On that note, man o wars are thought to be an example of a complex multicellular organisms partnering so closely that they lose their individualism. Basically every organ of this thing seems to at once have been a separate animal and can still survive on its own for a while
I suppose a better example of what I meant to talk about are lichen. Which are single species but technically a partnership between types of fungi and an algae.
In siphonophores, each specimen is actually a colony of minute asexually reproducing organisms called zooids that have to work together for survival. They are not "independent" in the sense that they would die without each other, but given the fact that they can reproduce independently, there's definitely some sort of independence there. It's like if all your organs were able to independently reproduce themselves.
What I mean is that in Physalia each individual in the floating city is still a clone of the other members of the colony. All members of the floating city came from an unique larva. This mean also that each Physalia is either male or female but not both.
https://en.wikipedia.org/wiki/Portuguese_man_o%27_war