Results for “GH”

Mollusca

Large, highly diverse invertebrate phylum. Members are difficult to define but generally possess a soft, unsegmented body, and often a shell or shell-like structure secreted by a mantle. Includes all bivalves, cephalopods, and gastropods.

mound spring

Natural, isolated, relict artesian springs found in arid, outback Queensland and South Australia. Water stored in deep aquifers seeps to the surface through fault lines in the rock, and the sediments and salts within the spring water form elevated mounds as it evaporates. Most such springs support marginal plant growth that help stabilise the sediment and provide shelter for animals. In South Australia mound springs form an arc of about 400km along the south-western edge of the Great Artesian Basin, although many have disappeared in the last 100 years as a result of water extraction.

Used in 1 profile

nitrate reactor

Piece of aquarium equipment that can be thought of as an anaerobic filter. Provides a means by which large enough populations of anaerobic bacteria can be maintained so that nitrates are actively removed from the water in the form of nitrogen gas, a process normally facilitated by regular partial water changes. Also known as a nitrogen filter.

nitrates

Any salt or ester of nitric acid, and the end product of the portion of the nitrogen cycle taking place in most closed aquarium systems (the conversion of nitrates to nitrogen gas in natural systems is carried out by anaerobic microorganisms not normally present in sufficient numbers in aquaria, though this process can be induced by installation of a nitrate reactor). While nitrates are less toxic than ammonia or nitrites, they are still potentially harmful to fishes and other aquatic organisms if allowed to accumulate unchecked, and must therefore be diluted via regular water changes. Aquatic plants also help since they are able to metabolise nitrates to an extent.

Used in 20 profiles

Nitrobacter

Genus of bacteria previously thought to reduce nitrIte to nitrAte in an aquarium, but which does not occur, or occurs in negligible quantities, in aquaria.

nocturnal

Active at night.

Used in 72 profiles

ocular

Of or related to the eye or sense of sight.

Used in 82 profiles

oesophagus

Muscular tube through which food passes from mouth to stomach in vertebrates; the gullet. Also spelled 'esophagus'.

ortho-

Prefix meaning straight, upright, or vertical.

Used in 1 profile

paedomorphism

Phylogenetic state in which juvenile or larval characters are retained in and throughout the adult stage. May arise via neoteny or progenesis.

paired fins

The pectoral and pelvic/ventral fins, both of which occur in pairs and are analogous to the fore and hind limbs in higher animals.

Used in 58 profiles

parhypural

The most posterior hemal arch with an open canal through which the dorsal aorta passes.

peat

A compressed accumulation of partially-decomposed, chiefly vegetable matter typically found in certain marshes, bogs, and peat swamp forests throughout the world. It forms via breakdown of various plants and other organic materials in water when full decomposition is prevented due to localised acidic, anaerobic conditions. As a result of this somewhat specific nature the organisms inhabiting peaty environments are often stenotypic and found nowhere else. Peat can be used as a fuel when dried and thus has industrial importance in some countries. Also used in aquaria, especially in order to simulate blackwater habitats, either in pure, artificially-granulated or liquid extract form.

Used in 268 profiles

peat swamp forest

Type of tropical moist forest lying over a thick bed of acidic peat, over 60% of which occur in Indonesia and Malaysia. Typically contain water with very low pH (<4.0) that is stained brown due to the release of various organic compounds from the decaying peat and thus often referred to as blackwater swamps. Usually contain some permanent water but also flood seasonally. Highly biodiverse when in pristine condition, with many species found nowhere else on earth, though increasingly subjected to intensive drainage, burning and subsequent conversion to agriculture in recent decades.

Used in 89 profiles

pectoral-fin

Anterior, paired fin attached to the pectoral girdle of fishes, usually just behind the opercle and corresponding to the forelimbs of higher vertebrates. Assists in controlling direction of movement and swimming speed. Frequently abbreviated to 'P' or 'P1' in scientific papers.

Used in 508 profiles

pelvic fin

Either of the pair of fins, also known as pelvic fins, attached to the pelvic girdle in fishes that help control the direction of movement. Correspond to the hind legs in higher vertebrates and vary in position depending on taxon. Sometimes absent entirely.

Used in 431 profiles

photoperiod

The duration of an organism's daily exposure to light; the period of daylight in each 24-hour cycle.

photophore

Light-emitting organ found in some fishes.

Used in 1 profile

photosynthesis

Chemical process occurring in the cells of plants, algae and certain other organisms by which carbon dioxide is converted into organic compounds, especially sugars, using the energy from sunlight.

pore

Small opening in a surface, especially the skin, through which gases, liquids or microscopic particles are able to pass, or through which a sensory organ obtains information.

Used in 99 profiles