Invertebrates

A tract of corals growing on a massive, wave-resistant structure and associated sediments, substantially built by skeletons of successive generations of corals and other calcareous reef-biota.

[NALT: Merostomata] [AGROVOC]

Elongated, cylindrical, unsegmented worm; includes a number of plant and animal parasites. 

Invertebrate organisms that live on or in another organism (the host), and benefit at the expense of the other. Traditionally excluded from definition of parasites are pathogenic bacteria; fungi; viruses; and plants; though they may live parasitically. [NALT]

An organism that lives at the expense of another (host) during some portion of its life cycle. Usually a parasite does not kill its host. [AGROVOC]

Shellfish is a colloquial and fisheries term for exoskeleton-bearing aquatic invertebrates used as food, including various species of molluscs, crustaceans, and echinoderms.