Thisglossary of ichthyology is a list of definitions of terms and concepts used inichthyology , the study of fishes.[ 1]
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 familyGoodeidae . 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 thepectoral fin axillary process An enlarged, pointed scale projecting from the insertion of the pectoral or pelvic fin. barbel An elongated fleshy projection, usually about the head. basal At or pertaining to 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 thegills branchial aperture The gill opening. branchiostegal membrane The membrane connecting the branchiostegal rays and enclosing the gill chamber ventrally. 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. caniniform Shaped like a canine tooth, conical in form. carapace A horny or bony covering encasing the body. cardiform Small set conical outgrowths in a close set patch or band; usually refers to a band of small, close-set, conical teeth. 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. 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 scale A rough-edged scale. cycloid scale A smooth-edged scale. 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 Having tooth-like projections. denticle, denticulate A little tooth, having an edge with small projecting teeth, theplacoid scales of cartilaginous fishes. depressed Flattened from top to bottom. dermal Pertaining to the skin. dewlap A fold of loose skin. 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. elasmobranchs Thecartilaginous fishes : sharks, rays, and allies. electrocyte A type of cell that generates electricity. elongate Extended, drawn out. emarginate Having the margin slightly hollowed. endemic Restricted to a particular region, for example endemic to Australia. entire Having 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. 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. 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 itspapilla gill arches The bony arches to which thegills gill cover A bony flap that covers thegills 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 The opening behind eachoperculum gills gill rakers A series of appendages along the anterior edges of the gill arches. gills , branchiaeOrgans for breathing the oxygen contained in water, and for excreting carbon dioxide from the blood. glossohyal The tongue bone. gonopodium A modification of the anal fin of males of certain live-bearing species in the familiesAnablepidae andPoeciliidae . 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. head length The distance from the tip of the snout (or upper lip) to the most posterior point of the opercular margin. heterocercal (of a fin) Not symmetric, e.g. in sharks. homocercal (of a fin) Symmetric. 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. ichthyoplankton The eggs and larvae of fish. illicium A "fishing rod-like" appendage on the head, usually a modified dorsal fin spine, used particularly inanglerfishes . imbricate Overlapping, like the shingles on a roof. incised Having 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 fertilizing 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. jugular Pertaining to the throat. juxtaposed (of two or more objects) Placed near each other. kidneys Organs involved in excretion and regulation of water balance. 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, the term usually refers to an "elongate highly compressed transparent, ribbon-like larval stage". 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. 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. melanophore A cell (chromatophore) containing melanin or other black pigment. 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 mucus or slime. myotomes Blocks of lateral trunk muscles. myomeres Blocks of muscle corresponding to number of vertebrae, easily seen in larval fishes and used for identifying specimens. 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. 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 theoperculum operculum The bony flap that covers thegills opercular Pertaining to theoperculum opercular spine A spine projecting from theoperculum orbit The eye socket. origin The mostanterior osseous Bony. ovate Egg-shaped. palate The roof of the mouth. palatines The set of bones on each side of the palate. papilla (papillae) A small fleshy projection(s). papillose Covered withpapillae 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 thepectoral fin 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 thepectoral fins pharyngeal bones Bones behind thegills 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 A spine positioned above and in front of the eye. preopercle , preoperculumThe bone between the cheek and the gill cover. preopercular spine A spine projecting from the preopercule (see preopercle). 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 Smallgills 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). ramus One branch or one half of the jaw. ray A jointed, segmented rod which supports a fin. redd Spawning nest made by some fishes. retrose Turned backward. rostrum A projecting snout or beak. rugose Rough. scalation 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 The point of junction of the two sides of the jaw. symmetrical Similarly arranged on both sides. teleost A member of Teleostei, an infraclass containing most of thebony fishes . terminal At the end. tessellated Marked with little checks or squares, like tiles. Tholichthys A larval stage ofbutterflyfish andscats in which the larva is armoured with large bony plates which extend onto the body from the head, the head also being enclosed in bony armour which is frequently silvery in colour. The tholichthys armour plates are lost as the larva metamorphoses into the juvenile stage. 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 Having three lobes. tricuspid Having 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 thetype specimen was collected. undulated Waved. urogenital papilla Apapilla vent The external opening of the alimentary canal, theanus . ventral Pertaining to the abdominal or lower surface. ventral fins Paired fins behind or below thepectoral 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. Weberian apparatus An adaptation found inOstariophysi to improve hearing; includes the Weberian ossicles. 
