Water containing no significant amounts of salts, such as water from RIVERS and LAKES.

A clear, odorless, tasteless liquid that is essential for most animal and plant life and is an excellent solvent for many substances. The chemical formula is hydrogen oxide (H2O). (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)

Paired respiratory organs of fishes and some amphibians that are analogous to lungs. They are richly supplied with blood vessels by which oxygen and carbon dioxide are exchanged directly with the environment.

The salinated water of OCEANS AND SEAS that provides habitat for marine organisms.

Means or process of supplying water (as for a community) usually including reservoirs, tunnels, and pipelines and often the watershed from which the water is ultimately drawn. (Webster, 3d ed)

A freshwater fish used as an experimental organism and for food. This genus of the family Cichlidae (CICHLIDS) inhabits Central and South America (one species extends north into Texas), West Indies, Africa, Madagascar, Syria, and coastal India.

The presence of bacteria, viruses, and fungi in water. This term is not restricted to pathogenic organisms.

A group of cold-blooded, aquatic vertebrates having gills, fins, a cartilaginous or bony endoskeleton, and elongated bodies covered with scales.

Anguilla is not a term with a widely accepted medical definition; however, it is the scientific name for the freshwater eel species, and if used in a medical context, it may refer to a rare condition called Anguillula nephria, which is an intestinal infection caused by a roundworm.

Degree of saltiness, which is largely the OSMOLAR CONCENTRATION of SODIUM CHLORIDE plus any other SALTS present. It is an ecological factor of considerable importance, influencing the types of organisms that live in an ENVIRONMENT.

Environments or habitats at the interface between truly terrestrial ecosystems and truly aquatic systems making them different from each yet highly dependent on both. Adaptations to low soil oxygen characterize many wetland species.

Chemical compounds which pollute the water of rivers, streams, lakes, the sea, reservoirs, or other bodies of water.

Large natural streams of FRESH WATER formed by converging tributaries and which empty into a body of water (lake or ocean).

A family of anadromous fish comprising SALMON; TROUT; whitefish; and graylings. They are the most important food and game fishes. Their habitat is the northern Atlantic and Pacific, both marine and inland, and the Great Lakes. (Nelson: Fishes of the World, 1976, p97)

A rating of a body of water based on measurable physical, chemical, and biological characteristics.

Common name for an order (Anguilliformes) of voracious, elongate, snakelike teleost fishes.

The balance of fluid in the BODY FLUID COMPARTMENTS; total BODY WATER; BLOOD VOLUME; EXTRACELLULAR SPACE; INTRACELLULAR SPACE, maintained by processes in the body that regulate the intake and excretion of WATER and ELECTROLYTES, particularly SODIUM and POTASSIUM.

The relationships of groups of organisms as reflected by their genetic makeup.

Infections caused by infestation with worms of the class Trematoda.

Various fish of the family SALMONIDAE, usually smaller than salmon. They are mostly restricted to cool clear freshwater. Some are anadromous. They are highly regarded for their handsome colors, rich well-flavored flesh, and gameness as an angling fish. The genera Salvelinus, Salmo, and ONCORHYNCHUS have been introduced virtually throughout the world.

A functional system which includes the organisms of a natural community together with their environment. (McGraw Hill Dictionary of Scientific and Technical Terms, 4th ed)

A family of extremely venomous snakes, comprising coral snakes, cobras, mambas, kraits, and sea snakes. They are widely distributed, being found in the southern United States, South America, Africa, southern Asia, Australia, and the Pacific Islands. The elapids include three subfamilies: Elapinae, Hydrophiinae, and Lauticaudinae. Like the viperids, they have venom fangs in the front part of the upper jaw. The mambas of Africa are the most dangerous of all snakes by virtue of their size, speed, and highly toxic venom. (Goin, Goin, and Zug, Introduction to Herpetology, 3d ed, p329-33)

Class of parasitic flukes consisting of three subclasses, Monogenea, Aspidogastrea, and Digenea. The digenetic trematodes are the only ones found in man. They are endoparasites and require two hosts to complete their life cycle.

Constituent of 30S subunit prokaryotic ribosomes containing 1600 nucleotides and 21 proteins. 16S rRNA is involved in initiation of polypeptide synthesis.

A large subphylum of mostly marine ARTHROPODS containing over 42,000 species. They include familiar arthropods such as lobsters (NEPHROPIDAE), crabs (BRACHYURA), shrimp (PENAEIDAE), and barnacles (THORACICA).

