Yes, a hydra is indeed a polyp.
Hydras belong to the phylum Cnidaria and the class Hydrozoa. According to introductory biology texts, the Hydra spends its entire life as a polyp and never goes through a medusoid stage. This means that unlike some other cnidarians that alternate between polyp and medusa forms, hydras exist exclusively in the polyp body plan.
Here's a breakdown:
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Polyp: A polyp is a generally sessile (attached to a surface) form of cnidarian characterized by a cylindrical body with a mouth surrounded by tentacles at one end.
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Hydra: The Hydra is a freshwater hydrozoan that exemplifies the polyp form. It attaches to surfaces via a basal disc and uses its tentacles to capture prey.
Therefore, the defining characteristic of a hydra is that it lives its entire life as a polyp, making the answer definitively yes.
