What is the Difference Between Coelenterata and Ctenophora: A Comprehensive Guide

If you’re a marine biology enthusiast or just someone who’s intrigued by the underwater world, you might have heard about the terms Coelenterata and Ctenophora. These are two separate groups of aquatic invertebrates, both of which are mesmerizing to observe in the wild. However, they have distinct biological features from each other that can tell them apart.

For starters, Coelenterata – also known as Cnidaria – consists of a diverse range of organisms that includes jellyfish, coral, hydroids, and sea anemones. These creatures share certain characteristics like stinging cells, radially symmetric body shape, and a simple digestive system. Meanwhile, Ctenophora pertains to a group of marine animals that are commonly called comb jellies. They have eight distinctive rows of combs or cilia that help them swim through the water and capture prey.

While Coelenterata and Ctenophora might seem similar at first glance, their morphological traits and evolutionary history place them into separate taxonomic groups. Understanding the differences between these two groups can deepen our appreciation for the diversity and complexity of marine life and the ecosystems that support them.

Overview of Coelenterata and Ctenophora

Coelenterata and Ctenophora are two different phyla of aquatic organisms. Both of them are simple, multicellular animals that do not have any organs for digestion, circulation or excretion. However, they have different characteristics that distinguish them from one another.

  • Body shape: Coelenterata have a sac-like body, while Ctenophora have a more elongated and comb-shaped body.
  • Cilia: Ctenophora have cilia that they use for movement, while Coelenterata use tentacles.
  • Nervous system: Ctenophora have a more complex nervous system than Coelenterata, with a distinct brain-like structure.

Coelenterata are also known as cnidarians, which include jellyfish, corals, and sea anemones. They have a radial symmetry, meaning that their body parts radiate out from a central point. They have stinging cells called nematocysts that they use for defense and feeding. Some species of Coelenterata are bioluminescent, meaning they can produce light.

Ctenophora, on the other hand, are commonly known as comb jellies. They have eight rows of cilia that they use for movement, giving them a shimmering appearance. Some species of Ctenophora are also bioluminescent, producing flashes of light through their bodies. Unlike Coelenterata, they do not have stinging cells, but instead use sticky tentacles to capture their prey.

Coelenterata Ctenophora
Radial symmetry Bilateral symmetry
Tentacles for feeding Cilia for movement
Nematocysts for defense and feeding Sticky tentacles for capturing prey

In summary, Coelenterata and Ctenophora are two distinct phyla of aquatic animals with different body shapes, modes of movement, nervous systems, and feeding strategies. Understanding the differences between them can help us appreciate the diversity of life in our ocean ecosystems.

Taxonomic Classification Differences

Coelenterata and Ctenophora share many similarities, but significant differences exist in their taxonomic classifications. Let’s take a look at some of these differences.

  • Phylum: Coelenterata is a phylum that includes several classes of animals such as Anthozoa, Hydrozoa, Cubozoa, and Scyphozoa. Ctenophora, on the other hand, is a separate phylum that only includes a single class – Tentaculata.
  • Cell Structure: Both phyla have radially symmetrical bodies and have two cell layers – the epidermis and gastrodermis which surround a gel-like layer called the mesoglea. However, coelenterates rely on cnidocytes or stinging cells, which they use for capturing prey and self-defense. Ctenophores have no such structures and instead use sticky cells on their tentacles to catch their food.
  • Body Shape: Coelenterata has two different body plans – the polyp and medusa – while ctenophores only have the medusa body plan.

It is worth mentioning that some biologists and taxonomists consider the phylum Ctenophora as part of the phylum Coelenterata. However, most modern classifications recognize them as separate phyla due to their clear differences.

Here’s a table summarizing the taxonomic classification differences between Coelenterata and Ctenophora:

Coelenterata Ctenophora
Phylum Includes Anthozoa, Hydrozoa, Cubozoa, and Scyphozoa Has only one class – Tentaculata
Body Symmetry Radial symmetry Radial symmetry
Cnidocytes Has stinging cells for capturing prey and self-defense Has no such structures and relies on sticky cells on their tentacles
Body plan Has two body plans: Polyp and medusa Has only one body plan: Medusa

In conclusion, despite sharing several similarities, Coelenterata and Ctenophora have significant taxonomic classification differences. These differences are important in classifying and understanding the characteristics of these animals.

Morphological Differences

Coelenterata and Ctenophora share some similarities in terms of their basic body plan, which is characterized by a radially symmetrical, sac-like body with a central mouth surrounded by tentacles. However, there are some key differences in their morphology that distinguish them from each other.

  • Body Structure: The body of the coelenterate is characterized by two layers of cells, with an inner gastrodermal layer that lines the digestive cavity and an outer epidermal layer that covers the outer surface. On the other hand, the body of the ctenophore is structurally more complex and consists of four distinct layers of cells. These layers include an outer epidermal layer, a middle mesoglea that acts as a hydrostatic skeleton, a gastrodermal layer lining the digestive tract, and a specialized layer of muscle cells.
  • Cnidae vs. Colloblasts: Coelenterates use stinging cells called cnidae to capture prey and defend themselves against predators. Ctenophores, on the other hand, use sticky cells called colloblasts to capture prey. While both cnidae and colloblasts are similar in function, they differ in their ultrastructure and biochemical composition.
  • Presence of Comb Rows: Ctenophores possess eight comb rows that run perpendicular to their body axis and are used for locomotion. These comb rows are composed of specialized cells called ctenes that are arranged in a precise pattern. Coelenterates, on the other hand, lack these comb rows and use a combination of muscular contractions and hydrostatic pressure to move around.

