What The...? Master List Of Definitions

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Air Bladder / Swim Bladder: An air-filled structure in many fishes that functions to maintain buoyancy or, in some species, to aid in respiration. Also called swim bladder.

Amyloodinium: Amyloodinium ocellateum is commonly called Oodinium, Marine Velvet, or Saltwater Ich. Possible signs of the disease are cloudy eyes, gasping for breath, listlessness, and white spots. Positive signs of the disease are gold or brown spots, rough skin, and rubbing against rocks, etc. Treatment can be done by a freshwater dip and copper (as long as inverts are not in the tank).

Annelid: Relating to or belonging to or characteristic of any worms of the phylum Annelida. Worms with cylindrical bodies segmented both internally and externally.

Asexual Reproduction: Asexual means having no sex or sex organs, therefore asexual reproduction would be reproducing by means other than sex.

Autotroph: Plants and bacteria that can synthesize organic compounds from inorganic nutrients.

Autozooids: Polyps with eight well-developed tentacles that function in feeding and defense. In monomorphic species, these are the only polyp type. In dimorphic species, it is the larger, more conspicuous type of polyp.

Bleaching: When corals or clams expel their zooxanthellae and appear pale or white.

Byssus Gland: The structure in clams that produces fibrous threads (byssus) that attach the clam to substrate. Sometimes permanent although more usually temporary attachment of tough organic threads secreted from a gland in the foot of the clam.

Calcareous: Composed of or containing calcium carbonate, calcium, or limestone.

Calcification: The process of extracting calcium from seawater and depositing it as calcium carbonate.

Carnivore: A flesh-eating animal.

Chitin -ous: A tough protective substance that is the principal component of crustacean shells.

Cilia / Cilium / Ciliated: A microscopic hairlike process extending from a cell or unicellular organism and capable of rhythmical motion. Ciliated means having cilia.

Cirri: A tendril or similar part; a slender flexible appendage.

Commensal / Commensalism: A symbiotic relationship between two organisms of different species in which one derives some benefit while the other is unaffected.

Cryptocaryon: Cryptocaryon irritans is a parasitic infection where white spots appear on the body and fins. Fish will scratch themselves against rocks and breathing may become rapid if gills are affected. Treatment can be done by copper or other anti-parasite remedies, but this is incompatible with inverts. Cleaner shrimps and wrasses will remove the parasites, but may not keep up with a major infestation. Cryptocaryon is often referred to as the marine equivalent of the freshwater white spot disease, Ichthyophthirius, or Ich.

Cyanobacteria: Cyanobacteria is commonly referred to as red slime algae by hobbyists although it is not really an algae. Poor water quality with excessive nutrients are the usual causes. To combat, do frequent water changes, siphon out detritus, and use a good protein skimmer.

Detritivores: Animals that eat detritus. Common detritivores are urchins, stars, hermits, etc.


Detritus: Piles of organic compounds that accumulate in the aquarium. Commonly will contain fish wastes, fragments of rock, leftover food, and so on. Usually detritus will accumulate in low water flow areas (tank corners, sumps, etc.). Detritus is rich in plant nutrients (in other words, the bad algae's food) and should be removed via mechanical filtration, good circulation, siphoning, and water changes.

Diatom: A diatom is any of a class of microscopic one-celled algae having walls of silica consisting of two interlocking valves. In the home aquarium, a diatom usually appears as a golden brown algae forming sheets or films on the rocks and glass often with oxygen bubbles tangled in them. You can control the growth of diatom algae by limiting nutrients through purification of make-up water, combined with herbivores eating the diatoms, and mechanical filters trapping their fecal pellets.

Dinoflagellates: A group of single-celled microscopic organisms with flagella that belong to the kingdom Protista. If they posses chlorophyll, they are considered plants and some are entirely photosynthetic while some ingest food. If they don't posses chlorophyll, they are more animal-like. The symbiotic algae zooxanthellae are dinoflagellates. "Red Tide" is caused by a dinoflagellate bloom that releases toxins into the water. Amyloodinium (Marine "Velvet") is also caused by dinoflagellates.

Dimorphic: Corals with two different kinds of polyps are called dimorphic. The polyps themselves can also be referred to as dimorphic. The two polyp types are autozooids and siphonozooids.

Dorsal: The dorsal fin is the fin directly on top of the body. For example, the fin that sticks out of the water on a shark.

