Adipose fin—A small, fleshy fin without rays.

Afferent—Conducting impulses toward nerve centers or blood toward the gills. Compare efferent.

Agonistic behavior—Aggressive and submissive interaction between individuals of the same species.

Albinistic—Displaying the characteristics of an albino; an organism that has deficient pigmentation and white, colorless, or translucent skin and hair.

Amphidromous—Regular migration between fresh and seawater at different stages in their development.

Ampulla—A sac- or pouch-like anatomical swelling.

Anal fin—Fin located on the undersurface of the body, behind the anus.

Andropodium—Modified anal fin exhibited by some males.

Anoxic—Extreme deficiency of oxygen.

Anthropogenic—Caused by the activities of human beings.

Antitropical—Found in both Northern and Southern Hemispheres, but not in equatorial regions.

Aplacental—Without a placenta.

Axial skeleton—Skeleton of the main body and head.

Axillary process—Modified scale present at the upper or anterior base of the pectoral or ventral fins exhibited by some fishes.

Barbel—Fleshy, tactile projection resembling tentacles located near the mouth, chin, or snout.

Basiocapital—Bone located at the back of the head or skull; the occiput.

Basioccipital—Base of the head or skull.

Bathypelagic—Living and/or feeding in open waters at depths between 3,280 and 13,125 ft (1,000 and 4,000 m).

Benthic—Relating to, living on, or occurring at the bottom of a body of water.

Benthopelagic—Relating to, living on, or occurring on the bottom or midwaters of a body of water, feeding on ben-thic and free swimming organisms.

Benthos—The bottom of a body of water.

Bilobed—The division of matter into two lobes.

Branchial—Relating to the gills.

Branchiostegal membrane—The gill membrane; supported by the branchiostegal rays (bones).

Buccal cavity—Mouth cavity forward of the gills.

Bycatch—Species that are not targeted as catch, but are caught along with a target species during fishing.

Carapace—A hardened shell, such as turtles or crabs have.

Catadromous—Living in freshwater, but migrating to saltwater for spawning.

Caudal fin—Fin located at the end of the body, also known as the tail fin.

Caudal keels—Ridges on either side of the caudal peduncle that often function in stabilization during fast swimming.

Caudal peduncle—A narrow part of the body located at the base of the caudal fin.

Cavernicolous—Cave dwelling.

Cecum—Cavity or pouch extending off the intestine that receives undigested food.

Cephalic—Relating or belonging to the head.

Clade—A group of biological taxa, such as species, that includes all descendants of one common ancestor.

Cladist—One who classifies organisms based on their evolutionary history.

Cleithrum—The major bone of the pectoral girdle.

Cloaca—Chamber into which the intestinal, urinary, and reproductive ducts discharge.

Confluent fins—Fins that are joined or run together, having no true separation.

Crepuscular—Active in the twilight or evening.

Crypsis—Patterns and/or coloration that make an organism more difficult for predators to detect; protective patterns or coloration.

Ctenoid scales—Scales having minute spines on exposed surface.

Cupula—A cup-shaped structure.

Cycloid scales—Scales having smooth edges, absent of spines.

Demersal—Living near, laying on, or sinking towards the bottom of the ocean.

Dentary—Lower jawbone of vertebrates.

Dentine—Material similar to but harder than bone and is the principal mass of teeth.

Dermal denticles—Teeth-like scales, also known as pla-coid scales, on the skin of various elasmobranchs that acts as a protective barrier and also enables faster swimming.

Dextral—Occurring on or relating to the right side of the body.

Diadromous—Regular migration between freshwater and seawater.

Dichromatism—Partial color blindness; the ability to recognize only two colors.

Diel—Involving a 24 hour period of time; occurring on a daily basis.

Diploid—Two sets of chromosomes existing in a cell or organism.

Dorsal fin—Spined or rayed fin on the dorsal surface of body.

Dorsal—Relating or belonging to the back or top surface of the body.

Dorsolateral—Belonging to, or orientated between the dorsal and lateral surfaces.

Dorsoventral—Belonging to, or orientated between the dorsal and ventral surface.

Ectodermal—Formed from the outer germ layer of an embryo.

Ectothermic—Cold-blooded animal.

Efferent—Conducting impulses away from nerve centers or blood away from the gills. Compare afferent.

Elasmobrand—Relating to the group of fishes that includes the sharks, rays, and skates.

Electric organ—Organ capable of delivering an electric shock or used to emit electrical discharges to stun prey, repel predators, or detect objects.

