Ichthyology terms

Ichthyology uses several terms that are unique to the science.

Contents: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z __NOTOC__

A

* Abdomen: belly
* Abdominal: pertaining to the belly
* Actinosts: a series of bones at the base of the pectoral rays.
* Acuminate: tapering gradually to a point
* Acute: sharp, pointed
* Adipose fin: a small fleshy fin which lacks fin rays.
* Adnate: joined together
* Adpressed: pressed against the body
* Anal fin: the fin on the median line behind the vent
* Anal fin origin: the most anterior point of the anal fin base
* Andropodium: a modification of the anal fin of males of certain live-bearing species in the family Goodeidae. It is used to transfer reproductive products to the female during mating.
* Ankylosed: grown firmly together
* Anterior: relating to the front portion
* Antrose: turned forward
* Approximate: placed close together
* Asperity: roughness of surface
* Asymmetrical: without symmetry
* Attenuate: tapering to a point, usually in reference to a tail
* Axillary: pertaining to the axilla or upper angle of the pectoral fin
* Axillary process: an enlarged, pointed scale projecting from the insertion of the pectoral or pelvic fin.)

B

* Barbel: an elongated fleshy projection, usually about the head
* Basal: pertaining to the base, at the base
* Base: the part of a projection, (commonly a fin), which is connected to the body
* Bathypelagic: living at a depth between 1000 m and 4000 m, but well off the bottom
* Benthic: bottom-dwelling, living on the sea bed
* Benthopelagic: pertaining to fishes that swim just above the seabed at depths below about 200 m (the edge of the continental shelf)
* Bicuspid: having two cusps or points
* Bifid: cleft in two
* Bifurcate: forked, or divided into two parts or branches
* Branchial: pertaining to the gills
* Branchial aperture: the gill opening
* Branchiostegals, Branchiostegal ray(s): bony rays supporting the gill membranes behind the lower jaw
* Bristle: a stiff hair-like projection
* Buckler: a bony shield
* Bycatch: species other than the target species that are caught incidentally in a trawl

C

* Caniniform: shaped like a canine tooth, conical in form
* Carapace: a horny or bony covering encasing the body
* Carinate: keeled, having a ridge along the middle line
* Caruncle: a fleshy outgrowth
* Caudal: pertaining to the tail
* Caudal fin: the tail fin
* Caudal peduncle: the region of the body between the end of the anal fin and the base of the caudal fin
* Ciliated: fringed with eyelash-like projections
* Cirri: small, thin appendages, often subdivided into branches.
* Cirrus: singular of cirri (see above)
* Claspers: the external reproductive organs of male sharks, rays and chimaeras
* Coalesced: grown together
* Compressed: flattened laterally
* Confluent: joined together
* Conical: cone shaped, with a cylindrical base and a pointed tip
* Corselet: a scaly covering behind the pectorals of some fishes
* Countershading: body colouration which is dark above and lighter below
* Crenulate: having the edge slightly scalloped
* Cutaneous: pertaining to the skin
* Ctenoid: rough-edged (referring to scales)
* Cycloid: smooth-edged (referring to scales)

D

* Deciduous: temporary, falling off
* Demersal: living on or near the sea bed
* Dendritic: resembling a tree or shrub
* Denature: the "unfolding" of a protein resulting in a lessening of its biological properties. In the case of some fish toxins, denaturing with hot water can lessen painful symptoms.
* Dentate: with tooth-like projections
* Denticle, denticulate: a little tooth, having an edge with small projecting teeth, the placoid scales of cartilaginous fishes
* Depressed: flattened from top to bottom
* Dermal: pertaining to the skin
* Dewl

* Disc: the flattened head and body of various fishes such as stingrays, which also commonly includes the pectoral and ventral fins
* Distal: remote from the point of attachment
* Dorsal: pertaining to the back
* Dorsum: the upper (dorsal) surface of the head or body
* Dorsal fin: the fin on a fish's back
* Dorsal fin origin: the most anterior point of the dorsal fin base

E

* Elasmobranchs: cartilaginous fishes - sharks, rays and allies
* Electrocyte: a cell that generates electricity
* Elongate: extended, drawn out
* Emarginate: with the margin slightly hollowed
* Endemic: restricted to a particular region, for example endemic to Australia
* Entire: with a smooth margin
* Epibenthic: referring to organisms living on the bottom surface
* Epipelagic: referring to organisms living in the region between the surface and 200 m depth
* Erectile: capable of being raised or erected, often referring to spines
* Esca: the lure or "bait" on the end of the illicium of some anglerfishes and relatives
* Estuarine: living in estuaries

F

* Falcate: scythe-shaped, long, narrow, and curved
* Falciform: curved like a scythe
* Filament: a slender or thread-like structure
* Filiform: thread-like
* Fimbriate: fringed at the margin
* Finfold: embryonic tissue which develops into a fin
* Finlet: a small fin, positioned behind the dorsal or anal fins, that is supported by a ray or rays
* Fluviatile: living in rivers
* Free rear tips (of fins): the posterior tip of the fin that is closest to the most posterior point of the fin base
* Frontal ridge: a ridge running along the top of the head along the midline
* Furcate: forked
* Fusiform: tapering towards both ends

