What makes a Portuguese man-of-war a colony?

[HerpetologyFangirl]

Hello. I was studying for my bio exam when I came accross this question. I understand that these jellyfish are made up of Hydrozoans, but I'm not sure what exactly makes it a colony as opposed to anything else. Are Hydrozoans capable of surviving independently? Is it because Hydrozoans are themselves multicellular organisms? What exactly is the definition of a colony anyway? I could use some insight on this topic. Thanks.

[Moontanman]

I think the idea is that the man o war is made up of different individuals cooperating.

 

http://en.wikipedia.org/wiki/Portuguese_Man_o'_War

 

While the Portuguese Man o' War resembles a jellyfish, it is in fact a siphonophore – a colony of four kinds of minute, highly modified individuals, which are specialized polyps and medusoids.[1] Each such zooid in these pelagic colonial hydroids or hydrozoans has a high degree of specialization and, although structurally similar to other solitary animals, are all attached to each other and physiologically integrated rather than living independently. Such zooids are specialized to such an extent that they lack the structures associated with other functions and are therefore dependent for survival on the others to do what the particular zooid cannot do by itself.

 

There are other colonial animals

 

Chondrophore

 

http://en.wikipedia.org/wiki/Chondrophore

 

They all live at the surface of the open ocean, and are colonies of carnivorous, free-floating hydroids whose role in the plankton community is similar to that of pelagic jellyfish. The chondrophores look like a single organism but are actually colonial animals, made up of an orderly cooperative of polyps living under a specialized sail-structure.

 

We get both creatures here where I live in the summer, they are thought by some to resemble the first animals with organs which were thought to be symbiotic partners. Don't ever pick one up, they will sting you, it feels like having boiling water poured over you.

 

There is evidence that the colonial organisms exstied as far back as 1.5 billion years ago far before the Cambrian explosion...

 

http://en.wikipedia.org/wiki/Francevillian_Group_Fossil

 

The Francevillian Group Fossil is an early, macroscopic organism. They were centimeter-sized highly organized, spatially discrete colonial organisms. Their fossils are found in the west-African country of Gabon in the Palaeoproterozoic Francevillian B Fromation, a 2.1-Gyr-old black shale province.[1]

 

The organism was 12 cm in size.[1] Their bodies were flattened disks with a characteristic morphology.[1] Their margins were scalloped and had radial slits.[2] They have an internal radial fabric.[2] The geochemistry of the fossil site indicates that they lived under 40 meters of water, and breathed oxygen.[1]

 

The lead author, Abderrazak El Albani, said, “The discovery is fantastic because it shows the existence of multicellular fauna 1.5 billion years earlier than what we know. … This is important to understand the evolution of life on Earth.”[3][4]

 

Charles Darwin predicted that fossils would be found in the Precambrian rocks. The discovery of these fossils adds to the Precambrian fossil record, and satisfies his predictions about evolutionary history.

[HerpetologyFangirl]

Don't worry, I know all about Nematocysts. I learnt about them in BIOL 102. Besides, I've always loved watching documentaries, especially National Geographic, and I saw a very informative one on jellyfish once. I have another question to try on you: Why aren't Cnidarians and Echinoderms considered to be closely related when they're generally both radially symmetrical?

[CharonY]

Genetic differences plus one exhibiting primary and the other secondary radial symmetry (depending a bit on which form of systematics you subscribe to).

[HerpetologyFangirl]

Genetic differences plus one exhibiting primary and the other secondary radial symmetry (depending a bit on which form of systematics you subscribe to).

 

I can't claim to know the difference between primary and secondary radial symmetry, but I found a solution in my notes after a bit of digging. Apparently they aren't closely related because Echinoderms have bilateral symmetry in their larval stages, unlike Cnidarians which have radially symmetrical polyps.

Edited November 9, 2010 by HerpetologyFangirl

[CharonY]

That is what it means.

[HerpetologyFangirl]

That is what it means.

 

Oh. Thank you. *blushes from embarressment* So much for being a BSc student...