Cnidaria vs. Ctenophora — What's the Difference?
By Fiza Rafique & Urooj Arif — Updated on May 8, 2024
Cnidaria includes aquatic animals like jellyfish and corals with stinging cells (nematocysts), while Ctenophora, or comb jellies, lack stinging cells but use rows of cilia for movement.
Difference Between Cnidaria and Ctenophora
Table of Contents
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Key Differences
Cnidaria is a phylum encompassing jellyfish, corals, and sea anemones, known for their specialized stinging cells (nematocysts) used to capture prey. Ctenophora, also known as comb jellies, lack stinging cells and instead rely on rows of comb-like cilia to swim and capture plankton.
Cnidarians exhibit both polyp and medusa forms, with some species switching between the two during their life cycles. In contrast, ctenophores typically only have a single form and resemble medusa-like jellyfish, but with distinctive ciliated rows.
Cnidarians use nematocysts to inject venom into prey, paralyzing them before consumption. On the other hand, ctenophores employ sticky cells called colloblasts to capture plankton and other small prey without venom.
Cnidarians have radial symmetry and a simple nerve net to detect changes in their environment. Ctenophores also have radial symmetry but possess a unique apical sense organ that helps maintain balance and direction.
Cnidarians can form large colonies like coral reefs, while ctenophores remain solitary, drifting in ocean currents.
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Comparison Chart
Common Names
Jellyfish, corals, sea anemones
Comb jellies
Movement
Pulsation of bell (medusa form)
Cilia rows ("combs")
Feeding Mechanism
Stinging cells (nematocysts)
Sticky cells (colloblasts)
Symmetry
Radial
Radial
Habitat
Marine and freshwater
Exclusively marine
Compare with Definitions
Cnidaria
Includes jellyfish, corals, and sea anemones.
Coral reefs are composed of colonies of tiny cnidarians.
Ctenophora
A phylum of marine animals known as comb jellies.
The aquarium had a tank full of colorful ctenophores.
Cnidaria
Found in marine and freshwater environments.
Cnidarians like hydra can even live in freshwater lakes.
Ctenophora
Lacks stinging cells, using sticky cells called colloblasts instead.
The comb jelly catches plankton with its colloblasts.
Cnidaria
Uses specialized stinging cells called nematocysts.
The jellyfish stung the swimmer using its nematocysts.
Ctenophora
Exclusively marine and solitary.
Unlike corals, ctenophores do not form colonies.
Cnidaria
Can switch between polyp and medusa forms.
Some cnidarians start life as polyps and transform into medusae.
Ctenophora
Has a unique apical organ to sense direction.
The apical organ helps ctenophores maintain balance in the water.
Cnidaria
A phylum of aquatic animals with stinging cells.
The divers observed various cnidarians, from jellyfish to sea anemones.
Ctenophora
Propels itself using rows of cilia resembling combs.
Ctenophores move gracefully using their comb-like cilia.
Cnidaria
Cnidaria () is a phylum under kingdom Animalia containing over 11,000 species of aquatic animals found both in freshwater and marine environments, predominantly the latter. Their distinguishing feature is cnidocytes, specialized cells that they use mainly for capturing prey.
Ctenophora
Ctenophora (; singular ctenophore, or ; from Ancient Greek: κτείς, romanized: kteis, lit. 'comb' and φέρω, pherō, 'to carry'; commonly known as comb jellies) comprise a phylum of invertebrate animals that live in marine waters worldwide. They are notable for the groups of cilia they use for swimming (commonly referred to as "combs"), and they are the largest animals to swim with the help of cilia.
Cnidaria
Cnidarian
Ctenophora
A phylum of invertebrates, commonly ellipsoidal in shape, swimming by means of eight longitudinal rows of paddles. They are commonly called the comb jellies, because the separate paddles somewhat resemble combs. This phylum was formerly classified as a subdivision (class) within the Cœlenterata.
Cnidaria
A comprehensive group equivalent to the true Cœlenterata, i. e., exclusive of the sponges. They are so named from presence of stinging cells (cnidae) in the tissues. See Coelenterata.
Ctenophora
Comb jellies; sea acorns; a small phylum formerly considered a class of Coelenterata
Cnidaria
Hydras; polyps; jellyfishes; sea anemones; corals
Common Curiosities
How do ctenophores catch their prey?
Ctenophores use colloblasts, sticky cells on their tentacles or body, to trap plankton and small prey.
Can cnidarians and ctenophores both form colonies?
Cnidarians can form large colonies like coral reefs, while ctenophores are typically solitary.
What are the main structural differences between cnidarians and ctenophores?
Cnidarians have nematocysts (stinging cells) and can switch between polyp and medusa forms, while ctenophores have ciliated comb rows and sticky colloblasts.
Are ctenophores dangerous to humans like cnidarian jellyfish?
No, ctenophores lack venom and pose no stinging threat to humans.
What is the role of nematocysts in cnidarians?
Nematocysts inject venom into prey, allowing cnidarians to capture and immobilize them.
How do cnidarians and ctenophores move differently?
Cnidarians move by pulsating their bell or floating passively, while ctenophores use rows of cilia for propulsion.
Are all cnidarians and ctenophores marine animals?
While all ctenophores are marine, some cnidarians can also live in freshwater environments.
Do cnidarians and ctenophores have the same type of symmetry?
Both groups exhibit radial symmetry, but ctenophores also have an apical organ for balance.
What role do ctenophore cilia rows play?
Ctenophore cilia rows, or "combs," are used for locomotion, refracting light to create a shimmering effect.
How do cnidarians and ctenophores differ in their ecological roles?
Cnidarians often form reefs or act as predators, while ctenophores are primarily open-water planktonic predators.
What life stages do cnidarians have that ctenophores lack?
Cnidarians can have both polyp and medusa stages, while ctenophores generally have one form.
Which phylum includes corals, cnidaria or ctenophora?
Corals belong to the phylum Cnidaria.
Why do cnidarians have a nerve net?
The nerve net helps cnidarians detect changes in their environment and coordinate simple movements.
Are ctenophores bioluminescent like some cnidarians?
Yes, many ctenophores can produce light through bioluminescence.
Are comb jellies considered true jellyfish?
No, comb jellies belong to a separate phylum and are not considered true jellyfish.
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Written by
Fiza RafiqueFiza Rafique is a skilled content writer at AskDifference.com, where she meticulously refines and enhances written pieces. Drawing from her vast editorial expertise, Fiza ensures clarity, accuracy, and precision in every article. Passionate about language, she continually seeks to elevate the quality of content for readers worldwide.
Co-written by
Urooj ArifUrooj is a skilled content writer at Ask Difference, known for her exceptional ability to simplify complex topics into engaging and informative content. With a passion for research and a flair for clear, concise writing, she consistently delivers articles that resonate with our diverse audience.