Endemic—The restriction of a species to a particular geographic area or continent; native.

Engybenthic—Organisms living or occurring at the bottom of a body of water.

Epibenthic—Living on the bottom of the ocean.

Epigean—Organisms that are not cave-dwellers and do not live underground.

Epipelagic—Living or feeding in the uppermost layer of water; from the surface to midwater depths of 656.17 ft (200 m).

Euryhaline—Ability to live in waters of varying salinity.

Exogenous—Introduced from, or produced outside the organism or system.

Facultative parasite—An organism that can exist off of its host.

Falcate—Having a hooked or curved shape.

Filiform—Having the shape or form of a filament.

Fin base—Portion of a fin that attaches to the body.

Fin spine—Bony structure that supports the fin in more derived fishes.

Holarctic—Relating to, or being from the northern parts of the world.

Finlet—A small, isolated fin, usually without rays, that ususally occurs dorsally or ventrally on the caudal peduncle.

Flange—A rib or rim that aids one object in attaching to another.

Flexion—The act of bending, extending or flexing; a physical structure having a bent shape.

Fry—Newly hatched juveniles, or very small adult fishes.

Fusiform—The tapering of each end.

Ganglia—Mass of nerve tissue containing nerve cells external to the brain or spinal cord.

Ganoid—Relating to, or having scales that are made of bone and an outer layer that resembles enamel.

Ganione—Substance that resembles enamel and makes up the outer layer of certain fishes' scales.

Gas bladder—Sac in the body cavity below the vertebral column; helps maintain buoyancy, may aid in respiration, and may help produce or receive sound. Also called swim bladder.

Gill—Organ for obtaining oxygen from water.

Gill cover—Flap made of bone or cartilage that covers and protects the gills. Also called operculum.

Gill rakers—Projections from the gill arch that help in retaining food particles.

Globose—Having the shape or form of a globule or ball.

Gregarious—Living in a group or colony.

Haploid—One set of chromosomes existing in a cell or organism.

Hermaphroditism—The presence of both male and female sexual organs in one individual. When both organs occur at the same time, the individual is bisexual or a simultaneous hermaphrodita; if they occur at different times, the individual is a sequential hermaphrodite.

Heterocercal—Upper lobe of the tail is larger than the lower lobe, and the vertebral column extends into the upper lobe.

Heterozygous—Having two alleles at corresponding loci on homologous chromosomes that are different.

Homocercal—A caudal fin in which all of the principal rays attach to the last vertebra.

Homologous—Structures or properties of organisms shared through common ancestry.

Hyoid—Belonging or pertaining to the tongue.

Hypogean—Lives underground.

Hypoxia—Deficiency of oxygen reaching the tissues of the body.

Hypural plate—Modified last vertebra, to which caudal fin rays attach.

Incisiform—Teeth that are flat with sharp edges.

Integument—A layer or membrane that encloses or envelopes an organism or one of its parts.

Intertidal—Shallow areas along the shore that are alter- S nately exposed and covered by the tides. A

Isosmotic—Having the same osmotic pressure on two sides of a membrane.

Isthmus—Narrow, triangular area on the underside of the body, between the gill openings.

Iteroparous—Successive production of offspring, annually or seasonal batches.

Lacustrine—Relating to, inhabiting, formed or growing in lake water.

Lamella—Thin plate or membrane; often refers to smallest divisions of gill.

Larvaceans—Small transparent animals found in marine plankton; belong to subphylum Urochordata.

Lateral line—A series of ampulla forming a sensory organ to detect movements in water. Scales are often modified with pores opening to a sensory canal on the side of a fish.

Lecithotrophic—Embryos feeding on the yolk stored in the yolk sac.

Littoral—Related to, inhabiting, or situated near a shore.

Lunate—Having the shape of a crescent.

Maxilla—Upper jaw bone.

Median fin—Fins located on the median plane.

Meiobenthic—Benthic organisms with dimensions less than 0.02 in (0.5 mm) but greater than or equal to 0.004 in (0.1 mm).

Melanistic—An organism that exhibits a high amount of melanin (black coloration) in the skin.

Melanophore—A cell containing melanin.

Mesentary—A membrane that attaches organ to the abdominal wall.

Mesopelagic—Relating to, inhabiting or feeding at midwa-ter at depths between 656.17 ft (200 m) and 3,280.84 ft (1,000 m).

Microphthalmic—Having eyes noticeably reduced in size.

Micropredator—A predator smaller than its prey that comes into contact with its host only when needing to feed.

