Is physalia and jellyfish same

Answer 1

Most people call Physalias jellyfish because they are gelatinous creatures floating around the oceans. Scientists, however, like to keep the title of jellyfish reserved for one specific class of Cnidarians, the Scyphozoans, named after the Greek word for cup, due to their shape. But go ahead and use the term any way you choose, scientists know what you mean.

Physalias belong to a particularly fascinating genus within the class of Hydrozoa, and each individual organism is a colony of attached polyps where each polyp began as an asexual clone of the founding polyp (the large float), and then differentiated into either an eating polyp, a predatory polyp, or a sexual polyp. Some people describe a Physalia as a collection of individuals that live together in a symbiotic relationship, but that description is more sensationalistic than descriptive. The morphogenesis of Physalia polyps is really much more like the differentiation of organs and appendages in a complex organism than say, a coral colony of identical replicas of the founding polyp.

Physalia colonies are also either male or female, and eventually reproduce sexually through broadcast fertilization, so that genetic variation is not simply limited to mutations. (Another reason to consider that the colony is an individual, instead of each polyp.) But however you choose to view this wonderful class of Hydrozoans, they certainly give us a glimpse about our ancestral heritage, and the possible variations that have sprung from that legacy.