Fluids composed mainly of water found within the body.

A subclass of GLYCOSPHINGOLIPIDS containing large polar heads made up of several sugar units. One or more of their terminal sugar units are bound to a negatively charged molecule at pH 7. Members of this class include: GANGLIOSIDES, uronoglycosphingolipids, SULFOGLYCOSPHINGOLIPIDS, phosphoglycosphingolipids, and phosphonoglycosphingolipids.

Diseases of freshwater, marine, hatchery or aquarium fish. This term includes diseases of both teleosts (true fish) and elasmobranchs (sharks, rays and skates).

Contamination of bodies of water (such as LAKES; RIVERS; SEAS; and GROUNDWATER.)

A climate which is typical of equatorial and tropical regions, i.e., one with continually high temperatures with considerable precipitation, at least during part of the year. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)

A family of CRUSTACEA, order DECAPODA, comprising the palaemonid shrimp. Genera include Macrobrachium, Palaemon, and Palaemonetes. Palaemonidae osmoregulate by means of gills.

Any of several processes in which undesirable impurities in water are removed or neutralized; for example, chlorination, filtration, primary treatment, ion exchange, and distillation. It includes treatment of WASTE WATER to provide potable and hygienic water in a controlled or closed environment as well as provision of public drinking water supplies.

A ubiquitous sodium salt that is commonly used to season food.

Substances or organisms which pollute the water or bodies of water. Use for water pollutants in general or those for which there is no specific heading.

The non-genetic biological changes of an organism in response to challenges in its ENVIRONMENT.

A multistage process that includes cloning, physical mapping, subcloning, determination of the DNA SEQUENCE, and information analysis.

A state in northeastern Australia. Its capital is Brisbane. Its coast was first visited by Captain Cook in 1770 and its first settlement (penal) was located on Moreton Bay in 1824. The name Cooksland was first proposed but honor to Queen Victoria prevailed. (From Webster's New Geographical Dictionary, 1988, p996 & Room, Brewer's Dictionary of Names, 1992, p441)

DNA sequences encoding RIBOSOMAL RNA and the segments of DNA separating the individual ribosomal RNA genes, referred to as RIBOSOMAL SPACER DNA.

A phylum of photosynthetic EUKARYOTA bearing double membrane-bound plastids containing chlorophyll a and b. They comprise the classical green algae, and represent over 7000 species that live in a variety of primarily aquatic habitats. Only about ten percent are marine species, most live in freshwater.

Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.

The variety of all native living organisms and their various forms and interrelationships.

The study of life and ECOLOGIC SYSTEMS in bodies of FRESHWATER.

The restriction of a characteristic behavior, anatomical structure or physical system, such as immune response; metabolic response, or gene or gene variant to the members of one species. It refers to that property which differentiates one species from another but it is also used for phylogenetic levels higher or lower than the species.

The protection, preservation, restoration, and rational use of all resources in the total environment.

One of the three domains of life (the others being Eukarya and ARCHAEA), also called Eubacteria. They are unicellular prokaryotic microorganisms which generally possess rigid cell walls, multiply by cell division, and exhibit three principal forms: round or coccal, rodlike or bacillary, and spiral or spirochetal. Bacteria can be classified by their response to OXYGEN: aerobic, anaerobic, or facultatively anaerobic; by the mode by which they obtain their energy: chemotrophy (via chemical reaction) or PHOTOTROPHY (via light reaction); for chemotrophs by their source of chemical energy: CHEMOLITHOTROPHY (from inorganic compounds) or chemoorganotrophy (from organic compounds); and by their source for CARBON; NITROGEN; etc.; HETEROTROPHY (from organic sources) or AUTOTROPHY (from CARBON DIOXIDE). They can also be classified by whether or not they stain (based on the structure of their CELL WALLS) with CRYSTAL VIOLET dye: gram-negative or gram-positive.

Marine, freshwater, or terrestrial mollusks of the class Gastropoda. Most have an enclosing spiral shell, and several genera harbor parasites pathogenic to man.

Community of tiny aquatic PLANTS and ANIMALS, and photosynthetic BACTERIA, that are either free-floating or suspended in the water, with little or no power of locomotion. They are divided into PHYTOPLANKTON and ZOOPLANKTON.

