Marine invertebrates » tags

Marine invertebrates are all multicellular 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.

As on land and in the air, invertebrates make up a great majority of all macroscopic life, as the vertebrates makes up a subphylum of one of over 30 known animal phyla, making the term almost meaningless for taxonomic purpose. Invertebrate sea life includes the following groups, some of which are phyla:

Acoela, among the most primitive bilateral animals;
Annelida, (polychaetes and sea leeches);
Brachiopoda, marine animals that have hard "valves" (shells) on the upper and lower surfaces ;
Bryozoa, also known as moss animals or sea mats;
Chaetognatha, commonly known as arrow worms, are a phylum of predatory marine worms that are a major component of plankton;
Cephalochordata represented in the modern oceans by the lancelets (also known as Amphioxus);
Cnidaria, such as jellyfish, sea anemones, and corals;
Crustacea, including lobsters, crabs, shrimp, crayfish, barnacles, hermit crabs, mantis shrimps, and copepods;
Ctenophora, also known as comb jellies, the largest animals that swim by means of cilia;
Echinodermata, including sea stars, brittle stars, sea urchins, sand dollars, sea cucumbers, crinoids, and sea daisies;
Echiura, also known as spoon worms;
Gnathostomulids, slender to thread-like worms, with a transparent body that inhabit sand and mud beneath shallow coastal waters;
Gastrotricha, often called hairy backs, found mostly interstitially in between sediment particles;
Hemichordata, includes acorn worms, solitary worm-shaped organisms;
Kamptozoa, goblet-shaped sessile aquatic animals, with relatively long stalks and a "crown" of solid tentacles, also called Entoprocta;
Kinorhyncha, segmented, limbless animals, widespread in mud or sand at all depths, also called mud dragons;
Loricifera, very small to microscopic marine sediment-dwelling animals only discovered in 1983;
Merostomata; also known as horseshoe crabs;
Mollusca, including shellfish, squid, octopus, whelks, Nautilus, cuttlefish, nudibranchs, scallops, sea snails, Aplacophora, Caudofoveata, Monoplacophora, Polyplacophora, and Scaphopoda;

Myzostomida, a taxonomic group of small marine worms which are parasitic on crinoids or "sea lilies";
Nemertinea, also known as "ribbon worms" or "proboscis worms";
Orthonectida, a small phylum of poorly known parasites of marine invertebrates that are among the simplest of multi-cellular organisms;
Phoronida, a phylum of marine animals that filter-feed with a lophophore (a "crown" of tentacles), and build upright tubes of chitin to support and protect their soft bodies;
Placozoa, small, flattened, multicellular animals around 1 millimetre across and the simplest in structure. They have no regular outline, although the lower surface is somewhat concave, and the upper surface is always flattened;
Porifera (sponges), multicellular organisms that have bodies full of pores and channels allowing water to circulate through them;
Priapulida, or penis worms, are a phylum of marine worms that live marine mud. They are named for their extensible spiny proboscis, which, in some species, may have a shape like that of a human penis;
Pycnogonida, also called sea spiders, are unrelated to spiders, or even to arachnids which they resemble;
Sipunculida, also called peanut worms, is a group containing 144–320 species (estimates vary) of bilaterally symmetrical, unsegmented marine worms;
Tunicata, also known as sea squirts or sea pork, are filter feeders attached to rocks or similarly suitable surfaces on the ocean floor;
Some flatworms of the classes Turbellaria and Monogenea;
Xenoturbella, a genus of bilaterian animals that contains only two marine worm-like species;
Xiphosura, includes a large number of extinct lineages and only four recent species in the family Limulidae, which include the horseshoe crabs.