What is unique about Hydrozoa?

Like all cnidarians, hydrozoans have special ectodermal cells called cnidocytes, each containing a single intracellular structure called a cnida (aka nematocyst). Cnidae are unique to the Cnidaria. Each cnida, when triggered by a mechanical or chemical stimulus, shoots out a tiny hollow tube at high speed.

Is a Hydrozoa a jellyfish?

Hydrozoans are related to jellyfish and corals and belong to the phylum Cnidaria.

Are Hydrozoa sessile?

Hydrozoa (phylum Coelenterata, class Hydrozoa) are coelenterates that are closely related to the hydra ,sea anemones , corals, and jellyfish . In addition, two main types of hydrozoa exist: a polypoid structure which is sessile, remaining in the same place, and a medusoid form which is free-swimming. …

Are cnidarians poisonous?

Cnidarians are the oldest extant lineage of venomous animals. Utilizing specialized penetrating nematocysts, cnidarians inject the nematocyst content or “venom” that initiates toxic and immunological reactions in the envenomated organism. These venoms contain enzymes, potent pore forming toxins, and neurotoxins.

Is Hydrozoa diploblastic?

Recent interpretations of the medusary nodule (the structure that, from a polyp, gives rise to a medusa by a special type of budding) suggest that the Hydrozoa are triploblastic. The polyp stage, thus, is diploblastic, whereas the medusae are triploblastic.

Does hydra form medusa?

Hydra, a well-known freshwater genus that has the distinction of being solitary rather than colonial, lacks a medusa stage.

What makes Cubozoa unique?

Cubozoans differ from Scyphozoans in their arrangement of tentacles; they are also known for their box-shaped medusa. Out of all cnidarians, cubozoans are the most venomous. Hydrozoans are unique from all other cnidarians in that their gonads are derived from epidermal tissue.