Deoxyribonucleic acid that makes up the genetic material of bacteria.

Genes, found in both prokaryotes and eukaryotes, which are transcribed to produce the RNA which is incorporated into RIBOSOMES. Prokaryotic rRNA genes are usually found in OPERONS dispersed throughout the GENOME, whereas eukaryotic rRNA genes are clustered, multicistronic transcriptional units.

Inorganic compounds derived from hydrochloric acid that contain the Cl- ion.

The flow of water in enviromental bodies of water such as rivers, oceans, water supplies, aquariums, etc. It includes currents, tides, and waves.

The relative amounts of the PURINES and PYRIMIDINES in a nucleic acid.

Wormlike or grublike stage, following the egg in the life cycle of insects, worms, and other metamorphosing animals.

Former kingdom, located on Korea Peninsula between Sea of Japan and Yellow Sea on east coast of Asia. In 1948, the kingdom ceased and two independent countries were formed, divided by the 38th parallel.

A member of the alkali group of metals. It has the atomic symbol Na, atomic number 11, and atomic weight 23.

Organic, monobasic acids derived from hydrocarbons by the equivalent of oxidation of a methyl group to an alcohol, aldehyde, and then acid. Fatty acids are saturated and unsaturated (FATTY ACIDS, UNSATURATED). (Grant & Hackh's Chemical Dictionary, 5th ed)

A mass of organic or inorganic solid fragmented material, or the solid fragment itself, that comes from the weathering of rock and is carried by, suspended in, or dropped by air, water, or ice. It refers also to a mass that is accumulated by any other natural agent and that forms in layers on the earth's surface, such as sand, gravel, silt, mud, fill, or loess. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed, p1689)

Common name of the order Siluriformes. This order contains many families and over 2,000 species, including venomous species. Heteropneustes and Plotosus genera have dangerous stings and are aggressive. Most species are passive stingers.

A subclass of cartilaginous fish comprising the SHARKS; rays; skates (SKATES (FISH);), and sawfish. Elasmobranchs are typically predaceous, relying more on smell (the olfactory capsules are relatively large) than sight (the eyes are relatively small) for obtaining their food.

The common name for all members of the Rajidae family. Skates and rays are members of the same order (Rajiformes). Skates have weak electric organs.

Cultivation of natural faunal resources of water. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)

A form-genus of CYANOBACTERIA in the order Chroococcales. Many species are planktonic and possess gas vacuoles.

A class in the phylum MOLLUSCA comprised of mussels; clams; OYSTERS; COCKLES; and SCALLOPS. They are characterized by a bilaterally symmetrical hinged shell and a muscular foot used for burrowing and anchoring.

The concentration of osmotically active particles in solution expressed in terms of osmoles of solute per liter of solution. Osmolality is expressed in terms of osmoles of solute per kilogram of solvent.

The enrichment of a terrestrial or aquatic ECOSYSTEM by the addition of nutrients, especially nitrogen and phosphorus, that results in a superabundant growth of plants, ALGAE, or other primary producers. It can be a natural process or result from human activity such as agriculture runoff or sewage pollution. In aquatic ecosystems, an increase in the algae population is termed an algal bloom.

Elements of limited time intervals, contributing to particular results or situations.

Procedures for identifying types and strains of bacteria. The most frequently employed typing systems are BACTERIOPHAGE TYPING and SEROTYPING as well as bacteriocin typing and biotyping.

Free-floating minute organisms that are photosynthetic. The term is non-taxonomic and refers to a lifestyle (energy utilization and motility), rather than a particular type of organism. Most, but not all, are unicellular algae. Important groups include DIATOMS; DINOFLAGELLATES; CYANOBACTERIA; CHLOROPHYTA; HAPTOPHYTA; CRYPTOMONADS; and silicoflagellates.

A family of freshwater fish comprising the minnows or CARPS.

A family of gram negative, aerobic, non-sporeforming, rod-shaped bacteria.

The withholding of water in a structured experimental situation.

A large stout-bodied, sometimes anadromous, TROUT found in still and flowing waters of the Pacific coast from southern California to Alaska. It has a greenish back, a whitish belly, and pink, red, or lavender stripes on the sides, with usually a sprinkling of black dots. It is highly regarded as a sport and food fish. Its former name was Salmo gairdneri. The sea-run rainbow trouts are often called steelheads. Redband trouts refer to interior populations of rainbows.

