Glossary

anal-fin

A median, unpaired, ventral fin located between the anus and caudal fin, usually in the posterior portion of the body. Used to maintain equilibrium and stability.

Used in 771 species profiles

Related terms

anal-fin origin
Anteriormost point at which the anal fin base is attached to the body.
andropodium
Modified, flexible anal fin rays present in males of some fish species (families Hemirhamphidae and Goodeidae) giving the fin a 'notched' appearance. Not used for insemination like the gonopodium in members of the family Poecillidae but to clasp the female during mating.
anus
Opening at the lower end of the alimentary canal through which solid waste is excreted.
body depth
The vertical distance between the dorsal and ventral margins of the body measured at the base of the pectoral fin where it joins the body. In most icthyological works the greatest dimension, normally anterior to the dorsal fin, is taken but in some cases body depth is measured at the origin of pectoral, pelvic and first anal. Fins or fin bases are not included in the measurement, however.
caudal peduncle
The typically narrow section of the body located between the posterior of the dorsal and anal fins and caudal fin origin. Its depth is measured vertically at the narrowest point.
caudal-fin
Also referred to as the tail fin, it's main purpose is thrust and propulsion.
gonopodium
Modified anal fin used in copulation for the transfer of male gametes to a female. In many cases only the anterior part of the fin is modified.
medial
Relating to, situated on or in, or extending towards the middle; median. Opposite of lateral.
posterior
Located near or towards the rear end; further back in position.
transverse scale row
Number of scales in the diagonal row between the orgins of dorsal and anal fins in a fish specimen, excluding the lateral line scales.
ventral-fin
Either of the pair of fins, also known as pelvic fins, attached to the pelvic girdle in fishes that help control the direction of movement. Correspond to the hind legs in higher vertebrates and vary in position depending on taxon. Sometimes absent entirely.
vertical fin
Unpaired, median fin, i.e., dorsal, caudal, adipose and anal fins.

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