Your question is very ambiguous, but the most notable feature the hydra lacks in senescence, this means its mortality rate does not increase with age. Blatantly, it does no age.
The hydras are gone.
there is not even hydras on clubpenguin
Hydras do not have a skeleton. They are multicellular organisms that belong to the phylum Cnidaria and are characterized by a simple body structure without bones or hard structures. Hydras have a flexible body made up of a layer of cells surrounding a central digestive cavity.
hydras have testes to produce and release sperm and ovaries to produce and release eggs
They are gone.
Yes.
The kingdom is animalia.
hydras carry out asexual reproduction (binary fission) whereas mammals carry out sexual reproduction (mating)
invertibrates
They are gone.
Cnidarians
hydras.