Adipose fin:
A small dorsal fin, lacking internal supports, situated between the dorsal
and caudal fins.The posterior border of this fin is sometimes fused to
the trunk (adnate).
Anal fin: A median
fin located just behind the anus on the underside of a fish.
Anterior: Toward
the front or head end.
Axillary process:
a fleshy projection at base of pectoral fins.
Barbels: Fleshy outgrowths
("feelers") around the mouth in some fishes.
Branchiostegal rays:
The elongate bones lying in a membrane (branchiostegal membrane) just below
the gill-cover (operculum).
Caudal fin: The tail
fin.This fin may be heterocercal (upper and lower lobes unequal in size),
diphycercal (tail tapers to a sharp point), or homocercal (upper and lower
lobes of equal size).The posterior margin of the fin may be forked, rounded,
or emarginate.
Caudal peduncle:The
tail region of the body from the posterior insertion of the anal fin to
the hidden base of the caudal fin rays.
Least caudal peduncle
depth:The narrowest portion of the caudal peduncle.
Caudal peduncle length:The
oblique distance between the posterior insertion of the anal fin and the
hidden base of the middle caudal ray.
Caudal peduncle scale
count: Determined by counting the number of scales around the body
at the narrowest portion of the caudal peduncle.
Cheek: Area on the
side of the head from eye to preopercle.
Dentary:The major
tooth-bearing bone of the lower jaw.
Depth, body:The greatest
vertical depth of the body, measured from the top of the back at the front
of the dorsal fin to the mid-line of the belly.
DIstal: location
on a structure farthest away from point of attachment
Dorsal: At or toward
the back (or top) of a fish.
Dorsal fin: The large
unpaired fin on the middle of the back.Some fishes have more than one.The
fin supports may consist of soft-rays, spines, or both.
Eye (or
orbit) diameter:The greatest distance between the free orbit rims.
Falcate: sickle-shaped
(fin usually).
Fin height: Measured
from the insertion to the tip of the anterior lobe.
Fin length:The greatest
overall basal length of a fin.
Fin ray: slender,
rod-shaped structures supporting fin membranes.
Fork length:The distance
from the most anterior part of the head to the deepest point of the fork
in the caudal fin.
Frenum: fold of skin
that limits movement, e.g., membrane across the snout of the longnose dace
connecting maxillary to the front of the head.
Gills:Organs for
obtaining oxygen from water.
Gill rakers: Bony
or cartilaginous structures (tooth-like, blade-like or filament-like) attached
to the medial surface of the gill arches and extending inward.
Gonopodium: Rays
of the anal fin modified into a copulatory organ in male live-bearers,
e.g., mosquitofish
Head length:Maximum
length from the front tip of the upper jaw to the posterior tip of the
opercular membrane.
Head width:The greatest
lateral dimension of the head with the gill covers closed.
Inferior:
Refers to being below or under something.
Inguinal process:
a fleshy projection at base of pelvic fins.
Isthmus: The ventral
aspect of the trunk anterior to a vertical line at the posterior margin
of the operculum.
Lateral: At or toward
the side.
Lateral line: A series
of tubes and pores (sensory) located on the head and on the body from the
posterior margin of the head backward along each side.On the body the pores
open through modified scales.The lateral line may run to the base of the
caudal fin or to the tip of the median caudal ray.Such a line is said to
be complete.If it runs only part of the way along the trunk, it is incomplete.
Lateral line scales:These
are the scales along the lateral line.
Length of eye:The
greatest distance across the cornea or between the margins of the cartilaginous
eyeball.Note the difference between this measure and eye or orbit diameter.
Length of longest finray:
Measured from the structural base to the tip of the longest ray.
Lower jaw length:The
length of the mandible.
Mandible:
Refers to the lower jaw of a fish.
Maxilla: The bone
of the upper jaw lying just above the premaxilla.
Membrane (of fins):
The thin web-like tissue connecting the fin rays.
Medial or median:
At or toward the midline of the body.
Nape:The region from
the occiput to the origin of the dorsal fin (same as nuchal).
Nostrils or nares:
Paired openings on the snout in most fishes (not paired in Cichlidae and
Pomacentridae).
Occiput: Dorsal base
of the skull.
Opercle:The large
bone of the gill-cover.
Operculum (gill cover):
A large flap consisting of several flat bones located on the side of the
head and covering the gill chamber.
Opercular membrane:
The soft flap of skin which borders the operculum.
Pectoral fins:The
paired fins on the sides just behind the head.
Pelvic (or ventral) fins:
The paired fins inserted on the side of the fish either below or behind
the pectoral fins.
Pharyngeal teeth:
"Throat teeth" located on the pharyngeal bones that lie on either side
of the pharynx at the beginning of the esophagus.
Posterior: At or
toward the rear or tail end.
Postorbital length of
head: The distance from the hind margin of the orbit to the bony opercular
margin.
Predorsal: That region
of the body extending from the origin of the dorsal fin to the tip of the
upper jaw.
Premaxilla: The bone
on each side of the upper jaw forming the margin of the jaw.
Preopercle:The L-shaped
bone (with the lower arm directed forward) which lies behind and downward
from the eye.In some fishes it assumes other shapes but is in the same
position.
Protractile: condition
of being able to extend premaxillaries forward. Protractile premaxillaries
are separated from the front of the head by a groove.
Pyloric caeca: Small,
blind finger-like outpouchings of the intestinal tract located at, or just
behind, the pylorus.Counts are made of all tips.
Rays:
These are supports within the fins.If they are soft and pliable, they are
termed soft rays; if hard and spinous, they are termed spines.
Rudimentary rays:
Short rays (at the front of median fins) which are not divided at their
tips.
Scales: Dermal structures
giving support and protection to the body and properly considered as an
exoskeleton.Scales are reduced or lacking in some fishes.Scales types include
placoid scales (dermal denticles) of sharks; ganoid scales, which are very
thick and hard and are arranged like paving blocks with very little overlap;
cycloid scales which are thin and overlap like shingles (imbricated); and
ctenoid scales which are like the cycloid type but have many tiny teeth
or spines on the exposed surface.
Scales above the lateral
line: The number of scale rows located between the origin of the dorsal
fin and the lateral line.
Scales below the lateral
line: The number of scales counted on a line from the front of the
anal fin obliquely forward to but not including the lateral line.
Snout: The region
between the eye and the front tip of the upper jaw.
Snout length:The
measurement from the most anterior point of the snout to the front margin
of the orbit.
Standard length:The
length from the tip of the upper jaw to the hidden base of the caudal fin
rays (the end of the last caudal vertebra).The position of the base of
the caudal rays is indicated by the sharp crease formed by bending the
caudal fin.
Total length:The
greatest length measured from the tip of the head (mouth closed) to the
extremity of the caudal fin (with the caudal rays squeezed together).
Upper jaw length: Measured
from the most anterior point of the premaxilla to the most posterior point
of the maxilla.
Ventral:
At or toward the belly (or underside) of a fish.
Ventrolateral: An
area on the body between the sides and the mid-line of the belly.
Vomerine teeth: teeth
on the vomer (bone in middle of roof of mouth).
Sources:
Woodling, J. 1985.
Colorado's little fish. A guide to the minnows and other lesser known
fishes in the state of Colorado. Colorado Division of Wildlife, Denver,
CO.
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