A superfamily of various freshwater CRUSTACEA, in the infraorder Astacidea, comprising the crayfish. Common genera include Astacus and Procambarus. Crayfish resemble lobsters, but are usually much smaller.

A class in the phylum PROTEOBACTERIA comprised of chemoheterotrophs and chemoautotrophs which derive nutrients from decomposition of organic material.

Class of BACTERIA with diverse morphological properties. Strains of Actinobacteria show greater than 80% 16S rDNA/rRNA sequence similarity among each other and also the presence of certain signature nucleotides. (Stackebrandt E. et al, Int. J. Syst. Bacteriol. (1997) 47:479-491)

Adaptation to a new environment or to a change in the old.

A family of microscopic freshwater EUKARYOTA, commonly known as golden algae. They share many features with the BROWN ALGAE but are planktonic rather than benthic. Though most are photosynthetic, they are not considered truly autotrophic since they can become facultatively heterotrophic in the absence of adequate light. In this state they can feed on BACTERIA or DIATOMS.

A phylum of oxygenic photosynthetic bacteria comprised of unicellular to multicellular bacteria possessing CHLOROPHYLL a and carrying out oxygenic PHOTOSYNTHESIS. Cyanobacteria are the only known organisms capable of fixing both CARBON DIOXIDE (in the presence of light) and NITROGEN. Cell morphology can include nitrogen-fixing heterocysts and/or resting cells called akinetes. Formerly called blue-green algae, cyanobacteria were traditionally treated as ALGAE.

The most diversified of all fish orders and the largest vertebrate order. It includes many of the commonly known fish such as porgies, croakers, sunfishes, dolphin fish, mackerels, TUNA, etc.

Encysted cercaria which house the intermediate stages of trematode parasites in tissues of an intermediate host.

The property of objects that determines the direction of heat flow when they are placed in direct thermal contact. The temperature is the energy of microscopic motions (vibrational and translational) of the particles of atoms.

One of the three domains of life (the others being BACTERIA and ARCHAEA), also called Eukarya. These are organisms whose cells are enclosed in membranes and possess a nucleus. They comprise almost all multicellular and many unicellular organisms, and are traditionally divided into groups (sometimes called kingdoms) including ANIMALS; PLANTS; FUNGI; and various algae and other taxa that were previously part of the old kingdom Protista.

The monitoring of the level of toxins, chemical pollutants, microbial contaminants, or other harmful substances in the environment (soil, air, and water), workplace, or in the bodies of people and animals present in that environment.

Group of fish under the superorder Acanthopterygii, separate from the PERCIFORMES, which includes swamp eels, mullets, sticklebacks, seahorses, spiny eels, rainbowfishes, and KILLIFISHES. The name is derived from the six taxa which comprise the group. (From http://www.nanfa.org/articles/Elassoma/elassoma.htm, 8/4/2000)

'Water softening' is a water treatment process that reduces the hardness of water by removing calcium, magnesium, and certain other metal cations (such as iron and manganese) through the use of ion-exchange resins or other methods like nanofiltration or reverse osmosis.

An order of mostly marine CRUSTACEA containing more than 5500 species in over 100 families. Like ISOPODA, the other large order in the superorder Peracarida, members are shrimp-like in appearance, have sessile compound eyes, and no carapace. But unlike Isopoda, they possess thoracic gills and their bodies are laterally compressed.

Cyclic heptapeptides found in MICROCYSTIS and other CYANOBACTERIA. Hepatotoxic and carcinogenic effects have been noted. They are sometimes called cyanotoxins, which should not be confused with chemicals containing a cyano group (CN) which are toxic.

The consumption of liquids.

A diverse genus of minute freshwater CRUSTACEA, of the suborder CLADOCERA. They are a major food source for both young and adult freshwater fish.

Contaminated water generated as a waste product of human activity.

A suborder of CRUSTACEA, order Diplostraca, comprising the water fleas. They are benthic filter feeders that consume PHYTOPLANKTON. The body is laterally compressed and enclosed in a bivalved carapace, from which the head extends.

A great expanse of continuous bodies of salt water which together cover more than 70 percent of the earth's surface. Seas may be partially or entirely enclosed by land, and are smaller than the five oceans (Atlantic, Pacific, Indian, Arctic, and Antarctic).