Encyst: To enclose or become enclosed in a cyst, which is usually defined as an abnormal membranous sac containing a gaseous, liquid, or semisolid substance.

Exoskeleton: An exoskeleton is a hard outer structure, such as the shell of an insect or crustacean, that provides protection or support for the organism.

Flagella / Flagellum: A whiplike extension of certain cells or unicellular organisms that serves in locomotion.

Genera / Genus: Genera is the plural of genus. In the taxonomy classification, the genus is the category ranking below a family and above a species. Simply said, it's a class, group, or kind with common attributes.

Gonads: Gonads are an organ in animals that produce gametes (a reproductive cell like sperm or an egg) such as a testis or ovary.

Gorgonian: A Gorgonian is a tropical or subtropical octocoral with upright branchy plant-like or fan-like growths and a skeleton made of a horny organic material. For example, the Sea Fans (Scientific names: Gorgonia ventalina, G. flabellum, G. mariae, Pacifigorgia spp.).

Head and Lateral Line Erosion: Also known as hole-in-head disease and lateral line disease. A fish with this condition will develop holes in it's head and sometimes along it's lateral line. The main cause is nutritional deficiency, especially vitamin C. Stress and poor water quality also play a role. Untreated cases will cause disfiguring or death. To combat and cure, ensure good water quality and provide vitamin enriched foods, especially vitamin C.

Hermaphrodites: An animal in which both male and female sex organs are present. Rarely do both systems operate simultaneously.

Heterotroph: Organisms which are not capable of producing their own food.

Hyaline Organs: Clear areas in the mantle of tridacnid clams that appear to focus light onto dense aggregations of zooxanthellae.

Hydrometer: A Hydrometer is an instrument used to determine the specific gravity of a fluid. Hobbyist grade hydrometers are temperature corrected to read the specific gravity at around 77F (25C) because specific gravity is temperature dependent.

Invertebrate: Commonly called inverts by many in the hobby. Invertebrates are animals without backbones like anemones, corals, shrimps, snails, and crabs.

Iridophores: Fixed cells in tridacnid clams that contain numerous UV protection pigments.

Larva -vae -vas / Larval: The newly hatched stage of any of various animals that differ markedly in form and appearance from the adult.

Lateral Line: The lateral line is a line of perforated scales along the flanks of a fish which lead to a pressure-sensitive nervous system. This enables the fish to detect vibrations in the surrounding water caused by other fish and their own reflected vibrations against obstacles.

Macerated: To soften or separate by soaking or steeping.

Mantle: Large, pigmented fleshy portion of tridacnid clams that is exposed to the light by gaping of the shell valves. Also called siphonal tissue. Also, the coral tissue in fleshy polyps (e.g. Catalaphyllia).

Matrix: Biologically speaking, matrix is the intercellular substance of a tissue.

Metamorphosis: A change in form and often habits during development after the embryonic stage.

Micron: A unit of length equal to one millionth of a meter. One foot equals 0.30 meters.

Molt: Molting is the periodic shedding of an outer covering, such as feathers or skin, for replacement by new growth.

Monomorphic: Corals with only one type of polyp are called monomorphic. The only polyps these corals have are autozooids.

Necrosis / Necrotic: Death of cells or tissues through injury or disease.

Neurotransmitter: A chemical substance, such as dopamine, that transmits nerve impulses across a synapse.

Nocturnal: A nocturnal animal is one most active at night.

Octocoral: An octocoral is a member of the phylum Coelenterata (Cnidaria) class Anthozoa characterized by having (normally) eight featherlike (usually called pinnate) tentacles surrounding the mouth of each polyp. Cnidaria was formerly the phylum Coelenterata. The name Coelenterata is still in common use. The class Anthozoa contains the "flower-animals" - corals, anemones, and anemone-like creatures. A subclass of Anthozoa, Octocorallia, contains the soft corals. Simply, octocorals have eight tentacles on each polyp. There are many different forms which may be soft, leathery, or even those producing hard skeletons.

Omnivore: An ominivore is an animal who will eat both meat and vegetables.

Opaque: Something is opaque if it is impenetrable by light or not reflecting light.

Palps: Flap-like structures in clams that direct food towards the stomach.

Parapodium / Parapodia: One of the lateral appendages of an annelid. Also called a foot tubercle. They may serve for locomotion, respiration, and sensation, and often contain spines or set[ae]. When well developed, a dorsal part (notopodium) and a ventral part (neuropodium) are distinguished.

