Based on california's experience with caulerpa the killer algae explain why it is important to regulate the pet and aquarium trade

Even species that are kept as pets and in aquariums should be regulated and tracked because their accidental release can have serious negative environmental impacts. Some owners and aquarium keepers intentionally release these species into the wild rather than destroy them, and accidental release is always a risk. Therefore, if a potentially destructive species is going to be kept as a pet or in an aquarium they should be regulated so proper safety precautions can be taken.

organisms that lack symmetry are called asymmetrical and belong to phylum porifera/sponges.

organisms with specialized stinging cells belong to phylum cnidaria. stinging cells are called cnidoblast cells.

cnidarians show two morphological forms : polyp (sessile) and medusa (mobile)

filter feeding is observed in porifera members.  

alternation of generation is observed in coelenterata or cnidaria. there is alternation of asexual polyp form and sexual medusoid form. it is also referred as metagenesis.