I read about the new discovered creature call Myxozoa and it say that Myxozoa is animal because of it possess cnidocysts like other cnidarian. But why doesn't it is a converge evolution ?
Myxozoa doesn't fit one of the most important characteristic of animal kingdom, "Multicellular". I know that all multicellular creatures aren't animals but all animals are multicellular until I read about Myxozoa.
Characteristic is like a rule without even a single exception for any specific group. Something that most of the group have in common, for example, "true tissue"(except sponge), "has limit life span" (except immortal jelly fish) etc. are important property that most of them have in common but not characteristic since some of them don't have.
I know it is hard to find any thing that all animals have in common without even a single exception for any specific group but it is important. We do need a check list to check if any creature is animal or not and to separate it from other eukaryote.
Here is my check list for animals which is from many source and my knowledge of all animal group which I try to separate animal from other eukaryote.
- Multicellular in all part of the life cycle except zygote state
- Heterotroph (No chloroplast but can be symbiosis with other creatures that have chloroplast.)
- Motile (relocate entire body) in at least one part of the life cycle
- No cell wall
- Aerobic respiration (has mitochondria)
- Has tissue - Has basic tissue (like sponge) or true tissue
- Have at least 5 different type of cell that do different job in at least one part of the life cycle (Sponges, comb jellies, Placozoa, Cnidaria and Xenacoelomorpha have more than 5 different type of cell. All more advanced bilateria animal obviously have more than 5 different type of cell. All Choanoflagellate have less than 5 different type of cell.) and at least 5 different type of cell that can communicate with each other.
I know I might be wrong but we really a check list to separate animal from other eukaryote. This is the best check list that I can make.
Myxozoa will not fit three of these list, "Multicellular", "Have at least 5 different type of cell that do different job in at least one part of the life cycle" and "Aerobic respiration" (A Myxozoa species call Henneguya zschokkei doesn't have mitochondria.). And if these characteristic is removed, we will not unable to separate all other eukaryote from animal.
Myxozoa should be another protist with its own group but not animal. I think it can possess cnidocysts due to the converge evolution or obtain cnidaria cnidocysts gene through horizontal gene transfer in some way in hundreds million years ago.