G

* Ganoid scales: Armor-like scales coated with ganoin found in gars and bichirs.
* Genital papilla: a small, fleshy tube behind the anus in some fishes, from which the sperm or eggs are released; the sex of a fish often can be determined by the shape of its papilla.
* Gill arches: the bony arches to which the gills are attached
* Gill cover: or bony flap that covers the gills, the operculum
* Gill filaments: a series of projections along the posterior edge of the gill arch, the site of gas exchange
* Gill membranes: membranes covering the gill openings, attached to the branchiostegals
* Gill opening: opening behind each operculum, leading to the gills
* Gill rakers: a series of appendages along the anterior edges of the gill arches
* Gills, Branchiae: organs for breathing the air contained in water
* Glossohyal: the tongue bone
* Gonopodium: a modification of the anal fin of males of certain live-bearing species in the families Anablepidae and Poeciliidae. It is used to transfer reproductive products to the female during mating.
* Gravid: Sexually ripe
* Gular region: pertaining to the region behind the chin and between the sides of the lower jaw

H

* Head length: the distance from the tip of the snout (or upper lip) to the most posterior point of the opercular margin
* Homology: similarity of features based on common evolutionary descent
* Hyperostosis: a condition resulting in enlargement of areas of bone.
* Hyaline: translucent or transparent
* Hypural joint: the joint between the caudal fin and the last of the vertebrae
* Hypural plate: the flattened bony plate at the posterior end of the vertebral column, formed from parts of the posterior vertebrae.

I

* Ichthyoplankton: fish eggs and larvae
* Illicium: a "fishing rod-like" appendage on the head, usually a modified dorsal fin spine
* Imbricate: overlapping, like the shingles on a roof
* Incised: with a notched margin (often referring to fin membranes)
* Incisors: the front or cutting teeth
* Inferior: pertaining to the lower side (usually of the head)
* Interdorsal: between the dorsal fins
* Interorbital: the space between the orbits
* Intromittent organ: a structure to facilitate sperm transfer in some internally fertilizating species
* Iris lappet: a fleshy flap or lobe-like structure in the eye, short and rounded, simple or multiply branched.
* Isthmus: the fleshy projection of the body separating the gill openings

J

* Jugular: pertaining to the throat
* Juxtaposed: placed near together

K

* Kidneys: organs involved in excretion and regulation of water balance

L

* Lanceolate: spear-shaped, gradually tapering toward the extremity
* Labial: pertaining to the lips
* Labial furrows: shallow grooves around the lips
* Labial papillae: small fleshy projections around the lips
* Lateral: at or toward the side
* Lateral line: a series of muciferous tubes forming a raised line along the side of the body
* Leptocephalic: tallness and narrowness of the skull - in fish usually refers to "elongate highly compressed transparent, ribbon-like larval stage" (source FishBase glossary)
* Liver: a digestive and storage organ
* Longitudinal series (scales): the number of scale rows above the lateral line from the first pored lateral line scale to the caudal fin base.
* Lunate: shaped like a crescent moon, with long upper and lower lobes

M

* Maxilla, Maxillary: the upper jaw, or pertaining thereto
* Maxillae, Maxillaries: the hindmost bones of the upper jaw; preceded by the premaxillaries
* Median, medially: pertaining to the middle
* Median fins: fins located on the median line of the fish; the dorsal, anal and caudal fins
* Mediolateral: between the middle and the sides
* Mesocoracoid: a bone of the pectoral arch or shoulder girdle
* Mesopelagic: refers to the region of the open ocean between 200 m and 1000 m in depth
* Mesopelagic fishes: fishes that live in the mesopelagic zone
* Midwater: the middle stratum of water, well below the surface and well above the seabed. See also mesopelagic.
* Midwater fishes: fishes that live in the midwater
* Molars: blunt and rounded grinding teeth
* Morphology: form and structure of an organism
* Muciferous: producing or containing mucous or slime
* Myotomes: blocks of lateral trunk muscles

N

* Nape: upper surface of the body behind the head and before the dorsal fin
* Nasal: pertaining to the nostrils
* Nasoral: between the nostrils and mouth
* Nictitating membrane: an inner eyelid
* Notochord: a rudimentary of embryonic spinal column
* Nuchal: pertaining to the nape

O

* Obsolete: faintly marked, scarcely evident
* Obtuse: blunt
* Occipital: pertaining to the posterior part of the skull
* Ocellus: an eye-like spot
* Ocular: pertaining to the eye
* Odontode: a dermal tooth
* Oesophagus: the gullet
* Opercle: the large bone which forms the upper posterior part of the operculum
* operculum: the bony flap that covers the gills
* Opercular: pertaining to the operculum
* Opercular spine: spine projecting from the operculum (view the fish figure)
* Orbit: the eye socket
* Origin: the most anterior point of a fin base
* Osseus: bony
* Ovate: egg-shaped