Family of small, surface-dwelling fish that inhabit fresh and brackish waters, and coastal marine areas.

Minute free-floating animal organisms which live in practically all natural waters.

The science dealing with the earth and its life, especially the description of land, sea, and air and the distribution of plant and animal life, including humanity and human industries with reference to the mutual relations of these elements. (From Webster, 3d ed)

An order of fresh water fish with 18 families and over 1600 species. The order includes CHARACINS, hatchetfish, piranhas, and TETRAS.

A colorless alkaline gas. It is formed in the body during decomposition of organic materials during a large number of metabolically important reactions. Note that the aqueous form of ammonia is referred to as AMMONIUM HYDROXIDE.

Divisions of the year according to some regularly recurrent phenomena usually astronomical or climatic. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)

##### I apologize, but the term "turtles" is not a recognized medical term or concept. It is commonly referred to as a group of reptiles with a shell, and does not have any direct relevance to medical definition.

The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.

The external elements and conditions which surround, influence, and affect the life and development of an organism or population.

A genus of dextrally coiled freshwater snails that includes some species of importance as intermediate hosts of parasitic flukes.

A family of freshwater mussels in the class BIVALVIA. They differ from ZEBRA MUSSELS in that they are larger and posses a larval stage called glochidia, which requires attachment to the GILLS or fins of particular species of FISHES.

Refuse liquid or waste matter carried off by sewers.

An algal bloom where the algae produce powerful toxins that can kill fish, birds, and mammals, and ultimately cause illness in humans. The harmful bloom can also cause oxygen depletion in the water due to the death and decomposition of non-toxic algae species.

The largest order of CRUSTACEA, comprising over 10,000 species. They are characterized by three pairs of thoracic appendages modified as maxillipeds, and five pairs of thoracic legs. The order includes the familiar shrimps, crayfish (ASTACOIDEA), true crabs (BRACHYURA), and lobsters (NEPHROPIDAE and PALINURIDAE), among others.

A process of separating particulate matter from a fluid, such as air or a liquid, by passing the fluid carrier through a medium that will not pass the particulates. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)

Organisms that live in water.

A phylum of bacteria comprised of three classes: Bacteroides, Flavobacteria, and Sphingobacteria.

Nonparasitic free-living flatworms of the class Turbellaria. The most common genera are Dugesia, formerly Planaria, which lives in water, and Bipalium, which lives on land. Geoplana occurs in South America and California.

A primitive form of digestive gland found in marine ARTHROPODS, that contains cells similar to those found in the mammalian liver (HEPATOCYTES), and the PANCREAS.

Preservation of cells, tissues, organs, or embryos by freezing. In histological preparations, cryopreservation or cryofixation is used to maintain the existing form, structure, and chemical composition of all the constituent elements of the specimens.

The sequence of transfers of matter and energy from organism to organism in the form of FOOD. Food chains intertwine locally into a food web because most organisms consume more than one type of animal or plant. PLANTS, which convert SOLAR ENERGY to food by PHOTOSYNTHESIS, are the primary food source. In a predator chain, a plant-eating animal is eaten by a larger animal. In a parasite chain, a smaller organism consumes part of a larger host and may itself be parasitized by smaller organisms. In a saprophytic chain, microorganisms live on dead organic matter.

An infraorder of chiefly marine, largely carnivorous CRUSTACEA, in the order DECAPODA, including the genera Cancer, Uca, and Callinectes.

A genus of planorbid freshwater snails, species of which are intermediate hosts of Schistosoma mansoni.

Infections with unicellular organisms formerly members of the subkingdom Protozoa. The infections may be experimental or veterinary.

An order of fish including smelts, galaxiids, and salamanderfish.

A phylum of acoelomate, bilaterally symmetrical flatworms, without a definite anus. It includes three classes: Cestoda, Turbellaria, and Trematoda.

Enumeration by direct count of viable, isolated bacterial, archaeal, or fungal CELLS or SPORES capable of growth on solid CULTURE MEDIA. The method is used routinely by environmental microbiologists for quantifying organisms in AIR; FOOD; and WATER; by clinicians for measuring patients' microbial load; and in antimicrobial drug testing.

A vegetative stage in the life cycle of sporozoan protozoa. It is characteristic of members of the phyla APICOMPLEXA and MICROSPORIDIA.

A class of porins that allow the passage of WATER and other small molecules across CELL MEMBRANES.