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Jellyfish Quiz Archive
Jellyfish: Anatomy, Life Cycles & Ocean Survival
Revisit this archived jellyfish challenge and explore water-rich anatomy, lightning-fast stinging cells, changing life stages, specialized senses, ocean food webs and glowing deep-sea survival strategies.
🌊 Jellyfish Quiz • ✨ 10 Verified Questions • ⏱️ 150 Seconds
🪼 Bells & Tentacles
⚡ Stings & Senses
🔄 Life Cycles
🌌 Deep-Sea Adaptations
This archived edition preserves the original questions, explanations and scoring experience.
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1
Jellyfish belong to which animal phylum?
Correct answer: Cnidaria. Jellyfish are cnidarians, a group of mostly aquatic invertebrates that also includes corals and sea anemones. A defining feature of the group is the presence of specialized stinging cells called cnidocytes.Body-plan insight: Many jellyfish have radial symmetry, so major body structures are arranged around a central axis rather than along a left-right body plan.
2
What is the thick, jelly-like middle layer of a jellyfish called?
Correct answer: Mesoglea. Mesoglea is the elastic, gelatinous material between the outer epidermis and inner gastrodermis. It makes up much of the jellyfish’s volume and provides support without the heavy bones or shell found in many other animals.Water-rich design: A jellyfish is about 95 percent water, which is why its body loses its familiar shape when removed from the sea.
3
What is the specialized stinging cell of a jellyfish called?
Correct answer: Cnidocyte. A cnidocyte is the specialized cell that contains a capsule called a nematocyst. When triggered, the nematocyst rapidly fires a threadlike structure that can help inject venom, entangle prey or defend the jellyfish.Precision matters: “Cnidocyte” names the complete stinging cell, while “nematocyst” usually refers to the firing capsule housed inside it.
4
Without a centralized brain, what helps many jellyfish detect and respond to stimuli?
Correct answer: A diffuse nerve net. Jellyfish generally lack a centralized brain, but a loose network of nerve cells coordinates basic movement and responses. This system can process information from sensory structures that detect such cues as light, orientation, touch and chemicals in the water.Important exception: A simple nervous system does not mean no sensory ability. Box jellyfish, for example, possess clusters of eyes, including some with lenses and retinas.
5
Which two body forms appear in the life cycle of many jellyfish?
Correct answer: Polyp and medusa. The polyp is usually a small, attached form, while the medusa is the familiar free-swimming, bell-shaped form. In many species, polyps reproduce asexually and medusae produce eggs and sperm for sexual reproduction.Life-cycle lesson: The drifting jellyfish seen in open water may represent only one stage of an animal whose earlier life was attached to a surface.
6
What is the juvenile jellyfish released from a strobilating polyp called?
Correct answer: Ephyra. During strobilation in many true jellyfish, the polyp forms stacked, plate-like segments. Once a segment separates, it is called an ephyra; it then grows and develops into the adult medusa form.Vocabulary link: “Strobila” describes the stacked structure, “strobilation” is the process and “ephyra” is the newly released juvenile.
7
What forms the main diet of the moon jelly Aurelia labiata?
Correct answer: Zooplankton. Moon jellies feed on tiny drifting animals and other zooplankton. Their short tentacles sweep food toward a mucus layer around the bell, after which cilia and oral structures help move captured material toward the mouth.Food-web insight: Jellyfish are predators, but they are also prey for animals such as sea turtles, ocean sunfish, fishes and even other jellyfish.
8
Comb jellies belong to which phylum, separate from true jellyfish?
Correct answer: Ctenophora. Comb jellies are gelatinous animals, but they are not true jellyfish. True jellyfish are cnidarians, whereas comb jellies are ctenophores and usually swim with eight rows of fused cilia called comb plates.Visual illusion: The rainbow shimmer along a comb jelly’s rows is generally caused by light scattering from moving cilia, not by bioluminescence.
9
Which statement about box jellyfish venom is most accurate?
Correct answer: Only a few of roughly 50 species have venom that can be lethal to humans. Box jellyfish vary greatly in danger. A small number, including the Australian box jellyfish Chironex fleckeri, can cause life-threatening envenomation, but it is inaccurate to treat every box-jelly species as equally deadly.Behavior insight: Box jellyfish are unusually active swimmers and possess clusters of eyes, features associated with more directed movement than the passive drifting often associated with jellies.
10
How may the deep-sea crown jelly Atolla use its blue bioluminescent display?
Correct answer: To startle an attacker and attract a larger predator toward it. When disturbed, Atolla can produce spinning patterns of brilliant blue light. The display may disorient the immediate attacker and work like a “burglar alarm,” drawing the attention of a larger predator that could attack the original threat.Deep-sea adaptation: Atolla also has a red bell that appears dark in deep water, helping it remain less visible where red wavelengths from sunlight do not penetrate.
Verification note: The anatomy, classification, life-cycle terminology, feeding ecology, box-jelly facts and deep-sea adaptations in this quiz were checked against NOAA Ocean Service, Smithsonian Ocean, Monterey Bay Aquarium and the Monterey Bay Aquarium Research Institute (MBARI).