would be almost impossible to guess exactly how they evolved.

Hope this helps!
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Re: siphonophores

Postby MeganRieff » Tue Mar 04, 2014 1:25 pm

I started reading about jellyfish this morning, and just couldn't stop. Then I discovered the term siphonophora and immediately had a ton of questions. What I don't understand is how the parts are considered "individuals" if they all come from the same egg, and could not survive on their own. Maybe I'm just lacking some basic understanding on how siphonophores function, or what makes something an individual. Could someone explain this to me? It is so interesting!

Thanks!
Megan
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