Midwater—The middle stratum of a body of water.

Milt—The combination of spermatozoa and seminal fluid in fishes.

Monogamy—Mating system in which a single pair joins together for spawning and may remain together for one or more seasons.

Monophyletic—Developed from or related to a single common ancestral form or stock.

Monotypic—A group containing a single representative.

Myoglobin—Protein pigment in muscles that contains iron.

Naked—A fish that has no scales.


Nasohypophysical—Nostril opening.

Nektonic—Organisms that swim strongly enough to move against currents.

Neural spine—The uppermost spine of a vertebra.

Notched fin—A fin that has patterned indentation.

Obligate air breathers—An organism that must receive a certain amount of their oxygen directly from air.

Ocelli—An eye-like marking.

Ontogenetic—Changes that incur from growth or age.

Oophagy—The process of embryos feeding on eggs produced by the ovary while still inside the uterus.

Osmoregulation—The regulation of water in the body.

Otoliths—Calcareous deposit in the ear capsules of bony fishes that show daily, seasonal or annual checks, rings or layers that can be used to determine ages.

Oviduct—Duct that serves as the passage of eggs from the ovary.

Oviparous—Production of eggs that develop and hatch outside of the mother.

Ovoviviparous—Fertilized eggs are retained in the mother's body during development.

Paedomorphic—Phylogenetic retention of larval or juvenile characters in the adult stage.

Paired Fins—Fins that occur in pairs, on each side of the body.

Paleoecology—The study of ecological characteristics in ancient environments and their relationships to ancient plants and animals.

Palp (Palpus)—Segmented and tactile process on the mouth.

PCBs (polychlorinated biphenyls)—Substances used as coolants and lubricants; their manufacture was banned in the United States in 1977.

Pectoral—Relating or belonging to the forward pair of ap-pendicular appendages.

Pectoral fins—Fins attached to the shoulder or pectoral girdle, just behind the head.

Peduncule—Narrow part by which a larger part or the whole body is attached.

Pelagic—Relating to, living or occurring in open ocean water.

Pelvic fins—Pair of fins attached to the pelvis or pelvic girdle.

Photophore—A luminous spot or light-producing organ.

Piscivorous—Diet consists solely of other fishes.

Planktivorous—Diet consists solely of passively floating or weakly swimming animal and plant life.

Polyandry—Females mate with more than one male in a season.

Polygamy—Mating system in which individuals mate with more than one partner in a season.

Polygyny—Males mate with more than one female in a season.

Sinistral—Occurring on or relating to the left side of the body.

Sinusoidal—Relating to, or shaped like the sine curve or wave.

Polyphyletic group—An assemblage consisting of different ancestral taxa, i.e., a group based upon convergence rather than on common ancestry.

Precaudal pit—Cavity just anterior to the caudal fin.

Prehensile—Adapted specifically to enable seizing, grasping, or wrapping around.

Promiscuity—Males and females spawn together with little or no mate choice.

Protandrous—Sequential hermaphroditism in which the fish functions first as a male and then a female.

Protrnsible mouth—Mouth which can project forward and out to help catch prey.

Protygynous—Sequential hermaphroditism in which the fish functions first as a female and then a male.

Ray—Segmented bony rod or element that supports a fin membrane.

Riffle stretches—Areas of rough water caused by submerged rocks or a sandbar.

Rostral—Located toward the mouth or nasal region.

Seamount—Submarine mountain rising above the deep-sea floor.

Sexual dichromism—Exhibiting both male and female forms and aspects.

Sister group—Closest relative to a taxa or group. The two groups share a common ancestor.

Spinules—Minute or miniature spine.

Standard length—Standard scientific measure of a fish's length; found by measuring from the most anterior part of the snout, lip or chin to the end of the last vertebra.

Subtidal—Zone just below the low-water mark of the tide that is never exposed, even at low tide.

Swim bladder—See Gas Bladder.

Syntopic—Sharing the same habitat within the same geographical range.

Tetraploid—Four sets (two homologous pairs) of chromosomes existing in a cell or organism.

Translocated—Transferred or dislocated specimens.

Tubercle—Nodule, growth, or knob present in an organ or on the skin.

Ventral—Relating to, or located in the abdomen or belly.

Vermicular—Relating to, caused by, or resembling worms.

Vestigial—Body part that was functional in ancestral sources but has become reduced or nonfunctional descendants.

Vitellogenesis—Deposition of yolk within the growing egg.

Viviparous—Producing live young.

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