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Pacific sea nettles, Chrysaora fuscescens. Cnidaria (/ n ɪ ˈ d ɛər i ə, n aɪ-/ nih-DAIR-ee-ə, NY-) [4] is a phylum under kingdom Animalia containing over 11,000 species [5] of aquatic invertebrates found both in fresh water and marine environments (predominantly the latter), including jellyfish, hydroids, sea anemones, corals and some of the smallest marine parasites.
Animals are multicellular eukaryotes, [note 1] and are distinguished from plants, algae, and fungi by lacking cell walls. [1] Marine invertebrates are animals that inhabit a marine environment apart from the vertebrate members of the chordate phylum; invertebrates lack a vertebral column. Some have evolved a shell or a hard exoskeleton.
Many have fluid-filled, hydrostatic skeletons, like jellyfish or worms. Others have hard exoskeletons , outer shells like those of insects and crustaceans . The most familiar invertebrates include the Protozoa , Porifera , Coelenterata , Platyhelminthes , Nematoda , Annelida , Echinodermata , Mollusca and Arthropoda .
Coral reefs are some of the most biodiverse habitats on earth, supporting large numbers of species of corals, fish, molluscs, worms, arthropods, starfish, sea urchins, other invertebrates and algae. Because of the photosynthetic requirements of the corals, they are found in shallow waters, and many of these fringe land masses. [24]
The taxonomic term Bivalvia was first used by Linnaeus in the 10th edition of his Systema Naturae in 1758 to refer to animals having shells composed of two valves. [3] More recently, the class was known as Pelecypoda, meaning "axe-foot" (based on the shape of the foot of the animal when extended).
Specimens of the sea urchin Calocidaris micans found in the vicinity of the crinoid Endoxocrinus parrae, have been shown to contain large quantities of stem portions in their guts. These consist of articulated ossicles with soft tissue, whereas the local sediment contained only disarticulated ossicles without soft tissue.
Found living anchored in live coral colonies in nature. Each worm has two crowns, which come in a variety of different colors, and are spiraled in the shape of a Christmas tree. 5 cm (2.0 in) Cluster duster [1] Bispira brunnea: Yes: Moderate: This species grows in groups of up to 100 individual tube worms, living together in a single clump.
In forms having only a top shell, such as limpets, the foot acts as a sucker attaching the animal to a hard surface, and the vertical muscles clamp the shell down over it; in other molluscs, the vertical muscles pull the foot and other exposed soft parts into the shell. [19]