Phylum Ctenophora | Zoology Optional Notes for UPSC PDF Download

Phylum Ctenophora

•  Ctenophores are marine animals that resemble jellyfish but belong to a different group called Phylum Ctenophora. 
•  Unlike jellyfish, which are part of the Phylum Cnidaria, ctenophores have unique characteristics that set them apart. 
•  These creatures are not as well-known as many other animals in the ocean, but they are fascinating in their own right. 

•  Ctenophores have a soft body and are free-swimming, which allows them to move through the water with ease. 
•  They exhibit biradial symmetry, meaning their body can be divided into similar halves in multiple ways, which is different from the more common radial symmetry seen in many marine animals. 

•  One of the key features of ctenophores is their comb-like ciliary plates, which they use for movement. These plates are made up of tiny hair-like structures (cilia) that beat in a coordinated manner, propelling the ctenophore through the water. 

•  Unlike jellyfish, ctenophores do not have nematocytes, which are specialized stinging cells found in many cnidarians. This absence is one of the distinguishing features of ctenophores. 

•  Ctenophores are commonly known as sea walnuts or comb jellies. These names reflect their appearance and the way they move through the water. 
•  Members of Phylum Ctenophora are exclusively aquatic and can be found living on the surface of the ocean or at its bottom. They are adapted to life in various marine environments, from the open ocean to the seafloor. 

Ctenophores are a unique group of marine animals that, while resembling jellyfish, have distinct characteristics that place them in their own phylum.  Their soft bodies, biradial symmetry, and comb-like ciliary plates for movement make them fascinating subjects of study in the animal kingdom. 

Definition of Ctenophora Phylum

• Ctenophora, commonly known as Comb Jellies, comprises bi-radially symmetrical marine invertebrates. These creatures are often transparent and colorful. Most species within this phylum are found in marine habitats, as they do not inhabit freshwater environments. Examples of animals in this phylum include the Sea Walnut, Sea Gooseberries, and Venus Girdle.

Classification of Ctenophora

• Class-1 Tentaculate. This class includes organisms that possess tentacles.
• Class-2 Nuda. This class comprises organisms that lack tentacles.

Characteristics of Ctenophora

• Habitat: Ctenophora species are exclusively found in the sea.
• Behavior: These animals are solitary and capable of free swimming.
• Body Structure: They have a diploblastic acoelomate body structure. Their bodies are translucent, gelatinous, soft, and segmented, with two long, solid, retractable tentacles.
• Symmetry: Ctenophora species exhibit bi-radial symmetry.
• Tissue Organization: These invertebrates have tissue-level organization.
• Locomotion: Movement is facilitated by eight rows of cilia, known as comb rows, which aid in propulsion.
• Reproduction: Ctenophora reproduce sexually and are hermaphroditic. They undergo external fertilization and have an indirect developmental process.
• Digestive System: They possess both an external and an intracellular digestive system.
• Sensory Organ: The statocyst, an aboral sensory organ, helps with balance.
• Respiration and Excretion: Ctenophora lack specialized organs for respiration and excretion; these functions are carried out by the body surface.
• Size and Shape: The size ranges from microscopic spheroids (0.04 inch) to lengthy ribbon-like forms (4.9 feet). Ctenophora are generally lobe-shaped animals.

• Aesthetic Appeal: Ctenophora contribute to beautiful underwater scenes, making them popular among divers and snorkelers.
• Genetic Research: The bioluminescent properties of Ctenophora are used as genetic markers in scientific studies. Researchers create glowing animals like cats and mice to study gene activation and the effects of genetic modifications.

• Plankton Control: Ctenophora reproduce quickly and are effective predators, helping to regulate plankton populations. 
• Adaptability: When food is scarce, Ctenophora can shrink and survive on stored energy. They can also adapt to higher temperatures, making them resilient to climate change.