P

* Palate: the roof of the mouth
* Palatines: the bones on each side of the palate
* Papilla (papillae): a small fleshy projection(s)
* Papillose: covered with papillae
* Pectoral: pertaining to the breast
* Pectoral fins: the anterior or uppermost of the paired fins, which correspond to the anterior limbs of the higher vertebrates
* Pectoral girdle: the bones to which the pectoral fin is attached
* Peduncle: usually referred to as the caudal peduncle, the region of the body between the end of the anal fin and the base of the caudal fin
* Pelagic: living on or in the open seas
* Pelvic girdle: the bones to which the ventral fins are attached
* Pelvic fins: paired fins behind or below the pectoral fins
* Pharyngeal bones: bones behind the gills in the oesophagus or gullet
* Pharyngeal teeth: teeth within the pharynx
* Pharynx: the back part of the throat, into which the gill slits open
* Photophore: a circular light-producing organ on the surface of a fish
* Placoid scales: Teeth-like scales found in sharks and rays.
* Posterior: towards the hind end of the fish
* Postorbital: behind the eye
* Precaudal: anterior to the tail portion
* Premaxillaries: two bones forming the front portion of the upper jaw
* Preocular spine: spine positioned above and in front of the eye
* Preopercle, preoperculum: the bone between the cheek and the gill cover
* Preopercular spine: spine projecting from the preopercule (see preopercle) (view the fish figure)
* Preorbital: the area under and in front of the eyes
* Protractile: capable of extending forward
* Protrusible: capable of extending forward, often referring to the jaws of fishes
* Proximal: nearest
* Pseudobranchiae: small gills developed on the inner side of the gill cover
* Pseudoclasper: stiff ossified lobes or prongs in the tip of the intromittent organ
* Pterygiophore: an internal cartilage or bone that supports a median fin ray or spine
* Pyloric caecae: finger-like pouches connected with the alimentary canal (the gut)

R

* Ramus: one branch or one half of the jaw
* Ray: a jointed, segmented rod which supports a fin
* Retrose: turned backward
* Rostrum: a projecting snout or beak
* Rugose: rough

S

* Scalation: pertains to the pattern/arrangement/presence of scales
* Scute: any external horny or bony plate
* Serrate: notched like a saw
* Setae: bristles or hairs
* Soft dorsal: the posterior part of the dorsal fin which is composed of jointed rays
* Spatulate: shovel-like; having a broad, flat and rounded shape
* Spine: a sharp projecting point; an unjointed support in the anterior portions of the dorsal and anal fins
* Spinous, spiniform, spinate: spine-like or composed of spines
* Spinous dorsal: the anterior part of the dorsal fin supported by spines
* Spiracles: respiratory openings behind the eyes in sharks and rays
* Standard length (SL): the length of a fish measured from the tip of the snout to the posterior extremity of the hypurals, the expanded bones at the end of the backbone that support the caudal fin
* Submarginal: almost at the edge
* Suborbital: below the eye
* Superior: above or on the upper surface
* Supracleithrum: the bone forming a connection between the back of the skull and the pectoral girdle
* Supralateral: above the side
* Supramaxillary: a supplemental bone lying along the upper edge of the maxillary
* Supraocular: positioned above the eye
* Supraorbital: above the eye
* Supraorbital tentacle: a flap or filament of skin positioned above the eye
* Suprascapular: a bone uniting the shoulder girdle with the skull
* Suture: the line of union of two bones or plates
* Swimbladder: a sac filled with gas, lying beneath the backbone
* Symphysis: point of junction of the two sides of the jaw
* Symmetrical: similarly arranged on both sides

T

* Teleost: a member of Teleostei, an infraclass containing most of the bony fishes
* Terminal: at the end
* Tessellated: marked with little checks or squares, like tiles
* Thoracic: pertaining to the chest
* Thorax: the chest region, just behind the head
* Total length: the length from the tip of the snout to the tip of the tail
* Transverse: crosswise
* Trilobate: with three lobes
* Tricuspid: with three cusps or points
* Truncate: terminating abruptly, as if cut off square
* Trunk: the region of a fish between the head and tail, or the last gill slit and vent
* Tubercle: a small, usually hard excrescence or lump
* Tubiform, tubuliform: resembling a tube
* Type locality: the location from which the type specimen was collected.

U

* Undulated: waved
* Urogenital papilla: a papilla through which the urinary waste and gametes leave the body

V

* Vent: the external opening of the alimentary canal, the anus
* Ventral: pertaining to the abdominal or lower surface
* Ventral fins: paired fins behind or below the pectoral fins
* Vertical fins: fins on the median line of the body; the dorsal, anal, and caudal fins
* Vestigial: reduced, or very poorly developed
* Villiform teeth: small, slender teeth forming velvety bands
* Vomer: a bone forming the front part of the roof of the mouth
* Vomerine teeth: teeth on the vomer (see above)

W

* Weberian apparatus: An adaptation found in Ostariophysi to improve hearing; includes the Weberian ossicles.