Modifiers matching echinoderm:

• mobile,
• sessile,

Simple categories matching sessile:

• protozoan,
• invertebrate,
• organism,
• predator,
• polyp,
• benthos,
• creature,
• mollusc,
• echinoderm,
• cnidarian,
• prey,
• ciliate,
• fauna,
• resource,
• animal,
• bivalve,
• shellfish,
• form,
• coelenterate,
• taxon,