Echinoderms also have a spacious coelom (an open, fluid-filled body cavity lined with tissue), large gonads, and (usually) a complete gut.
abdominal cavity
Protists do not have a body cavity.
Pisces or fish have true internal body cavity.
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legs.
what aver
like a starfishes....
Echinoderms are a phylum with usually 5 fold symmetry, spines and calcium carbonate plates.
The body cavity of a frog is much larger in ratio to its body than a man's body cavity is. A frog's body cavity is also much more condensed than a man's.
it is usually with 5 arms
thoracic cavity