Modifiers matching echinoderm:

• sessile,
• mobile,

Simple categories matching sessile:

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