In summary, while coelenterates and ctenophores share some common morphological features, such as a radially symmetrical body plan and tentacles surrounding a central mouth, there are fundamental differences in their body structure, cell types, and locomotion mechanisms that distinguish them from each other.

If we take a closer look at the structural differences between coelenterates and ctenophores, we can see that the latter has a more complex body structure with four distinct layers of cells as opposed to two in the former. Additionally, while both use specialized cells to capture prey, ctenophores use sticky cells called colloblasts, whereas coelenterates use stinging cells called cnidae. Finally, the presence of comb rows in ctenophores and their absence in coelenterates is another key feature that sets them apart from each other.

Coelenterata Ctenophora
Two layers of cells Four distinct layers of cells
Uses stinging cells called cnidae Uses sticky cells called colloblasts
Lacks comb rows Possesses eight comb rows for locomotion

Overall, the morphological differences between coelenterates and ctenophores are essential for understanding the phylogenetic relationships between these two groups of animals. As such, it is important to study these differences in detail to gain a better understanding of their evolution and ecological roles in marine ecosystems.

Reproductive Differences

Coelenterata and Ctenophora are two different phyla of marine organisms that share some similarities in their physical characteristics but differ in several ways. One of the distinguishing features between them is how they reproduce, with each phylum having its unique reproductive strategies and systems. Here are some of the reproductive differences between Coelenterata and Ctenophora:

  • Coelenterata: Members of this phylum reproduce both asexually and sexually depending on the species. In asexual reproduction, they can undergo budding, where the polyps produce genetically identical offspring. In sexual reproduction, they can either be monoecious, meaning having both sexes in one individual, or dioecious, having separate sexes. The fertilized egg develops into a free-swimming planula larva and settles on a surface to form a new colony.
  • Ctenophora: Members of this phylum reproduce only sexually and are hermaphroditic, having both male and female reproductive organs in the same individual. They release their gametes into the water where fertilization occurs, and the fertilized eggs develop into cydippid larvae. These larvae undergo metamorphosis and become fully formed adults.

As evidenced, the main difference in the reproductive strategies of these two phyla is that Coelenterata can reproduce both sexually and asexually, while Ctenophora only reproduces sexually. Additionally, Coelenterata can be monoecious or dioecious, while Ctenophora is hermaphroditic. However, both share the same mode of development, where the fertilized egg becomes a larva and undergoes metamorphosis to become an adult.

It is important to note that though their reproductive systems may differ, both Coelenterata and Ctenophora are capable of regenerating lost body parts or even the entire body, a unique characteristic that sets them apart from other phyla.


While Coelenterata and Ctenophora share similarities in some of their physical features, their reproductive differences further divide the two phyla. Coelenterata can reproduce both sexually and asexually, while Ctenophora can only reproduce sexually and is hermaphroditic. Nonetheless, both phyla share the remarkable ability for regeneration, which adds to the uniqueness and complexity of these marine organisms.

Phylum Reproductive Strategies Mode of Development
Coelenterata Asexual and sexual reproduction Planula larva settles on surface to form a new colony
Ctenophora Sexual reproduction only and hermaphroditic Cydippid larvae undergo metamorphosis to become an adult

The table above summarizes the reproductive differences between Coelenterata and Ctenophora.

Ecological Differences

Coelenterata and Ctenophora share many similarities in their ecological roles, but there are also significant differences between them. The diversity of habitats that these two phyla inhabit is substantial. Coelenterates are usually found in marine environments, while Ctenophores are found in almost every ocean in the world.

  • Coelenterata mostly live in shallow water environments, where they form large, coral-like structures called reefs.
  • Ctenophora, on the other hand, can be found in a wide range of water depths, from the surface to over 4,500 meters in the depths of the ocean.
  • Coelenterates are often associated with symbiotic relationships with other marine organisms such as fish, crabs, and shrimp.
  • Ctenophores, however, are more commonly found in the open ocean where their jelly-like body allows them to move rapidly, making them important predators in marine food webs.
  • Coelenterates are also important in providing shelter and food for other marine organisms, including fish and invertebrates.

Ctenophores, on the other hand, are primary consumers that feed on small planktonic organisms, such as zooplankton and krill. They also play an important role in recycling nutrients in marine environments, as their excretions are rich in nutrients that are important for the growth of phytoplankton.

Overall, while Coelenterata and Ctenophora may look similar at first glance, they have distinct differences in their ecological roles. These differences make them both important players in shaping the ecology of marine environments, each contributing in a unique way to the interconnected web of life that exists in the world’s oceans.

