Home > Organisms > Animals > Invertebrates Terms and Definitions
Invertebrates
| Definition: |
Animals that have no spinal column. |
| Notes: |
avoid: too general; prefer specific classes, orders, families & genera; IM; qualif permitted but use /embryol & /parasitol with caution |
| Also Called: |
Brachiopoda,Mesozoa |
Invertebrates Categories.
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Annelida - A phylum of metazoan invertebrates comprising the segmented worms, and including marine annelids (POLYCHAETA), freshwater annelids, earthworms (OLIGOCHAETA), and LEECHES. Only the leeches are of medical interest. (Dorland, 27th ed) |
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Arthropods - Members of the phylum Arthropoda of the animal kingdom, composed of organisms having a hard, jointed exoskeleton and paired jointed legs, and including among other classes, the ARACHNIDA and INSECTS, many species of which are important medically as parasites or as vectors of organisms capable of causing disease in man. (Dorland, 27th ed) |
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Bryozoa - A phylum of small sessile aquatic animals living as small tufted colonies. Some appear like hydroids or corals, but their internal structure is more advanced. Most bryozoans are matlike, forming thin encrustations on rocks, shells, or kelp. (Storer & Stebbins, General Zoology, 6th ed, p443) |
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Cnidaria - A phylum of radially symmetrical invertebrates characterized by possession of stinging cells called nematocysts. It includes the classes ANTHOZOA; CUBOZOA; HYDROZOA, and SCYPHOZOA. Members carry CNIDARIAN VENOMS. |
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Ctenophora - Phylum of marine colenterates characterized by eight comb rows of fused cilia on the body surface. In contrast to CNIDARIA they lack stinging cells, but they are voracious predators and possess sticky cells (colloblasts) for capturing prey. Most species are transparent and many exhibit BIOLUMINESCENCE. |
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Echinodermata - A phylum of the most familiar marine invertebrates. Its class Stelleroidea contains two subclasses, the Asteroidea (the STARFISH or sea stars) and the Ophiuroidea (the brittle stars, also called basket stars and serpent stars). There are 1500 described species of STARFISH found throughout the world. The second class, Echinoidea, contains about 950 species of SEA URCHINS, heart urchins, and sand dollars. A third class, Holothuroidea, comprises about 900 echinoderms known as SEA CUCUMBERS. Echinoderms are used extensively in biological research. (From Barnes, Invertebrate Zoology, 5th ed, pp773-826) |
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Helminths - Commonly known as parasitic worms, this group includes the ACANTHOCEPHALA; NEMATODA; and PLATYHELMINTHS. Some authors consider certain species of LEECHES that can become temporarily parasitic as helminths. |
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Mollusca - A phylum of the kingdom Metazoa. Mollusca have soft, unsegmented bodies with an anterior head, a dorsal visceral mass, and a ventral foot. Most are encased in a protective calcareous shell. It includes the classes Gastropoda, Bivalvia, Cephalopoda, Aplacophora, Scaphopoda, Polyplacophora, and Monoplacophora. |
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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. |
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Plankton - Community of tiny aquatic organisms, both PLANTS and ANIMALS, that are either free-floating or suspended in the water, with little or no power of locomotion. They are divided into PHYTOPLANKTON and ZOOPLANKTON. |
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Porifera - The phylum of sponges, the most primitive of multicellular animals. Their body is perforated with many pores to admit water, through which food is strained. All sponges are sessile and exhibit little detectable movement. Most are hermaphroditic. They are probably an early evolutionary side branch that gave rise to no other group of animals. Except for about 150 freshwater species, sponges are marine animals. They are a source of alkaloids, sterols and other natural products useful in medicine and biological research. (Dorland, 27th ed; from Barnes, Invertebrate Zoology, 5th ed, p71) |
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Protozoa - A subkingdom consisting of unicellular organisms that are the simplest in the animal kingdom. Most are free living. They range in size from submicroscopic to macroscopic. Protozoa are divided into seven phyla: SARCOMASTIGOPHORA; Labyrinthomorpha, APICOMPLEXA; MICROSPORA; Ascetospora, Myxozoa, and CILIOPHORA. |
Invertebrates Definitions and Terms
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