| Occiput |
the area where the dorsal musculature attaches to the
skull of a fish |
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| Octocoral |
any member of the anthozoan Subclass Octocorallia, including soft
corals and gorgonians, in which the tentacles are arranged in multiples
of eight |
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|
| Octopod |
any species of octopus or argonaut, cephalopod mollusks with eight
arms surrounding the mouth |
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| Octopus |
octopus, cephalopods with eight tentacles bearing suckers for attachments
and prey capture |
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| Oculina |
eye coral, a branching stony coral with prominent corallites, found
in the Atlantic and Gulf of Mexico and sometimes colonizing live rock
produced in these areas |
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| Odontosyllus |
stomatopod crustaceans commonly known as "Mantis shrimp"
because their raptoral appendages resemble those of the parying mantis
incect |
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| Olfactory |
of or having to do with the sense of smell |
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| Oligochaete |
segmented worms of the annelid Class Oligochaeta, nonparasitic forms
with few bristles on the segments, such as the common earthworm; certain
aquatic species are cultivated as fish food |
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| Omnivore |
an organism that feeds on both plant and animal matter |
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| Oocyte |
the cell that gives rise to the egg |
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|
| Oodinium |
a micorscopic dinoflagellate parasite of freshwater fish, producing
the condition known as "velvet disease"; usually fatal if
not treated |
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|
| Opaque |
impervious to light |
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|
| Opercle |
the flap that covers the gills of fish |
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| Operculum |
in snails and some annelids, a calcified or proteinaceous plate
used to cover the opening of the shell when the animal is withdrawn
inside |
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| Ophioblennius |
an Atlantic genus in the Family Blennidae, the most commonly imported
species of which is O. atlanticus, the red-lipped blenny |
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| Ophioderma |
a common genus of serpent stars collected in the Atlantic |
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|
| Ophiuroid |
any member of the echinoderm Class Ophiuroidea, the serpent and
brittle stars, characterized by a disk-shaped body from which radiate
five flexible arms bearing tube feet; in some members the arms branch
repeatedly, givinb the impression of many more than five |
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|
| Opisthobranch |
snails of Subclass Opisthobranchia, that have a single gill and
share similarities of larval development, and among which loss or
reduction of the shell and bilateral symmetry are common traits |
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| Opisthognathus |
type genus of the jawfish, Family Opisthognathidae, the only common
aquarium species of which is the yellow-headed jawfish, O. aurifrons |
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|
| Oral disc |
the upper surface of an anemone, bearing the tentacles and with
the mouth in the center |
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| Orbit length |
the maximum diameter of the eye of a fish |
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|
| Oreaster |
sea stars typified by the large West Indian species O. recticulata,
which is predatory on sessile invertebrates |
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| Orectolobus |
nurse sharcks, Family Orectolobidae, with distinctive nasal barbels;
a usually sluggish and sedentary species that can adapt to very large
aquariums |
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| Organelle |
any of various membrane-bound subcellular structures found within
the cells of eukaryotic organisms |
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| Organic |
Relating to carbon-based plant or animal constituents or products;
matter any substance produced by a living organism; usually refers
to nonliving remains, excreta, or the like |
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|
| ORP |
oxidation-reduction potential, the tendency for oxidation reactions
to occur in a soultion, determined by measuring the electrical potential
in millivolts across a standardized electrode; an oxidation potential
above 400 mV is considered a sign of good water conditions in a marine
aquarium |
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| Orthophosphate |
phosphate, PO4 3-, as measured in tests used for aquarium water |
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| Oryzias |
rice fish, or medakas, the most primative cyprinodontid fish, from
Indonesia and Southeast Asia |
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|
| Oscar |
Astronotus ocellatus, an Amazonian cichlid extreamely popular with
aquarium hobbyists because of its tendency to develop an individual
"personality" and to recognize its owner |
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| Osculum |
the opening through which water is discharged from the body of a
sponge |
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| Osmoregulation |
control of the water and electrolyte balbnce in the body of a living
organism |
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|
| Osmosis |
the movement of water molecules across a membrane from an area of
higher concentration to an area of lower concentration |
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|
| Osomotic |
pressure the tendency of water to move across a semipermeable membrane,
as a consequence of the difference between solute concentrations on
either side |
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|
| Osphronemus |
the giant gourami, Asian anabantid fish sometimes eshibited in large
freshwater aquariums |
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|
| Osteoglossum |
bony-tounged fish, Family Osteoglossidae, primitave species known
in the aquarium trade as "arrowanas"; the most common species
is from South America |
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|
| Ostracion |
type genus of the boxfish family, Ostraciidae, marine fish in which
the body is inclosed in a shell made of interlocking bony plates insead
of scales |
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| Outgassing |
the escape of free gasses, such as carbon dioxide or oxygen, from
the surface of a container or body of water |
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| Ovaries |
organs in which eggs are produced |
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| Oviparous |
reproduction by means of eggs released into the environment |
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| Ovipositor |
a structure through which a female fish or invertebrate introduces
eggs on or into a suitable substrate for incubation |
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| Ovoviviparous |
mode of reproduction in which fertilized eggs are incubated within
the body of one parent, usually the female, and the young are released
as fully formed miniatures of the adults |
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| Oxycirrhites |
hawkfish, Family Cirrhitidae, the most popular member of which is
the longnosed hawkfish, O. ytpus, from the Indo-Pacific |
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| Oxygen |
a chemical element existing normally as the colorless, orderless
gaseous form, O2 and required by all living organisms, with the eception
of certain bacteria, for the metabolism of food |
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|
| Oxymonacanthus |
the only commonly imported species of this genus, O. longirostris,
theorange-spotted file-fish; it seldom adapts to the aquarium because
it normally feeds only on coral polyps |
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|
| Ozone |
the triatomic form of oxygen, o3, with a characteristic ordor; it
is used in aquarium husbandry as a disinfectant and to increase the
ORP value of the water |
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|
| Ozonization |
the process of introducing triatomic ozygen directly into aquarium
water |
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|
| Ozonizer |
a device for the production of ozone, usually by exposing air to
an electric spark |