Evolutionary Relationships

The phylum Cnidaria, which includes coelenterates, and the phylum Ctenophora, which includes comb jellies, have a few similarities in terms of their developmental processes and morphologies. However, based on molecular and morphological evidence, they are distinct phyla. Molecular and embryological analyses have shown that coelenterates and comb jellies are sister groups, indicating that they have a common ancestor. The similarities between the two phyla were once believed to represent their evolutionary relationship, but further studies have found that these similarities may be homoplasious, meaning they evolved independently.

Key Differences Between Coelenterata and Ctenophora

  • Coelenterates have a single body opening that serves as both a mouth and an anus, whereas ctenophores have separate openings for each.
  • The body of coelenterates is composed of mesoglea, a jelly-like substance that is a combination of living and non-living matter, while the body of ctenophores is made up of true cells and is more cellular in nature.
  • Coelenterates have tentacles that contain specialized stinging cells called cnidocytes, which they use for feeding, defense and capturing prey, while ctenophores have sticky colloblast cells on their tentacles for capturing prey.
  • Ctenophores have an additional external layer of cilia, which they use for locomotion and self-propulsion, whereas coelenterates use their tentacles to move or drift.

Molecular Analysis of Evolutionary Relationships

Recent molecular studies have confirmed that the phylum Ctenophora is distinct and has its own unique evolutionary history. According to these studies, comb jellies diverged from coelenterates more than 550 million years ago, and they share a common ancestor with the other animal phyla. This indicates that ctenophores are not closely related to cnidarians and are instead derived from a separate lineage of early animal evolution.

Morphological Analysis of Evolutionary Relationships

Morphological analyses have shown that the morphological similarities between these two groups may be due to parallel or convergent evolution. For example, both groups have evolved traits like radial symmetry, tentacles, and a certain type of developmental morphology independently, which has led to their similarities. Morphological analyses have also shown that the distinct nature of these phyla is reflected in their embryonic development, where ctenophores differ greatly in their ability to perform regulatory functions during embryonic development.

Features Coelenterata Ctenophora
Body Symmetry Radial Symmetry Radial Symmetry
Number of Tissue Layers 2 2
Type of Body Cavity Acoelomate Diploblastic, gastrovascular cavity with external aids
Type of Digestive System Incomplete Digestive System Complete Digestive System
Type of Locomotion Medusa Flap, Passive Drift Swimming using cilia

Overall, both coelenterates and ctenophores have unique traits that distinguish them from each other and other animal phyla. The molecular and morphological evidence supports the idea that they are distinct phyla with their own evolving histories.

Economic Significance

The economic importance of coelenterata and ctenophora lies mostly in their negative impact on human activities. Both of these groups contain species that can be harmful to humans and their socioeconomic activities such as fishing and tourism. Below are some examples of their economic significance:

  • Some species of coelenterata, particularly jellyfish, are known to harm fisheries by clogging up and damaging fishing nets and gear. They also compete with fish for food, contributing to the decline of fish populations.
  • The venomous tentacles of some jellyfish can cause painful stings and reactions in humans, leading to medical expenses and lost productivity due to time off work.
  • Ctenophores, such as the Mnemiopsis Leidyi, have caused substantial damages to the Black Sea fisheries resulting in economic losses of up to $350 million annually. Fishermen had to adapt to the dramatic changes with catching different species and established a new market.
  • During the summer months, the waters off some coasts become inundated with harmful algal blooms (HABs) that contain coelenterates, which are toxic to humans and marine life. These HABs cause a loss of tourism in affected areas, and those who still choose to visit must avoid seafood and other activities that could put them at risk of exposure.

In addition to the negative impacts on human activities, coelenterata and ctenophora are also vital components of marine ecosystems and contribute to the planet’s biodiversity. Despite their negative economic significance, they are fascinating organisms with intricate life cycles, complex behavior, and unusual adaptations that offer a window into the wonders of the natural world.

What is the Difference Between Coelenterata and Ctenophora?

Q: What are coelenterata and ctenophora?
A: Coelenterata and ctenophora are two distinct phyla of aquatic animals that are classified based on their morphology, anatomy and behavior.

Q: What are the main differences between coelenterata and ctenophora?
A: The main differences between coelenterata and ctenophora are their body structure, the presence or absence of tentacles, the mode of reproduction, and the type of habitat they live in.

Q: Do both coelenterata and ctenophora have stinging cells?
A: Yes, both coelenterata and ctenophora have specialized cells called cnidocytes that are used for capturing prey and self-defense. However, the type of stinging cells and their arrangement varies between the two phyla.

Q: Are coelenterata and ctenophora closely related?
A: No, coelenterata and ctenophora are not closely related as they belong to separate branches of the animal kingdom. Coelenterata consists of jellyfish, corals, and anemones while ctenophora includes comb jellies.

Q: Where can I find coelenterata and ctenophora?
A: Coelenterata and ctenophora are found in marine environments around the world, from shallow rocky shores to the deep sea.

Closing Thoughts

So, that’s the difference between coelenterata and ctenophora. Understanding these differences can help you appreciate the vast diversity of life found in our oceans. Thanks for reading and we hope to see you again soon for more exciting marine biology topics.

Search Here