Qwiz5 Quizbowl Essentials – Phylum Cnidaria

The Cnidarians are an incredibly diverse phylum consisting of corals, sea anemones, jellyfish, and more. These creatures are united by the presence of a common self-defense mechanism, stinging cells known as nematocysts. Cnidarians also all possess radial symmetry, or symmetry around a central axis. Read on if you’re ready to Cnow more about Cnidaria! 

By analyzing questions, you can see patterns emerge, patterns that will help you answer questions. Qwiz5 is all about those patterns. In each installment of Qwiz5, we take an answer line and look at its five most common clues. Here we explore five clues that will help you answer a tossup on Phylum Cnidaria.  

MESOGLEA

Cnidarians are relatively simple from a structural standpoint. Their bodies consist of just two cell layers. The outer cell layer contains the nematocysts, which protect the creature. The inner cell layer lines the Cnidarians’ gut. Between these two layers is a gelatinous substance known as mesoglea. Mesoglea contains collagen fibers and helps to maintain the structural integrity of the other two cell layers. 

MEDUSA AND POLYPS

The Medusa stage and the polyp stage are the two possible stages of the Cnidarian life cycle. Some Cnidarians alternate between the medusa and polyp stage, while others remain in one stage for their entire lives. Polyps are sessile, meaning that they cannot move. Medusae, on the other hand, are the more complex of the two forms, and they have certain body parts that polyps lack. One such body part, the manubrium, connects the medusa’s stomach to its mouth. 

STROBILATION

While medusae reproduce sexually, polyps reproduce asexually. One way that polyps reproduce asexually is via a process known as strobilation. In strobilation, a polyp splits into flat segments stacked on top of each other. This stack, which is known as a strobila, then releases these segments as new polyps. 

ANTHOZOA

Anthozoa is a class of Cnidaria. Members of the Anthozoa class include sea anemones and corals. Adult Anthozoa attach to the sea floor, but in their larval stage members of this class are free-floating and thus can relocate to colonize other areas. 

CUBOZOA

The smallest Cnidarian class is probably the most famous one as well. Class Cubozoa contains the box jellyfish, which is named for its body’s shape. The stings of a box jellyfish can be quite painful and, in some cases, fatal. Although we refer to a variety of creatures as “jellyfish”, Cubozoa are different from other classes like Hydrozoa (which contains the Portuguese man o’war) and Scyphoza (“True Jellyfish”). 

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Quizbowl is about learning, not rote memorization, so we encourage you to use this as a springboard for further reading rather than as an endpoint. Here are a few things to check out: 

• Visit this website to learn more about the different kinds of Anthozoa. 
  

• Although often perceived as a jellyfish, the Portuguese man o’war is in fact a different kind of organism. 
  

• Jellyfish may not have a brain, but that’s no real loss to them. Why? Find out more here.

• Phylum Cnidaria is an ancient phylum. Some of its members are practically immortal! 

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