Modifiers matching echinoderm:

• mobile,
• sessile,

Simple categories matching sessile:

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