Phylum Ctenophora
டெனோஃபோரா தொகுதி
Do not confuse Ctenophora with Cnidaria. While both are diploblastic and radially symmetrical, Ctenophores lack the stinging cnidoblasts that define the latter. This distinction is a frequent source of negative marks in the Animal Kingdom section.
The idea
Ctenophores, commonly known as comb jellies, are exclusively marine organisms. They exhibit radial symmetry and are diploblastic with tissue-level organization. Their primary mode of locomotion is through eight external rows of ciliated comb plates. Notably, they exhibit bioluminescence, the property of a living organism to emit light.
Why it matters
Bioluminescence and ciliated plates are specialized adaptations for survival and movement in the deep-sea marine environment.
NEET lens
NEET focuses on the 'eight rows of ciliated comb plates' and the absence of cnidoblasts. Remember that they are hermaphrodites and reproduce only by sexual means. Do not mistake them for Cnidarians; memorize the unique feature of bioluminescence as a diagnostic trait for this phylum.
Clinical significance
Ctenophores are critical indicators of marine ecosystem health. Their population spikes often signal an imbalance in plankton levels, which directly impacts the food chain stability of marine vertebrates. They do not infect humans, but their presence regulates the biomass of the ocean.
Introduction
Ctenophora (comb jellies) are marine, diploblastic animals with comb plates (ctenes) for locomotion. They are NOT true jellyfish.
Core concept
Features: diploblastic, radially symmetrical, no nematocysts (unlike Cnidaria), have colloblasts for prey capture, bioluminescent. Example: Pleurobrachia. Move using 8 rows of cilia (ctenes).
Go deeper
Ctenophores are considered the earliest branching animal phylum by some researchers. They have a primitive nervous system (nerve net) but no true brain.
From Class 10
You've studied different animal phyla. Ctenophora is a small, often overlooked phylum of marine invertebrates.