Pathogen / Pathogenic: An agent that causes diseases especially a living microorganism such as a bacterium or fungus.

Pectoral: Of or situated in the breast or chest.

Pelvic / Pelvis: A basin-shaped structure of the vertebrate skeleton that rests on the lower limbs and supports the spinal column.

Pharynx: The section of the alimentary canal that extends from the nasal cavities to the larynx, where it becomes continuos with the esophagus.

Peduncle: A stalklike part or structure, foot.

pH: pH is the measure of the concentration of hydrogen and hydroxide ions. If the hydroxide ion is in greater abundance in a solution, the solution is alkaline or basic. If the hydrogen ion is more abundant, the solution is acidic. Values of pH range from 0 to 14.

Pheromone: A chemical stimulant/attractant released into the surrounding environment, either air or water.

Phylum: In the taxonomy classification, the phylum is the category ranking below a kingdom and above a class.

Phytoplankton: Microscopic algae which is suspended in the part of the water column that is penetrated by light.

Polyp: A polyp is the living unit of a coral.

Proboscis: A long, flexible snout or trunk, such as an elephant has.

Protandry / Protandric: A type of hermaphroditism in which the individual is a functional male first, then develops into a functional female.

Protozoan: A protozoan is a single-celled, microscopic (usually) organism. For example, an amoeba.

Rachis: The upper part of a pennatulacean (Sea Pen). The part of a Sea Pen which bears the polyps.

Salinity: Salinity is the measure of the quantity of dissolved solids in water and is used to measure the strength of a seawater solution. Full strength seawater has a salinity of about 35 parts per thousand.

Sclerites: Part of the skeletal/structural support in soft corals. They are composed of calcium carbonate imbedded in the tissue of most soft corals (octocorallia).

Sessile: Permanently attached. For example, a barnacle.

Set -ae: Any slender, more or less rigid, bristlelike organ or part; as the hairs of a caterpillar, the slender spines of a crustacean, the hairlike processes of a protozoan, the bristles or stiff hairs on the leaves of some plants, or the pedicel of the capsule of a moss. One of the movable chitinous spines or hooks of an annelid. They usually arise in clusters from muscular capsules, and are used in locomotion and for defense. They are very diverse in form.

Siphon: The inhalant and exhalant siphons of tridacnid clams are used to allow for gas exchange and to expel wastes.

Siphonal Tissue: Another description of mantle.

Siphonozooids: The smaller, less conspicuous polyp in dimorphic octocorals. These polyps are responsible for driving water currents through the large, fleshy octocorals.

Specific Gravity: As a hobbyist definition, specific gravity is the amount of salt in the water. See the hydrometer definition for more information. Specific Gravity of seawater ranges from 1.022 to 1.030.

Stolons: Ribbon or root-like growth extensions that adhere to the substrate and link the polyps in Stoloniferan soft corals such as Clavularia spp. (common name - Clove or Glove Polyps). Stoloniferan corals are defined as those corals that match this description (polyps linked with root-like extensions adhering to the substrate).

Swim Bladder: * see Air Bladder

Taxonomy: The classification of organisms in an ordered system that indicates natural relationships.

Terpenoid: Organic compounds produced by soft corals for defense and aggressive colonization of new substrate.

Trochophore: Free-swimming, first planktonic stage of mollusc larvae.

Tubercles: Wart-like projections on sclerites.

Ultraviolet (UV) Light: Ultraviolet is a high energy, short wavelength of light. It is shorter than violet in the visible spectrum and on the border of the x-ray region.

Umbo / Umbones (plural): The apparent "apex" or "beak" of each valve around which "radial" growth has proceeded.

UV Sterilizer: A UV Sterilizer is a device that uses ultraviolet light to make the water treated with it free of microorganisms which may cause disease.

Veliger: Second larval planktonic stage of molluscs where the foot, shell, and other structures first make their appearance.

Zooplankton: Animals that drift in the water column. Most zooplankton are microscopic and some are the larval forms of larger organisms.

Zooxanthellae: These are the tiny plants called dinoflagellates (single-celled microscopic organisms which belong to the Protista kingdom) that live symbiotically with corals, tridacnid clams, and some sponges. They provide food for the host and in return get the nitrogen, phosphorous, and carbon dioxide they need for growth. The scientific name is Symbiodinium spp.

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