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Siphonophorae are colonies composed of members that all belong to the same species right? Do the zooids each do their own reproduction, or do they just have on

Siphonophorae are colonies composed of members that all belong to the same species right? Do the zooids each do their own reproduction, or do they just have one reproductive member, or both?

retrac 4y ago
The members of one individual are all genetically identical, produced by budding/cloning, from a single zooid. Only the pro-bud, the first zooid of an individual organism, buds new zooids. But that's not exactly reproduction, it's more like cellular growth within a multicellular organism, or growing new organs maybe. Reproduction is the creation of a new colony. Most species reproduce sexually. There are specialised reproductive zooids. They produce a larval stage which floats free and then fertilizes or is fertilized (they have both eggs and sperm), and then it starts budding to form a new colony.
- lisper 4y ago
  How is this different from a true multicellular organism? From your description they sound the same modulo terminology.
  - Laaas 4y ago
    I don't think they are any different. Humans are also colonies of individual organisms.
  - retrac 4y ago
    Each zooid grows from an individual embryo, one cell, in the same kind of process of division and cell specialization all multicellular animals go through. For humans, or sven jellyfish, the embryo develops into an independent adult form. But in siphonophores, these individuals are completely specialised to one role within a colony, and can't survive without the colony.
    - lisper 4y ago
      > in siphonophores, these individuals are completely specialised to one role within a colony, and can't survive without the colony Again, I fail to see the distinction between what you are describing here and true multicellular organisms. My body can be viewed as a colony of individual cells. That colony consists almost exclusively of cells that are completely specialized to one role within the colony, and which cannot survive outside without the colony. (But there are exceptions, like HeLa cells.)
      - retrac 4y ago
        Because you start from only one embryo. Almost all animals start from one embryo. These animals are formed from thousands to millions of embryos. From a feature categorization perspective, I guess you have a point. They look a lot like non-clonal jellyfish in practice! But the implied underlying question is: how did that mechanism evolve? Two organisms may look similar but have completely different evolutionary histories and mechanisms to arrive at that appearance. Like eyes, which seem to have evolved independently multiple times. This is a completely different mechanism to construct a multicellular organism. Not stem cells, but embryos, cloning a specialized twin, each of which undergoes embryonic development into a sort-of-organ. In almost all other animals, all genetically identical specialized cells come from a single embryo, which splits into stem cells, which then specialize. That's why it's interesting and stands out, at least to me.

Siphonophorae are colonies composed of members that all belong to the same species right? Do the zooids each do their own reproduction, or do they just have one reproductive member, or both?

retrac 4y ago

The members of one individual are all genetically identical, produced by budding/cloning, from a single zooid. Only the pro-bud, the first zooid of an individual organism, buds new zooids. But that's not exactly reproduction, it's more like cellular growth within a multicellular organism, or growing new organs maybe. Reproduction is the creation of a new colony. Most species reproduce sexually. There are specialised reproductive zooids. They produce a larval stage which floats free and then fertilizes or is fertilized (they have both eggs and sperm), and then it starts budding to form a new colony.

lisper 4y ago
How is this different from a true multicellular organism? From your description they sound the same modulo terminology.
- Laaas 4y ago
  I don't think they are any different. Humans are also colonies of individual organisms.
- retrac 4y ago
  Each zooid grows from an individual embryo, one cell, in the same kind of process of division and cell specialization all multicellular animals go through. For humans, or sven jellyfish, the embryo develops into an independent adult form. But in siphonophores, these individuals are completely specialised to one role within a colony, and can't survive without the colony.
  - lisper 4y ago
    > in siphonophores, these individuals are completely specialised to one role within a colony, and can't survive without the colony Again, I fail to see the distinction between what you are describing here and true multicellular organisms. My body can be viewed as a colony of individual cells. That colony consists almost exclusively of cells that are completely specialized to one role within the colony, and which cannot survive outside without the colony. (But there are exceptions, like HeLa cells.)
    - retrac 4y ago
      Because you start from only one embryo. Almost all animals start from one embryo. These animals are formed from thousands to millions of embryos. From a feature categorization perspective, I guess you have a point. They look a lot like non-clonal jellyfish in practice! But the implied underlying question is: how did that mechanism evolve? Two organisms may look similar but have completely different evolutionary histories and mechanisms to arrive at that appearance. Like eyes, which seem to have evolved independently multiple times. This is a completely different mechanism to construct a multicellular organism. Not stem cells, but embryos, cloning a specialized twin, each of which undergoes embryonic development into a sort-of-organ. In almost all other animals, all genetically identical specialized cells come from a single embryo, which splits into stem cells, which then specialize. That's why it's interesting and stands out, at least to me.